Another B1 buffer PCB design question

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Hi,

I needed a buffer for my initially passive preamp. For some time I looked at the DCB1 by Salas but could not convince myself to burn so much electricity just for the sake of music... which is why I also never looked at any class A amp:) After a bit of research on the forum I finally decided to build a B1 buffer with dual polarity supply using the super regs from diyAudio store.

Recently I sketched a PCB for the buffer (see attached schematic and PCB) which is greatly inspired by the numerous B1 implementations here on the forum. But now I have a question. Could someone advise if I've done the audio and power grounds right? I used ground plane for power and pours for audio ground which meet just between the transistor pairs for each channel. Also if there are any other obvious mistakes I would appreciate any comments and suggestions.

Thanks,
Oleg
 

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Thanks a lot Andrew!

I always follow your "twisted pairs" advice:)
As for the PSU wiring I planned to use individual pairs (or quads if I use the sense wires as well) for pos and neg sides all the way from the super regs. Thus the pos and the neg supplies would only meet at the buffer board. Is there a drawback in such an approach?

Oleg
 
I've recently been looking at my audio setup and "discovered" that if I use stereo buffer, e.g. single PSU for both channels, I would share the grounds between left and right channels. Following the signal from the source, e.g. CD player, it goes via two separate cables using RCA connectors. In principle in most cases inside the CD player left and right channels share the ground, but if I now separate the grounds with two cables and then connect them again inside the pre-amp do I create a large area ground loop between two cables from source to pre-amp? Wouldn't it be safer to run the pre-amp dual mono and never let the signal grounds to connect? Is it really a problem or I should not worry and go stereo?

Regards,
Oleg
 
Yes, a common signal ground in a stereo source component running to a common signal ground in a stereo receiver component does create a ground loop in the stereo interconnects.
The signal ground is also the signal return and as such any interference that creates a voltage along either of these return wires will create an interference voltage at the input/s to the receiver.

The smaller the loop area the less the interference. A figure of 8 dual coaxial interconnect is one way to minimise this loop area. But this still leaves loops where the cables leave and enter the equipment at the ends.

Leach's alternative method of "grounding" at the input RCAs of the power amp seems from my experiments to result in the least interference pickup, but I never found any grounding method that eliminated the effect of this loop. Many other grounding methods (including Leach's grounding at the amp PCB) give much higher interference.

Very many Builders use their ears as measuring instruments and as a result their reports of "my amplifier is completely quiet" carry no scientific weight in my book and I end up having to completely disregard their claims due to a lack of any repeatable evidence.

Dual mono still uses one chassis and ultimately one "ground" and does not help in solving the loop problem. It can, if carefully implemented, help to attenuate the interference, but it does NOT eliminate the loop interference.
 
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Dual mono still uses one chassis and ultimately one "ground" and does not help in solving the loop problem. It can, if carefully implemented, help to attenuate the interference, but it does NOT eliminate the loop interference.
Dual mono does not eliminate the dual interconnect signal return/ground loop. They share the common chassis and ultimately must share a common signal ground. D.Joffe shows us how to attenuate the interference current in the loop.

A Mono Block amplifier where the two receiver inputs do not share the signal return ground is the only unbalanced way I know of that does eliminate this interference loop.
 
My power amp's left and right channels share the same chassis but their grounds connected to the chassis via ground lifts and the chassis is connected to PE. The same I plan to implement for the pre-amp. I understand that it does not eliminate the ground loop but it makes the loop impedance much higher.

Regards,
Oleg
 
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