If you hear a 120 Hz noise with the inputs open, but no noise with the inputs shortened, I'd guess you have some EMI/EMF noise pickup at the input. The noise most likely stems from the PSU / rectifiers. What happenes to the noise (with open inputs) if you switch the amp off? Does it stop immediately, or only after the PSU caps are discharged (which will take a second or two)?
It stops immediately. At this point I can here the buzz moving around within a small range depending on what I turn on in the system and where specifically it's plugged in. I have a power strip—but there's a TV and a Mac mini plugged into the same outlet—I'm not sure I'll be able to separate all of it fully. What if the amp was the highest thing in the cabinet with all other small devices below? Would the steel plate that's the base of the amp offer any protection? The cabinet itself is 1950s steel—there's a lot of factors. I might have to live with a buzz for now.
...Until I can make a dedicated listening room.
That is an excellent question. No, lid is on in fact—I don't want anyone accidentally doing anything since it's now in a common space... and not on my bench. I've been reading all the Bonsai stuff with system setup and making the ground loops as small as possible... I think the solution is within. Unless everyone thinks I can negate what is possibly system setup noise coming through the amp by modifying the amp itself... I might consider the amp dead quiet, since it WAS, plugged in to a different outlet, but with the amp in the exact same location...
I left the F5 plugged in where it was in the system (not the separate test outlet) and instead of the B1K inserted a passive (non-powered) volume control with 2 inputs. Powered up... Dead quiet with everything connected. So perhaps I could improve the B1K somehow... or the amp, if the combo has some noise...?
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Then the noise source is the transformer/rectifiers.
Do you have snubbers on the rectifiers to reduce EMI/EMF?
Also, since a different wall outlet seems to reduce the problem, is it possible you have some DC on the mains? This would stress the transformer, and might cause EMI/EMF issues.
Input snubbers yes, output snubbers no.
What do your mean DC on the mains? There’s: TV, Mac mini, Hard drive, DAC, 2 separate Turntables with motor controllers and preamps each, F5, B1K... though not all of that powered at once. Pretty sure I should at least separate the TV and computer/HD to a separate house circuit... which I can’t do without running one, which I could do.
When it’s plugged in to the same place all of that above is... with a passive preamp, the F5 is stone cold silent, now add playing content from a source like itunes and there’s definite background noise. Exchange the passive pre for the B1k, I get a buzz in left channel only. Take out pre all together and power up F5 I get buzz in both channels (and i mean it’s not loud). plug F5 in to an adjacent outlet that i know is a separate circuit we are back to silent F5 and it doesn’t matter what i attach to it...
There’s definitely some stuff to sort out. But not sure it’s F5 related.
THANKS ZM! for your diagnosis. I like it.
I found Rod Elliot rather easy to understand, you can find his writings on the matter in Mains DC and Transformers.
Hmm, crossposting with mbrennwa.
What happens when you swap the left and right RCA cables between F5 and B1K ? Does the buzz stay in the left channel, or does it move to the right ?
This would help determining if there is a higher sensitivity to buzzing in the left channel of the F5, or if it is in fact coming from the B1K ...
Best regards, Claas
This is all getting a little nuts, thank you though. Ha! Buzz is in RIGHT channel—I might have said left before.
—Cables either way, buzz is still on right.
So that's something related to the grounding/wiring schema compatibility between the F5 and B1K? F5 is dead quiet with cheap passive pre inline.
This is a whole new amp with the new internal layout—It's also raised the bar of all the other components involved. Kinda knew that might happen. For instance. I get some very weird clipping/fuzz from the turntable? with the passive (cheap) preamp, but that goes away if I put in the B1K instead, even though I get a slight buzz on the right...which I can't pick out at regular listening volumes. Music VERY clear though—Getz/Gilberto in this case. Hair raising—and not even loud.
Then the noise pickup might be from loop formed by the two GND connections which are joined at the B1K end. Did I mention hum breaking resistors?
Yes, you or someone did. I've looked into it far enough to realize that it's a bit stretching my understanding at the moment and where they go means very specific board modifications—and I'm not yet convinced of the solution—though everyone up here knows a lot more than I do—so it's all just instincts on my part.
If the amp itself needed sorting wouldn't the buzz be there regardless of preamp? Or be present with just the F5? That buzz changes when I mess around with the power cables of the F5 and B1K.... So ground loop is correct I think...But I think I need to look at the whole system and all the components and clean it all up—possibly to include running a separate house cable for the TV and computer/AV server. I wouldn't want to add a "fix" to the F5 that really is a problem that should be resolved elsewhere.
Per Jeff, I will try undoing my input ground connection inside the F5, just to see.
All said, properly recorded vinyl is sound just unreal—even with a little buzz on the right.
I have proven to myself that my instincts about upping my amp game was worth it sonically.
Your amp is fine, as Zen Mod wrote. However, if the system consisting of the GND wires, the preamp and the F5 form a loop that picks up noise, you might be able to improve the noise with hum breaking resistors.
