An illustrated guide to building an F5

[AndrewT]

are both the pads GND,
I can't tell by the pic.
Could those two adjacent pads be GND and signal return/ground?

I would expect signal hot and signal return to be adjacent.
Then power ground to be elsewhere.
the pic in post402 & post404 show that the two pads are different, one for power ground and the other (middle pad) for signal ground. The third pad is signal hot.

[AudioSan]

yes. the middle pad is signalground. but signal ground pad and power ground pad is conected together.

[AndrewT]

Ah!
breaks my rule of keeping Sig Gnd separate from Power Gnd.

But with the star ground so close (at the other end of that short wire) the effect is very small. I would still prefer to see sig gnd separate though. That keeps the option to insert a resistor, or to insert a link to maintain the voltage reference from in to out..

[AudioSan]

a resistor between input ground and power ground?

[AndrewT]

Yes just as Leach shows in Lo Tim and other designers use.

[AudioSan]

will a single resistor in series with signal ground do the job? so you separate it before the board?
i have never seen this done on a pass clone board.

[AndrewT]

No, the input socket is connected directly to the +IN and -IN pins of the amplifier.
The NFB if any is also connected to the signal -IN pin

The Power Ground is completely separate.

Then one finally references the signal ground to the power ground at the Main Audio Ground. The signal ground connection to this MAG can have a series resistor since it carries virtually no current (I'm talking pA here).

To allow this to happen the sig gnd must be separate from the amp Power Gnd. Many amplifier layouts maintain this separation.

[AudioSan]

aha. then it will be hard to "modify"
but seperat sig gnd will benefit most in stereo amps with common PSU i quess. in regard to ground loops.
with a dual mono you can break that groundloop with NTC's from gnd to earth.

[AndrewT]

with a true monoblock the resistor may well work best when 0r0.
But all multichannel amplifiers will probably benefit from a resistor >>0r0.

[prooptiki]

The speaker ground together with power ground and before the thermistor is a problem?