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Old 16th October 2012, 07:59 AM   #1
whitty is offline whitty  United Kingdom
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Default Amp6 hum when no music

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
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Old 17th October 2012, 01:26 AM   #2
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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.
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Old 17th October 2012, 07:27 AM   #3
whitty is offline whitty  United Kingdom
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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
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Old 17th October 2012, 09:04 PM   #4
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If your amps runs off say 30-0-30 then connect the 0v line to eart. This will help stop hum.
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Old 17th October 2012, 09:43 PM   #5
xslavic is offline xslavic  Moldova
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hi
try changing wires,resolder resistors and those caps,try replacing the caps
recalculate the filters -- and then throw it away
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Old 20th October 2012, 06:38 AM   #6
whitty is offline whitty  United Kingdom
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Problem solved, it was the poor grounding of the phone, tested with other cd players,ipad etc and its working perfectly.
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