PS Audio PowerPlant Voltage Regulation and Tube Amplifiers

[LEFASR160]

@amirm Amir suggested today that I create this thread so that tube amplifier designers on this web site can shed some light on this issue. I know nothing about it so it's being brought up here to get information about whether any of this makes sense vis a vis PS Audio Power Regenerators:

I know a guy who says that the voltage mains he has in Ohio changes several volts up and down depending upon the time of day and since he uses a tube amplifier, his bias voltage changes and he can hear the difference. With the PS Audio PowerPlant AC regenerator P20, he says it regulates his mains voltage more precisely and therefore stabilizes his tube amp bias and therefore the sound that he hears.

Does that make any sense ? He also told me his amp does not auto-regulate the voltage whereas, he said, some tube amps do and that the PS Audio P20 power regenerator regulates the voltage for his amp. I could not comment one way or the other nor was Amir able to comment any further since he doesn't have the schematic for the tube amp. His tube amp is a Convergent Audio Technology JL2 Signature Mk 2 Stereo Amplifier.

 

[DVDdoug]

He also told me his amp does not auto-regulate the voltage whereas, he said, some tube amps do and that the PS Audio P20 power regenerator regulates the voltage for his amp.

That could be true but I don't know anything about that amplifier. The bias is an "analog" voltage (related to an "analog" current) and it's never going to be "perfect". A good design wouldn't be that sensitive (even with an unregulated power supply).

The same could be true for a poorly designed solid state amplifier... But usually if you have an unregulated power supply the only result is drop in maximum power (clipping at lower output) as the line-voltage drops.

I think it would be rare to find a modern solid state amplifier with an unregulated supply. The voltage regulator helps to filter-out any AC hum that might be remaining from the main filters.

 

[LEFASR160]

@DVDdoug He claims that he can definitely hear it without the power regenerator in place because his amp does not auto-regulate voltage. I know nothing about this though. I'm just the messenger.

 

[amirm]

Calling @SIY....

 

[LEFASR160]

Calling @SIY....

@amirm Read this: https://www.thegearpage.net/board/index.php?threads/how-does-wall-current-affect-bias.258064/

 

[SIY]

If the bias is unregulated, which it ought to be, yes it will vary a bit with changes in line voltage. But the heater voltages will also change, so overall there’s much reduced change in idle current.

Audible? Seriously doubtful for normal variations in line voltage.

 

[LTig]

I think it would be rare to find a modern solid state amplifier with an unregulated supply. The voltage regulator helps to filter-out any AC hum that might be remaining from the main filters.

If the "modern solid state amplifier" is class D then yes, most of them use regulated switching power supplies. But as far as I know they need no bias adjustments like an class AB amplifier. Those on the other hand mostly use unregulated power supplies.

 

[threni]

I know a guy who says that the voltage mains he has in Ohio changes several volts up and down depending upon the time of day

I thought this was just a thing globally. Voltage varies randomly over a fairly wide range, and the frequency only has to average 50/60hz over a 24 hour period so that clocks don't gain/lose time?

 

[LEFASR160]

If the bias is unregulated, which it ought to be, yes it will vary a bit with changes in line voltage. But the heater voltages will also change, so overall there’s much reduced change in idle current.

Audible? Seriously doubtful for normal variations in line voltage.

@SIY @amirm If it can be heard, as is claimed by the person who owns the Convergent Audio Technology JL2 Signature Mk 2 Stereo Amplifier, then would there be value in voltage regulation with some tube amplifiers by means of a PS Audio Power Plant as is also claimed by that amp owner?

 

[amirm]

@SIY @amirm If it can be heard, as is claimed by the person who owns the Convergent Audio Technology JL2 Signature Mk 2 Stereo Amplifier, then would there be value in voltage regulation with some tube amplifiers by means of a PS Audio Power Plant as is also claimed by that amp owner?

What he claims is of little value. It is trivial for him to have convinced himself that regulation is better. It doesn't mean it is real.

 

[LEFASR160]

What he claims is of little value. It is trivial for him to have convinced himself that regulation is better. It doesn't mean it is real.

@amirm @SiR @DVDdoug So what is the absolutely certain conclusion, here? Or can one be absolutely certain ?

 

[SIY]

@amirm @SiR @DVDdoug So what is the absolutely certain conclusion, here? Or can one be absolutely certain ?

Most likely a brain issue, not an amp issue. And someone who’s itching to drop a few grand on a shiny object with a good story.

 

[LEFASR160]

If the bias is unregulated, which it ought to be, yes it will vary a bit with changes in line voltage. But the heater voltages will also change, so overall there’s much reduced change in idle current.

Audible? Seriously doubtful for normal variations in line voltage.

@SIY A change in the line voltage would indeed change the heater temperature so although A drop in voltage would cause the bias to go down and cause the tube to run a little hotter were it not for the lower temperature of the heater to compensate that and vice versa, it’s highly doubtful that the compensation would be exact. So any change in the voltage would I would think produce some net change in the idle current and I would say that that could produce a perceptible sound change especially if The time rate of change is high.

 

[SIY]

@SIY A change in the line voltage would indeed change the heater temperature so although A drop in voltage would cause the bias to go down and cause the tube to run a little hotter were it not for the lower temperature of the heater to compensate that and vice versa, it’s highly doubtful that the compensation would be exact. So any change in the voltage would I would think produce some net change in the idle current and I would say that that could produce a perceptible sound change especially if The time rate of change is high.

Compensation doesn't need to be exact, assuming you're not talking about gross changes (which suggests something different to fix). I run my designs at 110-130V during development (nearly a 20% change), and I assume that very basic design step is done by any competent engineer.

Idle current is not perfect anyway, unless you use an autobias system. And of course, cathode biased output tubes (very common topology) have yet another feedback system in place.

No, I think that without actual evidence, that audibility claim is dubious at best.

 

[LEFASR160]

@SiR It would probably not be so called cathode biased since it’s a 100W amplifier right? Aren't they usually so called fixed biased with a trim potentiometer? Aren’t the cathode biased designs usually in preamplifiers? I don’t claim to know much about this so I’m just asking.


We don’t know the design of his amplifier. if he says he can hear changes then you have to ask yourself: what is he hearing? Is he imagining it? You believe he is. It’s possible he is imagining it but then again it’s also possible he is not imagining it. I have to consider it as a possibility either way. If that’s true then voltage regulation becomes important for that amplifier design and then someone finally found a use for one of these power plant power regenerators or at least a voltage regulator.

Anyway neither of us are going to know the answer to this since you don’t have his amplifier or it’s schematic to look at it and we don’t know what voltage fluctuations are occurring in his mains AC.