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#122
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#123
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Stewart Pinkerton wrote:
You cannot draw any conclusions about AI's engineers with all this third hand information. They may not have had the budget or time to dig into anything - and assuming they are testing their gear before publishing specs, probably thought it was easier to pass up the sale than go any further. It would take about ten minutes with a signal generator and voltmeter to check this gross error. So much for engineering integrity, customer care and quality control....... It is unrealistic to expect the full force of a company to be used to address a single customer problem if it looks like it could be anywhere near time consuming. See above. If I were running such a company, a loud alarm bell would ring if a customer reported audible loss of bass on one of my units which was specified flat to 2 Hz.................... One possibility could be that the opamps in this unit would be RF-oscillating with the particular load in Mr. Langs setup. This will cause additional current consumption and the outcome could be a bass roll-off as described. It would account for a poorly designed piece of gear which should not be offered to the market -- ciao Ban Bordighera, Italy |
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#124
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Chung wrote in message ...
Mr. Art Ferris of Audible Illusions then sent me the Email that included the explanation that we *all* have taken issue with. While I agreed with their conclusion that the unit rolled off in my system, I certainly did not buy their explanation that I found convoluted, as to why it rolled off in my system. That's funny the way you put it. You agreed with their conclusion, which was that they agreed with your conclusion?  In other words, you simplyagreed with your conclusion. Yeah. I guess you are right. It does look like a case where the dog is chasing its tail. I could offer a clarification, but I would probably only dig a deeper hole for myself. Oh what the heck. My conclusion was a "general" conclusion and I dare say a "logical" conclusion. Mr. Ferris' conclusion, that has since been debunked in this thread as an "impotent" and "preposterous" conclusion, was the "official company" conclusion that validated, right or wrong, my "foregone" conclusion. I told you I would simply dig a deeper hole for myself. Robert C. Lang |
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#125
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Stewart Pinkerton wrote in message ...
On 29 Oct 2004 23:04:01 GMT, (Robert C. Lang) wrote: That was one of the best audio decisions I have made. I listened to in my system 4 other line stages from BAT, Ayre, Placette Audio, and one other. I settled on the Placette Audio for a number of reasons including it being a passive line stage. I like the philosophy. And yes, it passes that 23hz note with gripping realism. Interesting that you picked a unit which actually *would* be sensitive to cable capacitance! :-) Only in the high treble, of course. Ironic, yes it is. I'm no technocrat, but I was familiar enough with cable capacitance issues because of my experience with a passive line stage to know that Mr. Ferris' bass/cable capacitance explanation did not wash. Robert C. Lang |
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#127
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Chung wrote in message ...
Robert C. Lang wrote: This all could be true, I don't know. This also dovetails, I believe, to the questions that Mr. Chung asked yesterday. He asked: Did those people listen to the M3A in *your* system and agreed that the bass was indeed rolled off? Or did they simply agree with you without listening to it, but having made measurements on it? The answer to the first question is, of course, they agreed with my conclusion without having listened in my system, even though they had the opportunity to do so. That is a sign of incompetence, or at least (and even worse IMO), a lack of the intellecutal curiosity that is so common among the better engineers. I certainly would not expect a reputable company to simply accept your conclusion that 23Hz response is way down from this preamp. It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob |
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#128
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Ban wrote:
Stewart Pinkerton wrote: You cannot draw any conclusions about AI's engineers with all this third hand information. They may not have had the budget or time to dig into anything - and assuming they are testing their gear before publishing specs, probably thought it was easier to pass up the sale than go any further. It would take about ten minutes with a signal generator and voltmeter to check this gross error. So much for engineering integrity, customer care and quality control....... It is unrealistic to expect the full force of a company to be used to address a single customer problem if it looks like it could be anywhere near time consuming. See above. If I were running such a company, a loud alarm bell would ring if a customer reported audible loss of bass on one of my units which was specified flat to 2 Hz.................... One possibility could be that the opamps in this unit would be RF-oscillating with the particular load in Mr. Langs setup. This will cause additional current consumption and the outcome could be a bass roll-off as described. It would account for a poorly designed piece of gear which should not be offered to the market This particular amplifier is supposedly an SET. A tubed amp with no overall feedback. Hard to imagine it oscillating. That would be really bad engineering, if true... |
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#129
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On 7 Nov 2004 16:16:50 GMT, (Robert C. Lang)
wrote: Stewart Pinkerton wrote in message ... On 29 Oct 2004 23:04:01 GMT, (Robert C. Lang) wrote: Indeed, I *did* not, regarding the failure of certain well-regarded amplifiers when I was making a similar decision about eight years ago. It fails whatever test you set, you junk it. My only curiosity was why this unit was reportedly so *massively* outside its spec. Ah. Before reading this post I just hit the send button on a reply that made reference to your speakers, for which I have very high regard. They are known to have brought "mighty" amps to their wobbly topological knees. As far as I'm concerned the problem was the amp not the speaker. But I'm curious, looking at the specs, did you have advance warning that there would likely be a problem? That is assuming, of course, that I a guessing correctly that the reason for the amps failures in your system was due to the peculiarly low impedance load of your speakers. When I say 'failure', I was simply referring to the fact that some of the amps did not sound the same as others, not to an actual breakdown. The amps were mainly tested into a pair of Tannoy 633s, their intended load, and not a difficult one for most amps. I was simply using the Apogees as a 'wheat from chaff' differentiator for the better amps, I didn't really expect anything other than the Krell to be a good match for them. The Yamaha AX-570 did exceptionally well, with just a touch of treble brightness, while the Hafler XL-600 and Audiolab 8000P were not sonically distiguishable from the Krell when driving the Apogees. The Hafler had a very noisy fan, so I went for the Audiolab. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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#130
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Stewart Pinkerton wrote in message ...
On 28 Oct 2004 23:59:55 GMT, (Robert C. Lang) wrote: I was not going ignore my personal experience of the 3A in my system just because Stereophile had given it a glowing review on a single unit. This is why I, in part, reject your unrelenting reliance (you have held it up as being an unimpeachable reference several times) on a single measurement, done on a single hand picked unit, performed nearly 9 years ago by Stereophile. Scarcely scientific. I have done no such thing, I have simply pointed to its existence. That a production sample would have a bass rolloff significantly more than *ten times* the specified value beggars belief, even for a 'cottage industry' product. Hence, either your perception is wrong, the unit was *seriously* broken, you somehow wired it up wrongly, or there is something *very* peculiar about your system, mwhich other preamps don't reveal. If you have any other explanation, I'm sure we'd all be happy to know it. OK, I can't really disagree with your synopsis. Actually, in its barest form it's a summary that does reflect the possibilities. It does not, however, comment on the *likelihood* of each possibility. I wish to add the following comments: "Hence, either your perception is wrong" I am appreciative that you lowered the "red flag" from your earlier comment that remarked, "Your imagination seems to be the most likely culprit". I believe that of the four possibilities you have listed the "wrong perception" possibility, given the tangible physical phenomenon that occurred (or didn't occur) and experienced by me an one other person, is by far, the least likely. "or the unit was *seriously* broken" I agree with the possibility that it was broken. I also believe that this is the most likely possibility. In this case I'm defining "broken" as in it didn't meet spec, in my system, for the lowest octaves" because the unit I sounded great otherwise. It certainly, in my opinion and according to Audible Illusions, would not meet its published specs in my system. As you saw Audible Illusions would not admit that it was broken whether it was or not. But they probably are the only ones that may really know the truth. Questions: When a magazine makes a measurement, such as the bandwidth measurement that "Stereophile" conducted, is the test simulated? Would such a test always reflect real world load situations? Are these tests standardized? "you somehow wired it up wrongly" I raised this possibility here in this discussion and with Audible Illusions when this all took place in February 2000. With Audible Illusions I went over with them (the engineers) step by step on all connections, especially as it related to the crossover. My crossover is at a relatively high 200hz so my thinking is that if I had screwed up those connections somehow it would be immediately noticeable. Also, an errant hook it up wrong could have some disastrous consequences. As it was, as I said in my Audioreview.com comments, the Audible Illusions passed some *great* overall low bass, just not below 25hz. (I'm going on Telarc's literature that stated the 90-second organ note was 23hz). I believe an errant hook up is an unlikely possibility. But I never ruled it out. "or there is something *very* peculiar about your system, mwhich other preamps don't reveal" Again I appreciate you modifying your previous language in which you stated "unless there was something *seriously* wrong with your system", replacing "wrong" with "peculiar" even though a thin line that may sometimes be. "Peculiar" as a term related to an audio system is something I can live with. Some audiophiles might consider it a badge of honor. Some components that have had that label are of stellar quality. One that comes to mind are your speakers that I have always held in very high regard but were widely considered peculiar or quirky because of the alarmingly (for sheepish amplifiers not up to the workload) low impedances it presented. Interestingly around here (hometown for Audible Illusions) we have always considered Audible Illusions to be "quirky" or "peculiar". But it is, nonetheless, well regarded. Having said this, my system's components, if the manufacturer's specifications are to be believed, are plain Jane pedestrian; real chocolate and vanilla stuff. Although, Mr. Art Ferris of Audible Illusions thought my system presented a "peculiar" problem for its line stage. However, as noted other line stages, passive and active, work fine in my system. There may be other possibilities, including one that stems from a recent test conducted by "Stereophile" on another preamp. I may post it later. Robert C. Lang |
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#131
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On 7 Nov 2004 19:55:49 GMT, (Robert C. Lang)
wrote: Stewart Pinkerton wrote in message ... On 28 Oct 2004 23:59:55 GMT, (Robert C. Lang) wrote: I was not going ignore my personal experience of the 3A in my system just because Stereophile had given it a glowing review on a single unit. This is why I, in part, reject your unrelenting reliance (you have held it up as being an unimpeachable reference several times) on a single measurement, done on a single hand picked unit, performed nearly 9 years ago by Stereophile. Scarcely scientific. I have done no such thing, I have simply pointed to its existence. That a production sample would have a bass rolloff significantly more than *ten times* the specified value beggars belief, even for a 'cottage industry' product. Hence, either your perception is wrong, the unit was *seriously* broken, you somehow wired it up wrongly, or there is something *very* peculiar about your system, mwhich other preamps don't reveal. If you have any other explanation, I'm sure we'd all be happy to know it. OK, I can't really disagree with your synopsis. Actually, in its barest form it's a summary that does reflect the possibilities. It does not, however, comment on the *likelihood* of each possibility. I wish to add the following comments: "Hence, either your perception is wrong" I am appreciative that you lowered the "red flag" from your earlier comment that remarked, "Your imagination seems to be the most likely culprit". I believe that of the four possibilities you have listed the "wrong perception" possibility, given the tangible physical phenomenon that occurred (or didn't occur) and experienced by me an one other person, is by far, the least likely. Obviously I was not present, but IME that remains the most likely solution. "or the unit was *seriously* broken" I agree with the possibility that it was broken. I also believe that this is the most likely possibility. In this case I'm defining "broken" as in it didn't meet spec, in my system, for the lowest octaves" because the unit I sounded great otherwise. It certainly, in my opinion and according to Audible Illusions, would not meet its published specs in my system. As you saw Audible Illusions would not admit that it was broken whether it was or not. But they probably are the only ones that may really know the truth. Questions: When a magazine makes a measurement, such as the bandwidth measurement that "Stereophile" conducted, is the test simulated? Would such a test always reflect real world load situations? Are these tests standardized? If you look up the S'phile review, you'll see that they quote measured values for input and output impedances of the device, and they also quote the load values used when measuring FR. These values are all reasonably to be expected in normal use. The only scenario of which I'm aware that would have resulted in the effect you report, would be if a capacitor of less than ten times the required value had accidentally been fitted to *both* channels of your preamp. Even for a 'cottage industry' product, this seems unlikely. However, *if* we accept that your report is based on the physical reality of that 23 Hz note being significantly attenuated, there is no other sensible explanation. Such a gross error would of course show up immediately AI checked the unit. "you somehow wired it up wrongly" I raised this possibility here in this discussion and with Audible Illusions when this all took place in February 2000. With Audible Illusions I went over with them (the engineers) step by step on all connections, especially as it related to the crossover. My crossover is at a relatively high 200hz so my thinking is that if I had screwed up those connections somehow it would be immediately noticeable. Also, an errant hook it up wrong could have some disastrous consequences. As it was, as I said in my Audioreview.com comments, the Audible Illusions passed some *great* overall low bass, just not below 25hz. (I'm going on Telarc's literature that stated the 90-second organ note was 23hz). I believe an errant hook up is an unlikely possibility. But I never ruled it out. Seemed unlikely to me too, especially since you did not report problems with any other preamp. "or there is something *very* peculiar about your system, which other preamps don't reveal" Again I appreciate you modifying your previous language in which you stated "unless there was something *seriously* wrong with your system", replacing "wrong" with "peculiar" even though a thin line that may sometimes be. "Peculiar" as a term related to an audio system is something I can live with. Some audiophiles might consider it a badge of honor. Some components that have had that label are of stellar quality. One that comes to mind are your speakers that I have always held in very high regard but were widely considered peculiar or quirky because of the alarmingly (for sheepish amplifiers not up to the workload) low impedances it presented. Interestingly around here (hometown for Audible Illusions) we have always considered Audible Illusions to be "quirky" or "peculiar". But it is, nonetheless, well regarded. Having said this, my system's components, if the manufacturer's specifications are to be believed, are plain Jane pedestrian; real chocolate and vanilla stuff. Although, Mr. Art Ferris of Audible Illusions thought my system presented a "peculiar" problem for its line stage. However, as noted other line stages, passive and active, work fine in my system. Quite so, which would indicate that there's nothing unusual in the load presented to the preamp by your system. Hence, we may reasonably discount this possibility. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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#132
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B&D wrote in message ...
On 10/30/04 6:46 PM, in article , "Chung" wrote: That is a sign of incompetence, or at least (and even worse IMO), a lack of the intellecutal curiosity that is so common among the better engineers. You cannot draw any conclusions about AI's engineers with all this third hand information. Wait a minute. The conclusions drawn are based on the third hand info. If such info is wrong, then of course the conclusion is wrong. In other words, given what Mr. Robert Lang wrote, the conclusions are valid. *IF* he is privy to the whole story. He may not be. Agreed. And I would be surprised if I did have the whole story. I don't know why Audible Illusions was not more proactive in to getting to the bottom of the problem. Actually, at the time I thought they were, in fact, very proactive. They called at least twice and wrote me one or two emails. But lost forever are the complete contents of the phone calls most of which I have not conveyed in this thread. There is certainly some lost information. Who knows, some of it may have been pertinent. I am surprised with the passion that some have attempted to draw conclusions about this almost 5 year old story where clearly all the facts are not known. Robert C. Lang |
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#133
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B&D wrote in message ...
On 10/30/04 6:48 PM, in article , "Stewart Pinkerton" wrote: It is unrealistic to expect the full force of a company to be used to address a single customer problem if it looks like it could be anywhere near time consuming. See above. If I were running such a company, a loud alarm bell would ring if a customer reported audible loss of bass on one of my units which was specified flat to 2 Hz.................... The fact is, we don't know the whole story, the nature of the complaint and the real relationship between the poster and the company - it seems that there is a long one - so if they aren't taking it seriously there could be a reason. Just for the record my relationship with Audible Illusions was very brief. It extended from the time I borrowed a 3A from the dealer for an in-home demonstration that lasted for 7 days. If I recall correctly, my interaction with the company took place in two spurts. The first time when I called them (actually the dealer) about the problem of no or little bass below 25hz at which time they (Audible Illusions) responded with a phone call or two. The second time after I wrote my comments to Audioreview.com. I would say my "relationship" with the company extended 10 days. Either way - having been involved in field issues with electronic equipment, sure the actual measurement is quick to make - and they may have made it, but felt nothing to gain by correction - or it might be that this is a truly neutral piece of equipment, and there are other serious deficiencies in his setup or other equipment (though he claimed otherwise). And neither did Audible Illusions ever express that they thought there were any serious "deficiencies" in my system, except to say that there were impedance issues brought about about by what they said in writing, that I was running "several amplifiers" (four mono units) and an electronic crossover. So yes, they expressed that there were some "incompatibility" issues, but no "deficiency" issues with my equipment. We really don't have enough objective evidence to make any kind of judgement and be fair to AI at all. We just have 1 person's account of the story where he wasn't satisfied and is taking the story to this NG. Well, I certainly was not completely satisfied. But I did; nonetheless, in my Audioreview.com comments, give the 3A a positive review, because the 3A sounded very good. *Even* the bass sounded and performed great, just not below 25hz in *my* system. This is important because I have never made a "global" indictment of the 3A based on my singular and largely subjective experience. Indeed, I have recommended it to others, including an acquaintance who purchased the unit and kept it for several years. And as far as me "taking the story to this NG", this is true, but only to share my experience in response to the thread question "Do all preamps sound alike", not to indict or complain about the preamp. Naive though it may be, like a speaker (I realize that it is not entirely appropriate to compare speakers with electronics) that did not reproduce (specs not withstanding) the Poulenc organ 23zh note, I did not consider the 3A to have a latent defect. I simply viewed it as a piece of gear that did not perform to my complete satisfaction in my system and I moved on to explore a few of the other 200 preamps out there. For me, it was really that simple. Robert C. Lang |
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#134
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Stewart Pinkerton wrote in message ...
On 7 Nov 2004 16:16:50 GMT, (Robert C. Lang) wrote: Stewart Pinkerton wrote in message ... On 29 Oct 2004 23:04:01 GMT, (Robert C. Lang) wrote: Indeed, I *did* not, regarding the failure of certain well-regarded amplifiers when I was making a similar decision about eight years ago. It fails whatever test you set, you junk it. My only curiosity was why this unit was reportedly so *massively* outside its spec. Ah. Before reading this post I just hit the send button on a reply that made reference to your speakers, for which I have very high regard. They are known to have brought "mighty" amps to their wobbly topological knees. As far as I'm concerned the problem was the amp not the speaker. But I'm curious, looking at the specs, did you have advance warning that there would likely be a problem? That is assuming, of course, that I a guessing correctly that the reason for the amps failures in your system was due to the peculiarly low impedance load of your speakers. When I say 'failure', I was simply referring to the fact that some of the amps did not sound the same as others, not to an actual breakdown. The amps were mainly tested into a pair of Tannoy 633s, their intended load, and not a difficult one for most amps. I was simply using the Apogees as a 'wheat from chaff' differentiator for the better amps, I didn't really expect anything other than the Krell to be a good match for them. The Yamaha AX-570 did exceptionally well, with just a touch of treble brightness, while the Hafler XL-600 and Audiolab 8000P were not sonically distiguishable from the Krell when driving the Apogees. The Hafler had a very noisy fan, so I went for the Audiolab. Did the specs of the amps in question foretell that they would sound differently from each other? Were any of the amps that sounded differently from the others determined to be broken or out of spec? And, specifically, was there anything about the specs of the Yamaha AX-570, whether provided by the manufacturer or whether independently measured, that foretold that it would sound bright in your system? Robert C. Lang |
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#136
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#137
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(Bob Marcus) wrote in message ...
(Robert C. Lang) wrote in message ... I am surprised with the passion that some have attempted to draw conclusions about this almost 5 year old story where clearly all the facts are not known. Oh, come on. YOU'RE the one who is drawing conclusions from this episode, by siting it as evidence that preamps can sound different. We're just pointing out that it is evidence of no such thing. bob I drew my conclusion and formed my opinion 5 years ago based on my experience with a particular unit. I don't believe you have expressed your view to the question: Do all preamps sound alike? What is your opinion and based on what? Robert C. Lang |
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#138
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(Robert C. Lang) wrote in message ...
(Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". Quite simple, really. A large segment of the market for companies like AI is audiophiles who don't believe they are subject to psychoacoustic illusion, and take the suggestion as an insult. When confronted with a customer like that, there's no point in arguing with him. Nevertheless, the possibilities are limitless but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Indeed after going through all the responses to the riddle posed by my experience, while two or three have been irrelevantly baseless I think some have been very interesting and offered clearer insight. But in the end they have all been severely handicapped by lack of critical information. Well, as you're the source of our information... A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. I count 5 possibilities, and cannot imagine any others: 1) you were imagining things 2) the unit was defective 3) the design was flawed 4) your system wasn't properly set up 5) the unit wasn't compatible with something else about your system The information we're missing (valid listening tests, in situ measurements) wouldn't add to that list, but eliminate possibilities on it. Indeed one other possibility, the *official* response provided by Audible Illusions, has been completely dismissed by most in this group. Placing aside Mr. Ferris', comments about "capacitance" being a part of the problem, the core of his response remains the most likely possibility as far as I'm concerned. Again Mr. Ferris wrote: "that because I was driving several amplifiers, electronic crossover etc.", they believed that the "paralleled load impedance" of my amplifiers was well below the minimum load impedance of 20kohm". I thought the engineers here had pretty much debunked that. Their argument was that the only load the preamp saw was your crossover (since the amps were in series, not parallel), and that has a much higher input impedance, as you reported. Perhaps I'm not remembering this correctly, but that's my recollection of earlier posts. Mr. Ferris didn't just make that up. I know because in my discussions (interviews) with at least two design engineers at Audible Illusions, including one who had first hand knowledge with my John Iverson designed amplifiers used for my bass modules, they offered that same explanation to me. Unfortunately, Mr. Ferris embellished their informed explanation with his own, probably careless, comment about "capacitance". That comment served only to waylay or discredit the inmost core of his explanation. I don't know if the Audible Illusion explanation is right or wrong. But after looking at all the responses put forth in this thread, as a consumer, I am inclined to accept the official Audible Illusions response as the most likely cause of the 3A to fully perform in my system. They know their preamp best and based on information about my gear they could extrapolate best how they would all interact. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. How can you call this bewilderingly unexpected? Even Stereophile knows about it! ;-) A final thought: You got a product that your own ears told you did not meet spec, and could not pass a full-bandwidth signal that every other preamp you've ever tried could. And yet you wrote a glowing recommendation for the thing. Whether or not you were right, that's the sort of "criticism" that keeps incompetents in business. bob |
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#139
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Robert C. Lang wrote:
(Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". "Better light" in the sense that the AI engineers were not incompetent, but simply not wanting to argue with you whether your observations were correct. Nevertheless, the possibilities are limitless The possibilities are not limitless, but very limited. Either your observations were incorrect, or they had a bad unit. Note that other preamps apparently had no difficulty with that load. but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Indeed after going through all the responses to the riddle posed by my experience, while two or three have been irrelevantly baseless I think some have been very interesting and offered clearer insight. But in the end they have all been severely handicapped by lack of critical information. You provided all the information in this thread, and based on that information, we came up with the explanations. If that information is wrong, then of course there might have been other reasons. A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. The biggest unlikely possibility, IMO, is that a preamp can have a substantial roll-off at 23Hz. And I thought that the diagnosis offered so far has been meaningful. Indeed one other possibility, the *official* response provided by Audible Illusions, has been completely dismissed by most in this group. Placing aside Mr. Ferris', comments about "capacitance" being a part of the problem, the core of his response remains the most likely possibility as far as I'm concerned. Again Mr. Ferris wrote: "that because I was driving several amplifiers, electronic crossover etc.", they believed that the "paralleled load impedance" of my amplifiers was well below the minimum load impedance of 20kohm". Mr. Ferris didn't just make that up. I know because in my discussions (interviews) with at least two design engineers at Audible Illusions, including one who had first hand knowledge with my John Iverson designed amplifiers used for my bass modules, they offered that same explanation to me. Unfortunately, Mr. Ferris embellished their informed explanation with his own, probably careless, comment about "capacitance". That comment served only to waylay or discredit the inmost core of his explanation. I don't know if the Audible Illusion explanation is right or wrong. But after looking at all the responses put forth in this thread, as a consumer, I am inclined to accept the official Audible Illusions response as the most likely cause of the 3A to fully perform in my system. They know their preamp best and based on information about my gear they could extrapolate best how they would all interact. You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Or is there something unusual about your electronic crossover unit that you have not told us about? Note also that the other preamps did not have any trouble driving the crossover. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is the BAT spec'd flat down to 2 Hz? Even if the BAT's output impedance was 4.7K at 20Hz (about a 1.7uF cap), that would only give fractions of a dB droop at 20 Hz into 50K loads. In fact, the droop would be 3dB if the load is 4.7K, a highly unlikely scenario. And the AI is flat to 2Hz with a 50K load, according to its specs. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. |
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(Bob Marcus) wrote in message ...
(Robert C. Lang) wrote in message ... (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". Quite simple, really. A large segment of the market for companies like AI is audiophiles who don't believe they are subject to psychoacoustic illusion, and take the suggestion as an insult. When confronted with a customer like that, there's no point in arguing with him. How cunning of you. It is evident your allegations of conniving on the part of Audible Illusions, allegations you have oft-repeated and *defended* in this thread are a direct reflection of you and an unprincipled demeanor. This pointless allegation has been the cornerstone of your contribution to this thread. Please don't taint Audible Illusions with such blatantly unsubstantiated characterizations. Nevertheless, the possibilities are limitless but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. How can you call this bewilderingly unexpected? Even Stereophile knows Ø about it! ;-) What a specimen. Are you boasting that if the BAT VK-51SE was in your system and if there was a premature roll off of the bass that you would have figured out the problem independent of Stereophiles extensive tests and measurements? Or are you merely boasting that you can read? If you played a source in your system with a 23hz note would your system reproduce it? How do you know if your preamp can reproduce a 23hz note? I merely brought the Stereophile review of the BAT VK-51SE to the attention of the group because I thought that it *might* show some parallels, relationship or shed some light on the riddle that we have been grappling with relative to my experience with the Audible Illusions 3A. The results were very similar. And instead of commenting on the merits, either positively or negatively, all you can come up with is some incongruent "Even Stereophile knows about it!" A final thought: You got a product that your own ears told you did not meet spec, and could not pass a full-bandwidth signal that every other preamp you've ever tried could. And yet you wrote a glowing recommendation for the thing. Whether or not you were right, that's the sort of "criticism" that keeps incompetents in business. Ø bob Your complete thought is scrambled. First of all, Audible Illusions thought it was a decidedly negative recommendation. Which is why they contacted me. I gave it 4 of 5 stars, a good recommendation, certainly not "glowing". Secondly, you have tangled the order of events. I had tried only *one* preamp, which did pass the 23hz note, the PS Audio 4.5, before I auditioned the Audible Illusions. The other preamps that passed that note were auditioned *after* I made my written comments on the Audible Illusions. Thirdly, the Audible Illusions, except for not passing that Poulenc Concerto 23hz note, sounded very good in my system. I was not about to globally condemn the 3A on a single subjective audition conducted in my system. Besides 99% (guesstimate) of listeners, perhaps you included, don't have systems that will realistically (my view of realistic) reproduce a 23hz note or don't listen to music that goes down that low in a sustained manner. So they would never know about the shortcoming. Look, as far as I know I have responded to, certainly have attempted to respond to the best of my ability, every post that you have direct toward me. I have provided my full 7500 word Audioreview.com description, subjective though it was, of my audition of the 3A (that you clearly have not read) as well as produced information (not an easy task) provided to me from Audible Illusions 5 years ago, because the group expressed an interest in the riddle and I figured I could learn something. And I have. Unfortunately, I have not learned anything from you. Read my Audioreview.com and share with us how *you* would have handled that situation with a dealer loaned unit. I have responded to your posts, even though from the beginning they were laced with transparent smirks and were grossly insincere. You have intended to entrap but never help. But now you have lowered the level of discourse even further by repeatedly going into your lame comedy routine alleging Audible Illusions was double-dealing with the truth. I like comedy as much as the next guy, but why don't you at least *attempt* to provide pertinent discourse. Robert C. Lang |
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(Robert C. Lang) wrote in message ...
(Bob Marcus) wrote in message ... (Robert C. Lang) wrote in message ... (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". Quite simple, really. A large segment of the market for companies like AI is audiophiles who don't believe they are subject to psychoacoustic illusion, and take the suggestion as an insult. When confronted with a customer like that, there's no point in arguing with him. How cunning of you. It is evident your allegations of conniving on the part of Audible Illusions, allegations you have oft-repeated and *defended* in this thread are a direct reflection of you and an unprincipled demeanor. This pointless allegation has been the cornerstone of your contribution to this thread. Please don't taint Audible Illusions with such blatantly unsubstantiated characterizations. Apparently I'm too cunning by half, since my point here has passed you by. I was not criticizing AI at all here. Several people have noted the technical gibberish you were given as an explanation for what you heard, and expressed astonishment that AI's engineers didn't seem particularly interested in figuring out what the "problem" was. The implication was that they were lazy, incompetent, or both. By contrast, my hypothesis above suggests that they were just trying not to insult a reviewer whom they may have suspected didn't know what he was talking about. Nevertheless, the possibilities are limitless but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. How can you call this bewilderingly unexpected? Even Stereophile knows Ø about it! ;-) What a specimen. Are you boasting that if the BAT VK-51SE was in your system and if there was a premature roll off of the bass that you would have figured out the problem independent of Stereophiles extensive tests and measurements? No. I'm merely pointing out that it is hardly bewildering to anyone who understands the effect that such impedance mismatches can have on frequency response. Or are you merely boasting that you can read? If you played a source in your system with a 23hz note would your system reproduce it? How do you know if your preamp can reproduce a 23hz note? I merely brought the Stereophile review of the BAT VK-51SE to the attention of the group because I thought that it *might* show some parallels, relationship or shed some light on the riddle that we have been grappling with relative to my experience with the Audible Illusions 3A. The results were very similar. And instead of commenting on the merits, either positively or negatively, all you can come up with is some incongruent "Even Stereophile knows about it!" A final thought: You got a product that your own ears told you did not meet spec, and could not pass a full-bandwidth signal that every other preamp you've ever tried could. And yet you wrote a glowing recommendation for the thing. Whether or not you were right, that's the sort of "criticism" that keeps incompetents in business. Ø bob Your complete thought is scrambled. First of all, Audible Illusions thought it was a decidedly negative recommendation. Which is why they contacted me. I gave it 4 of 5 stars, a good recommendation, certainly not "glowing". Secondly, you have tangled the order of events. I had tried only *one* preamp, which did pass the 23hz note, the PS Audio 4.5, before I auditioned the Audible Illusions. The other preamps that passed that note were auditioned *after* I made my written comments on the Audible Illusions. Thirdly, the Audible Illusions, except for not passing that Poulenc Concerto 23hz note, sounded very good in my system. I was not about to globally condemn the 3A on a single subjective audition conducted in my system. Besides 99% (guesstimate) of listeners, perhaps you included, don't have systems that will realistically (my view of realistic) reproduce a 23hz note or don't listen to music that goes down that low in a sustained manner. So they would never know about the shortcoming. Nevertheless, in this day and age, it is relatively easy to deliver a full-bandwidth signal to the speaker terminals. Given that, I'd argue that it would be irresponsible to recommend a component that could not do so. And if you can't explain why it couldn't do so, then you probably have no business writing reviews. Look, as far as I know I have responded to, certainly have attempted to respond to the best of my ability, every post that you have direct toward me. I have provided my full 7500 word Audioreview.com description, subjective though it was, of my audition of the 3A (that you clearly have not read) as well as produced information (not an easy task) provided to me from Audible Illusions 5 years ago, because the group expressed an interest in the riddle and I figured I could learn something. And I have. Unfortunately, I have not learned anything from you. Read my Audioreview.com and share with us how *you* would have handled that situation with a dealer loaned unit. I have responded to your posts, even though from the beginning they were laced with transparent smirks and were grossly insincere. You have intended to entrap but never help. But now you have lowered the level of discourse even further by repeatedly going into your lame comedy routine alleging Audible Illusions was double-dealing with the truth. I like comedy as much as the next guy, but why don't you at least *attempt* to provide pertinent discourse. I have never accused AI of "double-dealing with the truth." For that matter, I haven't *accused* AI of anything. Like others, I have speculated on possible explanations for the set of facts you have laid before us. Granted, some--but not all--of those hypotheses (mine and others) have suggested incompetence of one form or another on the part of AI. But I have never presented them as anything but hypotheses, and I have never offered my own judgment on which hypothesis I thought most plausible. Until now. Weighing everything you have told us, I conclude that this preamp was a non-defective unit of a competently-made product that was, unfortunately for AI, subjected to a less than competent review. bob |
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Chung wrote in message ...
Robert C. Lang wrote: (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". "Better light" in the sense that the AI engineers were not incompetent, but simply not wanting to argue with you whether your observations were correct. There are serious problems with that reasoning. Is it not logical that if AI just wanted to conceal the truth and appease me they would have just said so *orally* that the 3A was not compatible in my system? Why would they submit a *written* explanation, especially since I never asked for any explanation written or oral? It is your right to defend Mr. Marcus' baseless and pointless speculations but it certainly lowers the level of the conversation. Nevertheless, the possibilities are limitless The possibilities are not limitless, but very limited. Either your observations were incorrect, or they had a bad unit. Note that other preamps apparently had no difficulty with that load. but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Indeed after going through all the responses to the riddle posed by my experience, while two or three have been irrelevantly baseless I think some have been very interesting and offered clearer insight. But in the end they have all been severely handicapped by lack of critical information. You provided all the information in this thread, and based on that information, we came up with the explanations. If that information is wrong, then of course there might have been other reasons. A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. The biggest unlikely possibility, IMO, is that a preamp can have a substantial roll-off at 23Hz. And I thought that the diagnosis offered so far has been meaningful. Indeed one other possibility, the *official* response provided by Audible Illusions, has been completely dismissed by most in this group. Placing aside Mr. Ferris', comments about "capacitance" being a part of the problem, the core of his response remains the most likely possibility as far as I'm concerned. Again Mr. Ferris wrote: "that because I was driving several amplifiers, electronic crossover etc.", they believed that the "paralleled load impedance" of my amplifiers was well below the minimum load impedance of 20kohm". Mr. Ferris didn't just make that up. I know because in my discussions (interviews) with at least two design engineers at Audible Illusions, including one who had first hand knowledge with my John Iverson You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. I am not at all suggesting that this alters any of the analysis that you have made thus far, but it does point to another one of many things that the AI engineers knew about my system that had not been considered in this discussion. Remember, the AI engineers called me on two occasions for a total of 45 minutes to an hour. They asked many probing questions about my system in their effort to resolve what happened before thay provided their official written response. (By the way, the conversations were always polite, non defensive and never confrontational). Unfortunately, I can only recall but a fraction of the information exchange that we had. Or is there something unusual about your electronic crossover unit that you have not told us about? Like what? I really don't know what might be unusual or usual about it. It did not come with specs or a manual. The AI engineers had access to the manufacturers phone number. I don't know if they called to get more info. Note also that the other preamps did not have any trouble driving the crossover. As far as I know this is true. All I know is that they all passed the 23 hz note. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is the BAT spec'd flat down to 2 Hz? Even if the BAT's output impedance was 4.7K at 20Hz (about a 1.7uF cap), that would only give fractions of a dB droop at 20 Hz into 50K loads. In fact, the droop would be 3dB if the load is 4.7K, a highly unlikely scenario. And the AI is flat to 2Hz with a 50K load, according to its specs. Correction. The Stereophile review was made in November 2003, not 2004. My apologies. This means you can probably check out the specs on line. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Robert C. Lang |
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Robert C. Lang wrote:
Chung wrote in message ... Robert C. Lang wrote: (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". "Better light" in the sense that the AI engineers were not incompetent, but simply not wanting to argue with you whether your observations were correct. There are serious problems with that reasoning. Is it not logical that if AI just wanted to conceal the truth and appease me they would have just said so *orally* that the 3A was not compatible in my system? Well, for one thing, we did not know that they wrote to you with this explanation. For another, it really does not matter whether they wrote or just called you up and told you. Why would they submit a *written* explanation, especially since I never asked for any explanation written or oral? Did they also write to tell you that high capacitance affect bass response? It is your right to defend Mr. Marcus' baseless and pointless speculations but it certainly lowers the level of the conversation. Actually I was not defending Mr. Marcus' position. I was trying to explain why it was "in a better light". I personally believe that AI was incompetent, given your account of the circumstances. But, hey, you are welcome to draw your conclusions. Nevertheless, the possibilities are limitless The possibilities are not limitless, but very limited. Either your observations were incorrect, or they had a bad unit. Note that other preamps apparently had no difficulty with that load. but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Indeed after going through all the responses to the riddle posed by my experience, while two or three have been irrelevantly baseless I think some have been very interesting and offered clearer insight. But in the end they have all been severely handicapped by lack of critical information. You provided all the information in this thread, and based on that information, we came up with the explanations. If that information is wrong, then of course there might have been other reasons. A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. The biggest unlikely possibility, IMO, is that a preamp can have a substantial roll-off at 23Hz. And I thought that the diagnosis offered so far has been meaningful. Indeed one other possibility, the *official* response provided by Audible Illusions, has been completely dismissed by most in this group. Placing aside Mr. Ferris', comments about "capacitance" being a part of the problem, the core of his response remains the most likely possibility as far as I'm concerned. Again Mr. Ferris wrote: "that because I was driving several amplifiers, electronic crossover etc.", they believed that the "paralleled load impedance" of my amplifiers was well below the minimum load impedance of 20kohm". Mr. Ferris didn't just make that up. I know because in my discussions (interviews) with at least two design engineers at Audible Illusions, including one who had first hand knowledge with my John Iverson You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. So the preamp drives an electronic crossover in parallel with a power amp. You think the combined load is less than 5K or so? I highly doubt it. In other words, there is no way there should be a droop at 23 Hz because of this load. I am not at all suggesting that this alters any of the analysis that you have made thus far, but it does point to another one of many things that the AI engineers knew about my system that had not been considered in this discussion. You are the one giving us the background info on this incident... Remember, the AI engineers called me on two occasions for a total of 45 minutes to an hour. They asked many probing questions about my system in their effort to resolve what happened before thay provided their official written response. (By the way, the conversations were always polite, non defensive and never confrontational). Unfortunately, I can only recall but a fraction of the information exchange that we had. Or is there something unusual about your electronic crossover unit that you have not told us about? Like what? I really don't know what might be unusual or usual about it. It did not come with specs or a manual. The AI engineers had access to the manufacturers phone number. I don't know if they called to get more info. So there is nothing unusual about your crossover. So why did they say you have an unusal load for their preamp? Note also that the other preamps did not have any trouble driving the crossover. As far as I know this is true. All I know is that they all passed the 23 hz note. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is the BAT spec'd flat down to 2 Hz? Even if the BAT's output impedance was 4.7K at 20Hz (about a 1.7uF cap), that would only give fractions of a dB droop at 20 Hz into 50K loads. In fact, the droop would be 3dB if the load is 4.7K, a highly unlikely scenario. And the AI is flat to 2Hz with a 50K load, according to its specs. Correction. The Stereophile review was made in November 2003, not 2004. My apologies. This means you can probably check out the specs on line. The specs of the AI was available online. The BAT's were not. Stereophile's concern with the BAT seems to be related to loads of 600 ohm, which is a totally different problem than yours. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. Only if the load is very low in impedance. The 4.7K at 20 Hz is fine for the usual 50K load. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Robert C. Lang |
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(Robert C. Lang) wrote in message ...
Chung wrote in message ... Robert C. Lang wrote: (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". "Better light" in the sense that the AI engineers were not incompetent, but simply not wanting to argue with you whether your observations were correct. There are serious problems with that reasoning. Is it not logical that if AI just wanted to conceal the truth and appease me they would have just said so *orally* that the 3A was not compatible in my system? Why would they submit a *written* explanation, especially since I never asked for any explanation written or oral? It is your right to defend Mr. Marcus' baseless and pointless speculations but it certainly lowers the level of the conversation. It is not logical to draw conclusions about what AI wanted to communicate based on how they chose to communicate. Written responses to reviews may be company policy. Perhaps they hoped a written response would shame you into pulling or at least correcting your review. As for my speculations, they were based on the information you provided. If that information was incorrect--as now appears likely--then I would agree that they were pointless. Nevertheless, the possibilities are limitless The possibilities are not limitless, but very limited. Either your observations were incorrect, or they had a bad unit. Note that other preamps apparently had no difficulty with that load. but given the concerned tenor of the Audible Illusions' staff discourse during this period there was no indication, not even in hindsight, that they had conspired to pull off some sophomoric ruse. Indeed after going through all the responses to the riddle posed by my experience, while two or three have been irrelevantly baseless I think some have been very interesting and offered clearer insight. But in the end they have all been severely handicapped by lack of critical information. You provided all the information in this thread, and based on that information, we came up with the explanations. If that information is wrong, then of course there might have been other reasons. A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. The biggest unlikely possibility, IMO, is that a preamp can have a substantial roll-off at 23Hz. And I thought that the diagnosis offered so far has been meaningful. Indeed one other possibility, the *official* response provided by Audible Illusions, has been completely dismissed by most in this group. Placing aside Mr. Ferris', comments about "capacitance" being a part of the problem, the core of his response remains the most likely possibility as far as I'm concerned. Again Mr. Ferris wrote: "that because I was driving several amplifiers, electronic crossover etc.", they believed that the "paralleled load impedance" of my amplifiers was well below the minimum load impedance of 20kohm". Mr. Ferris didn't just make that up. I know because in my discussions (interviews) with at least two design engineers at Audible Illusions, including one who had first hand knowledge with my John Iverson You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. This is news. Several of us had gotten the impression earlier that this was not so. (I'm sure you didn't intentionally mislead us, but I wish you had straightened this out earlier.) Now, perhaps you can supply the input impedances of the various items connected to your preamp outputs, and the engineers here can draw some conclusions for us. I am not at all suggesting that this alters any of the analysis that you have made thus far, but it does point to another one of many things that the AI engineers knew about my system that had not been considered in this discussion. Remember, the AI engineers called me on two occasions for a total of 45 minutes to an hour. They asked many probing questions about my system in their effort to resolve what happened before thay provided their official written response. (By the way, the conversations were always polite, non defensive and never confrontational). Unfortunately, I can only recall but a fraction of the information exchange that we had. Or is there something unusual about your electronic crossover unit that you have not told us about? Like what? I really don't know what might be unusual or usual about it. It did not come with specs or a manual. The AI engineers had access to the manufacturers phone number. I don't know if they called to get more info. Note also that the other preamps did not have any trouble driving the crossover. As far as I know this is true. All I know is that they all passed the 23 hz note. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is the BAT spec'd flat down to 2 Hz? Even if the BAT's output impedance was 4.7K at 20Hz (about a 1.7uF cap), that would only give fractions of a dB droop at 20 Hz into 50K loads. In fact, the droop would be 3dB if the load is 4.7K, a highly unlikely scenario. And the AI is flat to 2Hz with a 50K load, according to its specs. Correction. The Stereophile review was made in November 2003, not 2004. My apologies. This means you can probably check out the specs on line. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Fair enough. But I would suggest that anyone who wants to put together as complex a system as yours owes it to himself to learn what he needs to know of the technical side of things to do it correctly. That goes double for anyone who fancies himself a "reviewer." bob |
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Chung wrote in message ...
Robert C. Lang wrote: Chung wrote in message ... Robert C. Lang wrote: (Bob Marcus) wrote in message ... It occurs to me that there's another possibility here, one that puts AI and its engineers in a much better light. Suppose they examined Lang's unit, determined that it did indeed meet spec, and concluded from this that Lang's bass problem was psychoacoustic in origin. Do they tell Lang they think he's just imagining this lack of bass? Of course not. So they fudge, agreeing with his conclusion that there's something unusual about his system, and giving him a b.s. answer when he asks what that might be. bob I'm altogether lost as to how such a cowardly ploy would put Audible engineers in a "much better light". "Better light" in the sense that the AI engineers were not incompetent, but simply not wanting to argue with you whether your observations were correct. There are serious problems with that reasoning. Is it not logical that if AI just wanted to conceal the truth and appease me they would have just said so *orally* that the 3A was not compatible in my system? Well, for one thing, we did not know that they wrote to you with this explanation. For another, it really does not matter whether they wrote or just called you up and told you. I provided the written text early on in this discussion. It matters only that, right or wrong, the written word is indelible and is official. If it had only been oral we would have not had this discussion because, frankly, I simply did not remember exactly what Audible Illusion said until I dug their words from the archives and submitted to the group. Why would they submit a *written* explanation, especially since I never asked for any explanation written or oral? Did they also write to tell you that high capacitance affect bass response? True. But as I explained, in my conversation with the engineers, while they spoke of possibilities having to do with the amplifier and crossover loads they *never* made any reference to a high capacitance factor. It was clear to me at the time, that Art Ferris, founder and owner of Audible Illusions, took what the engineers had written and added his own "also perhaps" unprepared words, in a separate paragraph, about high capacitance. That was very unfortunate. I'm sure the engineers would have cringed if they had seen what Mr. Ferris wrote. But this is something that engineers often have to deal with in the real world where their bosses say or do something totally out of sync with the engineering perspective for marketing or political reasons. Can I assume that you are an engineer? If so, you can label the Audible Illusion engineers as incompetents for their explanation as to what happen but I believe that you should take pause before you attribute Mr. Ferris' inaccurate and extemporaneous remark about high capacitance affecting bass response to *any* engineer. It is your right to defend Mr. Marcus' baseless and pointless speculations but it certainly lowers the level of the conversation. Actually I was not defending Mr. Marcus' position. I was trying to explain why it was "in a better light". I personally believe that AI was incompetent, given your account of the circumstances. But, hey, you are welcome to draw your conclusions. You provided all the information in this thread, and based on that information, we came up with the explanations. If that information is wrong, then of course there might have been other reasons. I don't believe I have provided any "wrong" information. But there is no question that I have "omitted" information primarily because I simply don't recall or fully understand the highly technical conversations I had with the Audible Illusion engineers nor do I have any access or understanding to the schematics of the 3A. A meaningful diagnosis is simply not possible in this forum. That explains why the problem only has been narrowed down to 5 or 6, largely unlikely possibilities. The biggest unlikely possibility, IMO, is that a preamp can have a substantial roll-off at 23Hz. And I thought that the diagnosis offered so far has been meaningful. I think that your diagnosis has been both meaningful and enlightening. I've certainly appreciated it. But that does not mean that, through no fault of your own, that your diagnosis goes to the root condition of what happened with the 3A in my system. You can only go so far as the information that you have available to you. I had hoped to provide enough information that you and others could then fill the in gaps. But unless I can come up with more information about, the crossover, for example, or other information, it looks like critical information will be lacking. Who knows, may be I'll call Audible Illusions. You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. So the preamp drives an electronic crossover in parallel with a power amp. You think the combined load is less than 5K or so? I highly doubt it. In other words, there is no way there should be a droop at 23 Hz because of this load. I am not at all suggesting that this alters any of the analysis that you have made thus far, but it does point to another one of many things that the AI engineers knew about my system that had not been considered in this discussion. You are the one giving us the background info on this incident... With all due respect the information about the preamp driving both the crossover and amplifiers is not new information. This is *clearly* stated in the Audible Illusions written response that I provided to the group. In fact it seemed (i'm not sure) to be the basis of their response. The diagnosis either missed it or failed to consider it. But as it stands the Audible Illusions engineers that it was *very* pertinent and said so; you have dismissed it as being important. Perhaps this is a simple and understandable disagreement. But remember Audible Illusions had much more information than you upon which to base their diagnosis, including the unit in question and other information that neither you nor I is privy to. Remember, the AI engineers called me on two occasions for a total of 45 minutes to an hour. They asked many probing questions about my system in their effort to resolve what happened before thay provided their official written response. (By the way, the conversations were always polite, non defensive and never confrontational). Unfortunately, I can only recall but a fraction of the information exchange that we had. Or is there something unusual about your electronic crossover unit that you have not told us about? So there is nothing unusual about your crossover. So why did they say you have an unusal load for their preamp? Well, the Audible Illusion engineers asked for, and I gave them, the phone number of the manufacturer crossover. They clearly thought the crossover was a contributor to the problem. Whether they called the manufacturer I don't know. For what is worth the crossover is a custom design, but so are a lot of crossovers. Consider a review in the November 2004 issue of Stereophile. It is not intended to be a snug fit for what we have been wrestling with here and I will leave it to those of you who are technically endowed as to whether there are some similarities or parallels. On page 94 of the Stereophile review of the BAT VK-51SE it reads: "The balanced output impedance was twice what was specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20hz, due to the size of the output coupling capacitors. This will not be an issue with components, such as BAT's own power amplifiers, but it does mean prematurely rolled-off low frequencies with low load impedances, such as those offered by some solid state amplifiers". End of Stereophile quote. Is the BAT spec'd flat down to 2 Hz? Even if the BAT's output impedance was 4.7K at 20Hz (about a 1.7uF cap), that would only give fractions of a dB droop at 20 Hz into 50K loads. In fact, the droop would be 3dB if the load is 4.7K, a highly unlikely scenario. And the AI is flat to 2Hz with a 50K load, according to its specs. Correction. The Stereophile review was made in November 2003, not 2004. My apologies. This means you can probably check out the specs on line. The specs of the AI was available online. The BAT's were not. Stereophile's concern with the BAT seems to be related to loads of 600 ohm, which is a totally different problem than yours. Is it happenstance that such a conclusion would be published in Stereophile at the very time that we are befuddled by my experience with the 3A. Not really, it's not that uncommon. I've seen caveats like that stated before in Stereophile as well as the British press. At a minimum, this shows the bewilderingly unexpected can happen, unlikely though it may appear, especially if all the facts/specs are not known or confirmed (as what we have here) of all the interacting components. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. Only if the load is very low in impedance. The 4.7K at 20 Hz is fine for the usual 50K load. The fact that a load is very low in impedance doesn't matter to a layperson who would be completely lost in that situation because they don't have training in the discipline. Indeed, even the Stereophile engineer seemed surprised enough to express it as a noteworthy occurrence. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Robert C. Lang |
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(Bob Marcus) wrote in message ...
(Robert C. Lang) wrote in message ... Chung wrote in message ... Mr. Marcus, First I want to apologize for the terse tenor of my recent replies directed toward you. I accused you of lowering the level of discourse. Looking at what I wrote in response I lowered the level of the conversation. It is not logical to draw conclusions about what AI wanted to communicate based on how they chose to communicate. Written responses to reviews may be company policy. Perhaps they hoped a written response would shame you into pulling or at least correcting your review. As for my speculations, they were based on the information you provided. If that information was incorrect--as now appears Ø likely--then I would agree that they were pointless. I really don't believe that I provided any "incorrect" information. I clearly have not been able to provide pertinent information, or I omitted certain information simply because I didn't know it. You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. This is news. Several of us had gotten the impression earlier that this was not so. (I'm sure you didn't intentionally mislead us, but I wish you had straightened this out earlier.) Now, perhaps you can supply the input impedances of the various items connected to your preamp outputs, and the engineers here can draw some conclusions for Ø us. I have a two-part response here. As I explained to Mr. Chung the text of the Audible Illusions response that I provided to the group makes it fairly clear that they believe the preamp driving the combination of the crossover *and* the amplifiers caused the incompatibility of the 3A in my system. I assumed that when Mr. Chung and the other knowledgeable people in the group made their initial diagnosis they took the Audible Illusions statement into account. It looks like there was an assumption made that all amplifiers were connected to the crossover, like in many systems, and that the preamp did not directly "see" the amps. It looks like they did not look at Audible Illusions statement closely enough. But having said that, I too, missed it. While I certainly know how my system is hooked up, I completely missed that it may have been important that the preamp was "seeing" both a crossover load and an amplifier load until Mr. Chung spotlighted the seemingly inconsistency of the Audible Illusion conclusion. As far as providing the information you request the most I would be able to provide are "specs", not measurements, for the various components I have. And while specs are a starting point they may or may not reflect reality. But more importantly I have no specs (except for a single spec found in the Audio magazine buyers guide), on the custom made crossover that I utilize. The Audible Illusions engineers thought that the crossover could have very well be the wildcard, which is why they specifically asked for the phone number of the manufacturer. Further, as it turns out Mr. Chung doesn't think the dual load of the crossover and amplifier is important anyway. There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Fair enough. But I would suggest that anyone who wants to put together as complex a system as yours owes it to himself to learn what he needs Ø to know of the technical side of things to do it correctly. Firstly, I don't know of anything, with respect to putting my system together, that I have not done correctly. Indeed, everyone who has heard it believes I have done everything correctly. In my humble opinion it is among the best I have heard. (I admit I have not heard a lot of premium systems under ideal conditions). Second, if you think my sound system is complex you should see my video system (I am a professional videographer) or our 11 train, 32 switch, digital HO system. But seriously, I have been known to get in over my head on projects on occasion, but when I do I don't hesitate to call in the cavalry. And you know who I generally call first, engineers. I recently finished three complex projects around the house involving drainage, solar energy, and seismic retrofitting. Most of the neighbors would call a "contractor" who specializes in those respective areas. I call an engineer simply because its better. (And guess what? It's usually cheaper because I have the engineer to draw up the plans and specs and then bid out the work to 4 or 5 "contractors" and take the lowest responsible bidder. The savings can be staggering). I said all that to make a point why I took exception to your description that Audible Illusions may have been less that straight forward in how they dealt with me. Even though I got the written response from Art Ferris, I really don't believe that I ever spoke to a marketing or sales person at Audible Illusions. I only dealt with engineers. Engineers, certainly engineers that I know, tend to be as straight a shooter as anyone on the planet and would have a more difficult time in playing those sort of games, especially over an extended period. Having said all that, my system is only marginally complex. I would venture to say that many here would say that it is not complex at all. It has an electronic crossover but that simply involves connecting amps to the crossover instead of directly to the preamp. I have done this since my days with the old Ohm F speaker system when I connected a subwoofer to it in a futile attempt to extract more dynamic range from a speaker whose dynamics were inherently limited. My current system does have a little twist in that one set of amps connects directly to the preamp while the other set connects via the crossover. But when I do connect and disconnect things up, as I will be doing when I go multi-channel, I do it with a group of audiophile friends (including engineers) who know a whole lot more than I do. Ø That goes Ø double for anyone who fancies himself a "reviewer." In a previous post you said I "probably had no business writing reviews". And guess what, I *agree* with you. I am not qualified to write a review on an electronic device. Not to split hairs my comments about the 3A at Audioreview.com were far short of a "review" and were not intended to be held to that level. They were subjective comments based on visual and aural observations. It is important for those that don't know that Audioreview.com is a misnomer if there ever was one. It is not a place for "reviews" but merely a place for users to express their opinions on audio equipment that they have (hopefully) used or auditioned. It should be viewed as *nothing* more than that. Aside from revisiting what I said about the Audible Illusions back in February 2000, I believe it has been several years since I visited that forum. I only recall one submission that I thought even approached the level of a "review". Other than that they were all simply subjective comments, of varying quality, to be sure, and no more than that. I'm not sure why Audible Illusions were compelled to call me. It was very unorthodox. They indicated that they *never* had responded to an Audioreview.com commentary before. There are certainly far worse comments about the 3A, although may be mine, as written, were construed as more damaging. And as self-serving as this may appear to be they gave every indication that they found my comments to be "credible", almost as if what I had experienced had happened before on rare occurrences. All I know that they asked lots of questions with due diligence. Who knows maybe something I added caused them to make a change or two. Robert C. Lang |
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Robert C. Lang wrote:
snip There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. Only if the load is very low in impedance. The 4.7K at 20 Hz is fine for the usual 50K load. The fact that a load is very low in impedance doesn't matter to a layperson who would be completely lost in that situation because they don't have training in the discipline. Indeed, even the Stereophile engineer seemed surprised enough to express it as a noteworthy occurrence. Do you know of any power amp with an input impedance of 600 ohms? Note that the reviewer repeatably praised the bass performance of that preamp, despite horrible performance driving 600 ohms. There is nothing bewilderingly unexpected here. That BAT preamp is simply not well designed for driving low impedances. It simply fails to meet minimum requirements for fidelity with low-impedance loads which it was supposed to drive. On the other hand, the AI is not specified for driving low impedances. If your crossover in parallel with the power amp presents a very low impedance to that AI, then of course the result is a bass roll-off at a higher frequency. |
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(Robert C. Lang) wrote in message ...
(Bob Marcus) wrote in message ... (Robert C. Lang) wrote in message ... Chung wrote in message ... Mr. Marcus, First I want to apologize for the terse tenor of my recent replies directed toward you. I accused you of lowering the level of discourse. Looking at what I wrote in response I lowered the level of the conversation. An occupational hazard of Usenet is that people occasionally talk past each other. I think that's what we've been doing here. It is not logical to draw conclusions about what AI wanted to communicate based on how they chose to communicate. Written responses to reviews may be company policy. Perhaps they hoped a written response would shame you into pulling or at least correcting your review. As for my speculations, they were based on the information you provided. If that information was incorrect--as now appears Ø likely--then I would agree that they were pointless. I really don't believe that I provided any "incorrect" information. I clearly have not been able to provide pertinent information, or I omitted certain information simply because I didn't know it. I was referring there to the question of whether the preamp was seeing only the crossover load. Glad that's been cleared up. You seem to have missed the point that your preamp does not drive the power amps directly; it drives your electronic crossover. In other words, that preamp did not see the amplifiers as loads. Given that, how could the AI explanation possibly be accepted? Good point. Actually, the preamp does see an amplifier load. Please bear with me as I try to explain this. My electronic crossover serves only as a low pass crossover (even though it is capable of a three way operation). The bass amplifiers are connected to the crossover which is connected to the preamp. So the preamp does not directly drive the bass amplifiers. My satellite speakers have a switch that allows for either use of an external electronic crossover or the internal crossover. The manufacturer, that provides both the electronic crossover and the speakers (satellites and bass modules) recommends strongly that the internal crossover of the satellites be used for best results. This is how the manufacturer's rep set it up. Therefore, my satellite amps are driven directly by the preamp. This is news. Several of us had gotten the impression earlier that this was not so. (I'm sure you didn't intentionally mislead us, but I wish you had straightened this out earlier.) Now, perhaps you can supply the input impedances of the various items connected to your preamp outputs, and the engineers here can draw some conclusions for Ø us. I have a two-part response here. As I explained to Mr. Chung the text of the Audible Illusions response that I provided to the group makes it fairly clear that they believe the preamp driving the combination of the crossover *and* the amplifiers caused the incompatibility of the 3A in my system. I assumed that when Mr. Chung and the other knowledgeable people in the group made their initial diagnosis they took the Audible Illusions statement into account. It looks like there was an assumption made that all amplifiers were connected to the crossover, like in many systems, and that the preamp did not directly "see" the amps. It looks like they did not look at Audible Illusions statement closely enough. But having said that, I too, missed it. While I certainly know how my system is hooked up, I completely missed that it may have been important that the preamp was "seeing" both a crossover load and an amplifier load until Mr. Chung spotlighted the seemingly inconsistency of the Audible Illusion conclusion. As far as providing the information you request the most I would be able to provide are "specs", not measurements, for the various components I have. And while specs are a starting point they may or may not reflect reality. But more importantly I have no specs (except for a single spec found in the Audio magazine buyers guide), on the custom made crossover that I utilize. The Audible Illusions engineers thought that the crossover could have very well be the wildcard, which is why they specifically asked for the phone number of the manufacturer. Further, as it turns out Mr. Chung doesn't think the dual load of the crossover and amplifier is important anyway. Specs would be something, but if Chung doesn't think it's important, who are you and I to argue?? There is really nothing here that is bewilderingly unexpected, if you accept that (a) the unit may be bad, or (b) your observations may have been wrong. Well, to a lay person, without the hindsight benefit of the Stereophile review would have been completely lost as to why there was a premature bass roll off. At least, that's what Stereophile seems to think. A lay person may think that they have a bad unit when it reality the unit was not compatible with their system. Fair enough. But I would suggest that anyone who wants to put together as complex a system as yours owes it to himself to learn what he needs Ø to know of the technical side of things to do it correctly. Firstly, I don't know of anything, with respect to putting my system together, that I have not done correctly. Indeed, everyone who has heard it believes I have done everything correctly. In my humble opinion it is among the best I have heard. (I admit I have not heard a lot of premium systems under ideal conditions). If what the AI engineers said to you was correct (a big if), then what you were doing here was using a preamp that was inappropriate for your system. That's what I meant by "doing it correctly." If someone wants to assemble a complex system with tubes and such and all sorts of weird impedances, then they should learn enough about impedance-matching to avoid obvious mismatches. snip That goes double for anyone who fancies himself a "reviewer." In a previous post you said I "probably had no business writing reviews". And guess what, I *agree* with you. I am not qualified to write a review on an electronic device. Not to split hairs my comments about the 3A at Audioreview.com were far short of a "review" and were not intended to be held to that level. They were subjective comments based on visual and aural observations. I think you used the word "review" yourself. (But then, I also thought you said all your amps were plugged into your crossover!) Hence my comment. "Reviewing" a component in a system for which it is inappropriate would be irresponsible in the extreme. But I gather we're really just talking about user comments on a Web site--and the inappropriateness of this preamp to your system has not been confirmed. It is important for those that don't know that Audioreview.com is a misnomer if there ever was one. It is not a place for "reviews" but merely a place for users to express their opinions on audio equipment that they have (hopefully) used or auditioned. It should be viewed as *nothing* more than that. Aside from revisiting what I said about the Audible Illusions back in February 2000, I believe it has been several years since I visited that forum. I only recall one submission that I thought even approached the level of a "review". Other than that they were all simply subjective comments, of varying quality, to be sure, and no more than that. I'm not sure why Audible Illusions were compelled to call me. It was very unorthodox. They indicated that they *never* had responded to an Audioreview.com commentary before. There are certainly far worse comments about the 3A, although may be mine, as written, were construed as more damaging. And as self-serving as this may appear to be they gave every indication that they found my comments to be "credible", almost as if what I had experienced had happened before on rare occurrences. All I know that they asked lots of questions with due diligence. Who knows maybe something I added caused them to make a change or two. Most user comments are of the general "liked it-didn't like it" variety, and there's not much to say, or worth saying, about them. But your comments raised a particular technical point: Can this preamp pass a full-bandwidth signal? If I were an AI engineer, bells and red lights would have gone off when I read your comments. I'm sure that's why you got the attention you did. bob |
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