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#81
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Mark wrote:
Dan Kennedy wrote: You still don't understand the circuit, do you? When the base to output node voltage attempts to exceed the diode drop of the 1N4148 it clamps at a point within the dissipation ratings of the output devices and drivers. Simple and clever. Actually CR11 and CR12 work in conjunction with CR9 and CR10 and limit the base drive voltages to 3 diode drops away from the output node voltage. In other words CR9 CR10 and CR12 protect Q8 and CR9 CR10 and CR11 protect Q9. Yes. Very well spotted. On overload in the positive direction, CR12 turns on. Its cathode is held at 0V by the s/c, which forces the base of Q8 to be held at two Vbes above the anode of CR12, i.e. the 3 diode drops. So s/c current is 2Vbe/Re. Well, there you go...s/c protection at the 400ma level, when the max output is 24/75 ohm, or 32ma. Certainly a brute force approach. Pd at 24V at 400ma is 9.6W, so, so long as its not infinite time, it should hold up. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#82
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On Wed, 11 May 2005 18:51:52 GMT, "Lorin David Schultz"
wrote: "Kevin Aylward" wrote: The onus is on the person claiming similar amps sound different, to prove it. That's ridiculous. How can I "prove" what I hear and you can't (or won't)? It's like me telling a blind person that the top traffic light is a different colour than the bottom one. How can I "prove" it? Have him watch you pass an ABX test, then see if he can pass it. If he can't pass it, he can't hear it. I already told you that three similar power amps all sounded different in exactly the same setting, but you refuse to believe it, instead arguing some red-herring about insufficiently controlled scientific testing methods. What's left? I am absolutely NOT one of those audiophile types who makes ridiculous claims about cables and standing my CD player on spiky feet, but some things are just plain audible, even to me, and I ain't blessed with golden ears. ----- http://mindspring.com/~benbradley |
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#83
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Lorin David Schultz wrote:
"Kevin Aylward" wrote: The onus is on the person claiming similar amps sound different, to prove it. That's ridiculous. How can I "prove" what I hear and you can't (or won't)? It's like me telling a blind person that the top traffic light is a different colour than the bottom one. How can I "prove" it? By tests where amplifiers are switched without the user knowing if the amp has been switched or not. He just states whether he hears a difference or not. You do the same test many times. If he guesses correctly with significant statistical bias, then there may be a valid claim. I already told you that three similar power amps all sounded different in exactly the same setting, but you refuse to believe it, Because I have used quite a few power amps, and they all sound the same. That is, I have some person ad-hoc evidence against your view. instead arguing some red-herring about insufficiently controlled scientific testing methods. What's left? The only way to settle the debate is by controlled tests. However, for my mind, the tests have already been done 25 years ago. I would have to work a bit to locate the references, but as I have noted before, the were never ending letters on this stuff in Wireless World at that time. I recall Quad doing some proper tests, as well as others. All this stuff is trully old hat. I am absolutely NOT one of those audiophile types who makes ridiculous claims about cables and standing my CD player on spiky feet, but some things are just plain audible, even to me, and I ain't blessed with golden ears. Neither am I. Unless I know your actual set-up there could have been million of reasons why you thought they sounded different, and maybe they did due to the set-up, not the amps. Everything has to be identical, and only the amps switched. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#84
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On Wed, 11 May 2005 14:51:37 -0500, Dan Kennedy
wrote: Your not supposed to have to explain it to him... I didn't understand it myself, though I'd like to think if I hadn't read Mark's explanation, I would have figured it out on my own in a short time. But from Kevin's "Trust me on this" response, he DID have to explain it to him. Mark wrote: Actually CR11 and CR12 work in conjunction with CR9 and CR10 and limit the base drive voltages to 3 diode drops away from the output node voltage. A quick observation, using low-forward-drop Schottky diodes for CR11 and CR12 would allow lower values for resistors R13 and R14 while maintaining the same current limit. In other words CR9 CR10 and CR12 protect Q8 and CR9 CR10 and CR11 protect Q9. It is simple and clever. And brilliant! Mark ----- http://mindspring.com/~benbradley |
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#85
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Ben Bradley wrote:
On Wed, 11 May 2005 14:51:37 -0500, Dan Kennedy wrote: Your not supposed to have to explain it to him... I didn't understand it myself, though I'd like to think if I hadn't read Mark's explanation, I would have figured it out on my own in a short time. But from Kevin's "Trust me on this" response, he DID have to explain it to him. Oh? Missed one of my replies to pooh bear in this thread did you?:-) Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#86
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Yes. Very well spotted. Thank You (I've also been a (board level) circuit designer for a long time.) On overload in the positive direction, CR12 turns on. Its cathode is held at 0V by the s/c, which forces the base of Q8 to be held at two Vbes above the anode of CR12, i.e. the 3 diode drops. So s/c current is 2Vbe/Re. Well, there you go...s/c protection at the 400ma level, when the max output is 24/75 ohm, or 32ma. Certainly a brute force approach. Pd at 24V at 400ma is 9.6W, so, so long as its not infinite time, it should hold up. And each transistor is on for 1/2 the time so at +/- 24 Volts supply with a short circuit and a continuous large audio signal, the Pd of each device is 9.6/2 = ~=4.8 Watts. Mark |
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#87
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Regarding the current limiting of the 990 op-amp, here is a quote from
Deane Jensen's paper on the "JE-990 Discrete Operational Amplifier", available from Jensen Transformers and me by mail, or it can be downloaded directly from the AES (you have to buy it there): ================= 5.1 Current Limiting CR11 and CR12 The value of R13 and R14 also effects the current-limit magnitude. When the output current reaches a value which is just less than the current corresponding to two-diode voltage drops divided by R13 or R14, the base current is starved to the output node by a three-diode path including CR9, CR10, and either CR11 or CR12. Without heat sinks the MJE-171 and 181 transistors will reliably drive a full-level signal into a shorted output indefinitely. Thermal dissipation may be a packaging consideration. ================= John Hardy The John Hardy Co. www.johnhardyco.com |
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#88
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On Wed, 11 May 2005 10:45:54 GMT, "Kevin Aylward"
wrote: What I have shown is the intrinsic ability of a few different topologies. This is standard practise in any design. The object is to determine what is achievable in the ideal case. This is to avoid the case where much effort is expended on matters such as board layout, trying to obtain a performance that is not achievable in principle from the design. A basic design can easily be limited by the design itself, not the external factors. We need know what designs do that. I have several multi-drawer cabinets filled with completed designs already implemented, manufactured, and sold a few bucks a pop. One drawer is labeled AD797, but there are lots of drawers. I'm obviously missing your point, and the vice is verse. What feedback network? I believe that you haven't yet understood the design topology. Remember, this has to operate over a gain range of 60dB, or ideally more. This is done by changing the resister RE from say 50 ohms, to 5k. I had a strange premonition that you were actually going to say this. You're intending to switch emitter degenative resistors at DC and in real time? Can you say BANG? Or, with simultaneous muting, SILENCE? You really really need to rethink this, man. Usually the resister is a variable resister in series with a capacitor, so it don't pop or generate DC crackles, or effect DC levels. Do you understand what a topological design means? That would be pretty wacky to run DC open loop, but I'm enjoying the show. Keep it up. I suggest you start your topo sketch from the other end; Try sketching in all the not-opamp stuff and see if it still looks likely to you. Good fortune, Chris Hornbeck |
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#89
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Kevin,
Is your real name Phil by chance? In case you haven't heard... The two gentlemen you're about to get into an exchange with are REAL preamp designers. They both have REAL preamps that a lot of people have actually HEARD, USED, and KNOW sound great and perform remarkably well in a lot of challenging environments. You won't build much cred by comparing your simulations with their results. |
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#90
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On Wed, 11 May 2005 18:48:16 +0000, Kevin Aylward wrote:
Impossible dude. CR11 and CR12 are the wrong way round. The only way they can clamp is to exceed their reverse voltage breakdown, which is 75V. This would give 19A as a s/c current. At 15V that's 285W. Yeah, safe as skiing backwards through revolving doors, blindfolded. If you turn them round, then the circuit won't even work. The output current would be limited to delta_vbe of the output devices and the diodes Can we get a show of hands from people who've used John's preamps and know for a fact that it does work, (and works very well in fact)? Dan. You can't win. I've been at this way to long. What part of "I am an expert" are you stll having trouble with? ROFLMFAO |
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#91
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On Wed, 11 May 2005 20:13:12 +0000, Kevin Aylward wrote:
Lorin David Schultz wrote: I already told you that three similar power amps all sounded different in exactly the same setting, but you refuse to believe it, Because I have used quite a few power amps, and they all sound the same. That is, I have some person ad-hoc evidence against your view. If that's true, then you have absolutely no business designing amps of any kind. But it kind of explains why you put so much faith in sims. |
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#92
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#93
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#94
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Paul Stamler wrote: "Kevin Aylward" wrote in message k... As someone having the grandiose title of analogue ic design team leader at Texas Instruments for 3 1/2 years, Were you involved with TI's version of the NE5534? I've heard interesting things about various 'flavours' of the 5534 and presumably the 5532 too. Would you care to elaborate ? Btw - Philips have stopped making them ! Graham |
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#96
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"Kevin Aylward" wrote in message Because I have used quite a few power amps, and they all sound the same. That is, I have some person ad-hoc evidence against your view. Just like guitars then... geoff The only way to settle the debate is by controlled tests. However, for my mind, the tests have already been done 25 years ago. And are continued to be done today. And prove and disprove many things about amps, mics, cables, speakers, etc. They don't just disprove *everything*. geoff |
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#97
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"Agent 86" wrote in message Dan. You can't win. I've been at this way to long. What part of "I am an expert" are you stll having trouble with? ROFLMFAO This is what makes people thinkls that Kev from Anusoft is a troll - nobody in really life is so big-headed that they proclaim themselves to be an 'expert'. It's like sort of proving the opposite by what onw says. But I really do think he is for 'real'. Maybe his sort of attitude has something to do with the (evidently) mutliple ex-wives scenario ? geoff |
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#98
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On Thu, 12 May 2005 16:43:06 +1200, "Geoff Wood"
wrote: The only way to settle the debate is by controlled tests. However, for my mind, the tests have already been done 25 years ago. And are continued to be done today. And prove and disprove many things about amps, mics, cables, speakers, etc. They don't just disprove *everything*. Indeed; one cannot disprove a negative. It's such a subtle point that it *always* gets lost; and yet, many conclusions are still drawn. From little acorns... Testing is more important now than ever; testing is more difficult now than ever; the remaining issues in "listening", whatever the **** that means, are forever on hold. Or are they? Is there no possibility of collating the "un-structured" listening experiences of trained observers, such that their observation isn't tainted by the testing gig? Dunno, but unconvinced, Chris Hornbeck |
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#99
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Ben Bradley wrote:
On 11 May 2005 21:42:04 -0400, (Mike Rivers) wrote: In article writes: You know the Mackie thing verses, well...just about anything really? Well, if you check the electronics NGs, you'll find that EWB is the Mackie. Best of luck with your "Mackie". EWB? Please translate for those of us who don't speak British. And EWB is Electronics Workbench, an electronics simulation (or "design automation") program. I just looked them up (they're at the obvious URL) and learned that National Instruments bought them a few month ago. let's not have any implied Mackie bashing without good reason. I used it a little bit, I hated the schematic capture (I really like the Pspice capture program), but that's not the important thing with these things, it's the simulation accuracy that's important, and I didn't use it enough to make a judgement. I've used it ( EWB ) a bit too. It's now become Multisim IIRC. Graham |
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#100
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"Agent 86" wrote in message
news  Kevin, Is your real name Phil by chance? In case you haven't heard... The two gentlemen you're about to get into an exchange with are REAL preamp designers. They both have REAL preamps that a lot of people have actually HEARD, USED, and KNOW sound great and perform remarkably well in a lot of challenging environments. You won't build much cred by comparing your simulations with their results. Oh, and thousands upon thousands of people have chosen, after hearing and using the preamps they've designed, to part with hard-earned cash to buy them. They were all self-delusional, of course. All of them. And I am Marie of Rumania. Peace, Paul |
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#101
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"Pooh Bear" wrote in message
... I've heard interesting things about various 'flavours' of the 5534 and presumably the 5532 too. Would you care to elaborate ? Btw - Philips have stopped making them ! The Philips and TI versions had seriously different distortion spectra when I tested them. Peace, Paul |
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#102
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"Paul Stamler" "Pooh Bear" I've heard interesting things about various 'flavours' of the 5534 and presumably the 5532 too. Would you care to elaborate ? Btw - Philips have stopped making them ! The Philips and TI versions had seriously different distortion spectra when I tested them. ** Bet that is just as credible as all those WRONG and useless capacitor ESR test results you had the unmitigated gall to actually publish. Have you no integrity whatsoever - Mr Stamler ??? .............. Phil |
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#103
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John Hardy wrote:
Regarding the current limiting of the 990 op-amp, here is a quote from Deane Jensen's paper on the "JE-990 Discrete Operational Amplifier", available from Jensen Transformers and me by mail, or it can be downloaded directly from the AES (you have to buy it there): ================= 5.1 Current Limiting CR11 and CR12 The value of R13 and R14 also effects the current-limit magnitude. When the output current reaches a value which is just less than the current corresponding to two-diode voltage drops divided by R13 or R14, the base current is starved to the output node by a three-diode path including CR9, CR10, and either CR11 or CR12. Without heat sinks the MJE-171 and 181 transistors will reliably drive a full-level signal into a shorted output indefinitely. Thermal dissipation may be a packaging consideration. ================= The package on these devices on the the spec sheet I have is a TO-225. The spec on these devics are 12.5W at Tc=25 deg.C and 1.5W at Ta=25 deg.C, That is: Rja = 83.3 Deg/W Rjc = 10 Deg/W If we assume the AC condition, and therefore Marks figure of 4.8W. We have the temperature rise of the junction from ambient, with no heatsink as 4.8 * 83.3 = 400 deg C. So, no this device will not take a s/c indefinitely with no heatsink. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#104
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Mark wrote:
Yes. Very well spotted. Thank You (I've also been a (board level) circuit designer for a long time.) Well, its nice to know that some here actually have real experience. On overload in the positive direction, CR12 turns on. Its cathode is held at 0V by the s/c, which forces the base of Q8 to be held at two Vbes above the anode of CR12, i.e. the 3 diode drops. So s/c current is 2Vbe/Re. Well, there you go...s/c protection at the 400ma level, when the max output is 24/75 ohm, or 32ma. Certainly a brute force approach. Pd at 24V at 400ma is 9.6W, so, so long as its not infinite time, it should hold up. And each transistor is on for 1/2 the time so at +/- 24 Volts supply with a short circuit and a continuous large audio signal, the Pd of each device is 9.6/2 = ~=4.8 Watts. Yes. I usually tend to do my calculations by default on worst case for DC amplifies. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#105
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Ben Bradley wrote:
On 11 May 2005 21:42:04 -0400, (Mike Rivers) wrote: In article writes: You know the Mackie thing verses, well...just about anything really? Well, if you check the electronics NGs, you'll find that EWB is the Mackie. Best of luck with your "Mackie". EWB? Please translate for those of us who don't speak British. And EWB is Electronics Workbench, an electronics simulation (or "design automation") program. I just looked them up (they're at the obvious URL) and learned that National Instruments bought them a few month ago. let's not have any implied Mackie bashing without good reason. I used it a little bit, I hated the schematic capture (I really like the Pspice capture program), but that's not the important thing with these things, it's the simulation accuracy that's important, and I didn't use it enough to make a judgement. All spice simulators have, by and large, the same accuracy. Its the models that are the limiting factor, but these run on all simulators, usually, with a bit of a modification. This whole accuracy thing is really a red herring. 95% of simulators all use the same xspice code, pretty much as is. Its free. That's why we use it. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#106
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Agent 86 wrote:
On Wed, 11 May 2005 18:48:16 +0000, Kevin Aylward wrote: Impossible dude. CR11 and CR12 are the wrong way round. The only way they can clamp is to exceed their reverse voltage breakdown, which is 75V. This would give 19A as a s/c current. At 15V that's 285W. Yeah, safe as skiing backwards through revolving doors, blindfolded. If you turn them round, then the circuit won't even work. The output current would be limited to delta_vbe of the output devices and the diodes Can we get a show of hands from people who've used John's preamps and know for a fact that it does work, (and works very well in fact)? Who claimed that it didn't work? Who clamed that the specs were not respectable? Of course it works. Its been sold since 1979. Dah... Did you fail English compression 101? Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#107
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Geoff Wood wrote:
"Agent 86" wrote in message Dan. You can't win. I've been at this way to long. What part of "I am an expert" are you stll having trouble with? ROFLMFAO This is what makes people thinkls that Kev from Anusoft is a troll - nobody in really life is so big-headed that they proclaim themselves to be an 'expert'. Nonsense. Just about every independent consultant will refer to themselves as an "expert". Furthermore, I have much direct experience that when being interviewed for jobs, the hiring managers want to hear you actually say "I am an expert". They want to be absolutely convinced that you are trully confident in doing what you say you can do. If you go "well, I know a bit here and there, and that to err.. and maybe...", they usually start to roll their eyes. It's like sort of proving the opposite by what onw says. So, if some one goes around saying "deh..eyess be am idjoit", you believe that they are a genius? But I really do think he is for 'real'. Maybe his sort of attitude has something to do with the (evidently) mutliple ex-wives scenario ? Many have many-ex wives. Whats your point? Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#108
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Chris Hornbeck wrote:
On Wed, 11 May 2005 10:45:54 GMT, "Kevin Aylward" wrote: What I have shown is the intrinsic ability of a few different topologies. This is standard practise in any design. The object is to determine what is achievable in the ideal case. This is to avoid the case where much effort is expended on matters such as board layout, trying to obtain a performance that is not achievable in principle from the design. A basic design can easily be limited by the design itself, not the external factors. We need know what designs do that. I have several multi-drawer cabinets filled with completed designs already implemented, manufactured, and sold a few bucks a pop. One drawer is labeled AD797, but there are lots of drawers. I'm obviously missing your point, and the vice is verse. From reading below I certainly see your points. They are wrong. What feedback network? I believe that you haven't yet understood the design topology. Remember, this has to operate over a gain range of 60dB, or ideally more. This is done by changing the resister RE from say 50 ohms, to 5k. I had a strange premonition that you were actually going to say this. You're intending to switch emitter degenative resistors at DC and in real time? Nope. You should read the post first. Can you say BANG? Or, with simultaneous muting, SILENCE? You really really need to rethink this, man. Not at all, dude. Usually the resister is a variable resister in series with a capacitor, so it don't pop or generate DC crackles, or effect DC levels. Do you understand what a topological design means? That would be pretty wacky to run DC open loop, but I'm enjoying the show. Keep it up. Now, this is just getting a bit daft. You are obviously out of your depth on electronic design such that this discussion is getting pointless. There are no DC issues in placing a capacitor in series with RE. As I said, you haven't understood the topology in the slightest. And I mean the not the slightest. What part of "no global loop feedback did you not understand? There are no DC open loop conditions. There is local feedback from the input diff pair collector to its complementary transistor back to its emitter, but this is a *DC closed loop*. All DC potentials are perfectly well defined. The voltage on the emitters of the differential pairs are fixed by the voltage on their base. The currents in all transistor are fixed by current sources. This is trivial to see by simple inspection. I suggest you start your topo sketch from the other end; Try sketching in all the not-opamp stuff and see if it still looks likely to you. I suggest that you download my SS and actually run the sims, capacitor in series with RE and all, as you are clearly completely clueless on this. What's more so, is that this aspect is done in *all* mic preamps, using a basic diff pair configuration without global feedback, as a matter of standard practise. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#109
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Geoff Wood wrote:
"Kevin Aylward" wrote in message Because I have used quite a few power amps, and they all sound the same. That is, I have some person ad-hoc evidence against your view. Just like guitars then... Why should guitars sound the same? geoff The only way to settle the debate is by controlled tests. However, for my mind, the tests have already been done 25 years ago. And are continued to be done today. And prove and disprove many things about amps, mics, cables, speakers, etc. They don't just disprove *everything*. Well, technically, nothing is really "proved". Things are "verified" in a particular set-up. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#110
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Geoff Wood wrote:
But I really do think he is for 'real'. Maybe his sort of attitude has something to do with the (evidently) mutliple ex-wives scenario ? geoff I think you got that backwards. /martin. |
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#111
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Agent 86 wrote:
Kevin, Is your real name Phil by chance? In case you haven't heard... The two gentlemen you're about to get into an exchange with are REAL preamp designers. They both have REAL preamps that a lot of people have actually HEARD, USED, and KNOW sound great and perform remarkably well in a lot of challenging environments. You won't build much cred by comparing your simulations with their results. Oh dear...I have been a "real" analoge designer for 25 years mate. With all due respect to the designers of the John Hardy amp, as the amplifier appears to do its job well, typical successful designs of mine are rather more technically challenging then a simply diff pair, class A gain stage with output buffer. I have much street cred. However, it is not with non-electronic engineers that post to this particular NG. Despite my arrogance, you will not be able to find a credible professional analogue design engineer that finds my knowledge in analogue design lacking. It just the way it is. Mate. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#112
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John Hardy wrote:
Regarding the current limiting of the 990 op-amp, here is a quote from Deane Jensen's paper on the "JE-990 Discrete Operational Amplifier", available from Jensen Transformers and me by mail, or it can be downloaded directly from the AES (you have to buy it there): ================= 5.1 Current Limiting CR11 and CR12 The value of R13 and R14 also effects the current-limit magnitude. When the output current reaches a value which is just less than the current corresponding to two-diode voltage drops divided by R13 or R14, the base current is starved to the output node by a three-diode path including CR9, CR10, and either CR11 or CR12. Without heat sinks the MJE-171 and 181 transistors will reliably drive a full-level signal into a shorted output indefinitely. Thermal dissipation may be a packaging consideration. ================= The package on these devices on the the spec sheet I have is a TO-225. The spec on these devics are 12.5W at Tc=25 deg.C and 1.5W at Ta=25 deg.C, That is: Rja = 83.3 Deg/W Rjc = 10 Deg/W If we assume the AC condition, and therefore Marks figure of 4.8W. We have the temperature rise of the junction from ambient, with no heatsink as 4.8 * 83.3 = 400 deg C. So, no this device will not take a s/c indefinitely with no heatsink. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. I think the package was originally the TO-126, but it has evolved slightly over the years and been renamed as the TO-225. Actually, Deane referred to the "77-03" package in his paper. I am quite confident that Deane Jensen did some serious testing of the design in addition to breadboarding and modeling. However, I would certainly not want to rely on indefinite short circuits without a heat sink. I have been using aluminum potting shells since about 1988, with the metal plates of the output transistors bonded directly to the wall of the shell for maximum heat sinking within the dimensional limits of the "2520" style package (1.125" x 1.125" x .600"). There is a common problem regarding these, and other, transistors: There are three or four companies that make the MJE-171 and MJE-181 devices, but the chip size is different in each product. I think the Motorola (ON) parts have the largest chips, and those are the ones that I have been using, except for a brief period during the first year or two of manufacture (1979/80) when I sometimes used National Semiconductor versions. Thank you. John Hardy The John Hardy Co. www.johnhardyco.com |
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#113
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Agent 86 wrote:
On Wed, 11 May 2005 20:13:12 +0000, Kevin Aylward wrote: Lorin David Schultz wrote: I already told you that three similar power amps all sounded different in exactly the same setting, but you refuse to believe it, Because I have used quite a few power amps, and they all sound the same. That is, I have some person ad-hoc evidence against your view. If that's true, then you have absolutely no business designing amps of any kind. You have no business giving advice on the design of power amps as the reality is that just about all, like 99.999%, of those that design amplifies professionally, don't listen to them during their development. I have already explained in posts that there is no reason to listen to straight piece of wire with gain goaled amps. You simply don't have the background to understand why. Amplifier design is about gains, distortion, noise, slew rates, overload, CMRR etc. None of this require any listening tests, despite the irony. But it kind of explains why you put so much faith in sims. I can see where your comming from. Ignorance. Try actully arguing this point to any one of us 10,000's of analogue ic engineers that design 10000's of chips with 10,000s of transisters that work correctly first time. Disagreeing with the known facts makes you a flat earther. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. |
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#114
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Kevin Aylward wrote:
Well, there you go...s/c protection at the 400ma level, when the max output is 24/75 ohm, or 32ma. Certainly a brute force approach. It would be, but 24V across 75R is 320mA! Anahata |
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#115
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Chris Hornbeck wrote:
On Thu, 12 May 2005 16:43:06 +1200, "Geoff Wood" wrote: The only way to settle the debate is by controlled tests. However, for my mind, the tests have already been done 25 years ago. And are continued to be done today. And prove and disprove many things about amps, mics, cables, speakers, etc. They don't just disprove *everything*. Indeed; one cannot disprove a negative. It's such a subtle point that it *always* gets lost; and yet, many conclusions are still drawn. From little acorns... Testing is more important now than ever; testing is more difficult now than ever; the remaining issues in "listening", whatever the **** that means, are forever on hold. Or are they? Is there no possibility of collating the "un-structured" listening experiences of trained observers, such that their observation isn't tainted by the testing gig? Dunno, but unconvinced, I'll post my a quick resume of my own experience in this matter. Critical listening tests *cannot* be meaninfgfully conducted during daylight hours with all the attendant spurious ambient sounds. You can move to a 'soundproof room' perhaps but that destroys the natural ambience that we're used to hearing in a normal environment. Have you ever been in a true 'soundproof room' btw ? It's stunningly disorienting ! In fact I'd call it fairly freaky ! I certainly wouldn't want to use one for listening tests. So, all my listening tests have been conducted late at night with ambient SPLs that I doubt exceeded 20 dBA - in fact I'd reckon nearer to 10 dBA. In that situation - it's entirely remarkable just how much detail ( or lack of ) can be resolved. I did this once - no twice - at a friend's house ( he's really into esoteric speaker systems btw - I have a pair of a design we co-designed as my reference units as it happens ). On both occasions we were testing *his* preferred amplifier against a design of my own that I suspect comes close to the ultimate reference mosfet design. For example the THD of my design is only 15% greater than an Audio Precision test set residual @ 1 kHz ( at 600W into 4 ohms btw ! ) .. I suspect most of that is noise in my unit. The distortion trace shows nothing other than noise. We're talking -102dB sinad btw. At this level percentages are confusing. You lose track of the number of zeroes after the decimal point ! Anyway - on both occasions 'his' amps were deemed by the listening panel to be inferior. He subsequently dumped some very nice Denon 'monoblocs' - I forget the other unit. The ear has remarkable resolution. Since I'm sure you're curious - what made our listening panel like 'my' amp I'm sure you're thinking. We all analysed the sound and both sources were generally very good. In the end we homed in on some 'brush work' on the drums. It was some jazz but I forget who now. Simple explanation. The mosfet amp made it sound like someone was playing brushes on a drum - the other amp didn't - it sounded 'artificial'. That's why it went ! Graham |
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#116
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Kevin Aylward wrote: I have much street cred. Not in aapl-s for one matey ! You've shown youself up to be out of touch with reality. Now lighten up and learn some stuff from the very competent ppl who post here. Graham |
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#117
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Paul Stamler wrote:
"Pooh Bear" wrote in message ... I've heard interesting things about various 'flavours' of the 5534 and presumably the 5532 too. Would you care to elaborate ? Btw - Philips have stopped making them ! The Philips and TI versions had seriously different distortion spectra when I tested them. Would you care to choose one over the other ? Have you tried the JRC/NJR version btw ? Graham |
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#118
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Kevin Aylward wrote: If we assume the AC condition, and therefore Marks figure of 4.8W. We have the temperature rise of the junction from ambient, with no heatsink as 4.8 * 83.3 = 400 deg C. So, no this device will not take a s/c indefinitely with no heatsink. Are you here simply to irritate ppl who have actually manufactured workable, usable, reliable designs that deliver good results ? Graham |
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#119
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Kevin Aylward wrote: Furthermore, I have much direct experience that when being interviewed for jobs, the hiring managers want to hear you actually say "I am an expert". They want to be absolutely convinced that you are trully confident in doing what you say you can do. Sure. In interviewed once for a Project Leader position @ a well known pro audio company based in Welwyn Garden City. The owner / MD was once one of my colleagues at a company based nr Primrose Hill btw. I 'passed' the interview with flying colours as it happens. Then I mentioned that I liked to have more of a 'hands on' experience. The interviewer and I agreed that perhaps it wasn't the best option for me. Their idea of a Project Leader was almost exclusively managerial. We parted on good terms I'm pleased to say . There's no point in taking on a job that doesn't best fit your aspirations. Graham |
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#120
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John Hardy wrote:
John Hardy wrote: Regarding the current limiting of the 990 op-amp, here is a quote from Deane Jensen's paper on the "JE-990 Discrete Operational Amplifier", available from Jensen Transformers and me by mail, or it can be downloaded directly from the AES (you have to buy it there): ================= 5.1 Current Limiting CR11 and CR12 The value of R13 and R14 also effects the current-limit magnitude. When the output current reaches a value which is just less than the current corresponding to two-diode voltage drops divided by R13 or R14, the base current is starved to the output node by a three-diode path including CR9, CR10, and either CR11 or CR12. Without heat sinks the MJE-171 and 181 transistors will reliably drive a full-level signal into a shorted output indefinitely. Thermal dissipation may be a packaging consideration. ================= The package on these devices on the the spec sheet I have is a TO-225. The spec on these devics are 12.5W at Tc=25 deg.C and 1.5W at Ta=25 deg.C, That is: Rja = 83.3 Deg/W Rjc = 10 Deg/W If we assume the AC condition, and therefore Marks figure of 4.8W. We have the temperature rise of the junction from ambient, with no heatsink as 4.8 * 83.3 = 400 deg C. So, no this device will not take a s/c indefinitely with no heatsink. Kevin Aylward http://www.anasoft.co.uk SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design. I think the package was originally the TO-126, but it has evolved slightly over the years and been renamed as the TO-225. Actually, Deane referred to the "77-03" package in his paper. That was a Motorola designation back then IIRC. Doubtless before it was adopted as a JEDEC spec. I am quite confident that Deane Jensen did some serious testing of the design in addition to breadboarding and modeling. However, I would certainly not want to rely on indefinite short circuits without a heat sink. I have been using aluminum potting shells since about 1988, with the metal plates of the output transistors bonded directly to the wall of the shell for maximum heat sinking within the dimensional limits of the "2520" style package (1.125" x 1.125" x .600"). There is a common problem regarding these, and other, transistors: There are three or four companies that make the MJE-171 and MJE-181 devices, but the chip size is different in each product. I think the Motorola (ON) parts have the largest chips, and those are the ones that I have been using, except for a brief period during the first year or two of manufacture (1979/80) when I sometimes used National Semiconductor versions. Thank you. This has been interesting. Maybe time to starat a new thread ? Graham |
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