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#1
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Stereo receievers: THD of .04 vs. .08
Thanks all for the advice on B Stock merchandise.
Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Thanks. |
#2
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Stereo receievers: THD of .04 vs. .08
wrote ...
Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: Just ignore the forgers, the idiots, and the psychopaths. I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Considering that you will be listening through speakers with 10x or maybe even 100x more distortion, dunno how you would tell the difference? (That applies to ANY speakers, not just the ones you mentioned.) |
#3
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Stereo receievers: THD of .04 vs. .08
On Jan 9, 4:29*pm, "Richard Crowley" wrote:
wrote ... Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: Just ignore the forgers, the idiots, and the psychopaths. I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. *Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Considering that you will be listening through speakers with 10x or maybe even 100x more distortion, dunno how you would tell the difference? (That applies to ANY speakers, not just the ones you mentioned.) Thanks. So the 10x to 100x part is what applies to any speakers? I really didn't know that, nor did I, obviously, know what speaker spec to look at to find out how much distortion a speaker provides. |
#4
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Stereo receievers: THD of .04 vs. .08
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#5
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Stereo receievers: THD of .04 vs. .08
wrote ...
"Richard Crowley" wrote: Considering that you will be listening through speakers with 10x or maybe even 100x more distortion, dunno how you would tell the difference? (That applies to ANY speakers, not just the ones you mentioned.) Thanks. So the 10x to 100x part is what applies to any speakers? I really didn't know that, nor did I, obviously, know what speaker spec to look at to find out how much distortion a speaker provides. THD They don't generally even quote THD (or IM, or phase, or group or any other kind of distortion) specs for speakers at all. But the ones I remember seeing were much greater than 1% (and typically greater than 10%, even). Note that Infinity doesn't even mention distortion on the web page that describes your speakers. Very few (if any?) speaker makers do. That is why the general consensus is that you will hear a MUCH greater difference between transducers (microphones & speakers) and acoustics than you will between similar pieces of electronics. I would not base a decision on 0.04 vs 0.08% THD in the power amp. |
#6
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Stereo receievers: THD of .04 vs. .08
On Jan 9, 4:10 pm, wrote:
One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? These figure are specifications: they are written more as a legal document than anything else, e.g., you might bitch about the sound, but the manufacturer will put it on the test bench, measure the THD, show you that it meets that spec, and you're on your own. Further, THD is one of the LEAST useful measurements of audio equipment. Ignore it. |
#7
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Stereo receievers: THD of .04 vs. .08
Richard Crowley wrote: wrote ... Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: Just ignore the forgers, the idiots, and the psychopaths. I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Considering that you will be listening through speakers with 10x or maybe even 100x more distortion, dunno how you would tell the difference? (That applies to ANY speakers, not just the ones you mentioned.) The character of speaker distortion is quite different to typical amplifier distortion. Graham |
#8
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Stereo receievers: THD of .04 vs. .08
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#9
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Stereo receievers: THD of .04 vs. .08
Any ideas then on where I might get opinions on which of those two
receivers sound better, between the Onkyo and the Yamaha? I don't think any of the stores convenient to me carry both, so I don't know where I could check them out side-by-side. Thanks. |
#10
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Stereo receievers: THD of .04 vs. .08
Damon Hill wrote: wrote One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? None whatsoever, at such low levels. The amplifier distortion will typically be HIGHER than those figures at low levels. Possibly as high as 1% if the full power spec is as poor as 0.08. Graham |
#11
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Stereo receievers: THD of .04 vs. .08
Richard Crowley wrote: They don't generally even quote THD (or IM, or phase, or group or any other kind of distortion) specs for speakers at all. But the ones I remember seeing were much greater than 1% (and typically greater than 10%, even). At FULL power. At low power it will be much less. snip I would not base a decision on 0.04 vs 0.08% THD in the power amp. 0.08% is barely any better than the highly discredited 0.1% which was once considered a benchmark figure (DIN 45510 ? etc) . Amplifiers with full power THD ratings of ~ 0.1% are audibly defective IME at typical listening levels. Bear in mind that the 0.08% figure is a best case number measured at full power (this suits amplifiers).. At around a watt of output (which is where most listening is done) the THD is likely to have climbed to nearly 1% if it's a typical Class AB bipolar output stage. Graham |
#12
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Stereo receievers: THD of .04 vs. .08
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#13
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Stereo receievers: THD of .04 vs. .08
wrote in message
I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. Not relevant. Besides what Richard said about the speakers having tons more distortion, THD measurements like this can be fudged for marketing purposes, while being perfectly honest. A well made SS power amp usually has about 0.03% or less THD at all levels up to maybe 3/4 of the power level at which the amp clips. The THD then increases along a smooth curve to about 0.08% just below clipping, and rapidly to 30% or more above that. This is a big generalization, and some amps are either quite a bit better or quite a bit worse. For example, some amps will have only 0.02% THD just below clipping, and others will have 0.2%. Furhtermore amps put out less power at clipping at the frequency extremes. In fact a lot of receivers won't put out full rated power at 20 Hz. The good news is that a lot of receivers run their whole lives without getting above 20 watts. Just for grins but to make a point, lets say that Yamaha and Onkyo both have their receivers made in the same plant in China, and that those crafty Chinese put the identically same power amps into both receivers. The Onkyo marketing department decides that power is what sells receivers, so they rate their receivers for more power, which makes the distortion go up. The Yamaha marketing department decides that low distortion is what sells receivers, so they rate their receivers for a little less power, which makes the distortion go down. See my point? The actual distortion of the receiver at its rated power can be manipulated by juggling the rated power. The difference in rated power might be less than 10%, which has just about zero audible signficance. I THINK I have a pretty discerning ear. Let's stipulate that! ;-) Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Not a chance. I suspect that in a close AB test with levels matched and all the rest, the power amp in either receiver functions like the proverbial straight wire with gain. BTW Richard flinched at giving real world distortion numbers for speakers, but I won't. The distortion produced by a given speaker is strongly influenced by power and frequency. All speaker drivers tend to produce more distortion when operated at higher powers compared to their power capacity, and they also tend to produce more distortion when operated at lower frequencies compared to their low frequency limits. Sometimes drivers will also produce more distortion under other conditions. In the middle of its operational range, a good loudspeaker driver might have 0.1% distortion or a little less. At its lower limit but at moderate power levels, the distortion may increase to 5-10%. At low frequencies and high powers, the distortion can be truely large, on the order of 30% or more. Surprisingly, 30% distortion at say 40 Hz can be surprisingly acceptable, because musical instruments that operate in the bass range tend to produce a lot of harmonics of their own that tend to mask the distortion added by the speakers. Truely prodigious speakers can have as little as 10% distortion at 20Hz at very high sound levels like 120 dB. Your typical large floor-standing home speaker will probably have 10% THD by the time it is putting out 100 dB at 50 Hz, and things grow worse rapidly below that. Note that my estimated numbers for loudspeaker distortion tend to agree with Richard's general point, which is that speakers distortion is so large that it tends to wash out or mask the distortion in amplifiers. However, at medium power levels and medium frequencies, a speaker driver's distortion might be low enough that under ideal conditions, 0.1% THD might be audible. |
#14
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Stereo receievers: THD of .04 vs. .08
wrote in...
Any ideas then on where I might get opinions on which of those two receivers sound better, between the Onkyo and the Yamaha? I don't think any of the stores convenient to me carry both, so I don't know where I could check them out side-by-side. I would not expect to hear any difference between them. I would make the choice based on features that are most important to me within the price I'm willing to pay. You are far more likely to hear a difference moving your speakers or your listening chair a foot or two, than between any two similar power amps. But then this tends to be a more practical collection of people than other newsgroups which are more obsessive and believe they can actually hear a difference between 0.04 and 0.08% They also believe in magic cables, wooden knobs, and $3000 power cords, etc. Most of us lack such remarkable heights of faith. |
#15
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: wrote I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. Not relevant. Besides what Richard said about the speakers having tons more distortion, THD measurements like this can be fudged for marketing purposes, while being perfectly honest. A well made SS power amp usually has about 0.03% or less THD at all levels up to maybe 3/4 of the power level at which the amp clips. THD specs are typically made 'just prior to clipping'. The THD in the 100mW to 1W region will be significantly higher than the 'data sheet figure' though for all typical Class AB bipolar output stages. This is why amps that only make say 0.08% on the spec sheet ARE audibly inferior to their betters. My own benchmark of suitability for good quality audio is a 'spec sheet' figure of 0.01% which is likely to translate to ~ 0.1% at lower wattages. Look at this (page 9 "THD + N vs Output Power") for an example of what I mean. http://www.national.com/ds.cgi/LM/LM3875.pdf The LM3875 was popularly adopted as the 'Gainclone' in some circles some years back. Graham |
#16
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Stereo receievers: THD of .04 vs. .08
On Jan 9, 6:17 pm, Eeyore
wrote: Arny Krueger wrote: wrote I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. Not relevant. Besides what Richard said about the speakers having tons more distortion, THD measurements like this can be fudged for marketing purposes, while being perfectly honest. A well made SS power amp usually has about 0.03% or less THD at all levels up to maybe 3/4 of the power level at which the amp clips. THD specs are typically made 'just prior to clipping'. The THD in the 100mW to 1W region will be significantly higher than the 'data sheet figure' though for all typical Class AB bipolar output stages. This is why amps that only make say 0.08% on the spec sheet ARE audibly inferior to their betters. My own benchmark of suitability for good quality audio is a 'spec sheet' figure of 0.01% which is likely to translate to ~ 0.1% at lower wattages. Look at this (page 9 "THD + N vs Output Power") for an example of what I mean.http://www.national.com/ds.cgi/LM/LM3875.pdf The LM3875 was popularly adopted as the 'Gainclone' in some circles some years back. GIven the way THD is measured, an amplifier will have a THD spec which goes as the reciprocal of power, simply because THD is a broadband measurement and can't distinguish noise from harmonics. This is why the correct designation is THD+N. Thus, with a constant noise floor, for every halving of power, the THD+N figure will rise by about 40%. Secondly, THD as a measure of audibility has been pretty much shown to be useless, regardless of the claims seen here and elsewhere. These claims simply ignore significant factors such as masking. If you're claiming on reliably and repeatedly hearing duifferences at the levels of distortion you're claiming, look somewhere else, it ain't THD. |
#17
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Stereo receievers: THD of .04 vs. .08
wrote in message ... Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Thanks. Yamaha's quality is a mite better than Onkyo's - that would be MY criteria. Mark Z. |
#18
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Stereo receievers: THD of .04 vs. .08
wrote in message
GIven the way THD is measured, an amplifier will have a THD spec which goes as the reciprocal of power, simply because THD is a broadband measurement and can't distinguish noise from harmonics. This is why the correct designation is THD+N. Thus, with a constant noise floor, for every halving of power, the THD+N figure will rise by about 40%. Secondly, THD as a measure of audibility has been pretty much shown to be useless, regardless of the claims seen here and elsewhere. These claims simply ignore significant factors such as masking. If you're claiming on reliably and repeatedly hearing duifferences at the levels of distortion you're claiming, look somewhere else, it ain't THD. Agreed. THD|N measurements often raise unecessary concerns by presenting data that might in the worst case result from low-level distortion like crossover distortion. With FFT-based measurement software, ignoring almost all of the noise floor, and just measuring the actual harmonics is both feasible and often implemented. AFAIK this is done by first detecting the frequency of the fundamental. Only power that is in the FFT buckets that correspond to integer multiples of the fundamental are included in the final summary. Similar techniques can be implemented for IM measurements. When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. |
#19
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Stereo receievers: THD of .04 vs. .08
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#21
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. Pure nonsense. Crossover distortion remains the bete noire of conventional Class AB bipolar designs. Graham |
#22
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Stereo receievers: THD of .04 vs. .08
"Eeyore" wrote in
message Arny Krueger wrote: When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. Pure nonsense. Crossover distortion remains the bete noire of conventional Class AB bipolar designs. Please explain that in the context of the performance of this power amplifier: http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm For example, http://www.pcavtech.com/pwramp/macro...ex.htm#DR_001S represents the following test conditions. (1) 1 KHz was applied to the amp, and levels were set so that 1 watt was delivered to an 8 ohm resistive load. This corresponds to FS in the graphic. (2) The dynamic range test signal was applied. This test signal is composed of a 1 KHz tone at 60 dB below the signal used in step 1. (3) The graphic shows a spectral analysis of the output of the power amplifier, referenced to the signals observed in step (1). We see the following: (3a) 60 Hz hum with harmonics, none worse than about 95 dB below the 1 watt in step (1). (3b) The 1 KHz test tone, 60 dB below the 1 watt in step (1) (3c) All harmonics 120 or more dB below the 1 watt in step (1). Normally, crossover distortion produces a series of harmonics of the low level test signal. The test signal was about 85 dB below the amp's full rated power. There are simply no observable harmonics. Is it possible to have crossover distortion that generates no harmonics of such a low level test signal? |
#23
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Stereo receievers: THD of .04 vs. .08
wrote in message ... Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? **Not per se. The bottom line is this: Amplifiers (and speakers, for that matter) exhibit a large number of characteristics. THD (at one power level and frequency) is just one specification which may be meaningful for you and your speakers. Unless you have a fair depth of technical knowledge, it is virtually impossible to predict which amp will perform better on a given speaker system (if at all). Think of it this way: Which car accelerates and corners better: A 4.6 Litre V8 powered car, or a 1.8Litre 4 cyl one? Answer: It depends on the cars. In the above test, I chose a Ford Mustang and a Lotus Elise. The Lotus easily outperforms the Mustang. In every area. The Lotus handles better, will easily out accelerate a Mustang (or pretty much anything else on the road) and do it with far less power. Same deal with amplifiers and speakers. Without examining several pages of data (for both amps and speakers) it is virtually impossible to predict which will work best. Listen to both amps, through your choice of speakers and choose either whichever sounds best, or, if there is not sound difference (highly likely), choose whichever one you like the look of/better warranty/better features/etc. Trevor Wilson |
#24
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Stereo receievers: THD of .04 vs. .08
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#25
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: "Eeyore" wrote Arny Krueger wrote: When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. Pure nonsense. Crossover distortion remains the bete noire of conventional Class AB bipolar designs. Please explain that in the context of the performance of this power amplifier: http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm Is it a "conventional Class AB bipolar design" ? I suspect not. Graham |
#26
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Stereo receievers: THD of .04 vs. .08
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#27
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Stereo receievers: THD of .04 vs. .08
"Eeyore" wrote in message ... geoff wrote: wrote: Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Given that your speakers are likely to impart at least 2 % distortion at even low levels, then I doubt you will hear any difference in amp distortion. 2% at low level ? I wouldn't expect them to be quite that bad. **Indeed. ESLs can be orders of magnitude lower than that. Trevor Wilson |
#28
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Stereo receievers: THD of .04 vs. .08
With the distortion you mentioned, there will be no difference that you can
hear. Even at 0.1% THD distortion, you cannot hear that. Check to see the power level that the distortion was measured at. At lower volume levels, the distortion should be less. With efficient speakers, most likely you will never exceed an average RMS power of about 10 Watts when using high levels of sound. Normal listening levels would most likely be less than 1 to 2 Watts of average power. I would go for the higher power rating to be able to handle the peaks in the sound. This is especially with the bass frequencies if in the event you decide to sometimes use the amplifier on the loud side. To hear the THD distortion defects, a very hearing acute person cannot hear and THD distortion below about 2%. This is considered very high distortion for any audio device. There are some very high end amplifiers that have THD ratings in the 0.2% to 0.4% range. The bottom line is to listen to the different amplifier and speaker combinations. Then choose what sounds the best for your taste. -- JANA _____ wrote in message ... Thanks all for the advice on B Stock merchandise. Okay, I'm scared to mention non-high-end or non-scientific stuff here because of the flaming I once took from a forger, but here goes: I think I've decided on buying a pair of Infinity Beta 50 speakers. I'm among two receivers--a Yamaha 497 (75w per ch) and an Onkyo TX 8522 (100w per ch). One salient difference is that the Yamaha claims a 0.04 THD, and the Onkyo a 0.08. I THINK I have a pretty discerning ear. Do you think that difference in THD would make much of a difference between those two receivers, using that one pair of speakers? Thanks. |
#29
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Stereo receievers: THD of .04 vs. .08
"Eeyore" wrote in
message Arny Krueger wrote: "Eeyore" wrote Arny Krueger wrote: When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. Pure nonsense. Crossover distortion remains the bete noire of conventional Class AB bipolar designs. Please explain that in the context of the performance of this power amplifier: http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm Is it a "conventional Class AB bipolar design" ? I suspect not. It is class AB, and it is bipolar. It is Crown, so probably part or all of the output stage was turned on its head or split down the middle. ;-) It has a linear power supply. I should fetch up the measurements I made on the same day of a USA 850. Not easy, but on a hard drive someplace. Not as good, but not as bad as you seem to expect. Remember, 5532s are class AB and bipolar. ;-) |
#30
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Stereo receievers: THD of .04 vs. .08
JANA wrote: With the distortion you mentioned, there will be no difference that you can hear. Even at 0.1% THD distortion, you cannot hear that. The distortion spec is measured at close to full power. The real distortion at lower powers where most of the listening is done may be as much as TEN times higher with typical Class AB bipolar transistor designs. I once imagined what you said above to be true, that was back in the late 70s in fact. Until I listed to a top-notch 0.1% THD spec pro amplifier against a newer design using more advanced circuitry that had THD nearly ten times lower. The difference WAS NOT SUBTLE. Graham |
#31
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: "Eeyore" wrote in message Arny Krueger wrote: "Eeyore" wrote Arny Krueger wrote: When techniques like these are utilized, it is often found that SS amplifiers have negligable crossover distortion. Pure nonsense. Crossover distortion remains the bete noire of conventional Class AB bipolar designs. Please explain that in the context of the performance of this power amplifier: http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm Is it a "conventional Class AB bipolar design" ? I suspect not. It is class AB, and it is bipolar. It's not conventional. It is Crown, so probably part or all of the output stage was turned on its head or split down the middle. ;-) It has a linear power supply. I should fetch up the measurements I made on the same day of a USA 850. Not easy, but on a hard drive someplace. Not as good, but not as bad as you seem to expect. Remember, 5532s are class AB and bipolar. ;-) And the bias current in the output stage is a far larger fraction of the maximum load current. It may operate entirely in Class A with many or even most loads. Not many people are using 600 ohm working. Graham |
#32
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Stereo receievers: THD of .04 vs. .08
"Eeyore" wrote in
message JANA wrote: With the distortion you mentioned, there will be no difference that you can hear. Even at 0.1% THD distortion, you cannot hear that. The distortion spec is measured at close to full power. The real distortion at lower powers where most of the listening is done may be as much as TEN times higher with typical Class AB bipolar transistor designs. No way with modern amps. Any big rises at low levels that may be shown in published tests is due to noise. The truth outs if someone actually publishes a spectral analysis. For one thing, modern output transistors have Ft up in the megahertz range. Back in the 70s people were still struggling with output devices with Ft in the KHz range. But even so, the crossover spikes that remained were relatively small and outside the audio range. I once imagined what you said above to be true, that was back in the late 70s in fact. Until I listed to a top-notch 0.1% THD spec pro amplifier against a newer design using more advanced circuitry that had THD nearly ten times lower. The difference WAS NOT SUBTLE. That was like 30-odd years ago. Time for a modern level set, Graham! ;-) BTW Graham, why is it that when we get into discussions like this, its always me that does the lab work? |
#33
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: "Eeyore" wrote JANA wrote: With the distortion you mentioned, there will be no difference that you can hear. Even at 0.1% THD distortion, you cannot hear that. The distortion spec is measured at close to full power. The real distortion at lower powers where most of the listening is done may be as much as TEN times higher with typical Class AB bipolar transistor designs. No way with modern amps. YES Arny. The age of the amplifier is irrelevant. It's simple semiconductor physics as applied to the classic complementary emitter follower output stage. You can't change the physics of how semiconductors work ! The one thing you CAN do is to use cleverer designs that reduce the impact of the rapid change in device transconductance at lower currents. However very few designs actually do this. Naturally mine do of course but even they do still exhibit slightly higher THD at low power levels than at max output but by somewhat less than ten to one. This should be readily modellable with the best modern circuit simulation packages now btw. Graham |
#34
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: For one thing, modern output transistors have Ft up in the megahertz range. Back in the 70s people were still struggling with output devices with Ft in the KHz range. Has no influence on the change in transconductance of output devices with load current. Stop talking irrelevant nonsense. How many amplifiers have YOU designed btw ? When you can illustrate you actually know something relevant about the subject you'll be qualified to talk about it. Until then all you're doing is repeating popular myths and misapplying them. No better than the nitwits in r.a.t actually. I AM right about this point Arny ! (as I usually am - nothing beats hands-on design experience backed up by a solid understanding of the underlying physics ) Graham |
#35
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Stereo receievers: THD of .04 vs. .08
JANA wrote: With the distortion you mentioned, there will be no difference that you can hear. Even at 0.1% THD distortion, you cannot hear that. 0.1% distortion that's 2nd harmonic or say seventh harmonic ? You simply cannot make such broad statements. A serious limitation of THD measurements is that the *total* tells you very little about how audible it is. Graham |
#36
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Stereo receievers: THD of .04 vs. .08
Eeyore wrote:
Remember, 5532s are class AB and bipolar. ;-) And the bias current in the output stage is a far larger fraction of the maximum load current. It may operate entirely in Class A with many or even most loads. Not many people are using 600 ohm working. Let that apply for the poweramp too ... not at an unrealistic concept for home use ... and there is NO issue. Graham Kind regards Peter Larsen |
#37
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Stereo receievers: THD of .04 vs. .08
"Peter Larsen" wrote in message
Eeyore wrote: Remember, 5532s are class AB and bipolar. ;-) And the bias current in the output stage is a far larger fraction of the maximum load current. It may operate entirely in Class A with many or even most loads. Not many people are using 600 ohm working. Let that apply for the poweramp too ... not at an unrealistic concept for home use ... and there is NO issue. IME, most home systems spend much of their time running at very low levels where neither side of the output stage is ever cut off. |
#38
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Stereo receievers: THD of .04 vs. .08
"Eeyore" wrote in
message Arny Krueger wrote: For one thing, modern output transistors have Ft up in the megahertz range. Back in the 70s people were still struggling with output devices with Ft in the KHz range. Has no influence on the change in transconductance of output devices with load current. But it does have something to do with the shape of such transients as show up when you there is some crossover distortion. But thanks for bringing up the issue of change in transconductance of the output devices, particularly at low current levels. That's another issue that modern devices sometimes do better at. Stop talking irrelevant nonsense. Lighten up, Graham. So seem to forget about all the truely weird nonsense that we see on Usenet. How long has it been since you were on AAPLS? How many amplifiers have YOU designed btw ? More than I'd care to admit here. The experience made me a believer in commercial amps. :-( |
#39
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Stereo receievers: THD of .04 vs. .08
Peter Larsen wrote: Eeyore wrote: Remember, 5532s are class AB and bipolar. ;-) And the bias current in the output stage is a far larger fraction of the maximum load current. It may operate entirely in Class A with many or even most loads. Not many people are using 600 ohm working. Let that apply for the poweramp too ... not at an unrealistic concept for home use ... and there is NO issue. Would you seriously suggest an amp or so of quiescent current would be acceptable ? It certainly WILL fix the problem of course. Graham |
#40
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Stereo receievers: THD of .04 vs. .08
Arny Krueger wrote: "Peter Larsen" wrote Eeyore wrote: Remember, 5532s are class AB and bipolar. ;-) And the bias current in the output stage is a far larger fraction of the maximum load current. It may operate entirely in Class A with many or even most loads. Not many people are using 600 ohm working. Let that apply for the poweramp too ... not at an unrealistic concept for home use ... and there is NO issue. IME, most home systems spend much of their time running at very low levels where neither side of the output stage is ever cut off. It's not the cutting off per se that causes the distortion. Just modulating the collector current of an emitter follower output stage by any significant fraction of the quiescent value will cause distortion due to the change in transconductance of the output devices. Transconductance changes with current you see. This is semiconductor physics and its effect is most pronounced in this situation. A change in transconductance results in an unwanted voltage that adds to the signal and thereby causing the distortion. Graham |
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