Re: Doug's objectivity
No...not all power amp. parameters degrade at 6db per octave....depends on a whole host of things, not least the type of compensation.........amount of, and type of decoupling,....grounding schemes.........topology...etc
moreover, i think you'll find that in his specific article on PSRR, he gives precise counter measures for improving PSRR with respect to each supply rail for his adopted topology.....
.....further, PSRR is quoted for each supply rail....so...you would have to be more specific in respect of which supply rail you're refering to....
...and no...a PSRR of 70 db for both rails across the audio band is more than adequate.........
ALW said:
No...not all power amp. parameters degrade at 6db per octave....depends on a whole host of things, not least the type of compensation.........amount of, and type of decoupling,....grounding schemes.........topology...etc
moreover, i think you'll find that in his specific article on PSRR, he gives precise counter measures for improving PSRR with respect to each supply rail for his adopted topology.....
.....further, PSRR is quoted for each supply rail....so...you would have to be more specific in respect of which supply rail you're refering to....
...and no...a PSRR of 70 db for both rails across the audio band is more than adequate.........
Re: Re: Re: Re: ...to continue pan,
....for this assertion to be true in a rigorous blind test, at least two of the amps. you've listed would have produce a mid-band THD+N in the region of 30% !!
Pan said:
....for this assertion to be true in a rigorous blind test, at least two of the amps. you've listed would have produce a mid-band THD+N in the region of 30% !!
Use your ears
I can barely even bring myself to bother passing comment re: your total mis-reading of the actual words on DS's site and in my response
"...op-amps in particular excelling at power-supply rejection-ratio..."
That's what he says - he's wrong.
"Like almost all op-amps almost every parameter degrades at 6dB / oct above a certain point"
Note the words almost (twice) and op-amp.
".....further, PSRR is quoted for each supply rail....so...you would have to be more specific in respect of which supply rail you're refering to...."
It doesn't matter - both are relevant, the circuit won't work without both 🙄
My last word to you, ever - try LISTENING (with your ears)
Andy.
I can barely even bring myself to bother passing comment re: your total mis-reading of the actual words on DS's site and in my response
"...op-amps in particular excelling at power-supply rejection-ratio..."
That's what he says - he's wrong.
"Like almost all op-amps almost every parameter degrades at 6dB / oct above a certain point"
Note the words almost (twice) and op-amp.
".....further, PSRR is quoted for each supply rail....so...you would have to be more specific in respect of which supply rail you're refering to...."
It doesn't matter - both are relevant, the circuit won't work without both 🙄
My last word to you, ever - try LISTENING (with your ears)
Andy.
Re: Use your ears
Hi Andy,🙂
...actually Self DID have a point....op-amps DO excell at PSRR....for a randomly selected example see attached..
...a PSRR in the region of 90-100db across the audio band, while pleasant to have, is really not necessary, as 70db is quite sufficient......
PSRR can only degrade at 6db/octave, (usually but not exclusively for -ve supply), for single dominant pole compensation.......
i reiterate....not all power amp. parameters degrade at 6db per octave....depends on a whole host of things, not least the type of compensation.........amount of, and type of decoupling,....grounding schemes.........topology...etc
ALW said:
I can barely even bring myself to bother passing comment re: your total mis-reading of the actual words on DS's site and in my response
"...op-amps in particular excelling at power-supply rejection-ratio..."
That's what he says - he's wrong.
"Like almost all op-amps almost every parameter degrades at 6dB / oct above a certain point"
Note the words almost (twice) and op-amp.
".....further, PSRR is quoted for each supply rail....so...you would have to be more specific in respect of which supply rail you're refering to...."
It doesn't matter - both are relevant, the circuit won't work without both 🙄
My last word to you, ever - try LISTENING (with your ears)
Andy.
Hi Andy,🙂
...actually Self DID have a point....op-amps DO excell at PSRR....for a randomly selected example see attached..
...a PSRR in the region of 90-100db across the audio band, while pleasant to have, is really not necessary, as 70db is quite sufficient......
PSRR can only degrade at 6db/octave, (usually but not exclusively for -ve supply), for single dominant pole compensation.......
i reiterate....not all power amp. parameters degrade at 6db per octave....depends on a whole host of things, not least the type of compensation.........amount of, and type of decoupling,....grounding schemes.........topology...etc
Re: Use your ears
...No...i listen with my ~##£$***:~#😀
ALW said:
My last word to you, ever - try LISTENING (with your ears)
Andy.
...No...i listen with my ~##£$***:~#😀
The Amplifier Expert
As much as some folks here would like to, it's hard to dispute 99% of what Doug Self has written--both in his book and on his website. His points are clearly explained, based on sound engineering principals and well referenced.
I don't see anything wrong with the statement that ALW tries to discredit Self with. If ALW can demonstrate where Self is wrong, perhaps he can explain the issue further?
It's a fact that good amplifier stages ignore imperfections in their power supplies. To what degree they ignore them depends on many factors. It's also a fact that op-amps generally excel at PSRR. Even if the PSRR falls with increasing frequency, can anyone demonstrate a realistic condition where it will audibly affect the audio signal with any reasonable amount of power supply noise?
Does Doug Self have all the audio answers in the universe? Probably not. Has anyone proven what he has to say about amplifiers wrong? Not that I'm aware of.
http://www.dself.demon.co.uk/subjectv.htm
As much as some folks here would like to, it's hard to dispute 99% of what Doug Self has written--both in his book and on his website. His points are clearly explained, based on sound engineering principals and well referenced.
I don't see anything wrong with the statement that ALW tries to discredit Self with. If ALW can demonstrate where Self is wrong, perhaps he can explain the issue further?
It's a fact that good amplifier stages ignore imperfections in their power supplies. To what degree they ignore them depends on many factors. It's also a fact that op-amps generally excel at PSRR. Even if the PSRR falls with increasing frequency, can anyone demonstrate a realistic condition where it will audibly affect the audio signal with any reasonable amount of power supply noise?
Does Doug Self have all the audio answers in the universe? Probably not. Has anyone proven what he has to say about amplifiers wrong? Not that I'm aware of.
http://www.dself.demon.co.uk/subjectv.htm
Usually the PSRR vs. frequency curve of an opamp follows the open-loop gain vs. frequency characteristics. For example, if we look at the OP-77, we see that the PSRR exceeds 120dB at frequencies below 1Hz, but above that, deteriorates by a factor of 10 for every 10-fold increase in frequency. At 10Hz, the PSRR is 100dB, at 100Hz it is 80dB, at 1kHz 60dB, 40dB at 10kHz, and continues dropping at the same rate above 10kHz.
In my experience, it is possible to design a discrete-device amplifier circuit with considerably better PSRR characteristics than most opamps. Note: If you set out to do this, it is helpful to consider _both_ the device characteristics _and_ the topologies.
jonathan carr
In my experience, it is possible to design a discrete-device amplifier circuit with considerably better PSRR characteristics than most opamps. Note: If you set out to do this, it is helpful to consider _both_ the device characteristics _and_ the topologies.
jonathan carr
PSRR
To add to what jonathan says, I haven't dissected an opamp, but I've measured one or two. And I can read graphs. A cheezy opamp like an LF351 will have a PSRR of about 50 dB at 10KHz, and dramatically better performance at lower frequencies where the ear is more sensitive. A decent opamp like the AD797 (designed by one of my drinking buddies) will show something more like 80 dB at 10KHz.
Of course, the frequencies at which PSRR tails off are exactly those where proper bypassing can take care of things quite well.
To add to what jonathan says, I haven't dissected an opamp, but I've measured one or two. And I can read graphs. A cheezy opamp like an LF351 will have a PSRR of about 50 dB at 10KHz, and dramatically better performance at lower frequencies where the ear is more sensitive. A decent opamp like the AD797 (designed by one of my drinking buddies) will show something more like 80 dB at 10KHz.
Of course, the frequencies at which PSRR tails off are exactly those where proper bypassing can take care of things quite well.
SY: Sorry for sending this thread off into a somewhat different direction 😀, but do you reckon that the bootstrapping of the second-stage summing current mirror is partly responsible for the better-than-normal PSRR of the AD797? When I tried this, I remember that it certainly added loads of open-loop gain, but I don't seem to recall how it affected the PSRR.
regards, jonathan carr
regards, jonathan carr
Quick answer: I don't know off the top of my head. I'll take a look at the schematic. If necessary, I'll ask the designer to put down his glass for a moment and explain it to me.
Many thanks, Sy. I will start a new thread and respond there, as the message contents are unrelated to the present thread topic.
Besides, it wouldn't be polite to interrupt the fun that everyone appears to be having here 😀
regards, jonathan carr
Besides, it wouldn't be polite to interrupt the fun that everyone appears to be having here 😀
regards, jonathan carr
Re: Re: Re: Re: Re: ...to continue pan,
Do you really believe that Lars Clausen, Ole Lund Christensen , Bill Johnson and Nelson Pass are that bad at designing amps..?... 30%, uh please...
You don´t seem to get this at all.
The Patriot V100 from LC audio (Lars Christensen) is a fully balanced class A amp with BW of DC-4MHz. THD+N is about 0.01% 1W and 0.1% 100W. I normally play at low to medium levels and I guess I seldom ask the amp for more than 10W or so.
This very amp has a interesting feature in that you can set the BIAS low for "A/B" or 16W class A or 100W class A.
This amp also has the feature of setting the low level stages as standard symetric OR single end. In standard mode the dist. is 0.01% 1W and in single end mode 0.05% 1W with a higher level of 2nd and even order harmonics.
LC audio found out that a dominating 2nd was pleasing for some music and a dominating 3rd for other music (allready known by tons of people). So they set out to build in these options in one and same amp instead of making several amps at this high level.
Switching between these two modes makes it possible to add a slight amount of 2nd and even order and that really is fine for some music. It´s no problem at all to hear the difference between these two modes, and as I said, the difference at 1W is 0.01% vs. 0.05%.
Honestly the difference betwen these amps are night and day and anyone suggesting that a blind test is needed has some serious problems understanding high performance audio.
AND I do think BT and (of course) measurements has it´s merits and should be used, but sometimes it certainly is not necessary if we talk about differentiating (is that a word?) between gear with obvious differences in performance.
OH, BTW, a fun story;
I had the Aleph5 at home for test and I really liked the sound as it had a very strong feeling of "intimacy" and "presence" of the voices/music on the CD. In the set up I had then I heard the best 3d pin point imaging ever (even with my amps). My girlfiend and her daughter (28y and 6y old) made a visit in my listening room. While playing some tunes my girlfriend did not have any feeling at all for the 3d reproducion of the music, she only heard the sound and she could not get a grip of the hologhraphic part of the reproduction.
I knew exactly where in "space" behind the speakers the images was on different tracks and it was just sooo fun when the daughter suddenly stod up and pointed to a space 1.8 meters behind the speakers and said; Mo´m it sounds like the girl is standing there and singing. The daughter was 6y old and she heard Tracy Chapman from the exact point that I did. The mother was clueless....
There are listeners and there are listeners....
Happy listening by the way 🙂
/Peter
mikek said:
....for this assertion to be true in a rigorous blind test, at least two of the amps. you've listed would have produce a mid-band THD+N in the region of 30% !!
Do you really believe that Lars Clausen, Ole Lund Christensen , Bill Johnson and Nelson Pass are that bad at designing amps..?... 30%, uh please...
You don´t seem to get this at all.
The Patriot V100 from LC audio (Lars Christensen) is a fully balanced class A amp with BW of DC-4MHz. THD+N is about 0.01% 1W and 0.1% 100W. I normally play at low to medium levels and I guess I seldom ask the amp for more than 10W or so.
This very amp has a interesting feature in that you can set the BIAS low for "A/B" or 16W class A or 100W class A.
This amp also has the feature of setting the low level stages as standard symetric OR single end. In standard mode the dist. is 0.01% 1W and in single end mode 0.05% 1W with a higher level of 2nd and even order harmonics.
LC audio found out that a dominating 2nd was pleasing for some music and a dominating 3rd for other music (allready known by tons of people). So they set out to build in these options in one and same amp instead of making several amps at this high level.
Switching between these two modes makes it possible to add a slight amount of 2nd and even order and that really is fine for some music. It´s no problem at all to hear the difference between these two modes, and as I said, the difference at 1W is 0.01% vs. 0.05%.
Honestly the difference betwen these amps are night and day and anyone suggesting that a blind test is needed has some serious problems understanding high performance audio.
AND I do think BT and (of course) measurements has it´s merits and should be used, but sometimes it certainly is not necessary if we talk about differentiating (is that a word?) between gear with obvious differences in performance.
OH, BTW, a fun story;
I had the Aleph5 at home for test and I really liked the sound as it had a very strong feeling of "intimacy" and "presence" of the voices/music on the CD. In the set up I had then I heard the best 3d pin point imaging ever (even with my amps). My girlfiend and her daughter (28y and 6y old) made a visit in my listening room. While playing some tunes my girlfriend did not have any feeling at all for the 3d reproducion of the music, she only heard the sound and she could not get a grip of the hologhraphic part of the reproduction.
I knew exactly where in "space" behind the speakers the images was on different tracks and it was just sooo fun when the daughter suddenly stod up and pointed to a space 1.8 meters behind the speakers and said; Mo´m it sounds like the girl is standing there and singing. The daughter was 6y old and she heard Tracy Chapman from the exact point that I did. The mother was clueless....
There are listeners and there are listeners....
Happy listening by the way 🙂
/Peter
women
Yes Peter,
It's fantastic how non-audiophile women can be the best critics for sound quality.
My wife just ditched a sub I was testing in my room.
She said: "what have you done to the sound? It's boomy".
She didn't even knew there's a sub playing, she didn't see it.
Than came the worst part:
"What's that ugly thing? Are you going to leave it there, in the middle of the room?"
Well... in fact, it was almost in the middle of the room where it played better.
I said, "No, don't worry, I was only testing, it's not mine. I don't like it's sound anyway".😎
Yes Peter,
It's fantastic how non-audiophile women can be the best critics for sound quality.
My wife just ditched a sub I was testing in my room.
She said: "what have you done to the sound? It's boomy".
She didn't even knew there's a sub playing, she didn't see it.
Than came the worst part:
"What's that ugly thing? Are you going to leave it there, in the middle of the room?"
Well... in fact, it was almost in the middle of the room where it played better.
I said, "No, don't worry, I was only testing, it's not mine. I don't like it's sound anyway".😎
Op-amp Audio
From Walt Jung's EDN Article on amplifier error sources: -
"If you study a typical op-amp data sheet, you'll notice that there is a PSR spec for both +VS and -VS, as well as one for common-mode rejection (CMR). But, close inspection reveals that these are dc specs. Over audio frequencies, typical PSR behavior is plotted, and it degrades with frequency at 6 dB/octave. Common values are 100 dB or more of dc PSR (or CMR), dropping to 80 dB at 1 kHz. Ironically, such popular audio op amps as the 5532 and 5534 don't provide their users PSR and CMR curves!
Also, note that PSR will often be poorer for one of the supplies, sometimes noticeably so. CMR and PSR are related--both measuring front-end response to signals common to the normal inputs, or via the rail(s) as a signal source. It is typical to specify PSR for symmetrically varying (±) supply voltages. Unfortunately, real-world power sources don't always vary neatly. So, a realistic audio consideration would be to analyze things in terms of the worst PSR/CMR curve from the data sheet, and use that data at various frequencies. We'll assume an 80 dB/1 kHz PSR error in an example calculation.
An error 80dB down may sound good, until we add some mitigating factors. In Figure 1, for example, the 5X noise gain makes an 80 dB/1 kHz error about 14 dB worse, or 66 dB/1 kHz, as referred to the output. And in almost every case with conventional op amps, this still gets worse by 6 dB/octave with increasing frequency.
Putting it in perspective with an actual output signal, we'll talk in terms of op-amp input-referred errors (since that's where PSR errors couple). Assume 1 V p-p output at 1 kHz, and an op amp gain-bandwidth of 10 MHz. This means that to produce the 1 V p-p, the amplifier's input signal will be 100 µV p-p. If the supply rail sees a 1 mV p-p/1 kHz noise (for whatever reason), this noise referred at the amplifier input will be 0.1 µV p-p. The ratio of the desired signal to the noise is 60 dB--not such a good ratio. Also, consider the possibility that CMR or PSR could be worse than 80 dB, or the power-rail noise higher.
Another subtle point is that the PSR frequency-response corners for the +VS /-VS rails may vary from one another, and may also vary with respect to the open-loop-gain corner. Thus, the sample numbers used here could be different in reality.
The example assumed a 10-MHz gain-bandwidth op amp. But, if we consider an op- amp with ten times the gain-bandwidth (100 MHz), the input signal reduces ten-fold, to 10 µV p-p. With the same power-rail noise, this tends towards an effect of PSR errors of similar order (80 dB) being much more serious. In practice, such a higher gain-bandwidth op amp will very likely also have greater PSR.
The main general point being made is that real-world PSR and CMR errors can be much worse than a casual glance at a data-sheet curve may suggest. In fact, a better way to look at the topic of V3-V4 errors is to consider the rails of an op amp simply as another signal input, and proceed accordingly. Good supply regulation and bypassing will go a long way toward minimizing and controlling these errors. In fact, it isn't unrealistic to set V3-V4 error goals referred to a working op-amp input signal of -100 dB (or better). This will generally require some careful supply regulation, since you can't always count on an op amp providing 100 dB of V3-V4 error isolation over the applicable frequency range. Current-feedback types, for example, have typical PSR and CMR of 60-70 dB. "
Still happy with 70dB PSRR ?
From Walt Jung's EDN Article on amplifier error sources: -
"If you study a typical op-amp data sheet, you'll notice that there is a PSR spec for both +VS and -VS, as well as one for common-mode rejection (CMR). But, close inspection reveals that these are dc specs. Over audio frequencies, typical PSR behavior is plotted, and it degrades with frequency at 6 dB/octave. Common values are 100 dB or more of dc PSR (or CMR), dropping to 80 dB at 1 kHz. Ironically, such popular audio op amps as the 5532 and 5534 don't provide their users PSR and CMR curves!
Also, note that PSR will often be poorer for one of the supplies, sometimes noticeably so. CMR and PSR are related--both measuring front-end response to signals common to the normal inputs, or via the rail(s) as a signal source. It is typical to specify PSR for symmetrically varying (±) supply voltages. Unfortunately, real-world power sources don't always vary neatly. So, a realistic audio consideration would be to analyze things in terms of the worst PSR/CMR curve from the data sheet, and use that data at various frequencies. We'll assume an 80 dB/1 kHz PSR error in an example calculation.
An error 80dB down may sound good, until we add some mitigating factors. In Figure 1, for example, the 5X noise gain makes an 80 dB/1 kHz error about 14 dB worse, or 66 dB/1 kHz, as referred to the output. And in almost every case with conventional op amps, this still gets worse by 6 dB/octave with increasing frequency.
Putting it in perspective with an actual output signal, we'll talk in terms of op-amp input-referred errors (since that's where PSR errors couple). Assume 1 V p-p output at 1 kHz, and an op amp gain-bandwidth of 10 MHz. This means that to produce the 1 V p-p, the amplifier's input signal will be 100 µV p-p. If the supply rail sees a 1 mV p-p/1 kHz noise (for whatever reason), this noise referred at the amplifier input will be 0.1 µV p-p. The ratio of the desired signal to the noise is 60 dB--not such a good ratio. Also, consider the possibility that CMR or PSR could be worse than 80 dB, or the power-rail noise higher.
Another subtle point is that the PSR frequency-response corners for the +VS /-VS rails may vary from one another, and may also vary with respect to the open-loop-gain corner. Thus, the sample numbers used here could be different in reality.
The example assumed a 10-MHz gain-bandwidth op amp. But, if we consider an op- amp with ten times the gain-bandwidth (100 MHz), the input signal reduces ten-fold, to 10 µV p-p. With the same power-rail noise, this tends towards an effect of PSR errors of similar order (80 dB) being much more serious. In practice, such a higher gain-bandwidth op amp will very likely also have greater PSR.
The main general point being made is that real-world PSR and CMR errors can be much worse than a casual glance at a data-sheet curve may suggest. In fact, a better way to look at the topic of V3-V4 errors is to consider the rails of an op amp simply as another signal input, and proceed accordingly. Good supply regulation and bypassing will go a long way toward minimizing and controlling these errors. In fact, it isn't unrealistic to set V3-V4 error goals referred to a working op-amp input signal of -100 dB (or better). This will generally require some careful supply regulation, since you can't always count on an op amp providing 100 dB of V3-V4 error isolation over the applicable frequency range. Current-feedback types, for example, have typical PSR and CMR of 60-70 dB. "
Still happy with 70dB PSRR ?
Walt Jung
Walt Jung is one of the best specialists on this matter for many years, and you can trust him on anything related to op-amps.
I say: whatever the PSR of an op-amp, treat it's PSU well and it pays in sound quality.
I don't know of any component that likes voltage variations and the ripple of poor unregulated PSUs (worst still, when a bunch of components share that PSU line).
Walt Jung is one of the best specialists on this matter for many years, and you can trust him on anything related to op-amps.
I say: whatever the PSR of an op-amp, treat it's PSU well and it pays in sound quality.
I don't know of any component that likes voltage variations and the ripple of poor unregulated PSUs (worst still, when a bunch of components share that PSU line).
Re: Break-in
Andy, sorry for the late reply, have been away,
I am not sure I can follow you, but to clarify my point:
ASSUME that there is a physical change in a component, cable, etc during so-called break-in (and I am ready to admit they are there),
ASSUME that this change has an influence on the performance of a piece of equipment (and, OK, I also accept this),
Why is it that these changes ALWAYS lead to better sound? That is against all logic. Even in your comment, where you say you have seen/heard cases where it deteriorates DURING break-in, but at the END of it suddenly, magically, the result gets better.
Come on, give me a break folks!
Jan Didden
ALW said:
Andy, sorry for the late reply, have been away,
I am not sure I can follow you, but to clarify my point:
ASSUME that there is a physical change in a component, cable, etc during so-called break-in (and I am ready to admit they are there),
ASSUME that this change has an influence on the performance of a piece of equipment (and, OK, I also accept this),
Why is it that these changes ALWAYS lead to better sound? That is against all logic. Even in your comment, where you say you have seen/heard cases where it deteriorates DURING break-in, but at the END of it suddenly, magically, the result gets better.
Come on, give me a break folks!
Jan Didden
Jan
My theory is along these lines: -
Any component variations can introduce errors and unwanted signals into a system, this is engineering fact with many electonic components - they change as they warm up. Caps / resistors / semi's all do this, measurably.
Therefore at switch-on we have degrading effects which are audible, because they affect the ultimate precision and resolution of the system.
After the burn-in period the component changes are either absent, or below audible levels - hence the device will sound better, simply because there are less errors introduced to the system.
During burn-in though, things can get worse, it's not necessarily a steady decline, or maybe as resolution increases, due to an improvement in one circuit area, it makes other components, whose rate of stabilisation is longer, more obvious.
I'm not though sayigng the end result is always good, just that it is better than at the switch-on - I'd be less confident about the theory w.r.t. cables too...
It's worthy of some scientific analysis anyway...
Andy.
My theory is along these lines: -
Any component variations can introduce errors and unwanted signals into a system, this is engineering fact with many electonic components - they change as they warm up. Caps / resistors / semi's all do this, measurably.
Therefore at switch-on we have degrading effects which are audible, because they affect the ultimate precision and resolution of the system.
After the burn-in period the component changes are either absent, or below audible levels - hence the device will sound better, simply because there are less errors introduced to the system.
During burn-in though, things can get worse, it's not necessarily a steady decline, or maybe as resolution increases, due to an improvement in one circuit area, it makes other components, whose rate of stabilisation is longer, more obvious.
I'm not though sayigng the end result is always good, just that it is better than at the switch-on - I'd be less confident about the theory w.r.t. cables too...
It's worthy of some scientific analysis anyway...
Andy.
Born Again Virgin Amplifiers.
Jan,
I have consistently found a curious effect in my servicing work.
I commonly blanket resolder amplifier output stages as part of the job to ensure perfect long term reliability.
On first power-up after repair, I have often observed that the amplifier sounds 'wrong'.
I have tried allowing amplifiers to idle for extended periods to achieve thermal stability, and with the same results.
On run up to say quarter power on the first power-up, I have found amplifiers to sound clangy, 'congested and displeasing.
Running up to say 3/4 power, and then back to 1/4 power reveals a small change in sound, but still not 'correct' sounding.
On increasing power up toward clip, this effect worsens, until the amp hits momentary clipping, and then the sound suddenly changes, and becomes more relaxed, cleaner and more pleasing.
Power down, wait say 30 seconds, and then re-power and audition at the original quarter power level, and the sound is different, and remains different to before the amp hit clip for the first time.
I do not have a proper explanation for this effect, but I think that this may be a factor in the audiophile 'burn-in' period.
I run newly repaired amps into clip in order to ensure reliability, but I think that it is less likely that most 'audiophiles' will subject their expensive speakers to this kind of overload, even momentarily.
This effect is subtle, but once heard and noted is found to be consistent, and other fellow technicians have heard the effect when demonstrated to them.
Regards, Eric.
Jan,
I have consistently found a curious effect in my servicing work.
I commonly blanket resolder amplifier output stages as part of the job to ensure perfect long term reliability.
On first power-up after repair, I have often observed that the amplifier sounds 'wrong'.
I have tried allowing amplifiers to idle for extended periods to achieve thermal stability, and with the same results.
On run up to say quarter power on the first power-up, I have found amplifiers to sound clangy, 'congested and displeasing.
Running up to say 3/4 power, and then back to 1/4 power reveals a small change in sound, but still not 'correct' sounding.
On increasing power up toward clip, this effect worsens, until the amp hits momentary clipping, and then the sound suddenly changes, and becomes more relaxed, cleaner and more pleasing.
Power down, wait say 30 seconds, and then re-power and audition at the original quarter power level, and the sound is different, and remains different to before the amp hit clip for the first time.
I do not have a proper explanation for this effect, but I think that this may be a factor in the audiophile 'burn-in' period.
I run newly repaired amps into clip in order to ensure reliability, but I think that it is less likely that most 'audiophiles' will subject their expensive speakers to this kind of overload, even momentarily.
This effect is subtle, but once heard and noted is found to be consistent, and other fellow technicians have heard the effect when demonstrated to them.
Regards, Eric.
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