Help replacing a gain pot with a fixed resistor

[chuckmoose]

I am building this Rangemaster:



and I would like to replace the 10K gain pot with a resistor to give me max gain all the time.  I have tried a few things, putting a 10K resistor and then a jumper wire between the connections of pots 1 and 2, but both killed the circuit.  Fortunately nothing blew up and it works fine if I put the pot back in.

I've tried using the search function for the answer, but nothing that comes up is relevant or works for me so far.  Thanks for any suggestions.

[grolschie]

Measure the resistance between lugs 1 and 2, and between 2 and 3, and replace with 2 resistors. Most likely it's a 10k between 2 and 3, and a jumper between 1 and 2. Or vice versa.

[Ice-9]

Measure the resistance between lugs 1 and 2, and between 2 and 3, and replace with 2 resistors. Most likely it's a 10k between 2 and 3, and a jumper between 1 and 2. Or vice versa.

+1 on this. From the layout it looks like the first option (10k between 2 and 3, and a jumper between 1 and 2.)

[petemoore]

and I would like to replace the 10K gain pot with a resistor to give me max gain all the time.
  A 10k collector resistor, output right from the collector, should work exactly the same as a Rangemaster with it's 10k pot maxxed...which would be 10k collector resistor resistance [slightly less because it's a pot?].

[chuckmoose]

and I would like to replace the 10K gain pot with a resistor to give me max gain all the time.
  A 10k collector resistor, output right from the collector, should work exactly the same as a Rangemaster with it's 10k pot maxxed...which would be 10k collector resistor resistance [slightly less because it's a pot?].

I tried a 10K resistor from the output of the collector to the input of the C4 cap.  It didn't work.  Is this what you are suggesting?  Or are you suggesting bypassing the last cap altogether and taking the output straight from the collector after a resistor? 

Thanks for the suggestions everyone.

[Gus]

It look like you want a 10K between 1(collector) and 3(ground) then connect 1 to 2.

  1 and 3 are the outside lugs of the pot and 2 is the wiper

[Ice-9]

Tha way i would do this for maximum output is

1. remove the pot completely
2. place a 10k resistor from the collector to ground (on the vero layout between pot connection 1 and 3
3. place a link (short) across the tracks E and G (this would link the collector to c4 for the output signal)

[WLS]

The 10k resistor wouldn't be correct unless you intend your gain to be wide open. What was mentioned earlier and is the correct way to replace a pot with a perminit setting is:


1. Adjust the pot to where you want it.

2. Measure the resistance in the pot.

3. Use that value for the size resistor to perminitly use.

The place the resistor in place of the pot.


Bill

[MohiZ]

He stated in his opening post that he wanted the gain maxed all the time. +1 for what Ice-9 or Gus suggested.

[newfish]

Why not remove the pot (as suggested above), and put a volume pot (100K or so) on the output - giving maximum Rangemaster goodness and grit at any volume level.

Just a thought...

[chuckmoose]

Thanks for all the suggestions, I will do it this morning and report the results.

My plan is to put a pre-gain volume control in first (I'm debating the logic of this), running into the effect hard wired for max gain, then a mosfet boost stage after that for full output volume control.  I also hope to add an EQ section, selectable input caps, and I'd love to figure out a mod for a second selectable gain stage somewhere along the line as well. 

[slacker]

Why not remove the pot (as suggested above), and put a volume pot (100K or so) on the output -

The original pot is a volume control not a gain control. Removing it and replacing it with a different volume control seems a bit pointless, or a I missing something?

[chuckmoose]

The original pot is a volume control not a gain control. Removing it and replacing it with a different volume control seems a bit pointless, or a I missing something?

Yeah, I've been fuzzy on this point.  I seemed to get some varying results lowering the volume of the pedal vs lowering the volume of my guitar, and I tended to prefer a higher setting on the effect with a lower signal from the guitar.  I thought I might be able to replicate that setup by adjusting the volume before it ever gets into the circuit.  I should look at the circuit again and see exactly what the volume control is doing in there.  I am doing all this on a breadboard, so it's super easy to try and see if really makes any difference.

[slacker]

Yeah putting a volume pot in front of the circuit like you're talking about will give you different sounds. I meant I couldn't see the point of putting a different volume control after the circuit.

[chuckmoose]

Yeah putting a volume pot in front of the circuit like you're talking about will give you different sounds. I meant I couldn't see the point of putting a different volume control after the circuit.

I am really enjoying the effect with a higher value, more full range sounding input cap so that it acts as a low gain OD rather than a clean-ish treble boost.  I would like to make it even more flexible by adding an attenuator after the effect allowing me to use it as an overdrive without the added boost.  I am also going to put the original and new value caps on a switch so that it can also have the classic tone and boost if I want that.

[newfish]

OK.

To my ears it sounds like the higher you crank a Rangemaster, the more 'break-up' you get.

Maybe this is the way my amp responds to the pedal - and if it is, then I stand entirely corrected.

My adding of a second volume pot on a RM was an attempt to control the volume (but not the saturation / breakup) provided by the RM Pedal.

More book reading is required.

[chuckmoose]

And the answer is.... a 10K resistor from collector to ground and a jumper from the collector to the output capacitor.

I put a 100K audio pot as a volume on the output, and was surprised to find it's not overdriving as much as I thought.  My amps were breaking up very quickly with this particular boost, a little bit more quickly than is noticeable with my other boosts.  Maybe it's the frequency range.