How to test attenuation balance of autoformer modules

discussion of magnetic volume control design for both line and speaker levels.

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tuyen
Posts: 2
Joined: Fri Aug 26, 2011 1:38 pm

How to test attenuation balance of autoformer modules

Post by tuyen »

I have a pair of the dual mono autoformer modules that have he coarse and fine adjustment. They are fitted in a small alloy enclosure with 1 pair of inputs and outputs. Basically a simple passive volume controller.

I’ve consistently notice with more than 1 amp that the balance of the volume feels a bit off but I want to confirm/test somehow. The right side module seems 1 notch (with the fine adjustment control) louder than the left. The sound is a bit ‘scratchy’ when wriggle the volume knobs too. But perhaps that is normal (and not huge deal as it stops when it’s clicked into position).

My question is if there is a way on how to test for this confirm I don’t have a slightly dud unit?

It’s bugging me because I had plan to install these modules into my valve preamp project but want to get this figured out first.

Kind regards
Tuyen
dave slagle
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Post by dave slagle »

the easiest thing to do is to measure them with a test signal and DVM. The quickest thing to do is to simply reverse the input and output RCA's and see if the balance shifts to the other channel.

dave
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tuyen
Posts: 2
Joined: Fri Aug 26, 2011 1:38 pm

Post by tuyen »

OK did some playing around and it is the pots being dicky. If I use my finger to push the pots on different angles, the volume changes. I will attempt to take the pots apart and clean them with something!
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