Finally! The toroids are too close to PCBs! I tried to move them apart and the hum is little less. So I will arrange the transformers vertical to the front plate. Very funny as BA-3 didnt have any of this problems but it didnt have input transformers...But the best way to do it dual mono is in separate case!!!
It looks like the L of your C-L-C power supply has the the input line running through in between them. This would induce hum into your DC. Mount the L's on top of caps?
Also toroids are mounted on an iron plate same plate as L's and C's. This may also contribute to hum.
I was looking at those chassis in the store and didn't like the ferrous mounting plate. Should be aluminum.
Best to have star ground for each channel as close to last filter cap as possible, like the plate at last cap in your case. Then run wires to CL60, input, output from that point.
Cinco,
yes you probably right! I still have a little hum that has a little different modulation after I moved the toroids away to front plate. I will try to mount the inductors on top. What mounting position do you suggest? The winding side to direction of back plate or to the heatsinks???
Even though toroids transformers have lower electro-magnetic emission, it's not zero, especially for larger VA sizes. So mounting it to a ferrous plate will induce hum into the plate, it's a magnetic metal. So will running the mains next to it. Ask any of the old-timers on the tube amp forums. Back in the day all chassis were iron and were noisy with the power transformer mounted to it.
Ever seen power transformer mounted have in and half out of the chassis on a tube amp? This was to help reduce the problem by putting the chassis in the shadow of the transformer field.
Aluminum or stainless steel eliminate the issue. Besides, take a look at Papa's FirstWatt amps. Power supply and transformer mounted to the aluminum chassis bottom. No iron on the chassis at all.
Winding to the heat sink. Just getting them up off the plate and away from mains will help a lot though.
One other suggestion I have is using copper or brass for your power supply busses, better conductor.
Cheers!
Thx Cinco,
would you then suggest to eliminate any steel from the enclosure? (Except the shielding cans for the input transformers, I guess)
Similar to DIYspaceW my build has two stories:
Groundfloor on a steel plate is transformer, rectifiers, cap bank, softstart, and speaker protection.
Top floor, also built from perforated steel, carries my two proto board PCBs.
I can replace the bottom sheet for Aluminium, but should I also replace the top level?
I had hoped having a steel sheet between toroid and PCBs would act as a magnetic shield.
would you then suggest to eliminate any steel from the enclosure? (Except the shielding cans for the input transformers, I guess)
Similar to DIYspaceW my build has two stories:
Groundfloor on a steel plate is transformer, rectifiers, cap bank, softstart, and speaker protection.
Top floor, also built from perforated steel, carries my two proto board PCBs.
I can replace the bottom sheet for Aluminium, but should I also replace the top level?
I had hoped having a steel sheet between toroid and PCBs would act as a magnetic shield.
The last time I asked Jim 6L6 he said not.
Huh. That makes no sense at all. Its the best one of all.
Russellc
The last time I asked Jim 6L6 he said not.
Hope DiyAudio Store Team change his minds and make M2 boards run
, yes this is most cool diy amp with very affordable price of parts :
transformers and mosfets and big sonic satisfaction i guess.
GREAT
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Need help with a noisy channel. I've built an amp with Grimberg's nice boards. It plays music from both channels.
The right channel is good but I'm getting an intermittent crackle on the left channel. With inputs grounded there is no crackle. I've reflowed joints, replaced wires. No joy so then I replaced all the active components except the transformer. The noise persists. So I'm down to the Edcor tranny.
I've used a bench power supply to do some tests and the crackle is still there so I've ruled out the power transformer interference.
Ideas?
Cheers
Rick
The right channel is good but I'm getting an intermittent crackle on the left channel. With inputs grounded there is no crackle. I've reflowed joints, replaced wires. No joy so then I replaced all the active components except the transformer. The noise persists. So I'm down to the Edcor tranny.
I've used a bench power supply to do some tests and the crackle is still there so I've ruled out the power transformer interference.
Ideas?
Cheers
Rick