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Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 09 Oct 2015, 22:01
by maortojn
Answers from the man himself :D Greatly appreciated.
I guess I will use this as an incentive to try to learn more about this - the real DIY way! But if anyone wanna chime in with more info it's fine by me 8)

Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 12 Oct 2015, 15:55
by LM393
Brian makes some fantastic stuff and this OD is the best of the lot, IMO. Love this pedal :thumbsup still the best dirt I've ever used, hung on to it as long as possible before the name bothered me too much (judge me if you wish). I've owned a few different Mini's but without the envelope it's just not the same.

maortojn wrote:Answers from the man himself :D Greatly appreciated.
I guess I will use this as an incentive to try to learn more about this - the real DIY way! But if anyone wanna chime in with more info it's fine by me 8)

I've reasoned out how I would recreate the F, but I haven't had time to follow through. Hopefully my thoughts will help:

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.

Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 12 Oct 2015, 19:15
by maortojn
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.

Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 24 Apr 2016, 14:20
by tabbycat
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. http://freestompboxes.org/viewtopic.php ... 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 viewtopic.php?f=7&t=21845#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.

(jonasx26)
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).

dr quack
http://www.muzique.com/schem/quack.gif
nurse quacky
http://home-wrecker.com/nurse-quacky.png

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)
http://www.muzique.com/schem/quack.gif
between q2 (j201) and q3 (2n2222) of the barbershop schematic http://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.

https://www.youtube.com/watch?v=OW-pegj1yMY

Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 28 May 2016, 00:05
by tabbycat
tonegod's punisher (adapted from the dr quack envelope follower) is essentially the crackle effect. it's a bolt-on tweak that has been around a while. use this to misbias the 2n5457.

Image

http://tech.thetonegod.com/punisher/punisher.html

punisher values almost identical to those on the fuck pcb screen print here:

http://www.smallsoundbigsound.com/wp-co ... ture-3.jpg

following on from LM393's quote (above):

"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."

pcb screen print values for the fuck q1 (j201), q2 (2n5457) and q3 (j201) and the values for q1 (j201) and q2 (j202) of the barbershop are very close or identical. don't use anything after q2 of the barbershop.

place 'audio in' of the punisher between q1 (j201) drain and q2 (2n5457) gate of the three jfet gain stage set up as described by LM393 above.

use the 'power out' of the punisher to misbias the drain of q2 (2n5457).

as already mentioned (in p1 of this thread) after the third jfet gain stage (j201) add a 2n5089 emitter follower and a swtc for tone control to finish.

a sketch to colour in.

Re: smallsound/bigsound - Fuck Overdrive

PostPosted: 28 May 2016, 19:26
by smallsnd/bigsnd
you're pretty much there. i tried a few different envelope followers and always liked the crudeness of the quack. it does indeed misbias the 2n5457.
as for the gain stages - i chose straightforward values that worked well and kept it simple throughout the circuit. the beauty with such a basic circuit is that they can be tweaked to taste for the amount of treble/bass response, gain, etc.