Comments coming thick and fast! Thanks guys 
I've removed the transformer from the case, but that's as far as I have got as I have been quite busy with 'real' work this morning. I will extend the power lines to and from the transformer a little later, enabling me to fire up the amp with the transformer free of the enclosure.
I will report back....
I've removed the transformer from the case, but that's as far as I have got as I have been quite busy with 'real' work this morning. I will extend the power lines to and from the transformer a little later, enabling me to fire up the amp with the transformer free of the enclosure.
I will report back....
Both of the speaker leads connect to the amp pcb as per cvillers diagram.
Brass stand-offs: I wanted to use fibre washers when putting this together but didn't use anything in the end. I don't think the holes are conductive, I may be wrong.
I haven't tried disconnecting one channel. I'll try it tonight
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Could be.
I'll unscrew the screws from the brass stand-offs and place a piece of insulation tape between the board. It will be a good time to try this when disconnect one of the channels.
Thats great news Richard
Now you just have to work out a way to break it!!! The loop that is
Made a little progress on mine too...buzz still there but hum much quieter...i am going on holiday to cornwall though, so wont be able to do anymore until i come back...i hope you get yours sorted soon.
Alon
Now you just have to work out a way to break it!!! The loop that is
Made a little progress on mine too...buzz still there but hum much quieter...i am going on holiday to cornwall though, so wont be able to do anymore until i come back...i hope you get yours sorted soon.
Alon
Thats great news Richard
Now you just have to work out a way to break it!!! The loop that is
Made a little progress on mine too...buzz still there but hum much quieter...i am going on holiday to cornwall though, so wont be able to do anymore until i come back...i hope you get yours sorted soon.
Alon
And I'm going to Devon!
I read your post last night, very encouraging
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Have a great Holiday
Alon
Hmmm
You too
That is really good work what you have done so far.
It doesn't look like you have signal ground attached to earth, (it looks like you have everything floating at 0V).
Not necessarily a bad thing.
Now try connecting your star earth to chassis earth via a thermistor.
I am not sure this will solve the problem, but I suppose you have to eliminate this possibility.
Keep going. You are very close now.
Edit: On having a closer look. It looks like maybe you do have your star earth conected to chassis ground via a thermistor. If that is the case then try floating it (ie temporarily remove the star earth to chassis earth connection).
If you have any other interconnected equipment (eg cd player, dac, preamp) with star earth connected to chassis earth then that might be your problem. Everthing should be floating except for one of the pieces of equipment.
It doesn't look like you have signal ground attached to earth, (it looks like you have everything floating at 0V).
Not necessarily a bad thing.
Now try connecting your star earth to chassis earth via a thermistor.
I am not sure this will solve the problem, but I suppose you have to eliminate this possibility.
Keep going. You are very close now.
Edit: On having a closer look. It looks like maybe you do have your star earth conected to chassis ground via a thermistor. If that is the case then try floating it (ie temporarily remove the star earth to chassis earth connection).
If you have any other interconnected equipment (eg cd player, dac, preamp) with star earth connected to chassis earth then that might be your problem. Everthing should be floating except for one of the pieces of equipment.
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Hi
Thanks...it's a good start.
If it wasn't for the power LED I wouldn't know the amp was on. And that's with my ear pressed against the speaker!
I have a CL60 fitted between the power supply ground and safety earth. I have checked continuity before now.
Tripmaster you have made a very nice antenna pr picking up hum with your input capacitor.
You should also twin the loudspeaker outputwires. Remember taht all amplifiers with negative feedback takes the feedback from the output of the amplifier.
So when you have loudspeaker cables formed as a loop antenna (your picture) it may pick up some noice.
Look at rodeodaves wiring, nice twisted, but could be routed closer to the chassie walls.
Martin P
You should also twin the loudspeaker outputwires. Remember taht all amplifiers with negative feedback takes the feedback from the output of the amplifier.
So when you have loudspeaker cables formed as a loop antenna (your picture) it may pick up some noice.
Look at rodeodaves wiring, nice twisted, but could be routed closer to the chassie walls.
Martin P
Just in case you didn't see my edit.
"Edit: On having a closer look. It looks like maybe you do have your star earth conected to chassis ground via a thermistor. If that is the case then try floating it (ie temporarily remove the star earth to chassis earth connection).
If you have any other interconnected equipment (eg cd player, dac, preamp) with star earth connected to chassis earth then that might be your problem. Everthing should be floating except for one of the pieces of equipment. "
"Edit: On having a closer look. It looks like maybe you do have your star earth conected to chassis ground via a thermistor. If that is the case then try floating it (ie temporarily remove the star earth to chassis earth connection).
If you have any other interconnected equipment (eg cd player, dac, preamp) with star earth connected to chassis earth then that might be your problem. Everthing should be floating except for one of the pieces of equipment. "
Thanks Martin
I have only just added the caps for testing purposes. What is the best method of mounting the input caps?
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I have just disconnected the wires from the PS ground, but it still hums.
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I haven't tried it at the circuit board, however the hum stops if I attached RCA shorting plugs
I can also confirm there isn't a grounding issue associated with the brass stand-offs. I removed the screw and checked for continuity between pcb hole and pcb ground..nothing
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A two channel amplifier must be assembled completely differently from a pair of monoblocks.Hi Andrew
Disconnecting channel: good suggestion!
I disconnected the left channel, and the right is completely silent. The same applied to the right
Hum loop it is
In a monoblock the Main Audio Ground to which all the return routes connect can be almost anywhere. I prefer to keep it close to the centroid of all the modules that connect to it. The Safety Earth connection from Chassis to PE is at the mains cable incomer.
The Main Audio Ground to chassis can be anywhere. It plays no role in the sound reproduction. It is a route capable of passing a few kA for a few us until the fault current blows the fuse.
In a two channel amplifier, the two Main Audio Grounds need a complete re-think. At some point the two channels connect. There is your hum.
I have never been able to make a chassis mounted monoblock quieter than an uncased test layout.
I have never been able to make a steel chassis two channel as quiet as an uncased monoblock.
That's why I spend the money on extra transformers and chassis.
I suspect the Speaker Return going to the PCB may be part of the problem. It works for a monoblock that has one Main Audio Ground. Two Speaker Returns going to two PCBs forces the Main Audio Ground to be compromised.
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