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Want to do the Bass Big Muff volume mod

EvilLandshark

EvilLandshark

Guest
Apr 3, 2013
29
1
36
Kamloops
#1
Hey Tbers. I'm still kind of new to the forums, so sorry if this is in the wrong section or anything.

I recently started getting into effects, and the first one I bought is the EHX Bass Big Muff Pi. I love it, but I came across this thread by Dannybuoy from a few years back about adding a master volume knob to control the volume when blending the signal in dry mode.

http://www.talkbass.com/threads/bass-big-muff-volume-mod.713891/

This seems like something that I would be very interested in, but I have never done anything like it before. I have a little experience with soldering, but not really anything similar to what is described in this process.

What I want to know is:
How easy is this mod for someone at my skill level?
What are the chances that I screw up the pedal beyond repair?
What parts and tools will I need to do this?
And where would I buy these things? (I live in western Canada)

Thanks in advance for taking the time to read this.

-Stu@
 
#2
It makes the pedal MUCH better! It's super easy! (4-6 solder joints). Someone with a little experience can do it in 15 minutes or less... a newbie might take 30 or so. If you are patient it's pretty hard to screw up. I can't remember values, but it's as simple as a pot, a knob, solder, and heat shrink. Newbie tip: don't get a huge pot, and look twice before drilling to be sure of your placement.
 
#3
I'd never soldered anything before I did this and it turned out ok, so it can't be that hard!

Required equipment is in the other thread except the pot value it seems (which I think was a 50K audio taper mini pot):

- A soldering iron (read up on some soldering advice such as choosing the correct bit, tinning your bit as well as the wire ends and pot terminals, and use lead solder if possible, silver solder is difficult to work with!)
- A hacksaw or similar plus a file for cutting the pot shaft down to size.
- I have a 'helping hand' moveable clamp stand, which I found invaluable.
- A drill with the right bits! I needed 7mm and 12mm bits designed for cutting metal. If you're having trouble cutting through, you're probably using bits designed for cutting into wood.
- Heatshrink tubing or insulation tape.
- A craft or Stanley knife for cutting and stripping the ribbon cable.
 
#4
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#5
Wow thanks for the quick replies everyone.

Dannybuoy in the original thread I found that you said 100k audio/log. I don't really know what that means though... Or where to buy them. Haha

Johnk that thread for the mid control is actually how I came across dannybuoys original volume mod thread. I also like the idea of that one, but it seems a little more in depth. I'm going to try the volume one first and depending on how it goes, I might do the mid control after.

I also saw the feedback mod, but I'm not sure what that one does.
 
#7
If I said 100K in the original post then that would be what I used, I looked through it and couldn't find a mention!

I'm from the UK so will wait for others to recommend where you shop! In the US though, I hear Mammoth Electronics and Small Bear mentioned often.

BTW, if you're not comfortable with the mod, there is always the Deluxe version which has a proper blend control so does not need the mod.

There is also a nano version out soon, which I intend to get to replace my regular version (as long as there is room inside for the mods still!).
 
#8
Well it's done. I found a small hobby shop in town that had exactly what I needed.

Almost.

They didn't have a mini 100k pot so I had to remove the battery foam and mount it on the other side. Other than that, it went very well. I ended up unmounting the footswitch so that I had easier access to the ribbon. I tucked the wires underneath when I put it back in place. (it looks a little tidier)

For the mid control mod, can you do it and leave everything in place? Or do you have to get at the other side of the circuit board?

Thanks again for all your help!
 

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#9
How
EvilLandshark said:
Well it's done. I found a small hobby shop in town that had exactly what I needed.

Almost.

They didn't have a mini 100k pot so I had to remove the battery foam and mount it on the other side. Other than that, it went very well. I ended up unmounting the footswitch so that I had easier access to the ribbon. I tucked the wires underneath when I put it back in place. (it looks a little tidier)

For the mid control mod, can you do it and leave everything in place? Or do you have to get at the other side of the circuit board?

Thanks again for all your help!
Click to expand...
how
do you like it? Man I need to do this.... That would make the BBM a game changer for sure...
 
#11
zapped777 said:
How

how
do you like it? Man I need to do this.... That would make the BBM a game changer for sure...
Click to expand...

I love it. It makes it so that in loud settings you can adjust the volume in dry mode (otherwise there is a huge volume drop depending on how you have your settings.)

It was really quite easy once I got down to it. Check the thread mentioned in the first post for a detailed description of what you need to do.

I'm wanting to do the mid control mod now, but the hobby shop is closed until Monday. I'm going around tearing apart old electronics trying to find a .012 uf capacitor Haha.

On that note, is there any way I could substitute a 6 pin audio 20k pot for the 20k linear 3 pin one? It's all I've been able to find (out of a pair of old computer speakers)

EDIT: it was actually out of an old car stereo amp
 
#12
You could use 3 of the pins, but since it's a log taper, the first half of the dial wouldn't do much then the last half would be very sensitive. It'd be ok to use in a pinch but you might want to swap it for one with a linear taper later on.
 
#13
Ya I'm thinking I'll just pick up the proper one on Monday. I couldn't find the capacitor anyways so I'll have to grab one too.

Since I'm still very new at all this, is it possible to use a different capacitor? I'll end up getting the right one anyways, but what exactly does the capacitor do in this circuit? Is it what boosts the mids? If that's the case would a bigger one make more of a boost? What would be too big?
 
#14
If you can't find the correct capacitor, try to get close as possible, it will affect the frequency the mid control. Also you can add them by wiring them in parallel, e.g. for a 12nf you could combine a 10nf plus a 2nf.
 
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#19
That's too bad man, sorry to hear that. Do you remember what kind of capacitor you ordered? I'm a little confused on that part.

In johnk's original post he said that he used a 22n capacitor, but in the posted picture the code on top of the capacitor is 123j100. I'm still very new to all this so I did some research in to it. That is a 12000 picofarad 100v capacitor which is .012 uf
But a 22n capacitor is .022 uf

I really confused myself somewhere here haha. Did I mix something up?
 

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