mudbunny SUSTAIN control volume drop... (edit 1/16/13)

[greysun]

Hey everyone - was playing around on my mudbunny pedal yesterday and the knobs got all our whack from being moved around. Played with the settings and found something (possibly) odd...

when I turn the tone all the way down, I get no volume at all. The volume works properly, as does the sustain and the mids pot mod to R18 (I have the 2012 mudbunny version).

Should the volume drop completely when the tone is all the way down? The pedal screams otherwise, and the volume seems fine when the tone gets to like 30% and higher.

If this is not normal, what could be the culprit?

[DutchMF]

The only thing I can think of after checking the schematic is a faulty pot....... It's not normal at all, mine definitly doesn't do that. I think you should get out the old DMM an measure the resistance between lug 1 and 2 and lug 3 and 2 with the pot in the full CCW position. The first should read 0, the second the value of the pot. If this checks out ok, then something freaky is going on in your Mudbunny.....

Paul

[hammerheadmusicman]

is the pot shorting to ground, either?

George

[DutchMF]

is the pot shorting to ground, either?

George

If that was the case, you would still get signal through the other side of the tone circuit.... I think? This is a really weird problem!

[greysun]

I'll open it up probably this weekend to check it out. I need to take it all out to get the decal process going anyway.

I figured if it were a common thing, no big deal - but my suspicions were right. *sigh* always something...

I love the sound, though - It's a modified Mayo version (used some LEDs and a mix of trannies) - much fuller and richer than the little big muff I was trying to emulate. Hopefully whatever this problem is doesn't hurt the sound.

[DutchMF]

Well, I for one am interested in what trannies and diodes you used, I kicked a Little Big Muff off my board for this one... care to share your mods?

Paul

[hammerheadmusicman]

yeah paul, you're right, i didn't really read the post as well as i'd thought.. it just reminded me of my 91' TS9 which the gain control when i got up to the top of the pots travel the signal cut completely, final got round to opening it up and the top of the pot was shorting to ground, thus dumping the signal!

lesson learned!

G

[greysun]

Well, I for one am interested in what trannies and diodes you used, I kicked a Little Big Muff off my board for this one... care to share your mods?

Paul

This was a post I put in someone else's thread - never did a completed build doc for it, though. I'll get around to it eventually, hehe. Anyway, here's the mods based on the Mayo schematic from madbeans build doc:

Here are the components I changed:

D1 - diffused red 5mm LED
D2 - waterclear red 5mm LED
Q1 through Q3 - 2N5088 transistors (Q4 stays as BC550, which has a reversed pinout, mind you)
C2, C5 and C8 - 560pf caps

The reasoning and building process:

The Mayo was too clean, and I wanted something more like the IC muff (without having gotten an IC muff board) - it had the tone, but not the grit or power - so I swapped parts around like crazy until I got where I wanted. I had it next to a little big muff (the new one, not the one from the 70s) to compare sounds.

I started out by swapping one transistor at a time - the 2N5088's are definitely less bass-y, maybe a little dirtier. But having ALL 5088's was a little too gritty - adding back in 1 550 smoothed it out for sure.

I had swapped out D1 and D2 with diffused LEDs at first, but it got a little too dirty, but when I put the 1n914  back in, it lost too much - so I heard that waterclears are smoother so I stuck one in and it did the trick.

It was still VERY bass-y, though, so I swapped all of the ceramic 470p caps for 560s - worked out GREAT!

If you're building the Mayo spec and want that classic Pumpkins / silversun pickups / IC muff sound, you might want to try those mods - they worked really well for me. It's not exact - it's still a TOUCH more bottom heavy, but nothing that some tone and mids mod EQ-ing wouldn't fix (if you want it exact - get an IC muff board - I got this version of the board so I could mod it for something different).

[greysun]

So I made a slight miscalculation - the tone knob works fine... the SUSTAIN knob is what drops completely. My apologies, I added the mids mod and haven't decal'd any of my enclosures yet.

So yea, it's not the mids or tone pot - it's the sustain pot.

Does anyone else find they have this issue with that pot? I know that my little big muff doesn't do that...

[jeffaroo]

pull the dmm out
maybe even unbox it