Amp6 hum when no music

[whitty]

Hi All

Ive just done my first ever DIY build of the Amp6 and eventually got it up and running, Ive still got to add a volume control and a selector control, but the amp itself is working and sounds amazing.

My problem is that when there is no music playing the amp has a constant hum as soon as the music starts the hum goes, at the moment i've only tested with a phone playing mp3s so Im wondering if the poor grounding from the phone is to blame? I will test with a cd player once i get the time.

The amp is mounted in a metal case, do I need to ground the case and if so where from? There a GND hole on C6 that hasn't been used do I connect a wire from that to the case itself? Or is it to do with the DC wiring?

Also there seems to be some hiss on low level pieces is there a way to eliminate this?

Ive attached a pic if that helps?

Thanks

Andy

 

[nigelwright7557]

I always ground the case for safety.
I then connect the zero volts line to earth on the case.

After that you can get ground loops if you havent used star grounding.

 

[whitty]

Thanks nigel

Sorry for my lack of knowledge but by that do you mean I attach a wire to the DC - and link that to the casing?

then another wire from the GND on the PCB to the above part on the case?

Many thanks

 

[nigelwright7557]

If your amps runs off say 30-0-30 then connect the 0v line to eart. This will help stop hum.

 

[xslavic]

hi
try changing wires,resolder resistors and those caps,try replacing the caps
recalculate the filters -- and then throw it away

 

[whitty]

Problem solved, it was the poor grounding of the phone, tested with other cd players,ipad etc and its working perfectly.😀