Alright, installed in a case! It works! Room EQ Wizard reports 0.05% THD, but it's ugly as hell, and there's a 60 Hz component up to +60 dB, which somehow didn't show up on my listening tests. One of the 6BL7's lights up a lot brighter than the other, but it follows the tube, not the socket. I'm gong to continue experimenting with ripple, try some new caps, and see if I can observe ripple on any of my instruments. I'll also switch my focus to building the case, so I can have something proper to work in to isolate noise and grounding issues.
Attachments
nice cheap case ...
turn volume down all the way then put your ears next to both speakers to see if you can hear anything.
btw, the heater current for series is 1/2 so you're alright at 1.8A for all tubes. the circuit is 2A.
My hum problem was 2 parts: the PT location, then a bad resistor on one channel. Took a while to figure out the resistor. Then dead silent after that., no more hum. I haven't put on the scope yet so I don't what it would show.
turn volume down all the way then put your ears next to both speakers to see if you can hear anything.
btw, the heater current for series is 1/2 so you're alright at 1.8A for all tubes. the circuit is 2A.
My hum problem was 2 parts: the PT location, then a bad resistor on one channel. Took a while to figure out the resistor. Then dead silent after that., no more hum. I haven't put on the scope yet so I don't what it would show.
It was hard. At first I thought ground loop or the input with the pot. then compared every single point on both side to find out 1 voltage lower. The burn resistor dropped to 100R from 300R but still work though.
You can see the light burn in the middle compare with a good one on top
Cool tool to check parts
You can see the light burn in the middle compare with a good one on top
Cool tool to check parts