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Popping step attenuator volume pot

C

Conn

Member
I recently installed two high quality stepped attenuators. One of them has started popping when I rotate the attenuator. The others are dead quiet when I rotate them. I know that this can be caused by dirt or a weak wiper, but I don't think that's the problem. I think the attenuator is fine. In time, I will probably switch it with its mate to see if the problem follows. In the meantime, I suspect there can be circuit or grounding problems that can cause this. Does anyone have any thoughts on this?
 
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A bit more detail on the circuit topology and the model itself would help. With the info available, I'd suggest there's a coupling cap leaking DC onto the switch. This would account for the noise when switching.

Cheers,

David
 
dshoaf said:
A bit more detail on the circuit topology and the model itself would help. With the info available, I'd suggest there's a coupling cap leaking DC onto the switch. This would account for the noise when switching.

Cheers,

David
Click to expand...

+1:thmbsp:
 
Redboy said:
Perhaps you've got a non-shorting switch in your attenuator.
Click to expand...

A strong possibility. New pots can suffer from dirt as well as old ones. Might not hurt to try some LPS-1 on it if it is just a pot with a gear on the back.
 
To be clearer, what I mean is that maybe your new attenuator is the type which breaks contact from the one position before making contact with the next - a "break before make" switch as opposed to the other type which is "make before break." The popping may be the sound of the "gaps" in between.
 
Agreed, and understood -but there are some "step attunators" that have a cogging gear on the back and it is otherwise just another pot, and that can be just as prone to dirt from storage conditions as new as can an old one. If it is the break before make stepped resistance, the dirt issue is a non factor, if it is supposed to be a make before break stepped resistance, dirt can be an issue.
 
The preamp is a modified MFA Luminescence. There are two single pots that I use for phono. They connect wide open to a stereo pot when I'm using CD or tuner.

I first thought it could be coupling cap leaking DC. That cap is connected to the pot when phono is engaged. However, when phono is bypassed for CD, the pot still pops, so I'm assuming it's not that cap, since it is cut off from the cap by a switch.

I think they're make before break, but I wrote the manufacturer and asked. I don't see any kind of gearing on these things. The other pots, same kind, are silent.
 
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