Is this a high pass filter...

[knockbill]

with the pot out of the ckt? It seems to be a bass blocker... I removed the pot and want retain the treble ckt,, seems that's what its doing with the resistor and .003u cap in series... the .1 is the coupling cap from pre amp tube...
Thanks

 

[gadget73]

Its a variable low pass. If you pull the pot out of the circuit, it technically does work as a high pass, but its down 3db at 1.6 hz, well below the point where it matters. I'm guessing this is a treble control in a guitar amp?

 

[knockbill]

It's a tone pot in a git amp... with the pot out and the R/cap in the ckt, it has the sound i would want... To be honest, I had it wired wrong,,, mistook one end of the pot in the schem for a ground symbol, it was just a big dot... can't imagine why it would have any marking on an unused terminal, but it confused me, for a bit... Old eyes!
Thanks for replying...

 

[gadget73]

yank it then. All its going to do is knock down the highs.

 

[knockbill]

Just remove the pot and leave the R/cap in, to keep the highs?

 

[Retrovert]

A guitarist does not necessarily want those highs, hence the attenuator. When the amplifier is being fed a highly distorted signal from effects boxes (normal practice) the upper harmonics above about 7k Hz can be harsh and often are attenuated. Hence the utility of the variable low-pass filter. It leaves some air, but removes the overpowering levels. Variable attenuation also permits adjustable balance with the other instruments.