martin manning wrote: ↑Mon Aug 21, 2017 1:10 am
Does the hum go away if you turn the pot on the back panel all the way up?
All the way up? As in maxed out? No, the hum doesn't go away. But it's not like that pos is causing it. With that pot all the off, there is no hum. But that makes sense since there would be no signal with it off. Same thing in my other builds.
That should be the same as grounding V2A's grid.
No. With the pot all the way off, it's like grounding the grid. With the pot all the way up, the pot is at 100% and fully on, so to speak.
I don't know what to think about that pot on V2A's grid and the 1n cap from V1B's grid being grounded at the same point and way off the bus... doesn't seem like a good idea.
It's like that in my other builds and there's no hum.
Is there a dropping resistor missing from your schematic? There should be one between the PI plate resistors and the CF anode, I believe.
Nope. Not in this design apparently. Only two droppers in the amp. One on the screen filter cap (between each positive lug) and one between the lugs on the 50+50 cap on the turret board. Screen cap (after dropper), PI node (before plate resistors), first half of 50+50 preamp cap, and CF anode all have the same B+. It's not like a regular 2204 or JTM45 where there are additional droppers. Unless I made a mistake on the schematic. Maybe I put a filter cap in the wrong spot?
Take a look at the layout. Maybe I did the schematic wrong:
http://www.ceriatone.com/ceriatone/wp-c ... t-2015.jpg