Technology of the Big Muff - What does what?

[quarara]

just to clarify, I didn't accuse you to have taken that idea from Skreddy. I have never attempted to modify my triangle based muff accordingly to Skreddy's specs, but after your explanation I surely will

[bumblebee]

I never took it that way dude!

[quarara]

I never took it that way dude!

well, English is not my mother-tongue and sometimes I cannot grasp nuances of your languange
however, your previous post about the boominess of triangle muff is great indeed. I'm still a little bit unsatisfied about chords sounds with my muff and now I know where I should put my hands. Thanks!

[WhenBoredomPeaks]

I remember of a discussion way before i started diy where guys argued about the capacitors in the triangle version.
They told that one must use ceramic caps in them. Does it really matter? (Wouldn't it sound better with film caps?i know, this is subjective)
Sigh, i  must breadboard this before soldering, too many options.

[Joe Hart]

Very interesting thread. I'll have to build a BMP now.
-Joe Hart

[bumblebee]

Some triangle muffs use film caps and electro's not ceramics. Some use ceramics. Some use a combo of each so no its not true! Some use .1uF caps and some use 1uF caps and some use both, there's no ONE triangle muff (nor any other muff) schematic that covers EVERY pedal. There's the official EHX schems but EHX never stuck to that real well anyways in the old days.
Big muffs, each individual pedal, are as varied as the people that use them and that is why some people (like myself) have so many and continue to build and modify them.

I never took it that way dude!

well, English is not my mother-tongue and sometimes I cannot grasp nuances of your languange
however, your previous post about the boominess of triangle muff is great indeed. I'm still a little bit unsatisfied about chords sounds with my muff and now I know where I should put my hands. Thanks!

no problem.

[asatbluesboy]

God damn it... I love this place. Thank you so much.

[Mike Burgundy]

I'm looking into putting a blend switch/knob in the BMP. I'm guessing since the first stage is a buffer, is it possible to get a bypass by connecting the collector of Q1 through a 0.1 capacitor to lug 1 of the volume pot, turning it into a blend pot? Or simply take a concurrent dry output from there?

Or is it better to make another buffer stage and split right at the input?

It happens I'm working on a Muff with active bass blend (not clean blend, bass blend) for bass. Have it up on breadboard, had it in the studio and got some major trouser flapping going. I like it so far, but I'm not done with tinkering. It should be no problem to voice the original circuit, well, "original", remove the lowpass filter from the blend driver and go from there and have a straight clean blend in there. I might influence the straight (no-blend) muff sound though - you'll have to see.
PCB V1 is done, but not verified yet. I was going to wait until I was happy with it, but I'll get it posted soon to give you some ideas.

[white paw]

changing c8 to .004uf will give you flat mids on the NYC reissue version.

[brett]

Hi

I skipped the tone circuits because Jack's done those to death at his site. It's an overlapping blend between a single-RC high pass and low pass. Twiddling the overlap gets you a whole lot of different over/underlaps.

is 99% of the tone section story. If you SPICE the tone section, it becomes obvious that the results depend on the impedance of the next section. In the BMP, it's not very high (around 80 Kohms), so there are some differences from the theoretical mix of the two filters. Higher impedance (e.g. 1M+) would give a "pure and stiff" blend. 

Also, this is one  place (of very few IMO) where the tolerance in cap values can be heard. +/- 10% can change the depth of a mid scoop. Changing a value by 20 to 50% is enough to get a significantly different BMP. Which might explain some of the differences between square and triangles, colour vs bw, NY vs Moscow, etc.

I just remembered - most of these variables can be checked out using Duncan's Tone Stack Calculator (if it is still on the www)
cheers

[R.G.]

It's hard for beginners to get and remember, but there are always two more impedances involved with any circuit fragment - the source impedance driving it and the load impedance after it. Those simply have to be considered.

[stringsthings]

... this is one  place (of very few IMO) where the tolerance in cap values can be heard. +/- 10% can change the depth of a mid scoop. Changing a value by 20 to 50% is enough to get a significantly different BMP. Which might explain some of the differences between square and triangles, colour vs bw, NY vs Moscow, etc. ...

good point ... i've had excellent success in experimenting with C10 ( one of the capacitors in the tonestack ) ... my current favourite is a polystyrene capacitor that i had from way back when ...

here's an example from a surplus store: http://www.allelectronics.com/make-a-store/item/CS-472/4700-PF-POLYSTYRENE-CAPACITOR/1.html ... cheap and cheerful

IMO, this type is awesome in critical fuzz-box ( is that an oxymoron? ) filterapplications ... and they look pretty cool to boot  

[Cortex]

Hi guys, this is an unbelievable thread! Sorry for ressurecting it, but my question is in the vein of it...

I recently built the Black Arts Pharaoh Fuzz which is a muff with some altered values. I accidentally put bc550c transistor with reversed pinout in Q1 [could not get hold of a mpsa18] and while it did hum a little more, the sound was PERFECT. It was everything I ever wanted of a fuzz pedal, I was thinking to myself gooood damn this is what I want my fuzz face to sound! [of course cleaning up the BM with your volume knob  never is a particularly nice endeavor]
From a point of how things work, how could one achieve a similar response in the later stages, as with reversing the Q1 would affect them?

I don't know if this was just a happy coincidence but it sounded f-in fabulous! Since then I returned the Q1 like it should be, and while I like the sound, reversed Q1 is better.
I should note that the muff was running on a power supply. When I attempted the same with a battery [reversed Q1] all I could hear was a loud hiss, no alterations on the tone whatsoever, no distortion, nothing.

[matt239]

Do we think the first transistor contributes any distortion, with "typical" guitar pickups?
What about with humbuckers, say P.A.F.s?

[thermionix]

I don't know if there's any actual clipping happening in the first stage, I would assume very little if any.  But for a given set of circuit values (pick your version!), the hFE of Q1 definitely does have an effect on just how fuzzy the BMP gets.  I think it might be the most critical transistor gain in the circuit, because Q2 and Q3 are limited by their clipping diodes, and Q4 is more about volume that dirt.

[antonis]

What thermionix said..!! 

"Rough" Q1 stage gain is about 12 (470k/39k) due to NFB bias configuration but, as R.G. said somewhere inside this thread, there always been 2 more impedances than "obvious" ones - In & Out impedances..

That said, you have to take into account driver(guitar) source impedance in series with input resistor (39k) resulting in lower than calculated gain..

It actually should also be taken into account lower base bias resistor and effective Collector load (Collector resistor in parallel with Q2 input stage impedance) but it should result in too complicated calculations..
(Voltage-Sunt Gain w/o & w feedback formulae, resulting in about 9.6 (calculated) or about 6.8 (simulated)..)

So, we shake hands and call Q1 stage as:
>Booster who sets the pedal input impedance, shapes the frequency response and adds "some" gain..<
(ElectroSmash^Copyright)