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Old 6th December 2012, 03:39 AM   #61
dazed2 is offline dazed2  Canada
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Have you tried not connecting the ground at the amp board at all?
Seemed to work for me.
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Old 6th December 2012, 08:51 AM   #62
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Have you measured the hum in a scope? Is it the same for both channels? What is its frequency?
I really do not like that mains wire running all the way through the case
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Old 6th December 2012, 09:18 AM   #63
AndrewT is offline AndrewT  Scotland
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Originally Posted by Tube_Dude View Post
Hi Powerflux

A AMP unhappily don't work without a source, so, think for a moment in your first option, the one you say is a better alternative. In the moment you connect a source, the commom ground of the source will shunt both RCAs grounds together, even worst, they do it remotely at the end of interconnect cables, and you end with a nice and BIG ground loop.

We must think in the concept of grounding, in real operation conditions...
Originally Posted by powerflux View Post
you are right
post53: left diagram is wrong.

It sounds OK (no noise) when the two inputs are shorted with shorting plugs.
It sounds OK when one interconnect is sending music or sending silence and the other input is plug shorted.
But when one connects two interconnects with the Source component using a shared signal ground on it's outputs then the system has a loop in the signal grounding. That equals noise. Leach's commoned RCA barrels reduces this noise more consistently than any other method that I can find for a multichannel amplifier. With monoblocks, Leach's fix is not required.

BUT !!!!!!!
Leach did not ADD an extra RCA barrel grounding common link.
He told us to MOVE the grounding link from the PCB to the input barrels. That way he does not create the loop.
regards Andrew T.
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Old 6th December 2012, 11:32 AM   #64
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Originally Posted by Tube_Dude View Post
Have you measured if CL60 is not burned? Try to short it for some tests ...
The CLC is ok, if you short it is the same with this hum.

Pre is turned off with all other pre RCAS removed, and the hum is present.

Simply connect only the F5 and speakers and now I hear a little buzz in toroidal, and hum in speakers.

Hang up and just touch the RCA + with positive in RCA panel, F5 already enters the Hum...

I tried connecting in series a Wima 3.3uf in the + RCA and nothing, a 22K between mass and + but nothing, is even a very high impedance input that has F5...
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Old 6th December 2012, 11:41 AM   #65
AndrewT is offline AndrewT  Scotland
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Not one I have tested (yet). But does it make any difference if the two connected interconnects that create the HUM condition are closely coupled?
Try big separation of the leads and then compare to a pair that are bound together with some sewing thread.

Or even more extreme:
remove the outer insulation from the coax of both interconnect.
Then bind the two so that the coax shields are in electrical contact. Is that an effective ZERO AREA ground LOOP?
regards Andrew T.
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