Rangemaster Mods: More boost selections?

[igore42]

Brand new to the forum, a friend told me about "the bean", glad he did!  I've been jonesin' for a Ge treble boost but didn't really want to shell out $180 to $350 when the parts count is less than 10   ? Not only that, I'm a tinkerer and have done some Monte Allums mods to production pedals.  My question is this, the MB rangemaster clone has treble and mid boost but I've noticed other pedals have bass, mid, treble, or the small bear clone (am I allowed to mention that here? ) has a 6 position rotary switch.  How hard would it be to mod the MB RM circuit to have at least bass, mid, and treble, or even more?  How would you know what cap values to use?

Thanks,

Doug

[jkokura]

The Mid and Treble settings on the Madbean project is essentially a switch between two caps, the input cap actually. Go pull up the Madbean project and you'll see what I mean in my next paragraph.

So the signal goes into the input on the left. C1 and C2 both connect to the input. If you follow through to the other side of C1 and C2 you'll see the two pads for the 'T/M' boost selector. So what that does is bring in the second Capacitor in PARALLEL to the first. Remember, when capacitors are PARALLEL to each other the ADD to each other, so if a 5nF and a 10nF capacitor are in parallel, they equal 15nF. Resistors in parallel divide.

Essentially what they're doing is acting in conjunction with the following resistors as a filter. It's like a 'low cut' or 'high pass' filter. As the signal travels through the cap and resistor to ground, you lose something of the original signal. Pedals do that all the time, but they usually find a way to either add it back in, or do it later one where the signal has been boosted and now you need something filtered out. But what's important is the value of that capacitor right? The higher the value, the farther back the 'low cut' happens. SO when you add in the 10nF cap, and raise the filter to 15nF, you add in some more of the mids. Add in a 22nF cap and you'd add in even more 'mids' and perhaps some of the low frequencies. I know there are calculators and simulators that will show you precisely what combination of caps would give you boost at what frequency, but I don't worry to much about that. I just build.

So from that, you can now begin to customize your own Rangemaster. Raising the value of those two caps will bring more mids in. I kinda want to take mine apart and switch the caps, making C1 10nF and adding in 5nF for just a bit more mids, but I usually have my rangemaster in mids mode anyway because of my amps and guitars. I'm sure if I were playing a wooly AC30 it'd be different.

So the long answer is - yes, you can tinker with this thing. I hope this sheds some light on how it all works! Maybe Brian will follow up with some math so you can make some calculations and find just what you're looking for. Links are always fun.

Jacob

[dbharris]

It sounds like what you want is a Germanium Boy type pedal.  To implement a rotary switch you would need a 1P12T (one pole with twelve throws) rotary switch.  C1 would always be in the circuit.  Then you need to decide how many other tonal options you want.  You could have up to 11 capacitors to add in parallel but that is prob overkill.  I would choose 3-5 other values.  

For the mod:
Run a wire from the positive ("In") pad of where C2 is on the board, to the pole of the switch.  The lugs are normally numbered but you can test with a DMM for continuity.  Leave the first position or throw open, nothing is attached and this just leaves C1 acting alone.  Then take the capacitors that you ordered and from the smallest value to largest solder one leg (if polarized, then use the positive leg) to each subsequent throw starting with the second throw on the switch.  Once you have every capacitor attached then solder all the legs of the opposite side together (if any caps are polarized then this is the negative side) and finally connect them to a single wire.  Run this wire to the either the negative pad of C2 or the "M" pad, it shouldn't matter which one.  Lastly, I do not think it is necessary but you could solder a wire from the first throw to where all the caps connect together, just for redundancy.  

If this doesn't make sense to you I can draw a picture.

Now you have position (throw) 1 of switch = C1
                    position 2 = C1 + C2(a)    (a) denotes C2's value that you have placed in throw 2
                    position 3 = C1 + C2(b)     where (b) denotes the value in throw 3 and so on
                    position 4 = C1 + C2(c)  etc.

-Dan

[igore42]

Thanks for the help Jacob and Dan!

[Diamond]

I actually prefer a blend pot in a Rangemaster type circuit, like in the Easy Face schematic: LINK. The input wire goes to the 100k lin pot. Use 4n7 for the treble cap and something like 1uF or even 2.2uF for the bassy cap and you're done! You can now dial in anything from the standard treble boost to a mid boost, full boost and even bass boost.

[bigmufffuzzwizz]

Thanks for that description Dan! I've thought about this many times and its making more sense to me the more i review it. Soon i'm just gonna go for it! But some great suggestions in this thread to give other options to an already great pedal!

[bigmufffuzzwizz]

I actually prefer a blend pot in a Rangemaster type circuit, like in the Easy Face schematic: LINK. The input wire goes to the 100k lin pot.

I'm trying to figure out how you attach this blend knob in here. That schem has the input signal going into lug 2 (of the blend pot) which is connected to lug 1. Out lugs 1 and 3 into the caps and then they all connect again. How would you wire it up?

[Diamond]

Like in the attachment. You can use different values for the caps if you want more/less treble/bass. Works excellently in this circuit!

[attachment deleted by admin]

[bigmufffuzzwizz]

Very useful. The layout makes sense now that i look at your drawing. I'm gonna try different caps and see what i get for those two values.
Between this and the 1P12T switch I have quite a versatile project now.

[igore42]

Thanks for the pot idea, I was wondering if that could be done!

[dbharris]

The blend pot is a really cool idea too, I've never thought of that before.

[phil esposito]

Well hot damn....that blend mod is just what I was looking for!  I do have a couple of questions, when the pot is turned all the way down, will the cap value at input be the 5n or will the 1uf still have an impact?

Also, has anybody changed the output cap value?  Would that be any benefit or is the input caps where the magic takes place?

Thanks!

[phil esposito]

Well I answered my own question....I put a 4n7 and a 470n on the front end.  It bottoms out at about 5n5 which is close enough for me.

Once I'm done I'll report on the sound.

[Diamond]

Also, has anybody changed the output cap value?  Would that be any benefit or is the input caps where the magic takes place?

I tried changing the output cap in combination with the input cap blend pot, but I preferred the original value of 10nF. I tried 22nF, but didn't like it.

[phil esposito]

Also, has anybody changed the output cap value?  Would that be any benefit or is the input caps where the magic takes place?

I tried changing the output cap in combination with the input cap blend pot, but I preferred the original value of 10nF. I tried 22nF, but didn't like it.

Thanks!  I think I'll leave it. I'm going to try a 25K linear pot instead of the 10k audio as well....I've heard it does nice things.