No one here is talking about 0.01 ohm psu source impedance for a 2A3 set..
An improvement from 50 ohms to 3.5 ohms though is likely to be audible. (And is a pretty good result IMO for a tube based regulator.) I'm a pretty strong proponent of active voltage regulation in tube electronics and have used it for a long time. Interestingly enough many people I have met who aren't have either never heard a tube amplifier with well designed electronic regulation or have some philosophical objection relating to technical purism. (It wasn't done in the day.....)Electronic regulation is both less expensive in many instances particularly in low noise/moderate current applications and weighs a lot less than the iron required to achieve good noise performance particularly in higher power designs where CRC filters are not viable - and in terms of source impedance I have never seen a passive supply that could match the source impedance of a well designed active regulator. Obviously carrying it to an extreme is silly, but a couple of ohms is not that extreme and can be accomplished with rather simple circuitry as Sqerus has amply demonstrated. The payback of course is less interaction between the various amplifier stages, much less decoupling needed, and complete independence of circuit operating points from mains disturbances.
Arguably overkill, but such amplifiers (mine and others) have also generally acquitted themselves well against the competition and I attribute some of that to the use of voltage regulation.
No one here is talking about 0.01 ohm psu source impedance for a 2A3 set..
Well, I made that comment earlier in this thread when one such (well sub 100 milliohm anyway) supply was being discussed; not being critical of that design or anything.
Not going to comment on the general subjectivism of regulated power supplies, other than to point out that the is no shortage of tubeheads who adamantly prefer tube (Hi-Z) rectifiers with choke filters.......................
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Bas, note his use of the word "think."
Since a high Z supply (as Kevin points out) will objectively decrease the accuracy of the amplifier (i.e., raise distortion, reduce power, reduce stability, worsen overload recovery), and the claims of the superiority of high Z supplies are never backed up by any sort of technical explanation or actual subjective test, it's reasonable to attribute this preference to factors unrelated to actual amplification as the most likely explanation.
Since a high Z supply (as Kevin points out) will objectively decrease the accuracy of the amplifier (i.e., raise distortion, reduce power, reduce stability, worsen overload recovery), and the claims of the superiority of high Z supplies are never backed up by any sort of technical explanation or actual subjective test, it's reasonable to attribute this preference to factors unrelated to actual amplification as the most likely explanation.
Unless you are talking about a specific power supply in a particular amplifier with a particular speaker. Any blanket statements about increasing distortion, stability etc..etc. Is pure conjecture. You know as well as I do that a rectifier alone does not alone determine the stability of a power supply or the distortion. And you could build a regulated or low z psu that has worse stability or create more distortion.
But psu's aside. Making an assumption on why some might prefer "adamantly prefer tube (Hi-Z) rectifiers with choke filters" is preposterous.
But psu's aside. Making an assumption on why some might prefer "adamantly prefer tube (Hi-Z) rectifiers with choke filters" is preposterous.
Not conjecture, just basic engineering. If someone tells me that their concert experience is improved by wearing earmuffs, it's not a reach to attribute that to psychology rather than acoustics.
BTW, you misunderstand what I meant by "stability." I'm talking about the stability of the amplifier. Crosstalk and unintended positive feedback are the inevitable consequence of high power supply impedance. Amp instabilities are exacerbated by the inevitable droop and recovery after transient demands- the higher the power supply Z, the bigger the droop. This is a vital part of the "sound" of a guitar amp, but is not fidelity to the input signal for hifi application.
As previously pointed out, you can quickly get to the diminishing returns part of the curve. And sure, you can design and build a lousy regulator. That part is optional.
BTW, you misunderstand what I meant by "stability." I'm talking about the stability of the amplifier. Crosstalk and unintended positive feedback are the inevitable consequence of high power supply impedance. Amp instabilities are exacerbated by the inevitable droop and recovery after transient demands- the higher the power supply Z, the bigger the droop. This is a vital part of the "sound" of a guitar amp, but is not fidelity to the input signal for hifi application.
As previously pointed out, you can quickly get to the diminishing returns part of the curve. And sure, you can design and build a lousy regulator. That part is optional.
There is not evidence for this statement either. There is no objective way of measuring an amplifier and saying that it is more accurate.
If an amplifier measures 0.01% THD and 10 out of 11 people think the amplifier with 0.1% distortion is more realistic, the "objective" measurement about the "accuracy" of the amplifier is pointless, certainly for that group of people.
Now if you wanna bang that drum, you should also refrain from blanket statements.
To use THD as anything but a pointer, has been proven long ago, to not fit in with reality.
You kinda made a good example yourself, as you pointed out, that in some cases, higher THD may be preferred.
What has also been proven (by for instance Nelson Pass), is that people don't respond equal to even and odd harmonic distortion.
Now it could then be interesting to see, if a high Z PSU will shift the respective harmonic distortion, up or down in order, or from dominant even to odd.
All this naturally regards the following amp as wire with gain, as I am perfectly aware, that shifting the distortion with the amp topology is also an issue.
Magura
I seem to have have touched a nerve.
My experience, over many years, is that many, many people voice opinions based on closed-minded pre-determined psychological bias rather than open-minded observation and free-thought. Obviously this does not apply to everyone.
It is not just confined to audio power supplies. For example, I've seen one person chosen over another because of bias against skin colour, gender, age, without actually knowing the people at all. It's simple ignorant bias.
The same happens in audio. For example I know a guy that will not let a transistor inside his amplifier even if just to switch a relay! People often persue their dogmatic views even when it is clearly nonsense, and then they spread their opinion as if it is fact. That then serves to confuse those that follow who are seeking advice and guidance.
And so to amps and power supplies… Surely we have all come across the hard-of-thinking "boat anchor" clan, who insist that the only way to do an amp is "iron, iron, and more iron". That’s fine for them, but it is not fact.
It is true that these people exist. It is sad that their small-minded opinion is pushed forward as if it is fact. Sad but true.
My experience, over many years, is that many, many people voice opinions based on closed-minded pre-determined psychological bias rather than open-minded observation and free-thought. Obviously this does not apply to everyone.
It is not just confined to audio power supplies. For example, I've seen one person chosen over another because of bias against skin colour, gender, age, without actually knowing the people at all. It's simple ignorant bias.
The same happens in audio. For example I know a guy that will not let a transistor inside his amplifier even if just to switch a relay! People often persue their dogmatic views even when it is clearly nonsense, and then they spread their opinion as if it is fact. That then serves to confuse those that follow who are seeking advice and guidance.
And so to amps and power supplies… Surely we have all come across the hard-of-thinking "boat anchor" clan, who insist that the only way to do an amp is "iron, iron, and more iron". That’s fine for them, but it is not fact.
It is true that these people exist. It is sad that their small-minded opinion is pushed forward as if it is fact. Sad but true.
Just pointing out that subjectivism doesn't mean much. Heck, this thread started out with someone claiming that regulated supplies essentially make little, if any difference, did it not? Who is one to believe?
I'd prefer technical arguments as to why, not subjectivist anecdotes. In an otherwise properly engineered design, beyond a point there is little to be gained with regulated supplies, except perhaps really low (or even, actually preferable, inaudible) hum when you press your ear against your speakers tweeter (not that that isn’t a nice thing to aim for).
As far as stability goes, regulated not, for the best performance the input and driver circuity is better run from an independent supply (ie not one for the power output stage as well). These stages will generally be decoupled from each other with local RC filtering / decoupling anyway.
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Allen Wright, who certainly has different views than I do about audio, said something in his Preamp Cookbook that is simple but quite profound. (Quoting from memory) "Anything meant to move in a circuit should be able to move, free and fast. Anything meant not to move should be tied down very very tight."
Again, I'm not talking about guitar amps and effects boxes.
Again, I'm not talking about guitar amps and effects boxes.
I did not say that the high THD may be preferred. What I said is that an amp that has higher THD MAY be preferred in some cases.
Sure they exist. Most people I know who prefer tube rectifiers are people who have been building valve amps for decades and have tried everything. Meaning they have tried solid state rectifiers and preferred tube rectifiers. Or they'll admit that bass is tighter with solid state rectifiers but the mids and highs sounded better with the tube rectifier.
I have never met someone who pushes this forward as a general fact. Most say that his is what works for them or it is what they prefer.
Not the way I see it. That is why the language we all use is maybe not conducive to discuss things.
What I meant to say is that the amp that has higher THD may be preferred because of other things than THD. Not that it is preferred because it has higher THD.
Or maybe you said it best:
To use THD as anything but a pointer
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