Iron Bell / Collossus Fuzz

[luks999]

Hi Guys

need your help. Anyone built the Iron bell or the colossus fuzz?
theyre based on the muff circuit (p19 skreddy i think)

i found this:
http://www.madbeanpedals.com/forum/index.php?topic=7849.0
(thanks croquet hoop for the schematic)

unfortunately i cant find a schematic for the colossus anywhere, but i think theyre very similar.

what confuses me now is, that i also found this iron bell circuit:
http://www.bigmuffpage.com/images/schematics/Iron%20Bell%20Schematic.jpg
in the circuit from the bigmuffpage there are some strange things:
-) C16 never appears in any muff circuits ive seen so far
-) R28 never appears in any muff circs too
-) the diodes seem to be on the wrong place? in most schematics they are after the 0.1uF cap
the rest of the values seem accurate

so i trust the circuit of the madbean forum more

sorry if thats a stupid question all hints are welcome

thanks
luki

[bordonbert]

C16 - Bleedthrough capacitor for tonal adjustments.  Adds (bleeds) more high frequency into the signal as Sustain control is turned down.  As the Sustain is turned up it has less and less effect.  Try without it and with it see which you prefer.  Remember it acts only as the Sustain control is turned down.  It's often seen in preamp circuits and even in certain Strats to emulate Teles.

R28 - Oddity.  Marked as 560pF.  Should it be a small cap?  Can't see a reason for it, pot ensures DC level stays at 0V when disconnected.

Diodes - Diodes are right, not really sure what you mean?  If you mean the capacitors C6 and C7 compared to C6 and C9, then it makes absolutely no difference, they are in series.  If you mean they should be after their transistors not around them, there are 2 ways of using them.

• You can produce a large signal with a basic amplifier and slap it across the diodes which are connected to ground and just let them cut the top and bottom off passively.
• You can put them in a feedback loop and let them do the same thing as part of an active approach.  That's what is happening here.  They are within the feedback loop of the transistors they are across.

[luks999]

thanks dude great answer

c16 - thanks didnt know that, ok ill experience with it
r28 - yes strange i think its an mistake. its an res symbol, but has a cap value? i leave that one
diodes - for sure! youre right, thought they are parallel first, sorry

also some values are slightly different between these two schematics. wonder which one are the right ones. but i guess the one from the mb forum is more accurate

[luks999]

btw ive read, the Iron bell is based on the P19 and the Collossus on the Russian/Civil War Muff
maybe its the same schematic as the IBell but with russian values

[luks999]

One thing still thing makes me wonder:
in the IBell schematic
https://dl.dropboxusercontent.com/u/1042331/Pedals/Iron%20Bell/IBell_sch.PNG

there is this R24, what for? never seen this anywhere

btw heres the vero:
http://tagboardeffects.blogspot.co.at/2013/04/mojo-hand-iron-bell-fuzz.html

values seem to be the same as in the schematic above, except:
R16: 33k <> 30k (guess it doesnt make much difference)
and one uses 2n5088 and others 2n5089

The P19 schematic shows: BC550 (Q1) and 2n5088 for the rest

I think im trying out the 2n5088

[bordonbert]

R24 - Changes the amount of high frequency available at the top end of the tone control.  When it's dialled down to 0 it increases the tone control cap C10 from 6n8 to 39n8.  Heap BIG change!

R16 - Do you mean R18?  Dropping the value 9% will change the high frequency end of the tone control slightly.  Probably not even enough to notice.  33k is common value, 30k not so common.  If you don't have one solder a 330k in parallel with the 33k which will give you 30k.  Then see if it makes a difference.

2N5088, 2N5089, BC550 - already answered to death.

[luks999]

will do a search for the trannys in the forum
just want to know whats the best for the iron bell, but since the original seems to use 2n5088, i think im stuckin with these.
(maybe i socket the trannies)

sorry, yes i meant R18 looks to me as a high pass? so that mean chaning it to 30k would cut off more high frequencies right?
hmm i think i experience with that

R24 - ok i see. never saw this resistor before, thought first it lowers the voltage available to the circuit

[bordonbert]

Doohhh! - - - Last time I promise.  If they're in working order and general purpose or better, in this type of circuit there is no best, they're all the same!  It's a myth staqrted by those who don't know enough to understand how the circuits work!!!

[luks999]

okok easy:-) thanks. thats what i guessed.
never built a muff type pedal before