The amazingly versatile Mofeta board

[TucsonSean]

After building my first Mofeta board and playing around with it and letting my bass player use it (and ultimately keep it), I decided to make a second one. I made provisions for a few tweaks but ended up using the stock components for that build as well. I have really enjoyed the different sounds that I can get from that pedal that are not the typical "Marshally/Fendery" type sounds. Still, I wanted to see how much further I could take it. I wanted MORE!

So I kept thinking about the schematic of the Mofeta board and realized that a 1987 Plexi has a simliar architecture. So I present to you all, the little board that could...

Sound like a Marshall 1987 Plexi

I have taken the Mofeta parts list and changed a few components (14) and added two new components (cap and a switch) and I have what I believe is a very convincing Plexi in a box pedal. Here are my changes:



With these changes, the Mofeta sounds incredibly close (to my ears) to a Marshall 1987 Plexi. I first installed the bright cap to the brite pot and found at lower levels (12 o'clock and under), the treble dominated the sound so I put the bright cap on a switch (gut shot pic3 shows its placement below the DC jack) . Now it is much more usable and I can switch it in/out whenever I want.

Since I have built this pedal and am very pleased with its amp-like performance. I believe it offers a very convincing Plexi sound and feel at all different drive levels. With this success, I have decided to see what other amps I can simulate with this board. I will be posting my next modded Mofeta board as soon as I get a change to build it.

Also, I will be posting sound samples as soon as I get access to my recording setup (hopefully before this coming weekend).

Let me know if you try this mod. I would like to know if I am truly hearing what I think I am or if I'm getting crazy in my old age.

-Sean

 

[enrosenzweig]

Very cool!

A while back, I was wondering if something like this was possible, but making a Laney Superlead instead. There seemed to be a decent amount of overlap between the Mofeta and the jfet versions of the Laney, but I’m certainly not brave enough to try!

 

[owlexifry]

With these changes, the Mofeta sounds incredibly close (to my ears) to a Marshall 1987 Plexi.

got evidence?
(this is a request for a demo )

 

[TucsonSean]

Evidence

Settings:
Everything on 10 except Volume (output level)

- Recorded directly into Reaper using a UAD Volt 276 and Line 6 Helix Native software for speaker emulation, no eq or effects
- Speaker emulation used on -01: Dual 4x12 1960A, stock settings (mic: 57, Position: Cap Edge, Distance: 1", no low or hi cut)
- Guitar: ESP LTD EC1000 Deluxe with EMG 57TW/66TW (humbucker/singlecoil mode set to humbucker mode), vol and tone set to max
- Pedal: All on 10 except Volume (output level) = 4, brite cap switch=on

I'll get some more clips recorded with different pedal and guitar volume settings.

-Sean

 

[owlexifry]

Evidence

Settings:
Everything on 10 except Volume (output level)

- Recorded directly into Reaper using a UAD Volt 276 and Line 6 Helix Native software for speaker emulation, no eq or effects
- Speaker emulation used on -01: Dual 4x12 1960A, stock settings (mic: 57, Position: Cap Edge, Distance: 1", no low or hi cut)
- Guitar: ESP LTD EC1000 Deluxe with EMG 57TW/66TW (humbucker/singlecoil mode set to humbucker mode), vol and tone set to max
- Pedal: All on 10 except Volume (output level) = 4, brite cap switch=on

I'll get some more clips recorded with different pedal and guitar volume settings.

-Sean

ayyy that’s the spirit! nice work.

sounds great.
i reckon if you back off on the bass knob just a bit that’d be just about bang on

keen to hear what it’d sound like with a TS in front to boost the mids some more

 

[TucsonSean]

TS5 (only TS that I have on hand) into the Plexfeta(TM). Switched to Greenback 25 speaker emulation.

Everything on 10 except Volume (output level)
- Recorded directly into Reaper using a UAD Volt 276 and Line 6 Helix Native software for speaker emulation, no eq or effects
- Speaker emulation used on -01: Dual 4x12 Greenback 25, stock settings (mic: 57, Position: Cap Edge, Distance: 1", no low or hi cut)
- Guitar: ESP LTD EC1000 Deluxe with EMG 57TW/66TW (humbucker/singlecoil mode set to humbucker mode), vol and tone set to max
- Plexfeta: All on 10 except Volume (output level) = 4, brite cap switch=on

TS5 settings:
Level = Max
Tone = 12:30
Drive = 9 o'clock

I start off the clip without the TS5 then kick it on about 1.4 seconds into the clip. Hopefully you can hear the difference it makes.

-Sean

 

[TucsonSean]

Here's a favorite setting on the Plexfeta that I think shows a good dynamic capability from fairly dirty to clean.

- Recorded directly into Reaper using a UAD Volt 276 and Line 6 Helix Native software for speaker emulation, no eq or effects
- Speaker emulation used on -01: Dual 4x12 Greenback 25, stock settings (mic: 57, Position: Cap Edge, Distance: 1", no low or hi cut)
- Guitar: ESP LTD EC1000 Deluxe with EMG 57TW/66TW
- Plexfeta:
Brite = 1 o'clock:
Norm = 11 o'clock
Volume = 11 o'clock
brite cap switch=on
Bass = 5 o'clock
Mid = 4 o'clock
Treble = almost 3 o'clock

Clip starts out with bridge pickup (humbucker mode) full volume then rolled back to half then switching to the neck pickup (single coil mode) full volume then rolled back to half.

This has become my main pedal setting when playing as I can get a nice drive sound then switch to a clean sound just by switching pickups.

-Sean

 

[TucsonSean]

TS5 into the Plexfeta(TM). Switched back to 1960A speaker emulation.

Everything on 10 (max) except Volume (output level)
- Recorded directly into Reaper using a UAD Volt 276 and Line 6 Helix Native software for speaker emulation, no eq or effects
- Speaker emulation used on -01: Dual 4x12 1960A, stock settings (mic: 57, Position: Cap Edge, Distance: 1", no low or hi cut)
- Guitar: ESP LTD EC1000 Deluxe with EMG 57TW/66TW (humbucker/singlecoil mode set to humbucker mode), vol and tone set to max
- Plexfeta: All on max except Volume (output level) = 11 o'clock, brite cap switch=on

TS5 settings:
Level = Max
Tone = 12:30
Drive = 9 o'clock

I start off the clip without the TS5 then kick it on about 4 seconds into the clip.

-Sean

 

[tegendemuur]

I made provisions for a few tweaks but ended up using the stock components for that build as well. I have really enjoyed the different sounds that I can get from that pedal that are not the typical "Marshally/Fendery" type sounds.

You mean the components market with the *, or did you figure out more tweaks that weren't mentioned here? Besides the C8 mod to clear up some mud, your post is the only one mentioning tweaks.

 

[TucsonSean]

Hi tegendemuur,

My typical tweaks involve putting in sockets for various components so I can swap out different components. Any build that i do that has a transistor (BJT, JFET, etc...) I almost always put in a socket so I can change it out easily for a different one or replace if needed. I do the same for the ICs in my builds.

For the Mofeta I built in the same enclosure with the Kliche, the only mods that I made were mainly to the Kliche (ChuckD bass mods) since this was used primarily for a bass guitar. The Mofeta only got transistor sockets. Also since this was a bass pedal, I did not mess with C8 as it sounded fine the way it was.

For what its worth, I have read that some of those who did the C8 mod did not hear any difference to the sound. I think the biggest difference to the sound that I made when I was tweaking to get the Mofeta to sound like a Plexi was changing C11 to a lower value. If anyone wants to brighten up the Mofeta, this is the cap that I would change. Maybe I will go back and change C8 now that I have lowered C11 and see if that makes a difffence. Maybe I save that for my super secret build, the Mofeta Special, built with all sockets to try out various components and even difffent architectures.

-Sean

 

[jesuscrisp]

Since the Model T, Bassman and Supergroup (plus some others) are basically the same preamp with some minor changes, it would be easy enough to adapt the Mofeta in those directions.

Sexond to last clip sounds cool, the high gain clips sound like a Line 6 POD to me though.

 

[Feral Feline]

@TucsonSean,

Hope you and @Robert don't mind, but I took the liberty of adding your tweaks to the schematic (and I changed the "f" in Plexfeta to uppercase because it looked better):





I also grouped some of the mods together to be able to switch sections' values around... 3 Toggles was the goal, but that would leave some components still off a switch, though ALL doable if going with a rotary switch.
For instance, I'd just leave C12 @ 470p all the time, which would save from having to go to a rotary and just stick with a 4PDT for the MO/PLEXI switch.
The CHARACTER toggle could be an on-off-on and include another value for each component position (more BASS!), but you mentioned that you liked the Mofeta as is for bass, so it might be better to just have that toggle on-on like the other two.

All the toggles up = PLEXFETA
All toggles down = MOSFETA

C1000 : Making the BRIGHT pot a push-pull switch would be a way to go, saves having yet another toggle...

BRIGHT — NORMAL — VOL
BASS — MID — TREBLE
MO/PLEX — CHARACTER — SIZZLE

 

[TucsonSean]

Awesome Job Feral Feline!

One other bit of information, I ended up changing C8 to see what the effect would be and with it and the C11 change, it may have that top-end sizzle that you want, in excess. I don't know if you need to make any of the changes in the diff-pair/output stage of the circuit to enact the sizzle with those two cap changes, though you may like it.

My latest idea for this board, and I have one patiently waiting, is to essentially install sockets for everything so I could tweak to my hearts content and see what other sounds I could coax from this board. My thoughts were Laney Supergroup (simple mods to the Mofeta), blackface Fender (yes, i am crazy like that), JCM800 (should be doable with this board), and a tweed Bassman/JTM45, and HiWattt DR103. I believe that all of these are possible with this board. My only problem is time and work. I have a major project on the table, both for actual work and my fun-time, which is my own pcb design on an amp i used to own.

-Sean

 

[Feral Feline]

I’ve fully socketed a couple of muff boards, and a Dist+/250 … it’s totally the way to go if you’re planning extensive tweaks/revisions.

Now if only I had the golden ears to hear any differences.

 

[fontoponto]

Any recommendations in regards of two switches to do some fancy tweaking? I drilled an enclosure for six pots and two switches. Now I need tweak ideas for the Mofeta.
Edit: I have small pcbs for a phat F* boost and a black eye boost. Maybe one of them switchable and the boost pot into the second hole. Or and a switchable C11.
Edit again: the sizzle alone seems to be interesting but I think a 3pdt won‘t fit.

 

[fontoponto]

@TucsonSean,
I also grouped some of the mods together to be able to switch sections' values around... 3 Toggles was the goal, but that would leave some components still off a switch, though ALL doable if going with a rotary switch.

What if you use transistors for switching? Add a switching pcb and do it Tech21 style with 12 transistors (without the bias trimmers), 12 Diods, 12 Resistors, 12 caps, a CD4013 + a few other parts.
It would be easier to add another Mofeta pcb but it wouldn't be awesome

 

[tegendemuur]

Any recommendations in regards of two switches to do some fancy tweaking? I drilled an enclosure for six pots and two switches. Now I need tweak ideas for the Mofeta.
Edit: I have small pcbs for a phat F* boost and a black eye boost. Maybe one of them switchable and the boost pot into the second hole. Or and a switchable C11.
Edit again: the sizzle alone seems to be interesting but I think a 3pdt won‘t fit.

I decided to put all the switches sideways on my build, so there's left/right movement. Perhaps an idea? You might even do a 4PDT that way

 

[fontoponto]

I decided against it. Two 4 PDT would fit now but it sounds good as it is. Maybe I build another one with Plexfeta values. Thanks for this thread!!

 

[fontoponto]

I tinkered a bit with a dual version + boost. Only the parts for low gain, character and sizzle are switchable via dip switches for both *feta versions. Pots in a row + a boost in an XX enclosure. labeling not finished and the negative supply is missing…



I did two variants, one with all the dip switches and one a little bit smaller pcb without dip switches and fixed values.
And I used an autorouter after getting crazy for hours...