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Originally Posted by Zac.R /img/forum/go_quote.gif
Apologies, but I am little confused. I am not very technical when it comes to the finer details of electronics, but what I gathered from the article in the link you posted contradicts what you said 'Power supplies can definitely make a difference'.
From the article - "...speed is valid for a regulated supply for a critical application, but is completely meaningless for a power amplifier with an unregulated supply - which is 99.9% of them."
"I can make a power supply "slow", simply by placing some resistance in series - the caps will no longer be able to discharge at their maximum rate. Will this affect an amplifier? Only in that the maximum power will no longer be achieved, but this will also happen if the AC mains supply is 10% low. Does this somehow degrade the sound of an amplifier? I think not."
For a layman such as myself, I am getting a little lost...
I guess all I can do is an A/B test for myself (which in themselves are flawed as you know which component you are listening to before the test starts).
Some hard, scientific evidence for one way or the other would be great!
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It's difficult. You want hard scientific evidence, but then you say you're a layman, as am I. We have to look at evidence we cannot fully understand. I was actually referring to the thread, not the article, especially where nikongod and others was talking about PSRR. People knowledgeable in amp design, imo, have spoken to the importance of power supplies, and an appeal to authority is necessary in my case because I am a layman. Nevertheless, I will try to set this out as scientifically as I can. I apologize to any technical person, engineer, hobbyist or scientist, who finds this posts rather poor.
I cannot find an article that says A/B tests say that power supplies make a difference. However, I do have several technical articles. I infer from this National Semiconductor
article that in analogy circuits noise can be reduced either at the supply or by making circuits more resistant to noise. This
Tangent Article talks about power supplies with regards to opamp performance:
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Contrast a constant 120 Hz ripple like you get from some wall power supplies: this will add a constant 120 Hz undertone to the music, which is far more audible. |
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Does power quality matter? Certainly. Should you avoid unregulated power supplies for op-amp audio? Yes, unless you add external regulation. Are batteries and linear power supplies the only suitable power sources, then? Well, no. Modern switching power supplies have ultrasonic switching frequencies, and a good switcher will have low ripple as well. True, this is not technically ideal, but in practice this noise doesn't usually affect sound quality for low-gain amplifiers.
As for ripple, you can sometimes get away with constant low frequency ripple if your op-amp has a high PSRR rating at the ripple frequency. But in my opinion, power supply ripple is worth spending time and money to avoid. Induced ripple due to current demands is also worth getting rid of, but it's not nearly as big a concern as noise and constant ripple. |
Yes, the article refers to op-amps not your tube amp. For tube, I gather from this
post applies also to tubes, as it does for all analog electronics. More
posts are useful. From my research it seems that having a low noise supply won't always help, if your circuit has a good PPSR, but it depends on the design of the circuits. That's just one dimension, power supply noise. On a more basic level, that's what an amplifer really is - a device that takes power from batteries or wall wart to to amplify a signal. The power supply, logically, is going to need a good level of performance. Frankly, the wealth of technical information about power supplies and their effects is quite rich, even for a layman, maybe you should do the research yourself rather than going "oh, but maybe it's placebo" "oh I want science!!!!"