[Sathimas]

I have a strange problem with my SOHA II.
 
When I turn the amp on there's a relatively quiet hum in the background.
That hum does not change with the volume - it stays constant.
 
Over several minutes ( two or three ...) it becomes louder, then a quiet hiss joins in.
Then this hiss gets louder while the hum becomes quieter.
Both fade out together - then the amp is dead quiet.
 
The amp runs without problems apart from that - sounds wonderful!
 
I hope somebody has a clue...
 
Thx
Sathimas

 

[holland]

pull the tubes out, with the power off, then power it on.  is the noise still there?  it might be from the tube/input stage.  It sounds like a combination of electrical and transistor noise.  Check your solder joints, particularly on the input side, if there is no hiss with the tubes out.

 

[Sathimas]

Thanks for the advice.
 
I just tested it without tubes - there's no noise then.
 
I'll try to reflow the solder joints as next step.

 

[Alcaudon]

Hi Sathimas, did you reflow the solderings? did it solve the problem? I'm asking because I'm having the same issue with my soha.
 
Thanks!!!

 

[Jaivan]

I had this problem with my SOHA II when it was running a pair of 12AU7s, but I recently switched to the 6DJ8s and there is no hiss at start up anymore...
Also as a side note my amp seems to run cooler with the 6DJ8s but has lesser gain than the 12AU7s.
 
Edit: Weird I just rolled my 12AU7s in and it's different from before, I can now max the pot with out going deaf. They now have about the same gain as my 6DJ8s...
Maybe running the amp at 6.3v did something?
 
Edit2: Turns out one of the 12v inputs came loose *doh* everything back to normal now, I didn't think it would work with just one 12v input into it...interesting...

 

[Sathimas]

I did not have the time to resolder the soha yet, hopefully I'll do that this week.