# Question about pot taper.



## keeperofthegood (Apr 30, 2008)

What are or should be the tapers of the three pots used in this circuit?


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## WCGill (Mar 27, 2009)

Very similar to the Brown Fender tonestack, 250kA for the bass and B for the treble. Volume will be A. Of course you can try any taper anywhere and see if it suits your purpose.


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## keeperofthegood (Apr 30, 2008)

AH thank you 

I am trying out a "reworking" of this. Yes, used in Fender and in VOX and a couple others out there.

This is my version I hope to wire up and fire up soon:


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## keeperofthegood (Apr 30, 2008)

OH AND


Is there anything to change if I used a 12AU7 instead of a 12AX7? Any resistor values in any particular direction? I am going to actually be using a 6BQ7 dual triode which is more similar to a 12AU7 than a 12AX7. I just have 30 or so 6BQ7's and exactly 0 12AX7's on hand >_>


The Fender Versions:










Same tube, double the voltage, and lower resistors?

I have 1K5 3watt resistors on hand, and I have some 100K 1/2 watt on their way this week. I don't have 0.05uf caps, but I do have an abundance of 0.022uf and 0.015uf caps (enough 0.022uf's that I can parallel a couple easily), will these do ok or will they block too much of the low end?


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## WCGill (Mar 27, 2009)

Well, you'd probably want 47k for Ra and between 900R and 1.5k for Rk, but it may not have enough gain and the tone might not be great either. But how will you know if you don't try? As far as caps go, I rarely use anything bigger than .022. With a 25/25 cathode bypass cap, you'll have ample bass.


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## keeperofthegood (Apr 30, 2008)

Worst comes to worst, I could run the triodes in parallel and use two tubes :/

I have some 56K on their way, and some 68K's and some 470R's so should have enough values I hope. If there isn't enough gain with this triode driving a tone stack, maybe there would be for a delay line or clipper stage like this, without the tone components, just the diodes in place:


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## Jean GODBOUT (Oct 31, 2009)

Hello

This last schematic look interesting, where does it go ? Do you have a complete schematic (or layout) of the toy you are building ?

Jean


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## keeperofthegood (Apr 30, 2008)

Jean, it is an interesting one eh. I have followed this idea for a bit, this thread did the best exploration of the idea AX84.com - The Cooperative Tube Guitar Amp Project which is where I got that last image. I have some 30AG11's that I will try this with (same as the mentioned 6AG11 just heater differences). 

What confuses me in how this schematic is drawn up, typically the 1meg goes from grid to ground, and the switch puts either the diodes or the 50K to ground, I would have thought them to be reversed and the diodes to parallel the grid resistor or not. MEH I will build it and see


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## keeperofthegood (Apr 30, 2008)

Just an update, got the main part wired up, just need the pots and an assortment of resistors now.


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