Rangemaster clone, will this work?

[Ell]

IT'S ALIVE!
I made my first ever audio probe and realised that I had a cut in the wrong place by the output capacitor. It sounds good. I need to put it in a proper enclosure and finish it up, but all working nicely.
I had to substitute a few pot values.
I have a 20k pot for output, and a 220K pot for filter. Am I missing out on anything by not using the proper values? Does it matter?

[FSFX]

IT'S ALIVE!

I have a 20k pot for output, and a 220K pot for filter. Am I missing out on anything by not using the proper values? Does it matter?

Congratulations for doing the Vero layout and getting it working.

Using a 20k pot for the output will have a couple of consequences but nothing major. It will give a bit lower output impedance, probably closer to the original DRM but as long as it is driving another pedal or amp with a quite high input impedance then it will make little difference. It will also reduce the overall gain a little bit as the collector load value to AC will be that 20k pot in parallel with the 12k collector resistor.  Another effect will be to change the low end cutoff frequency a little as the output coupling capacitor and the pot form a high pass filter.
However most of these as quite small differences which you are unlikely to really notice and, as germanium transistors vary wildly in performance, no two Rangemasters ever sound or perform identically anyway.

Using a different value pot such as you did on the input filter will also affect the frequency response a little bit but probably again unnoticeably. Using the correct taper pot, i.e. and audio taper (A) or reverse audio taper (C) and having it connected the correct way around will affect the smoothness of the control you have with adjusting the input filter.

That all said. Well done building it and I hope you like using it.   

[Ell]

A low Q fixed bandpass hitting a variable high Q bandpass, please try it!

mac

You're right! There are some cool settings in combination with the Nurse Quacky! It opens up the envelope filter to the high strings a lot more.

Congratulations for doing the Vero layout and getting it working.

It will also reduce the overall gain a little bit as the collector load value to AC will be that 20k pot in parallel with the 12k collector resistor. 
Using a different value pot such as you did on the input filter will also affect the frequency response a little bit but probably again unnoticeably. Using the correct taper pot, i.e. and audio taper (A) or reverse audio taper (C) and having it connected the correct way around will affect the smoothness of the control you have with adjusting the input filter.

Hmmm. I'm going to try to find the right pots then. Most of the tone changes from the filter are all within a very small range on the control. Might be nice to have a hair more gain as well. Thank you for all of your help FSFX, this is a more useful pedal thanks to your contributions. This is a nice little secret weapon!


Here is my final layout of this little project. It seems to work for me. If anyone else ever uses this layout and has success or failure please feel free to let me know. The only real changes are for readability, and for the correct wiring of the potentiometers.

[FSFX]

Hmmm. I'm going to try to find the right pots then. Most of the tone changes from the filter are all within a very small range on the control.

The pot and capacitor as a input filter is a bit of a compromise. The circuit actually works better with switched capacitors on the input and that is just what others have done with their Rangemaster builds. The PCB version has 3 values of input capacitor. With a rotary switch, you could have a much wider range of input capacitors.

The image here shows the ideal characteristics of the series tone pot on the input and the resultant frequency response with both a single pickup direct drive to the pedal and the response when driven through a buffer or from an active pickup.