Mudbunny Mayo Issues

[greysun]

Hey guys! I finally got around to building out my first of 4 mud bunnies this weekend (well, with sockets, anyway). I also, for good measure, built a testing rig per jkokura's thread at the top of the tech help page. I tested THAT on a slow loris build I had and it worked great.

I got everything on the mudbunny, gave it a once-over to be sure I had the right components (I could probably stand to do this again more thoroughly), then hooked it into the testing rig... AND... WAH WAH...

I got sound - it wasn't like a faint fizzle, but it definitely was NOT the muff sound I have come to love over the years - It was more like what you'd hear if you were under water and a muff was playing poolside. So it had volume, and a LITTLE distortion, but no muff mojo.

When I turned the tone knob, that definitely worked fine - when I turned the volume knob, it also worked - when I turned the sustain knob, it almost acted like a volume and went almost all the way down - weird. All the connections seem okay and there's no bleed over with solder that I can see on the back. I also double checked to ensure that everything was pressed into those sockets well.

I'm posting pics below, but I'm not sure how much help they will be here - if there are better ones needed, just let me know how to take them and I will.

Being a noob, I need to start with the troubleshooting - after doing some searches, it seems as though problems usually start at the transistors - Can anyone help me to know how to test that stuff with my meter? I feel like I've done it before for my slow loris, but can't remember how (embarrassing).

Some technical stuff - 1) I put in a mids pot hooked up to a switch in R18; this I don't think is the issue, as it works. 2) For the 4n cap, I used a 4.7n cap in its place. 3) for the 500pf caps, I used 470pf caps in their place. Those were the only values available to me.









Let me know if you guys notice anything or have any advice for me to get this thing running right. As always, thanks in advance!

[Haberdasher]

have you tried facing your transistors the other way around?  bc550's have the opposite pinout of 2n5088, so depending on what type you used they could be in backwards.

[greysun]

You, my friend, may be right - They're in there according to the outline on the board. I'll reverse them first thing when I get home. Thanks for the quick reply!

Will the ones that are in there now have been blown by having them in backwards, or no?

[Haberdasher]

That's probably it, then.  I remember when I made my mayo the layout showed the 2n5088's orientation, although mine was the earlier etched edition.

Your transistors should be fine.

[greysun]

That did the trick! Worked perfectly!

Compared with my little big muff (which probably compares best with an IC muff), it's a little smoother, not as much bottom or sustain (though it has plenty of both). It also may have a spot of clarity to it... It's not the all out attack that I can get with the LBM, but it's probably perfect for live muff-ness.

With the mids pot, I almost feel like it takes more mids out. Maybe that's what it's supposed to do, but at 100% it had the same sound as just a resistor, and turned down it seemed to scoop them more. Hmmm....

I wonder if I can change out a cap or something to get a little more bottom to it, but I'd have no clue how to work the math out. Anyone have any ideas?

I plan to do a violet rams head next. We'll see how they compare.

[mgwhit]

With the mids pot, I almost feel like it takes more mids out. Maybe that's what it's supposed to do, but at 100% it had the same sound as just a resistor, and turned down it seemed to scoop them more. Hmmm....

I wonder if I can change out a cap or something to get a little more bottom to it, but I'd have no clue how to work the math out. Anyone have any ideas?

Have you tried out the Duncan Tone Stack Calculator? There's a Big Muff tone stack modeler in there.  It's strangely addictive.

[greysun]

Alas, I'm on a Mac. Says it only works with windows.

[greysun]

I'll post pics when I build this out without sockets, but...

I made some modifications - 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. Here are the components I changed:

D1 - diffused red 5mm LED
D2 - waterclear red 5mm LED
Q1 through Q3 - 2N5088 transistors
C2, C5 and C8 - 560pf caps

So 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).

Thought I'd share - I'll share again in my completed build thread in a couple weeks (I'm building a bunch, and it'll be a bit before I house them).