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 

Could it be the speaker cable?
I think we can help you, by the process of elimination you describe, but your description of each change you make needs to be clearer and more specific.

For instance, what's the difference between swopping the monoblocks and hooking them up to opposing speakers?

In each instance we need to know what is hooked up where, and if there is any noise from either speaker.

For instance, when you hooked right mono to left speaker, did you also hook left mono to right speaker?  Was there noise is either channel?  Which speaker cable did you use?
If you reed the post he did swap monoblock

"swap the mono block - still the same noise"

Ok in order try these they cost nothing.. The way a mechanic would kinda do it..

1. Noisy valve, ay? You have a tube making noise? (Swap valves left to right for a check)

2. The mono blocks aren't on the same plug? Make sure they are plugged into the same rail on the meter. For now the same wall plug, or maintainer will work.

3. Make sure the IC (source to preamp AND preamp to amp) are tight, clean, and plugged all the way in. 

4. Get a cheater plug for the ground. Eliminate the ground with the cheater, ONE amp at a time. Repair the ground loop as needed. add a ground wire between the two amps, chassis to chassis.

You gave a good report, OP a lot better than most..

I'll give it a guess, a noisy valve, or a ground loop issue between the two monoblocks..

Happy hunting.


+1 oldhvymec
My guess is noisy valve only because he said he just noticed it...
@dill I did using a different speaker cable, but still have same problem 
@twoleftears i did swap left mono to right mono speaker , but the noise didn’t move, noise only come out from right channel, im using audioquest rocket88 speaker cable
1 i will try to swap the tube later today 
2 the 2 mono block plug on the separate wall plug before they make noise, i then plug them to the same power strip, still have the noise at right channel 
3 the ic connection is good, it still make noise when I remove all the ic
4 ground loop should not be the problem, if i plug only 1 amp it still make same noise 

thank for the suggestion 

@tomcarr i will try to swap the tube later to see what happens 
If you have swopped over each single component in turn and kept every other variable the same, and the noise never follows to the other channel one particular component, but sometimes goes away in both channels after you've made the change, then it is intermittent and, as already suggested, probably affected (temporarily cured) by the simple act of swopping something over.
Let us know what fixes the problem :)
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....
you already swapped tubes. You swapped the entire amps!
As always, make sure no modems or routers are nearby. 
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.
After swap the power tube the problem still there so i swap the 2 driver tube and still the same
i then looking at the power circuit, find out that its the same circuit which i recently move the wifi router 
Unplugged it then the noise is gone
A very stupid mistake 
thank for helping me out with this

Way to go noromance! I’ve got an Ethernet switch in my system. Though I’ve not noticed any problems, how do I know? It’s always been there. Will a switch potentially cause cause the same problem as described above? 
@mbw Any electronic device can mess up the sound. In this case, it was a wi-fi transmitter which is as bad as it gets! Listen with your switch on and off. Any difference? That's your answer.
Those wifi router really bad
Post removed 
@oldhvymec i think I will looking for a isolated transformer, but not sure yet 
Post removed 
Just for some folks info not sure if it applies in this case.  I had a ground issue once and I solved it by connecting the ground wire of my Rel Speakon connection to the Preamp.  The left and right channels were being driven by the speaker outs on the power amps.  This happened with both two channel amps and mono blocks.

oldhvymec1,304 posts10-30-2020 9:36am

Ya know OP Erik has a "clean side", "dirty side" solution. He might chime in. I’m sure the transformer is an option, but "dirty, clean" power supply is a LOT less expensive..

In my case being VERY careful how I routed cables has always fixed my issues.. I’ve done it a LOT of time through the years for friends too. They are just astonished that cable routing could cure a noise problem AND over all, sound better...

Will try and let see how it’s going