2. amps-preamps
  3. 134032-70

Rectifier Hum

I have a Dennis Had Inspire Fire Bottle SEP HO amp that supposedly will work with just about any rectifier. I was using a new Gold Lion GZ34/U77 for a while and recently noticed a low hum from my subs. Took everything apart, checked cables, etc., and finally got to the tubes and discovered that swapping out the GZ34 with a Shuguang 274B fixed the issue. Assuming the GL had gone bad, I bought another GZ34, a JJ this time, stuck it in and there's the hum again. I also tried the originally supplied JJ 5Y3S and it hums also, but less than the Gold Lion or the new GZ34…why? I don't want to send the amp back to Dennis as it does work fine with the 274b, but it's on my mind so I seek counsel. Help me…help me…Atmasphere? 

wolf_garcia

Showing 7 responses by wolf_garcia

wolf_garcia OP
6,628 posts
 
I did and haven't heard anything yet.
wolf_garcia OP
6,628 posts
 
I'd be surprised if it has a solid state device anywhere, but that's interesting!…and the issue is a new one for this amp so it remains a mystery...I did send off for another 274b to have as a backup. 
wolf_garcia OP
6,628 posts
 
The most mystifying thing is the fact that the 274b tube is dead quiet (no low hum) relative to the other tubes mentioned. But I soldier on…I'll report whatever Had says when and if he responds.
wolf_garcia OP
6,628 posts
 
By the way, this is a new issue as previously with any of the rectifiers mentioned the amp was utterly quiet with zero pesky extra low bass noise. So something wearing out makes sense, and note the 274b remains utterly silent…the plot thickens!
wolf_garcia OP
6,628 posts
 
When the amp showed up with the JJ 5Y3S (10 months or so ago) I thought it was surprisingly quiet, and I had tested the subsonic noise by simply touching one of my sub's driver cones…then more recently I noticed the audible low noise and sure enough, the sub drivers had a vibe goin' on. That may have been coming on gradually…not sure to what degree as I hadn't notice it recently until it became audible. 
wolf_garcia OP
6,628 posts
 
The hum is very low, inaudible mostly but I can feel it when I touch the sub driver…with its permission of course.
wolf_garcia OP
6,628 posts
 
I forgot to follow up with the solution...the two subs had opposite grounding (one was lifted one not). Lifted the ground on the other sub and hum is now gone.
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