Good morning,
It's cool, last project I revisited after almost 10 years laying in garage 😊
This morning with my coffee I looked at wiring and PCBs from posts 5&6.
Very nice project you have here, I love it. My best Amp is very similar, I posted 2 pictures in introduction post, and works fantastic for over 10 years, no hum or buzz whatsoever, just small buzz from massive transformer (it's there with speakers disconnected too).
I have 2 suggestions :
1. Make star ground chassis post (strong brass bolt anchored in chassis metal) close to input XLR socket. (Ps I would remove rca unbalanced all together as such nice fully differential Amp deserves balanced input). Attach XLR pin 1and shield together directly to that bolt. Many nice neutrik connectors have this connected internally already so no wiring is needed.
Attach mains earth (green yellow) also directly to that bolt. Attach PS ground (zero volt from capacitor bank "clean" side) also directly to that bolt (this last one you can do also via ground loop breaker, but I think in your Amp just short thick wire will be best).
Now, take pin1 ground to your front end board. This is signal ground now.
I don't know if you can completely separate signal ground and power ground at front end pcb? If you can, deliver ground from PS supply to decoupling capacitors, and signal reference ground from XLR pin 1 separately.
Like this you will have complete star ground and no chance for loops. All grounds attached together with chassis at only one place near XLR
2. I see you use mains filter. They are great in removing garbage from mains voltage, but what they do is dump all that garbage into mains earth (which is connected to our "clean" ground. That's why mains earth (green yellow) should be connect to chassis star After the mains filter, and also then only on one spot, one thick wire.
That way garbage cleaned from mains is closer to wall socket earth, and further away from our "clean" ground.
Please note that if you use internal filter, ground must go through it in direct and thick way.
I only use power sockets with integrated filter in a can, with them earth going to chassis is automatically after filter. Alternatively I put mains filter in separate box somewhere on mains cable.
Hope this helps, if it still buzzes after you wired it like this, there is or faulty capacitor or oscillator hidden in the diagram.
It's cool, last project I revisited after almost 10 years laying in garage 😊
This morning with my coffee I looked at wiring and PCBs from posts 5&6.
Very nice project you have here, I love it. My best Amp is very similar, I posted 2 pictures in introduction post, and works fantastic for over 10 years, no hum or buzz whatsoever, just small buzz from massive transformer (it's there with speakers disconnected too).
I have 2 suggestions :
1. Make star ground chassis post (strong brass bolt anchored in chassis metal) close to input XLR socket. (Ps I would remove rca unbalanced all together as such nice fully differential Amp deserves balanced input). Attach XLR pin 1and shield together directly to that bolt. Many nice neutrik connectors have this connected internally already so no wiring is needed.
Attach mains earth (green yellow) also directly to that bolt. Attach PS ground (zero volt from capacitor bank "clean" side) also directly to that bolt (this last one you can do also via ground loop breaker, but I think in your Amp just short thick wire will be best).
Now, take pin1 ground to your front end board. This is signal ground now.
I don't know if you can completely separate signal ground and power ground at front end pcb? If you can, deliver ground from PS supply to decoupling capacitors, and signal reference ground from XLR pin 1 separately.
Like this you will have complete star ground and no chance for loops. All grounds attached together with chassis at only one place near XLR
2. I see you use mains filter. They are great in removing garbage from mains voltage, but what they do is dump all that garbage into mains earth (which is connected to our "clean" ground. That's why mains earth (green yellow) should be connect to chassis star After the mains filter, and also then only on one spot, one thick wire.
That way garbage cleaned from mains is closer to wall socket earth, and further away from our "clean" ground.
Please note that if you use internal filter, ground must go through it in direct and thick way.
I only use power sockets with integrated filter in a can, with them earth going to chassis is automatically after filter. Alternatively I put mains filter in separate box somewhere on mains cable.
Hope this helps, if it still buzzes after you wired it like this, there is or faulty capacitor or oscillator hidden in the diagram.