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Old 18th June 2014, 11:50 AM   #71
Dinithm is offline Dinithm  Sri Lanka
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option - 1
the best way to solve this,use one power supply circuit.

option - 2
if u whant to use two power supply circuit you should use two trasfomers.
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option - 3
isolation amplifire
I never try this,I cannot say this is 100% working
but you can try if you whant.
Low Phase Noise Design: Isolation Amplifiers
http://www1.futureelectronics.com/do...%20BA3121N.pdf

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Old 18th June 2014, 04:25 PM   #72
kaos is offline kaos  United States
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Maybe Iím rehashing the obvious, but are you absolutely sure you have the transformer wired exactly the same to both power supplies (nothing cross-wired)? If not you could short a winding through the bridges when the grounds are connected together.
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Old 19th June 2014, 08:14 AM   #73
tomchr is offline tomchr  United States
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Quote:
Originally Posted by dhanigan View Post
If I put them on either PS in parallel, hum is gone.
Then do that. I actually suggested this a while back...

If you only have one transformer, the best way to wire it is to have one supply feeding both channels. If you had two transformers (or a transformer with four secondary windings) you could use two supply boards.

~Tom
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Old 19th June 2014, 09:41 PM   #74
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Quote:
Originally Posted by tomchr View Post
Then do that. I actually suggested this a while back...

If you only have one transformer, the best way to wire it is to have one supply feeding both channels. If you had two transformers (or a transformer with four secondary windings) you could use two supply boards.

~Tom
Isn't the benefit of having separate PS to get better channel separation? I could go with 1 PS I suppose.

Allan from Chipamp.com called me yesterday 2 hours after I sent an email and is working with me to troubleshoot. Darn good customer service.

I suppose part of the reason I'm so relentless with this is that I'm still puzzled how WWWJD over at parts-express forum can have the exact same rig and no noise.
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Old 19th June 2014, 10:32 PM   #75
tomchr is offline tomchr  United States
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Quote:
Originally Posted by dhanigan View Post
Isn't the benefit of having separate PS to get better channel separation? I could go with 1 PS I suppose.
The same argument can be said for having separate transformers, separate enclosures, separate mains circuits, etc. How much channel separation do you need? How much are you getting with one supply? How would the performance be if you used all the supply caps in one supply feeding two channels?

Quote:
Originally Posted by dhanigan View Post
I suppose part of the reason I'm so relentless with this is that I'm still puzzled how WWWJD over at parts-express forum can have the exact same rig and no noise.
I see no reason it shouldn't work. My guess about the mismatch between diodes is a bit far fetched. You should be able to make it work with one transformer, two supply boards.

You could also set up a simulation in LTspice with two rectifier bridges, caps, and mismatched current loads. See if that provides any clues to what's going on.

~Tom
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Old 19th June 2014, 11:48 PM   #76
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I find when using a floating mobile phone or mp3 player I need to earth the zero volt line of my amplifier.

The other point I have had problems with is making sure the flow of wires through the rectifier and smoothing is split between the input side and amp side.
If you mix these the charging impulses into the smoothing caps will modulate your zero volt line.
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