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Can someone tell me what wrong

Hi there
i need some held with speaker hissing noise
i recently noticed some noise come from my right speaker 
the speaker is venture audio grand mk3 and driven by vta m125 tube mono block, it’s kind of loud, i can hear it from 4 feet away the speaker with the preamp turn off, it doesn’t effect by the preamp volume 
so here is what i did
Remove the preamp - still the same noise
swap the mono block - still the same noise
swap the speaker cable between left and right - still the same noise
hook up a vintage dynaco st70 - no more noise
hook up the right channel mono block to the left speaker - no noise 
so what could be wrong here?
I didn’t have that noise before 
This thing really drive me nut
Thank in advance 
 

128x128ownut
tomcarr
1,490 posts
 
Let us know what fixes the problem :)
itsjustme
681 posts
 
If every test is as you say, I'm baffled. The ONLY answer is that a) its the amps and b) they both changed at the same time.  And suddenly.
This is very unlikely.
Speakers don't generate hiss.
Passive components don't generate (meaningful) hiss.

You removed the preamp.
You swapped mono amps with no impact (are you sure?)
It is coming up to Halloween and a Full Moon....
itsjustme
681 posts
 
you already swapped tubes. You swapped the entire amps!
noromance's avatar
noromance
9,737 posts
 
As always, make sure no modems or routers are nearby. 
arnoldo
26 posts
 
I had a similar problem with my tube amp.  After giving manufacturer a hard time about it turned out my outlet wasn't grounded and way amp was designed the ground is important.  Wasn't a problem with previous amp because it was vintage and two prong plug.  Ran a ground wire directly to fuse block and solved problem.  Can get one of those $5 outlet testers to check and see what manufacturer says about it.
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