Big Muff "No Diodes" Mod

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mewithoutus
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Big Muff "No Diodes" Mod

Post by mewithoutus »

so, i did this mod tonight to my NYC big muff. it involves removing the four clipping diodes in the feedback circuit.

very awesome results.

more volume, more mids, and a more "open" sound. sort of an overdrivey fuzz.


more usable? for me, hell yes. theres more note definition, great sustain, more volume, and the fuzz is more fuzzy rather than distortion like. hard to explain.

if you dont like how dark the muff is, this can help, along with some cap swaps in the tone stack.

i will post sounds when i have a chance.

its a very easy mod and the results are worth a try. you could always put the diodes back in, or try other stuff like LEDs, germaniums, and other stuff.

i was gonna post a pic, but i already reassembled it... :cry:
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Post by Doog »

Is it just a snippy job ala the Ruetz Rat, or does it need solderstyle?
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Post by Mike »

Doog wrote:Is it just a snippy job ala the Ruetz Rat, or does it need solderstyle?
You should just be able to clip them, like the Ruetz Rat. The diodes clip the signal and compress it.

Removing the first two diodes improves the bass response lots and is a common mod for Bass players.
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Post by Sloan »

balls. i should have tried this before i ebay'd mine. :(
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Post by mewithoutus »

mike is right. i could just clip the leads, but i desoldered them for neatness sake.
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Post by Mike »

This explains how diode clipping works:

Image

If you look at the bottom case, this "back to back" placement is a common configuration in fuzz/overdrive pedals to clip up the signal. What a diode does is to conduct current in only one direction, when the voltage across the diode is above a certain threshold level. Basically this arrangement means you clip both the top and the bottom halves of the wave form (a guitar signal is AC in that it has positive and negative components to it - that's why capacitors are used to couple stages without DC offset, but I digress). This way when the voltage signal exceeds the diode threshold, it turns on and conducts, clipping this additional signal from the output. People use different types of diodes in this arrangement to mimic asymmetrical clipping, which is considered to be valve-like in sound and response.

I'm obviously simplifying this, as much because I don't have all the answers myself, but you get the idea.

In the TS808 and Big Muff they're actually used in the feedback of the amplifier stage(s) so it's a little more complicated, but the same principle is occuring.
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Post by mewithoutus »

yep. thats pretty much what its all about. i have heard that the LED mod is popular, because of the point at which they start conducting.

i am going to build a muff some time soonish to try different diode configurations. i would love to be able to toggle between different ones. seems like it would be fun and educational.

i really like the big muff sound so anything that brings something new to the table is always cool with me.
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Post by Mike »

Big Muffs use the ubiquitous 1n4148 I believe, which I think has a threshold voltage of like 0.6V. I think most common LEDs are more like twice that, around 1.2V, so you're going to get a lot less clipping and compression at the same volume levels.
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Post by Doog »

So there's more mids and low end with the mod? I might do it to Spud's NYC Muff, although he's got a twin channel amp now, might be a bit of a waste o'time.
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Post by Mike »

Worth a go, definitely.

Like I said you want to do the first stage. Let me see if I can find a NYC Pi schematic.
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Post by Mike »

Useful webpage ahoy!
http://www.student.ru.nl/r.kerkhof/Taas ... 20Muff.htm

Apparently these are pictures of the NYC board
Image
Image

Unfortunately I can't find a schematic to see if it's D1/D2 or D3/D4 you need to remove. it'll be the ones that are nearest the input in terms of the circuit itself (not necessarily physically)
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Post by mewithoutus »

d1/d2 are the first pair of diodes in the circuit.
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Post by Mike »

I would have suspected that, since component numbering is normally done from i/p to o/p and then on power filtering. I hadn't seen his small font face detailing the pairs - give them a clip Doog.

It just seems stright they would have the circuit that way round, since the input is on the left side of the board when viewed from below, but whatever, it's EHX. They move in mysterious ways.

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Post by Doog »

I guess I'll ask Spud what he reckons, don't think he really uses it anymore since the dual channel Marshall bass head graced our presence, but could be worth a fiddle, so to speak.

Nice work, dudez!
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Post by mewithoutus »

thanks doog. its real easy. nothing crazy about it, thats why its such a cool little mod.

i LOVE those pointer lookin knobs on the earlier big muff RI. some internet place has them and i wanna get em for my big muff and future DMM. yay.
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Post by Mike »

Unfortunantely Pointy knobs = Shit bypass.
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Post by mewithoutus »

yeah, tru dat. luckily, when you buy replacement pointy knobs, installing them doesnt shit up yer bypass. **happy**
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Post by BradK »

Wow, I actually remember some of these rules about electronics from my Physics classes haha. I really wanna get a big muff sometime to mess around with, and I'd love to try out this mod. I love this board hah.
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Post by mewithoutus »

this board loves you.
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Post by kim »

dammit i gotta find my US bmp, no idea where the fuck it is...


more mids.. that got me interested.

it's funny, i bought mine secondhand off some dude and it came in a wooden box but it doesn't have the pointer knobs, i wish it had the pointer knobs, now it has marshall knobs on it
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