leave 5K timpot in place , just dial it all the way on other side
meaning of my post was not making "cover it all" solution ( which Mark already gave) but to help you in your situation
if you need lesser displacement of offset setting ( again - for your case only!) , use 470K as parallel cure
meaning of my post was not making "cover it all" solution ( which Mark already gave) but to help you in your situation
if you need lesser displacement of offset setting ( again - for your case only!) , use 470K as parallel cure
If you use some chip quick or equivalent specialty low melt point solder it will make removing the pots much easier.
I almost did this myself and I used someone else's BOM. I think one of the part numbers might of changed with Mouser, luckily I caught it after comparing the Mouser final invoice to the schematic (I labelled the parts on order).
Ok both the channels dialed the offset to 0.8-1mV and pretty stable for more than an hour. Set it aside and rechecked ran on my test speakers no issues. Now with temporary housing in my old preamp cabinet it is singing beautifully on my Frugal Horns 
Thanks all.
Thanks all.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I should have added to my post that the majority of the noise present at the output of the amplifier was 100Hz hum from the power supply, not 50Hz induced hum from the mains toroidal transformer although there was some very small 50Hz component visible on the oscilloscope trace. Yes, I believe the 50Hz component could be reduced by mu-metal shielding over the EDCORE coupling transformers. I did experiment with some steel magnetic shielding strategically placed between the mains transformer and the EDCORE transformers and was able to realise a 2dB improvement at 50Hz. A proper shielding arrangement may very well have achieved better results.
If the amplifier was mine (the test results were taken after a repair / rebuild of a fellow diyAudio's amplifier) I would have seriously considered upping the capacitance in the power supply C-R-C filtering design as IMHO the CMRR of the amplifier leaves something to be desired.
Cheers,
Alan R.
If the amplifier was mine (the test results were taken after a repair / rebuild of a fellow diyAudio's amplifier) I would have seriously considered upping the capacitance in the power supply C-R-C filtering design as IMHO the CMRR of the amplifier leaves something to be desired.
Cheers,
Alan R.
No absolutely no hum at all and this is my 5th power amp build and out of the box with this of chassis and wiring using crocodile clips/jumper wires without any soldering yet. Amazed with this amp being so silent I just used one cable to connect from the psu ground to the chassis ground. All the input RCA and speaker jacks are isolated from the chassis.
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