2. amps-preamps
  3. 170302-99335

120hz hum coming from all-tube system - but only at high volumes

I generally listen to my system at 8-9olcock on the volume dial.  A friend and I were pushing the dial up to 11-12 oclock and a fairly loud 120hz hum would start to appear after a while.

Bringing the dial back down would eliminate it.  You could then pushing it back up and it'd be fine for a bit and then then hum would reappear.

Do I have bad tubes somewhere?  Ground loop that only rears its head occasionally at high volumes?


(System is Manley Steelhead pre, Manley Mahi's mono amps, Forman Elite-15 PFi power conditioner, schiit yggdrasil DAC, Klipsch Forte IV speakers)
otherones
mijostyn's avatar
mijostyn
8,226 posts
 
Both channels?
ddude003
161 posts
 
I could be several things including tubes or ground as you mentioned... Read the FAQ on the Manley web site and/or call Manley tech support... I would also double check if they recommend using a power conditioner with their Preamps and Amps...  It could also be vibration / microphonics...
millercarbon's avatar
millercarbon
12,531 posts
 
If it was there all the time and only became audible at high volume then I would say it is just the way it is, perfectly normal run of the mill noise, and you can track it down if you think it is worth it. But "occasionally" and "fine for a bit" then reappears indicates to me this is heat or power related. Could be a tube, could be something else, but more than likely not right.   

Since you run mono then if it is both then probably not the amps, but more likely the preamp.
audition__audio
1,336 posts
 
First you need to be aware of the difference between a hum and tube/system noise. To me at least the 2 are not easily confused. 

Usually microphonics is a ring or a howl, but to be certain tap around your components to see if the tapping transfers.
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