#1
I just traded for a Russian muff pedal and it's good but I think it could be better so I've looked at some schematics and come up with a couple ideas. If you pedal modders could tell me what you think it would help a lot.

1st mod is to add a 9volt jack to the pedal because this one only runs off batteries

2nd mod is to add a 250K pot to load down the signal and help me simulate a dying battery. I was thinking of setting it up as a variable resistor rather than a voltage divider.

3rd mod is to add a switch with either a .001uF cap or a 500pF cap to the sustain/gain pot so that it doesn't get so muddy when the gain is low.

4th mod is to run a switch that jumps over the tonestack. My plan isn't to do a true bypass so the tone stack might still effect the tone but it would be minimal. The purpose of this is to boost midrange and gain.

Here is a schematic of what I have planned. Tell me if you think it'll work and if you have better suggestions feel free. I'm looking for quick and easy.

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#2
would just sticking a resistor in like that really work for the second mod? i was under the impression that you would still need a voltage divider even if you use something variable. i guess loading it like that would cause it to load down and have a lower voltage, but it is hard to know what value pot would have the best effect. if you grounded the other end of the pot then you could swing from ~9V to ~0V for the voltage. thats probably how i would do it anyway.
#3
^A voltage divider would have a MUCH bigger impact, that's for sure, but there are a few boutique guys out there selling boxes that load down power supply with a variable resistor and they claim that it sounds more organic than a voltage divider. I don't know if it's true or not but figured I'd give it a try. I'll probably try it both ways and may try different value pots too. The 250K was just a random guess based mostly on the fact that I have a lot more 250K pots laying around than 500K and 1M. If anybody has experimented with this I'd love to hear their experience with it.
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#4
hmm, thats worth keeping in mind then. if you try it out, be sure to let me know how it goes, youve got my interest piqued. if it sounds good, i may have to throw something like that into my fuzz.
#6
^what I'm worried about with the tonestack bypass is that it isn't a true bypass. Everybody I know that has done this sort of mod has compleatly bypassed it while I want to go the cheap and easy rout and just jump it. I'm not sure how well it's going to work.

I will let you all know how the variable resistor goes and what value I settle on.
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#7
Cord, I don't know what will happen if you merely jumper it.
Here is what I am thinking, and I would love to be corrected if wrong. (Both of you know far more about electronics than I.)
Electricity always takes the path of least resistance to earth. When you jumper a single resistor, obviously the path of jumper + rest of circuit is easier than the path of resistor + rest of circuit. But this is more complicated because the tonestack includes an additional path to earth. I see three possibilities here, (again, correct me if I am wrong):
1) no effect, if the resistance of the tonestack is always less than the rest of the circuit.
2) all of the current would travel through the jumper, until the tone pot was rotated to the breakpoint where the resistance of the tonestack was less than the resistance of the end of the circuit. Past this point, the tone knob would function as normal. Up to the breakpoint, the tone knob would have no effect. (I would expect this if the resistance of the two is close to the same.)
3) all of the current would flow through the jumper, bypassing the tonestack. (if the resistance of the tonestack is always higher than the resistance of the remaining circuit.)
Last edited by cedricsmods at Jul 31, 2009,
#8
^that was my thought too which is why I wanted to do it by simply jumping it.

I went ahead and didn't a couple of these mods today. They still aren't perfect but I'm working in the right direction.

Mod 3, a .001uF cap on the sustain seems to work OK but not great. If you have the sustain low and really listen for the change you can hear that the tone is a bit more open but it's very subtle. Next I think I'm going to up it to .002 and see what that does.

Mod 4, jumping the tonestack, worked but not exactly how I thought it would. The tone knob did have an effect on tone, which I expected, but what ended up happening is if the tone was set lower then half way it sounded great and if it was set higher it would sound very buzzy. Turn it up 3/4 of the way and the volume went away almost completely except for some random spurts of fizzyness that would come and go. What I ended up doing is adding a resistor to the tonestack bypass circuit to stop all the lows and midrange from being filtered off. I'm still playing around trying to find the right value but so far 1.5K seems to be working very well. With the 1.5K resistor the tone knob acts like a tone knob but is very subtle and just lest you filter out a tiny bit of boom or slightly compress the highs. The boosted midrange with slightly compressed treble makes it sound more like a fuzz face than a big muff. It's very cool.

I'm still waiting on a jack so that I can mess around with the power supply so mods 1 and 2 will have to wait but I'm going to keep trying to dial in the other two mods and when I get them just right their will be soundclips.
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#10
^thanks for the link. Pretty basic stuff there but it's always nice to see stuff that confirms what I already think I know

A quick update one what going on. I've connected a temporary lead to a power supply so that I can play the the resistor that will be changing voltage. What I figured out is that this pedal needs it's voltage. Having 10K resistance on the positive completely turns off the pedal. I've done some playing around and found that 6.8K is almost perfect for the dying battery tone so what I'm going to do is add a button to the top of the pedal, rather than a pot, so that I can have it foot switchable. That way I can have the quieter "chunky" tone it gives when it's underpowered for rhythm and when I need the extra cut I can simply step on the switch and it'll boost output, definition, and treble all at once.

For the mods to the sustain pot I've settled on 2 .022uF caps in series which actually gives me .011uF capacitance and then on the same switch I've added a 500pF cap to the volume pot with a 820ohm resistor in series. This gives me a treble boost on the volume and on the sustain and it's a very thick treble boost which I really like. It also means that I only lose the top boost if my sustain and volume are both maxed.

I'll get a new schematic up tomorrow and post pics of the mods inside the pedal as soon as the jack for the power supply comes. Soundclips will come when I can get around to them.
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#11
Something tells me that a pot wouldn't like haveing ground and +V on the same deal there.

But anyway, if you simply jump the tonestack, it'll still load the signal a bit, since it's just like the hardwire bypass in a wah.

However, if you use a dpdt and connect the other pole to where the hardwire is, it'll TB the tonestack.
#12
Quote by Invader Jim
Something tells me that a pot wouldn't like haveing ground and +V on the same deal there.


The boutique guys making the voltage knob stop boxes said they used bother preferred a variable resistor. My own logic tells me that a voltage divider would never be completely removed from the circuit and would therefor always effect tone some. Is that what you were getting at or are you imagining a different problem? Either way I'm going to stick with a single 6.8K resistor because I like the way it sounds... I'm just curious what problems you think might happen.

But anyway, if you simply jump the tonestack, it'll still load the signal a bit, since it's just like the hardwire bypass in a wah.

However, if you use a dpdt and connect the other pole to where the hardwire is, it'll TB the tonestack.


Yeah. In my tinkering over the last couple days I've done a true bypass and a hardwire bypass and I've decided to not go with either one. I'm using a 1.5K resistor in parallel with the tonestack which is giving me a significant mid boost but still routing enough of the signal through the tonestack that it has a notable effect. I think it sounds best this way.

Here is the updated schematic

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Last edited by CorduroyEW at Aug 3, 2009,