Multiple components. Best ground design?

[AndrewT]

Since I am not going to sell

Sorry.
I miss-read that !

Let me withdraw.

 

[Alexontherocks]

and by the way I tested the amp (all channels) and there is not a noise,hum or hiss to be heard.

 

[AndrewT]

What are the test measurements at the various spkr terminals?
mVdc (output offset) & mVac (output noise).

 

[Alexontherocks]

I haven't done any but if at maximum gain and no signal I do not hear hiss, hum or noise with high sensitivity speakers and my ear stuck right to the speaker I am happy and satisfied. I will take measurements as soon as I get my oscilloscope.

 

[AndrewT]

Use the 200.0mVdc and 200.0mVac scales of your DMM

These tests should be done before any speaker or other load is connected to the spkr terminals.

You should also check for changes in output offset, with the inputs shorted, with the inputs open circuit and with the inputs connected to their source equipment.

 

[AKN]

Hi,

One thing to look out for is possible input ground current between channels.
Local decoupling means current in respective amplifier ground. When tying ground together in he other end (source) currents can flow in signal ground. Possible solution to this is separate small signal and power (decoupling) ground.

Test with all signal ground connected together. Does all channels stay completely silent? Test one channel, does the other channels stay silent?

 

[Alexontherocks]

this is what I got after calibrating my soundcard and using an oscilloscope software.

 

[richie00boy]

What is that software you used?

 

[Alexontherocks]

Visual Analyser 2011 (waiting on a usb hatek scope)

I am not sure I set the pc correctly. IT would seem there is sume 50hz main line noise. Are the best amps devoid of such noise even on an oscilloscope?

Is it ground loop hum?

Thanks

 

[richie00boy]

It's probably stray mains pickup, hum in an amp would be 100Hz.