Low pass effect on volume decrease to increase (206)

[Jtrunzo7743]

Hi guys,

Currently re capping a wurli and a bit new to this. I'm using just some music as a sound source now through the amp and I'm noticing that as the volume is turned up, so does the frequency range of the amp. Almost like it's raising the freq on a low pass filter. Is this normal or should I anticipate this dissapearing as I continue to recap the board?

It's a 1969 revision 206 amp btw

[pianotuner steveo]

I don't know if it is normal, but remember that the frequency range of a Wurltzer is only 55hz to a little over 2k. ( plus overtones) It doesn't need to sound like a 20-20000 hz stereo amp as far as frequency range goes.

[Jenzz]

Hi .-)
This is normal due to the 100nF (Part 18) cap at the power amp Input. With the 3k volume pot, this forms a low pass. I.e., if you turn the volume half way up (1,5k), this forms a low pass at roundabout 1kHz. The more you turn the volume up, the more treble you get....

Jenzz

[DocWurly]

Wow!  Weird fact!

[Jtrunzo7743]

Good to  know thanks!

Is there also some weird effect when you turn the trem up all the way?