volume Pot noise

[bernat123]

Hello, I replaced the cheap volume pot in my integrated tube amp with one of the Ebay Stepped attenuators but when change the volume there is an horrible "chak " noise out the speakers, Any idea how to solve this? Is this normal with this kind of attenuators?

 

[BrassTeacher]

It sounds as if they built the attenuator with a break-before-make switch instead of a make-before-break switch. If that is the case, there's really nothing you can do about it other than replace the attenuator.

 

[DF96]

Are there couping caps on both sides of the attenuator? You need to keep DC well away, even the tiny input currents to an opamp or valve grid.

 

[bernat123]

Thanks for reply, Do you know any reasonable priced "noise free" stepped volume pot?

 

[bernat123]

Are there couping caps on both sides of the attenuator? You need to keep DC well away, even the tiny input currents to an opamp or valve grid.

No Caps, is installed with the instruction provided by the seller, maybe this is the problem, if I move the pot fast there is no noise but when slow souns like an electrostatic discharge

 

[DF96]

No Caps

I think you have your answer. You can sometimes get away with omitting caps for a normal volume pot (although still not ideal) as the resistance variation is smooth. For a switched attenuator the variation is stepped so any DC turns into clicks.

One thing to try as a workaround is adding a high value resistor from output to ground. This may help if the problem is caused by the switch being break-before-make - or return it under warranty?

 

[bernat123]

I will try the resistor, thanks for your help
Kind Regards
Bernat

 

[Navyblue]

Actually I believe they are supposed to be make before break switches, but in practice the wiper don't always have good contact. I have a few of those in my builds. It is annoying, but there are workaround:

- If they are new, or they haven't been used in a while, give them A LOT of exercise. You might find that there are some steps that are more problematic than the others, focus on them.

- If they are working well, try not to pull or push the shaft when rotating.

- The pop noise can be reduced by turning the knob very slowly (it becomes more like a scratchy noise than a really loud pop).

It is frustrating at first, but after a while you will be able to learn their temper.

 

[DF96]

Another option is just to use a pot, of whatever price you feel is necessary. What was wrong with the original pot? Have you swapped an imaginary problem for a real one?

 

[bernat123]

Another option is just to use a pot, of whatever price you feel is necessary. What was wrong with the original pot? Have you swapped an imaginary problem for a real one?

this tube amp is a cheap chinese music angel Kt88, some parts are Ok, others like the wiring and pots are crap, Is my hobby and anti-stress therapy, I hard wired all the circuit, i Learned a lot but is a very dangerous work !! thanks God for read before some guidelines about working tube amps, one hand always in my pocket when working probably saved my life, I still have my ear bleeding when my screwdriver made a 450v short !! Now the amp sounds much better than before, there are a lot of parts changed like teflon wiring, capacitors and resistors, the pot is just a small part in the chain. I will attach some pictures of the work later. Thanks for read

 

[DF96]

OK. The Chinese do have a reputation for cutting corners when they think nobody is looking.

 

[bernat123]

OK. The Chinese do have a reputation for cutting corners when they think nobody is looking.

Yes, you are right, the outside is beautiful but inside i noticed they use a lot of old used parts, one of output caps had a big hole leaking the electrolite