Rangemaster Mod Help

[Phil Divine]

I just bought a Rangemaster copy used. Seems like the standard copy, but has a switch for a mid boost, and the regular treble boost. It appears to just have 2 different caps. I assume they are input caps.
Can I just use a pot for this instead? What value would I use?

I have been to the GEOFEX site and it talks about using pots to dial in the voltage and bias. I will likely do that as well, once I figure out which resistors those are on mine. But for now, I'd like to know what value pot would work for dialing in the input cap value. I tried a 50K, but I think that's too much.

[Brad J]

A pot is a variable resistor, you are replacing capacitors.

You could set up a rotary pot with a few different cap values on it, or wire in a blending pot setup.

[Phil Divine]

Uh, good point. I should have mentioned that I am no expert! OK, so instead of the switch in there that connects the 2 caps, can I just have a pot that sweeps between them?

Will using the pot instead of the switch change the tone at all? What value of pot/caps would you recommend to take me from standard treble boost, to full bass boost and anywhere in between?

[fuzzo]

you can do that, yes (I'll make a clone with that range pot)

To be clear, your both cap is placed in parrallele 5n and a big one (2u2 for bass boost). your pot (wired like a variable resistor) allows to pass more or less your signal into the big cap. (two cap in //, their values are added).

At max, your signal goes into the 2u2 in the same time it goes to the 5n. that gives you a 2,205uF (bass boost). In the same way, when you turn down your pot, the signal doesn't go to the big one, only into the 5n, so you've the treble boost.

With that, you can have all range possibilities you want between min and max pot. values.

D*A*M uses that trick to his "red booster". I can draw a schematic if isn't clear (personally I prefere schematic to understand that works)

Salut.

EDIT: for you want, (like I'm gonna do mine) you can use a 5n and 2u2 or maybe 3u3 for bass boost.

[Phil Divine]

Thanks very much. I am not that great with schematics, so you are best to walk me through it.

Right now, there's a simple toggle switch with the small cap on one side, and the the big cap on the other. So I can just move those to either side of a pot, and have the out going to the middle, right? Does the value of the pot matter?

[fuzzo]

Actually, the switch installed on your pedal (2 posistions) selects the little one and big ones. Never both together.

So I can just move those to either side of a pot, and have the out going to the middle, right? Does the value of the pot matter?

Yeah you can do that way too.

Like you discrebed, wirring the input to middle lug and 2 caps on other lugs. Then Both free legs caps connected together, and linked to the input circuit (transistor's base).


I think some old Vox booster pedal used that wirring to have a range pot.

Otherwise, you can use the pot like a variable resistor. So you just need two legs to make that range pot. You wire one of lugs of your pot. to the 5n cap (input side). Wire a 2u2 (or higher) cap to the wipper (middle lug) and connect the free leg of this cap to the other side of 5n cap.


Both methods Give the same result. first methode, you send the signal more or less in one cap whereas in the second method you increase the cap value of input cap.

Try both and keep the one you prefer.

[imguitardan]

Sorry to hijack the thread but I was wondering if any one here knew the values on the Treble and Mid boost switch on the Keeley Java Boost? I played on the other day and it sounded great (didn't care for the full boost). The mid boost was actually my favorite. Which resister is that? Thanks, again sorry to hijack.

[fuzzo]

The keeley switch values are :

10n (top)
6n8 (middle)
47n (bottom)

[TheLemon]

You would want to do something like this:

http://img207.imageshack.us/img207/1456/trebleboosteruw3.png
Use a 100k linear taper pot

[Phil Divine]

Thanks folks. And the value of the pot? Does that matter? Will a 1 meg sound different than a 50K?

[Phil Divine]

One more question for anyone who's still watching. I have 2 caps in there now. One that reads 5N2K and one that reads 4F7. Can anyone tell me what values these are, and if they will get me from treble to full boost?