MMR fuzz

Stompboxes circuits published in magazines, books or on DIY electronics websites.

MMR fuzz

Postby Nocentelli » 23 Apr 2017, 22:42

Simple(ish) two transistor fuzz with a wide range of dirt sounds and decent clean up from the volume knob:

MMR fuzz_nocentelli.bmp


I figure some people may well have a 100kB dual-gang pot kicking around if they've ever built a klon (for the bass control), but it can be replaced with a single gang 100kB in front of the first stage or omitted altogether (replace 10n with 100n and lose the 1uF + pot gang)
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mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.

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Re: MMR fuzz

Postby mirosol » 01 May 2017, 13:07

Here's a stripboard layout. Not verified yet.
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Re: MMR fuzz

Postby roseblood11 » 02 Jun 2017, 08:33

Looks interesting. Would really like to hear it!
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Re: MMR fuzz

Postby Timpanogos Slim » 16 Aug 2017, 21:54

I finished building one of these today, based on the transfer layout at the effects layouts blog, here:

https://effectslayouts.blogspot.com/201 ... -fuzz.html

I used PN2222A because i have stock on hand. I am under the impression that these are just a plastic 2n2222 but perhaps they are too different.

The tone stack works. It makes my bass louder. I'm not sure whether there is really "dirt" here.

Is there a recording of how it is supposed to sound?
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Re: MMR fuzz

Postby Nocentelli » 18 Aug 2017, 12:33

Timpanogos Slim wrote:'m not sure whether there is really "dirt" here.

Is there a recording of how it is supposed to sound?


No recordings, but it's really quite fuzzy, especially with the gain and bass up. I can't vouch for the layout or build, however.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
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Re: MMR fuzz

Postby mirosol » 18 Aug 2017, 22:25

Just checked the schematic against the layout again and didn't see anything off.

Altough. The was an error earlier on the layout. A missing strip cut above the Q2 emitter. Here's the fixed one.
+m
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Re: MMR fuzz

Postby Timpanogos Slim » 20 Aug 2017, 18:37

Alright. Just wondering if my expectations are correct. I'll go over the schematic and board to look for mistakes at some point.

If anyone does have a recording, I'd appreciate hearing it.
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Re: MMR fuzz

Postby Timpanogos Slim » 23 Aug 2017, 06:52

With every knob at full clockwise and an OCD overdrive clone in front of it, it does sound pretty good.

But i feel like it should have a lot more gain with the gain knob all the way up (it's not much more than unity). And the fuzz level is milder than the germanium fuzzface i built, and like not a fuzz at all compared to my green russian BMP clone, much less the blowerbox clone.

Went over storyboardist's layout and the schematic and the component side of my board and didn't see anything awry. Sorry i don't have a camera handy at the moment. I'll get some good photos the next time i have it open.

I guess the next task for me is to desolder the pots and check the solder side for errors.
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Re: MMR fuzz

Postby Timpanogos Slim » 24 Aug 2017, 01:39

The ground plane around the bass pot was kind of a minefield when getting that part soldered, so i went ahead and trimmed it off after removing the pots to double check.

I don't see any bridges. *shrug* there might have been a bridge to ground under the bass pot on one of the inner legs, it's hard to see in there.

20170823_182554.jpg

20170823_182528.jpg
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Re: MMR fuzz

Postby Nocentelli » 27 Aug 2017, 19:43

I breadboarded this circuit again to check I wasn't imagining things, or if I had perhaps left some errors on the schematic, used a different transistor type to that specified etc etc...

Here is the circuit exactly as per schematic, with 2N2222 transistors hFe Q1 = 267, Q2 = 257. I must apologise for the playing:


Link


Timpanogos Slim wrote:i feel like it should have a lot more gain with the gain knob all the way up (it's not much more than unity).
With the volume on half, it is way over unity. The extreme, super sustain-y and feedback generating fuzz is towards the end of the gain knob's travel, maybe a reverse audio pot might be better.

And the fuzz level is milder than the germanium fuzzface i built
This is possible, they are both two transistor fuzzes (i.e. so similar in what they can achieve in terms of gain) but there is a treble filter that rolls off a fair amount of the hiss and very high end and perhaps makes the MMR seem a little less aggressive. You could just leave off the treble pot altogether for a harsher sound.

not a fuzz at all compared to my green russian BMP clone
I hold my hands up to this one, but the BMP is FOUR high gain transistor stages in series, with two sets of clipping diodes; This circuit is a single high gain stage smashing into a second stage, with no hard clipping other than that generated by the transistors themselves.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.

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Re: MMR fuzz

Postby Timpanogos Slim » 28 Aug 2017, 08:42

Nocentelli wrote:I breadboarded this circuit again to check I wasn't imagining things, or if I had perhaps left some errors on the schematic, used a different transistor type to that specified etc etc...


I really appreciate it. You're a better guitarist than i am. But, I'm (1) just starting to learn, and (2) more interested in playing bass. And (3) exploring a musical space somewhere between Merzbow and the Spaceshipp project that Jason Pierce of Spacemen 3 did with jazz pianist Matt Shipp.

Lets just say i have 6 working delay pedals and have been known to chain 4 or more at a time. And i have your King Dubby design finished and waiting to be enclosed with some enhancements like expression pedal control of the speed and selectable latching for the foot switch functions. Mad props for that design. Thanks.

Nocentelli wrote: With the volume on half, it is way over unity. The extreme, super sustain-y and feedback generating fuzz is towards the end of the gain knob's travel, maybe a reverse audio pot might be better.


So mine is certainly not working properly. Given where the bass pot is in the circuit and the potential that there might have been a solder bridge that was hard to see, I wonder if that was the whole issue with mine. I'll reassemble it and inspect it with a usb microscope if i have to. I scraped away a lot of the ground plane near that pot so it should be more straightforward. I also fixed my hot air system and have some solder paste so i might try that for the hard-to-reach inner pin.

And the fuzz level is milder than the germanium fuzzface i built
This is possible, they are both two transistor fuzzes (i.e. so similar in what they can achieve in terms of gain) but there is a treble filter that rolls off a fair amount of the hiss and very high end and perhaps makes the MMR seem a little less aggressive. You could just leave off the treble pot altogether for a harsher sound.


I'm not convinced that my fuzzface is working properly, fwiw.

not a fuzz at all compared to my green russian BMP clone
I hold my hands up to this one, but the BMP is FOUR high gain transistor stages in series, with two sets of clipping diodes; This circuit is a single high gain stage smashing into a second stage, with no hard clipping other than that generated by the transistors themselves.


Yeah that's a pretty crazy pedal. But your demo sounds good too.
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Re: MMR fuzz

Postby Timpanogos Slim » 30 Aug 2017, 19:53

I think i did have a short on the board somewhere under the bass control pot. It's working a lot better after rework. I also checked the hfe of my transistors and found them at about 200 and 260 (I forget which positions) and wonder if the hfe range is a concern, and maybe i should look through the bag for another one around 250 to replace the lower hfe piece.
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Re: MMR fuzz

Postby Nocentelli » 31 Aug 2017, 10:24

What guitar are you using? The demo was recorded using an epiphone semi with medium-high output humbucker p'ups.
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Re: MMR fuzz

Postby Timpanogos Slim » 31 Aug 2017, 17:03

Nocentelli wrote:What guitar are you using? The demo was recorded using an epiphone semi with medium-high output humbucker p'ups.


Kaman GTX 51 P-bass.

I'll throw some knobs on it and record a video later today. My amp is a Kustom KMA-100 keyboard amp. Not great for guitar, more than fine for bass with its 15" celestion and built in compressor. As a keyboard amp, many criticized it for being too bass heavy. And it cost me $5 and a single power amp chip that i already had on hand. I'm installing a better horn so it has some meaningful response in the guitar range, and some day I'll have to build one of the various amp emulator guitar pedals.
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Re: MMR fuzz

Postby RomYch » 08 Sep 2017, 08:15

Hello!
First, I want to thank Nocentelli for an interesting scheme.
I don't have 2222 transistors, so I will conduct experiments with other transistors (945, 1815, etc.).
I developed my PCB for this scheme. Dimensions of the board are 67x23mm. If it will be useful to you - welcome.
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