Hi 

Hoping you can help me as I am currently trying to do the same project. 

I have managed to get sound out of the speakers but and getting hum at the same time.

I've used 5V on pin1 of P57 of the amp in order to get it to unmute however the hum is driving me crazy as I cannot figure out what is causing it.

did you have hum issues with your project? how did you solve it?

Many thanks in advance.

John

Hi 

Hoping you can help me as I am currently trying to do the same project. 

I have managed to get sound out of the speakers but and getting hum at the same time.

I've used 5V on pin1 of P57 of the amp in order to get it to unmute however the hum is driving me crazy as I cannot figure out what is causing it.

did you have hum issues with your project? how did you solve it?

Many thanks in advance.

John

hi John, I connected P57-1 to P77-3 (9V) to there, it works great. but the hum may be from the grounding...

https://www.dropbox.com/s/i3sui881uuqvmyy/IMG_9059.JPG?dl=0

Frankie

Many thanks for the info Frankie, I did not think of using the 9v output from P77 and ended up building a 5v regulated feed from the +20v line to trigger the mute off.

I doubt that the 5v PSU could be causing the hum but I might bypass the PSU and use the 9V source you've suggested as I've checked for grounding or interference problems with no improvements. 

Do you if its best to run the ground cable separately from the +20V and -20 from the power supply as I currently have all 3 on a 80cm cable loom.

Any ideas greatly appreciated

Regards,

John

Hello, I was able to get this system to work with an asymmetric power supply 0/20 volts. What limitations will there be if the tension is asymmetrical? Is it just performance limited?

Best regards

Hi Frankie,

I am still struggling to understand where the hum/buzz is coming from however today I accidentally left the power supply Ov reference disconnected and noticed that the amp worked fine but the buzz was completely gone. I am unsure how this is working as I would have thought that a ground reference is required to turn the amp on. It worries me that I might be causing damage with only the -20v and +20v supply's but no ground ref.

any ideas  from the forum are more than appreciated as this is driving me bonkers.

many thanks John.