Quote:
Originally Posted by pechelman
also have some quiet 120Hz buzz that i've been trying to isolate with the new 3.1 ultra preamp. Can really only detect it in very quiet sections of music or between tracks.
It appears to not be a ground loop, tried a cheater plug and a humx adapter. Have tried 2 different rectifier tubes, but both seem to still produce appx the same amount as the "5Y3GT" Sovtek rectifier he supplied with it. I put that in quotes because as I understand it isnt a real 5Y3 since it is indirectly heated.
I'm 100% certain the buzz is coming from the preamp as when I removed it and kept all the other components in the signal path, all is dead quiet. Any other thoughts where I should look? Possibly the 6BX7 buffer? There's about ~12" between components on my shelves. Will try the tip above at physically moving the preamp a little.
Should I look for some different rectifier types? Since the Sovtek appears to have less voltage drop than a regular 5Y3 I'm guessing I'd be safe to look at other tubes without rebiasing or worrying about filter caps? Like 5AR4/GZ34, 5V4, 5W4, or 5Z4? Or am I just barking up the wrong tree here trying to remove this buzz?
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I do not own the 3.1 but do the 27a and 3a. I can say that neither is dead silent. As I understand, as Dennis revised his preamp circuit beyond the lp-2, the improvements in dynamics and soundstage also came with a hum and that was my experience. As the efficiency gets toward 100db/... this hum starts to become actually bothersome IMO. I had a ~99db/ efficient setup in a bedroom which I ended up abandoning and using the equipment elsewhere. Anyway, Dennis can confirm but, the hum is inherent as I understand it so tube and cap swaps l doubt will have much effect.
I am sure some may see this as a flaw in the design and maybe they are right, but as I have read and listened to interviews with Dennis over the years I can appreciate that he refines by ear and not by test bench readings. That being said his reference speakers are in the low 90s efficiency and therefore the 120hz hum is barely noticeable. I recall he has had a couple khorn owners that have had issues.
As before best to contact the man himself and discuss.