112A DHT Preamp Part Whackahum 69

Wrong kind of sharks…

I’ve been on the path of hum tracking in this preamp for a while now. I fixed lots of little basic errors I made. The voltages stabilized but so much hum. I’d like to find a 60 sec delay relay for the MV but that is the next path. Chris of course when I started mentioned some changes I should make and I made some of them but I didn’t want to make others because I did not want to add holes to my beautiful front panel express top plate. Was he right? Of course… I had one power transformer powering both Slagle Filament supplies. I just powered only one filament supply instead of two and hum was vanquished. I must admit I don’t understand why. Howeverm If I take this to the extreme does this mean everything would be happier with its own power supply?? I can feel amps getting heavier..

This is the ancient triode we are working with.

Things to do:

I’ve ordered another transformer for the other filament supply.

I’m looking for a delay relay for the mercury vapors. Any suggestions?

I’d like to swap the LED bias to SIC bias. Any suggestions for SIC’s to replace three green LED’s?

Now to finish the front plate design as it is almost ready for the rack.