Tube amp problem - loud pop/thump noise!

[Holloway88]

Hi all, recently acquired a used Separo E34i valve amp, been working fine until last few days, everytime I turn on the amp and around 30 secs later, I can hear some sort of static noise and then a loud popping and thump noise coming from one of the speaker! After that, all quiet and amp working fine.

The tubes have been replaced recently by the seller and I have checked all the connection and all seems fine. So what can be the problem? Quite disturbing and worried if I continue using the amp, it might do some damage to the speakers! Your help and commments appreciated. Cheers.

 

[speedysteve1]

Where do you have the volume setting when this happens?
I would always turn it to 0 before powering up or down.
It might not be this of course.

Do you have the preamp / other upstream gear already on? What happens without any other gear turned on?

Try swapping the tubes right / left and see.

Do you have to adjust bias or is it auto?

Is the noise louder than you would normally listen to some heavy music / deep bass.
If it is not then it's probably not going to damage your speakers but I would not enjoy it either...

 

[chris@panteg]

My mate had a similar problem with his 2nd audio's ! Though he described it as a banging and crashing sound , turned out to the caps , but they were 13 years old .

 

[ampman]

I think it might be a faulty tube.

Do you have a spare set? Try progressive rotation and see if the problem goes away. If it does, you will have isolated the problematic tube.

I was using a set of old mullards in a leben cs300x and I had the same thing - small clicks and pops (not loud really) that went away after the first few minutes. I tried the above and discovered it was one of the tubes causing it and nothing wrong with the amp, so I put the original set of tubes in and also some sovteks and no problems at all. I even tried the problem tube in another leben I had and the same thing but less pronounced happened.

May not be this but worth a look.

 

[Holloway88]

Thank you all for your inputs. My setup is quite modest really the amp connected to a Lenco TT via Graham Slee phono stage and also using an old Sony DVD player as a cd player (DVP-S7700) but quite surprised how good it sounds perhaps being a top of the range model in it's days with dual laser for DVD and CD helps! The speakers are the ProAc Ref 8 Signature Tablettes (bought from TonyL).

Anyway I pulled the tubes out one by one and reinserted back in the sockets and the connections are quite stiff had to jiggle them to pull them out and reinserting them though. Switch on amp with volume level at 0 now can hear the static crackling noise coming out from both speakers but no loud pop/thump! Tried 3 times today and all sounding ok no loud thump! Will monitor and see how it goes. The tube amp is my first and bought it to try out really and being an unknown brand and at a decent price offered from fellow PM member selling on behalf of a friend. Now I have caught the valve bug! Really like the warm smooth sound to my ears there is no harshness to the music anymore. Well I will stop rambling on and get on with some listening lol.