Hey there,
I'm about to mod the Green Russian Big Muff circuit. Now I want this thing to sound a bit fuzzier (know that's a wide ranged term). I increased the collector resistor(20k) and decreased the emitter resistor(600R) of the last transistor stage. Also changed the transistor, now it's an germanium pnp. Seems like there isn't a really big difference in tone whether the emitter goes to gnd and collector to +9V or the other way around. It both sounds quite ok. But will this transistor have a long and healthy life?
(https://i.postimg.cc/wyfr2KZJ/V7-BMP-Schematic-Green-Civil-War-Tall-Font-Russian.jpg) (https://postimg.cc/wyfr2KZJ)
I know it wouldn't end up sounding like a univox super fuzz, but are there other ways to make the tone kind of gnarlier? Already read the big muff mods page and a few others, unfortunately nothing there really did the job for me. I'm not afraid to build another transistor stage if that will get me closer.
By looking at the superfuzz schematic I spotted those two transistor with collector and emitter tied together to another, what's the effect of that?
Thanks for any kind of help!
(https://i.postimg.cc/N95DgKC9/univox-superfuzz-schematic-1.gif) (https://postimg.cc/N95DgKC9)
so if I'm reading your post correctly, you replaced an npn transistor with a pnp transistor? interesting
what about replacing the first transistor (q4 in your schematic) with a Darlington like an mpsa13 and/or decreasing the emitter resistors? there are some big muff circuits with 150r resistors
i think the green Russian is preferred for those who like it lower gain/for bass, so hopefully it's not an original you're modding
I think the last stage is only for volume, doesn't really contribute to the fuzziness.
Have you considered clipping diodes with lower Vf, like Ge or Schottky?
Try making the 470k base-collector resistor in the second clipping stage a higher value, like 560k or 680k, and lift/omit the cap/s running in parallel with it.
Quote from: thetragichero on September 30, 2019, 02:10:52 PM
so if I'm reading your post correctly, you replaced an npn transistor with a pnp transistor? interesting
what about replacing the first transistor (q4 in your schematic) with a Darlington like an mpsa13 and/or decreasing the emitter resistors? there are some big muff circuits with 150r resistors
i think the green Russian is preferred for those who like it lower gain/for bass, so hopefully it's not an original you're modding
I just build all of the circuit on breadboard, not modding an original one here. Saw a couple of circuits with npn and pnp transistor and gave it a shot. I was surprised by the good result, but I really don't know if the transistor get's damaged with time. Already put in a transistor with a higher hfe in q4, but maybe a darlington can give me something here. Changing the emitter resistor didn't result in what I was looking for.
QuoteI think the last stage is only for volume, doesn't really contribute to the fuzziness.
Have you considered clipping diodes with lower Vf, like Ge or Schottky?
I know it's usually only for compensating the volume-loss, but it has given me the best results changing those resistor values. Also tried a bunch of different diodes, but the change in tone isn't as essential as I'm looking for.
QuoteTry making the 470k base-collector resistor in the second clipping stage a higher value, like 560k or 680k, and lift/omit the cap/s running in parallel with it.
Did this. A lower cap value really brought me closer, but the larger resistors only resulted in a bit more saturation.
Thanks for all your answers!
Sounds like the op amp big muff might be closer to the sound you're after to moi.
put an LPB in front of the whole thing :) I did, and it cranks it up quite a bit.
http://beavisaudio.com/techpages/HIW/hiw1.gif (http://beavisaudio.com/techpages/HIW/hiw1.gif)
love me an op amp big muff! that was my other thought
I've also spliced an op amp muff clipping and recovery circuit after a transistor big muff input booster with good results (instead of going lower Vf diodes in the clipping i went with a standard Si in series with LEDs)
MPSA13 or MPSA18 with jumpered emitter resistors will give you lots of gain. Possibly some more noise, depending on the rest of your setup. As others have mentioned, a boost before it (and almost any fuzz) will give you extra-fuzzy results as well.
If you're looking at more of a crunchy fuzz, look at the Hoof variants, and what they do to the circuit.
Remove C10a, C10b, C12a and C12b. This will gve you some more high end initially.
Change D3 and D4 to BAT48 or similar Schottky diodes (or even germaniums). This will make the first diode stage clip off more of the amplified signal.
Optionally, you can reduce the value of R14 to 51k ohms. This will make Q4 clip asymmetrically.
The two transistors with collector and emitter tied together in the Univox Superfuzz are a full wave rectifier to produce an octave-up sound.
regards, Jack
What's not immediately clear is whether the OP is interested in some particular portions of the spectrum being more obvious, as opposed to introducing more clipping. As a double-clipper, the BMP is already pretty dang close to maximum squareularity. Although a standard BMP tonestack does have a bit of a midscoop (which Jack addresses nicely on his site), a Superfuzz has an even more pronounced (and wider) midscoop, leaving only big bottom and searing top. So maybe the recipe for more "gnarliness" (from the OP's perspective) is to widen the scoop beyond what the stock tonestack values provide for.
Turn the third stage into a Bazz Fuss--that ought to garnly it up for you.
Yeah maybe the opamp big muff after the first stage is a thing to try. I will also build an booster in front of that whole thing and see if that gets me forward. Already put a fuzz face with low fuzz settings in front but it doesn't turn out so nicely.
QuoteOptionally, you can reduce the value of R14 to 51k ohms. This will make Q4 clip asymmetrically.
This really gave me a nice shape of the tone, especially in the high frequencies.
QuoteThe two transistors with collector and emitter tied together in the Univox Superfuzz are a full wave rectifier to produce an octave-up sound.
Alright, nice to know. So maybe an octave up will sound good. I always thought an octaver is recommended to put in front of a fuzz. So does the Superfuzz gets it's unique sound by putting it behind the fuzz stages?
QuoteSo maybe the recipe for more "gnarliness" (from the OP's perspective) is to widen the scoop beyond what the stock tonestack values provide for.
Making C9 smaller is also a nice addition to shape the sound, although I wouldn't characterize it as a rise in "gnarliness" :D
QuoteTurn the third stage into a Bazz Fuss--that ought to garnly it up for you.
I will try this too and get back to you guys later. If all the things you suggested sound great, then I guess I need a lot of switches ;D
Quote from: pokus on October 02, 2019, 02:30:47 PM
Alright, nice to know. So maybe an octave up will sound good. I always thought an octaver is recommended to put in front of a fuzz. So does the Superfuzz gets it's unique sound by putting it behind the fuzz stages?
You must drive the back-to-back transistors with signals of equal volume but opposite polarity, which is coming from the transistor preceding them in the Super Fuzz.
Also, much of the fuzz is being generated by the clipping diodes that follow the octave stage. It is very common to follow a full-wave-rectifier octave-up stage with clipping diodes in order to enhance the effect.
regards, Jack
What about removing the diodes at Q2 and/or Q3?
mac
i have had good results with removing or jumpering C6, yes, both jumpering and removing yield quite diferent effects, you could even wire it up in a on-off-on 3 way switch for stock, jumpered and open connection, for three distinct sounds.
(https://i.postimg.cc/m1ZDsGGq/bmp-switch-mod.png) (https://postimg.cc/m1ZDsGGq)
You might be able to move the feedback resistors from the Collector side of the collector ressistor to Mains voltage and mess around with different values. Big muffs usually have enough gain and fizz so the only real way to go is to make it gaty and sputtery like a fuzzface. Changing the layout might make for an interesting sound.