The 2N5133's may be a little difficult to source (and as expensive as the ?Lady pro rata), so try every bi-polar NPN you've got in there and stick with the best results. And please don't buy any 2N5133's off eBay unless they guarantee gain around 500-700 hfe. These have already been cherry picked to death so you'll pay a lot of money for a transistor with nothing like enough gain to sound amazing in a muff.
Info from the Muff Master himself (that sounds sooooo wrong):
Skreddy Pedals™ ? Lady:
Thick and huge-sounding, this 1973-era-based fuzz is fat on chords and riffs and soars with infinite sustain on single-note runs. Much more corpulent and "vintagey" sounding than a typical muff--it's got a bit of 60's flavor added in.
Has a wide useable tonal range with a rich midrange and an aggressive, fuzzy breakup..
Sounds like a vintage fuzz feeding a cranked up vintage amp, with as much output volume as you could ever want.
what's strange is that the data sheet for a 2N5133 states that it should have an hfe of a minimum of 60. smallbear is a reputable dealer and has them (for $1.50 ea) and says his are a minimum of 50 but recommends that you want a higher hfe version with the same sonic signature to get the Fairchild SE4010 (minimum hfe of 140). I've always heard that the hfe rating doesn't matter all that much in a muff circuit, although higher hfe's generally equate to them having lower noise. that's probably why a lot of people use 2N5088's or BC549's or BC550's use them nowadays.
ReplyDeleteThat's true. Electronically speaking if the sounds depends a lot on the qualities of the transistors, it's just bad design. We of course know that it's part of the magic. That's why Fuzz Faces are so fun. The gains in actual muffs have varied at least from 150 to 750. The sound does differ but not so much that you should worry about it. Just experiment and see what you like best.
DeleteWhilst other factors in the transistors may well come into play, I've found that muffs with low gain transistors sound farty and never sustain as much as higher gain. And if you're paying a premium for the transistors you don't want to end up with something that sounds inferior to 2N5089's at least in some ways, but that you end up keeping in there just because you bought in the transistors specially. I've got some lower gain 2N5133's and they aren't a patch on the higher gain 2N5828's from the same sort of era.
Deletei think the bias on the transistors has more to do with the fartiness than just the hfe. i think what happens is when we throw low hfe transistors in a circuit without changing the bias on them, they're out of bias (duh) and sound farty...i do think you can make a really cool low hfe muff, but you'll have to tweak the collector values (or emitter, or both).
ReplyDeleteHi Mark.
ReplyDeleteI built your tranny matcher and read each leg of several transistors, writing down the readings on each. Not for this build but this one is most current.
When I get these readings am I just looking for values as close as possible on each leg.
Can you point me to a user friendly source to explain tranny matching?
dale
that transistor matcher is for Jfets. i'm not sure if it works or how accurate it is on BJT's.
ReplyDeleteThanks John.
ReplyDeleteMy question is a general one about matching. If matching JFETS. Is the goal to get as close to exact readings from all 3 legs? Is one leg more/less important than another.
I've built (only counting successes) about 50 or so pedals but have never really applied the matching process to a pedal. I'm working on another pedal that requires matched JFETS but as I say, I really don't know what I am looking for.....exactly. Thanks again for the help.
dale
The only thing I would ever bother matching for is JFETs in a phaser where having them closely matched will affect the quality and depth of the phasing, or maybe a differential pair used in an octave effect when having them matched in gain may potentially make the octave more prominent.
DeleteAs far as something like a Big Muff goes I would try to aim for gain between 500 and 700 hfe (or of course whatever the measured values were from an original if you can find that out). I've never been much of a fan of lower gain transistors in a Muff, you may be able to get round it by changing some values of the surrounding passives, but then if you do that you haven't built the pedal the layout was for. This is particularly relevant for the Muff based pedals because it's those subtleties that differentiate them (think of the different collector resistor values which are one of the well known differences between the Rams Head and Triangle for instance).
Can I use the hfe tester on my multimeter to check Jfets, and if so, which way round would I connect them?
ReplyDeleteNo, you can't. JFETs are not equivalent to BJTs in terms of gain readings.
Delete+m
You could build yourself the JFET matcher project on here, or alternatively the Peak DCA75 will measure a lot of the JFET characteristics that you might want to match such as vgson for a phaser, as well as vgsoff, idss and transconductance. They're not cheap but worth it imo to make matching as simple as measuring gain in a bipolar transistor, so I intend to upgrade from the DCA55 at some point.
DeleteI've made to attempts att this layout but I cant get it to work, volume is very, very low. Any ideas?
ReplyDeleteHave not built this effect, but is an Big Muff, so it must be really loud. Can you check your voltages on every pin of the trannies?
DeleteThe only time that I had problems with a BMP effect, was whenm i forgot to solder Q4 collector, and so, te output was really low (doesn't mean that this is your problem, by the way).
J.
C B E
DeleteQ1 3.67 0.59 0.02
Q2 6.12 0.61 0.02
Q3 2.15 0.62 0.02
Q4 2.21 2.21 1.62
I think there's something wrong in the collector voltages of 2,3 and 4. and even Q1 is a bit low, they all should be ~4-4,2v.
DeleteMost suspectious one is Q4 with collector and base at the same (and low) 2,21v. Take a look to see if there's a solder bridge between c and b rows, that would explain the low output.
J.
You can verify this one! I used BC239c's. Q1 and Q2 need to fliped 180 degrees. From their the circuit works at a medium high gain. If you flip both Q3 and Q4 180 also, you get a crazy amount of gain, that doesn't clean up when turned Counter Clockwise. If you flip just Q3 along with Q1 and Q2, you get a nice amount of gain but also doesn't clean up. Flipping Q4 along with Q1 and Q2 180 degrees was my favorite combo. High gain, yet clean cleans up when the gain knob is rolled back. Thanks for awesome site!
ReplyDeleteExcellent, thanks for verifying
DeleteThis piece of information here is pure gold! I have built a couple big muffs and after reading about flipping the transistors, I revisited them and wow! I'm getting the tones I've been looking for. Thank you for this.
DeleteP.S. It sounds Great!
ReplyDeletehi guys so i have a batch of 2n5133 transistors perfect for this build if youre interested email me inaki.font@correo.unimet.edu.ve
ReplyDelete