maortojn wrote: LM393 wrote:
Start with the straightforward circuit: input J201 gain stage -> 2N5457 gain stage -> second J201 gain stage -> 2N5089 emitter follower. Use the already-traced sorta-similar Fairfield Barbershop
as a starting point, and the BOM/PCB screen in this thread to reason out component values. Set up the gain, hicut, and volume pots and make sure this circuit works as you'd expect.
After that, use a pot or two to deliberately misbias the 2N5457 until you get the desired heavy crackling/light cutout effect (toggle), note the bias voltages, then reproduce these voltages by using the envelope follower circuit of the Dr. Quack
to screw with the 2N5457's biasing. This'll require some experimentation; maybe have the envelope BJT open/close a path to a parallel biasing resistor.
The momentary footswitch and associated on/off toggle either completes or kills the input to the envelope follower.
Nice! I was also thinking of starting with the Barbershop. It shares the same vibe, and I might just build that one first since it's pretty straightforward and also very nice sounding. After that I will try to work out how to connect all the dots together for the fuck-od.
am very interested in the crackle trashed amp effect side of this pedal. am not a very big overdrive person, more fuzz, but the extreme quality of the crackle plus the overdrive here presses my buttons.
so i want to experiment with adding the crackle control from the fuck to the fairfield barbershop, for which a reliable schematic and vero is already out there. https://www.freestompboxes.org/viewtopic.ph ... 43&#p61743
brian (bigound smallsound) has already confirmed that the 'crackle' feature of the fuck is basically an 'envelope follower' that has much in common with that of the dr quack (probably also nurse quacky) used to dynamically modulate the bias of the 2n5457 in the signal path j201 > j201 > 2n5457 > 2n5089
following comments from p1 of this fuck thread https://www.freestompboxes.org/viewtopic ... 45#p216443
"(brian) the fuck is 3 jfet (2 j201, 1 2n5457) gain stages in series with the dual pot (gain) controlling the volume of the first 2. final 2n5089 is an emitter follower. SWTC for the high-cut control. the rest of the components are for an envelope follower aka the "dynamically modulated sag feature". it's modulating the voltage on the 2n5457 for the crackle and gnar gnar... i tried modulating each different stage, two at a time and all three but the particular stage was the best choice for a number of reasons.
Hmm.. Looks like the yellow LED anode is connected to pin 5 of the TL072.
Bet its used for the offset-bias-trick used in many envelope-followers. Dr. Q etc..
(brian) right you are."
my (admittedly slight) understanding of the basic principle is that the part of the quack/quacky that sits between q1 and q2 in the quack/quacky schematic (lower half, which contains the sensitivity and range controls) should be patched into the barbershop overdrive circuit, between source of q1 and gate of q2, to effect (dynamically modulate) the final jfet of the gain stages (offset bias).
the values of the patched in envelope follower borrowed from the quack/quacky can then be tweaked to give best results in their new context.
i can (struggling) just about grasp that basic concept. but wanted to clarify my approach before getting too carried away.
am i placing the envelope follower (part of above quack schematic between q1 source and q2 gate of the quack/quacky)
between q2 (j201) and q3 (2n2222) of the barbershop schematic https://www.freestompboxes.org/download/file.php?id=3285
as long as that is kind of what i am aiming for the values can all be tweaked with pots etc on the breadboard. i just need a nod from a wiser head to let me know i'm (at least) pointing in the right direction.
many thanks to anyone who manages to amke sense of my post, and can offer some wisdom.
the sound i am after (called 'crackle' in the fuck) is on show in this demo at 1m45s on. that's what i'm aiming for.