Modding a Neo Muff

[Mark Hammer]

I picked up a Neo Muff overdrive for $25 over the weekend at a guitar show and swap meet, under the assumption that it could be easily modded to do more tricks, and I was not disappointed.  The original Muff Fuzz was essentially a silicon Fuzz Face with preset gain and a couple of clipping diodes, and a simple volume control.  The original used 2N5133 transistors, and the Neo Muff Overdrive drops the gain just a bit, and swaps the 2N6133s for 2N5088s.  The conversion is shown below.

Upper left you see the copper side, upper right the component side and the parts of relevance are noted in red.  You can see that there is some room to work to the side of the pot.  My plan was to add a gain control and an SWTC-type tone control to soften the fuzz at highest intensities (the stock Neo Muff is actually pretty warm).

I removed the 3k3 gain-setting resistor, and replaced it with a 5k pot and a 33uf cap joining the wiper and ground connection, in order to provide variable gain.  This will yield softer grunts than stock, and a more serious fuzz that deserves to be called fuzz.  I decided to leave the clipping diodes alone, but if you want to monkey with them (see the Lava Rim thread), they are shown here.

I removed the 3k3 (lower left), and unsoldered the input lug of the volume pot.  I drilled a pair of holes and applied some legending with rub-on letters (unfortunately, the little dab of clear nail polish appeared to dissolve a letter or two).


Because I was cheap, and used the 9mm pots with the black plastic shaft, that don't/can't mount to the chassis, I secured them to the chassis with a bit of Bondo epoxy.  So far it seems to work just fine.  The knobs stick out just far enough to get a good grip, and the knobs turn freely.  I attached wires and additional components to the pots first, using the 24-gauge stranded wire from Small Bear, that I like so much.  The 33uf was mounted to the pot, and the 10k Tone control had a 1/8w 1k resistor soldered to the pot lug, and secured with a piece of shrink-tubing over it, in addition to a .018uf cap connected between the wiper and ground.  Once I had the wires soldered to the pots, and stripped the free ends, I connected the two outside lugs to where the 3k3 used to be, soldered the 1k resistor that was soldered to the 10kp pot to where the input lug of the volume pot used to go to, and the other outside lug of the tone pot to volume pot lug I had clipped and lifted from the board.

I now have a 3-knob Muff Overdrive/Fuzz with a tone control.

[pinkjimiphoton]

mark, this is a very awesome thread brother. well done!!

[Gus]

The 1K gain with 5K bias I use in FF like builds is fun.

[Mark Hammer]

Thanks for the idea.  I'm also a big fan of monkeying with the value of the Q2-emitter-to-Q1-base resistor.  Ever since I saw it played with in the ZVex Wooly Mammoth, I've been tinkering with it, and it provides other flavours of distortion.  I may decide to add a toggle to this thing, and vary that resistor (currently 100k, as per spec) but for now I'm happy...and not exactly hurting for clipping pedals.

[matlevo12]

Thanks for the idea.  I'm also a big fan of monkeying with the value of the Q2-emitter-to-Q1-base resistor.  Ever since I saw it played with in the ZVex Wooly Mammoth, I've been tinkering with it, and it provides other flavours of distortion.  I may decide to add a toggle to this thing, and vary that resistor (currently 100k, as per spec) but for now I'm happy...and not exactly hurting for clipping pedals.

Hi,
I got a muff overdrive, and your mod (the gain and tone one) seems really interesting. By any chance do you, or anyone still have the pictures ? Photobucket likes to blur things after a few years...
Thanks a lot !

Edit : Thanks Chrome and photobucket hotlink fix extension

[tubegeek]

Edit : Thanks Chrome and photobucket hotlink fix exte sion

Oooooooh now THERE'S some useful info THANKS!

[matlevo12]

Edit : Thanks Chrome and photobucket hotlink fix exte sion

Oooooooh now THERE'S some useful info THANKS!

Haha. Well thank google, it was pretty easy.
Do you think it should be broadcasted in dedicated topic ?

[tubegeek]

Actually yes. The photobucket debacle has left many threads here looking pitiful and the Chrome extension does the job!

[willienillie]

Neo Muff or Nano Muff?

Nano Neo?  Neo Nano?

Nanu Nanu?

[matlevo12]

Actually yes. The photobucket debacle has left many threads here looking pitiful and the Chrome extension does the job!

Alright, I'll do it later, not sure in which section, but if someone wants to do it first please do so !

Neo Muff or Nano Muff?

Nano Neo?  Neo Nano?

Nanu Nanu?

That's true, the topic's title is misleading. It's a nano muff overdrive. But I found it using the search engine without entering neo, so I guess that's fine.
I'll post some schematics when I have the time to actually do and test the mod.

[matlevo12]

Hey

I'll finally have time to do this mod next week.
I draw a quick layout of my understanding of the mod, here it is :




The green line is just there to show where ground is.

I hesitated a bit for the tone pot wiring, but if I'm not mistaken it's like that :
- pot turned down = high R = lower frequency cut in the low pass filter = less treble
- pot turned up = low R = higher frequency cut in the low pass filter = more treble

[j_flanders]

I hesitated a bit for the tone pot wiring, but if I'm not mistaken it's like that :

Reading Mark's explanation of the mod, your drawing looks correct to me.

[matlevo12]

I finished the mod today (and followed the layout following Mark Hammer's explanations) and it works perfectly !

I might want to change the tone cap in order to lower the cutoff frequency and really darken it more when turning the tone pot down, but that's just my taste and apart from that it's really good !
Goes from a good overdrive to a kind-of-bitcrushing fuzz  !

Thanks Mark Hammer

[Mark Hammer]

You're welcome, but thank all the good folks who here who taught me.

EHX had a tradition of turning out pedals with one knob and a switch that were capable of SO much more.  This site taught me much about how to explore and exploit what those designs had to offer.

[matlevo12]

Here's another topic with mods for this pedal.
https://www.diystompboxes.com/smfforum/index.php?topic=82158.0

Thanks to it, I realised my Q1 (2n5088) was upside down (collector to ground).
Oh and I changed to output cap to 100nf (was 1uf) as well.

[iainpunk]

Thanks to it, I realised my Q1 (2n5088) was upside down (collector to ground).

this is sometimes done deliberately to lower the hFE of a transistor, it also makes it even less linear in its operating region. the hFE is cut by anywhere from 10% to 95%, but this percentage is quite consistent within the same part number.

cheers

[matlevo12]

this is sometimes done deliberately to lower the hFE of a transistor, it also makes it even less linear in its operating region. the hFE is cut by anywhere from 10% to 95%, but this percentage is quite consistent within the same part number.

cheers

Thanks for the tip!

It does sound different (and better imo) this way.