Listening to power supply noise...
Apr 29, 2002 at 3:57 AM Thread Starter Post #1 of 14

Joe Bloggs

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Sounds nutty huh?

I was just wondering, with the discussion that went on about switching and linear PSUs, how much noise they actually make...

Since the potentiometer doesn't affect the gain of the amp, would the same amount of PSU noise be heard when the pot is at minimum as at maximum?

I.e. I just turn the pot on my Porta Corda above the off position, and I immediately hear all the noise I will ever hear due to the PSU--any noise above that when I crank the knob up would be due to other noisy electronics inside the amp.

True?

Well I hear just about nothing with the pot on min. and nothing connected to the amp's inputs, with *any* PSU I've used, even the unregulated one--is this an indication that PSU noise is not all that it's cracked up to be?
 
Apr 29, 2002 at 8:11 AM Post #3 of 14

Joe Bloggs

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Gee, thanks A&M
rolleyes.gif


Update: For testing at first I used the Sony EX70, which at 16 ohms and 100dB/mW are pretty sensitive already. Then I decided to break out my old Sony E837SP, which were even more sensitive. I could still hear nary a whisper from the new 15V regulated PSU but when I tried the old unregulated PSU I could hear a loud hum. BUT switching to the EX70 I could again hear *nothing* at all--also, when I touched the connection of the extension cable the hum would go away even on the 837.

confused.gif


Just because I can't hear power supply hum by itself doesn't mean that the quality of the power supply would not affect the soundstage, sound quality, etc. hey?
confused.gif


Or does it?
 
Apr 29, 2002 at 8:48 PM Post #4 of 14

dvw

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I have no experience in in-wall PSU. But with DYI project, I found subsonic ripple does adffect sound even if I can't hear it.

This particular PSU (linear) voltage fluctuates when music is playing. The result is undefined bass and violins sound like saw. The solution was to add more capacitance at the PSU output.

Hum etc are usually caused by ground loop or 60Hz AC coupling. I have my share of that too.

If you can hear PSU noise, you can fix it . If you can't hear it, it might or might not be there.
 
Apr 30, 2002 at 4:48 AM Post #5 of 14

bootman

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IMO the most adverse affect that a subpar PS makes on the music is in dynamics. (running out of gas so to speak)
A supply could be generating noise/hum and this would affect sound but if a supply was that noisy to begin with (very audible) I doubt it would be used for audio applications, or its defective.
 
Apr 30, 2002 at 5:56 AM Post #6 of 14

Joe Bloggs

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So, provided that you don't hear noise from the power supply with no music playing, the only remaining thing you have to worry about is whether it's beefy enough not to suffer voltage sag when your amp is running?
 
Apr 30, 2002 at 5:36 PM Post #7 of 14

dvw

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IMO, yes. Joe, if you are worrying about PSU for your corda. I don't think you got too much to worry. I think the Corda has reasonablly good power filtering (if the schematic is the same as posted on Jan's web site.
 
Apr 30, 2002 at 8:06 PM Post #8 of 14

puppyslugg

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Originally posted by dvw
[
"This particular PSU (linear) voltage fluctuates when music is playing. The result is undefined bass and violins sound like saw. The solution was to add more capacitance at the PSU output."

IMO: More capacitance helps if there is no other option, but not as good as a well regulated psu.
 
Apr 30, 2002 at 9:09 PM Post #9 of 14

dvw

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"IMO: More capacitance helps if there is no other option, but not as good as a well regulated psu."

True; in this case I was using a linear regulator. Current is adequate (so adding a pass transistor is not going to help). The only other good solution will be have a servo sense loop. That's too much work and take up too much space. Putting bigger caps at supply pin of ICs are easier.
 
May 3, 2002 at 10:58 PM Post #10 of 14

bootman

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Quote:

Originally posted by Joe Bloggs
So, provided that you don't hear noise from the power supply with no music playing, the only remaining thing you have to worry about is whether it's beefy enough not to suffer voltage sag when your amp is running?


To put it simply, yes.
smily_headphones1.gif

But there is much more than just that.
You can change a cap value in a PS design and it will change how the amp will sound. It is very possible to build a bullet proof PS that still makes the amp sound like crap.
 
May 4, 2002 at 3:00 AM Post #11 of 14

Joe Bloggs

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Hmm and what cap value might that be?

Also it seems that higher-end amps (and equipment in general) are much more picky about power... even the power upstream of the transformer. True?
 
May 4, 2002 at 1:15 PM Post #12 of 14

bootman

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I'm no audio engineer, but having read many DIY post I can tell you that has been the case. I'll dig one up by that specificly mentions this.


Here is a perfect one.

http://head-fi.com/forums/showthread...er+supply+caps

Now don't ask me why this is the case. I'm still trying to figure it out.
wink.gif

This would be a good question to ask over at the DIY section.
 
May 4, 2002 at 3:39 PM Post #13 of 14

Joe Bloggs

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Cool, thanks for that line.
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Now to find a way to find out what caps my PSUs use... >_<"

"Also it seems that higher-end amps (and equipment in general) are much more picky about power... even the power upstream of the transformer. True?"
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