Fargen Sonic edge J&J overdrive

[Borderline]

Hello Guys,

I've Just joined and wondering if anyone can help me.

I've got the J&J overdrive which i really like but wish it was a bit brighter. it seems to be a really simple circuit and proberly instantly recognisable to the experienced eye with common mods to this type of circuit. I've attached a picture of the board and marked all the capacitor values. I have a few questions and would appreciate in advance if someone could help.

1. How could I make it brighter overall ? even with the tone knob ( which sounds like a cut only ) all the way up , the highs are ever so slightly muffled and i'm losing sparkle. where could i experiment ? the C1 input cap or something in the tone stack ?

2. What can i expect if i mess around with the trimpots ? can i increase the amount of gain or is it more like a bias thing and in a optimal postition ?

3. Is C2 in the audio path ? I've got some phillip blue caps lying around and was thinking of replacing like for like. ( am i right in thinking C8 -100uf is something to do with power and will make no difference.

Many thanks,

Geoff.

[alexradium]

its impossible to mod it without tracing the actual circuit.
post detailed pictures of the other side of the board,pot values,transistor type.

[Borderline]

I'm sorry about the quality of the pictures.

The input would be on the right.

The pots left to right are - Vol - b100k - Tone - b100k - Gain - A1M.

The transistors both are - Fba19 J201.

This is a true overdrive in that it only sounds as good as your amp does and works best driving an already slightly driven amp - I love how this pedal feels , it makes everything sound bigger much like a Micro amp ( as his blurb says “the authority of a vintage micro amp, the heart and soul of a tube screamer and the touch responsiveness of a Class A tube amp.” )

but I wish it was brighter ( again from his blurb “ Pure,vintage overdrive that’s not too dark and not too bright.” ) so its actually designed and voiced this way which I'm sure would suit certain amps to a T but I want to remove that blanket darkness. Like i said even with the knob fully right I'm losing a certain sparkle that sounds inherently filtered out.

not too much of an issue but do you think the trimpots would add more gain ?

I hope the photos suffice and thanks for replying.

[Borderline]

another pic.

[karul]

Those pictures are unusable - they are too blurry and only a segment of pcb is visible - no one can trace from those pictures. Maybe you need more light, or a better camera.

Can you read the markings on the transistors ? I can see two of them.

If you want us to trace the pedal, you must provide us with usable information.
We need a clear picture of the front and back of the pcb to be able to see what is connected to what. No one can see through the potentiometers. You got to help us somehow.

Btw, do you have a DMM ? Maybe you can trace it by your self. If you haven't done it yet, maybe it's good time to start.

Browse through the forum and see some pictures from pedals being traced from.

That circuit is not too complex, maybe something can be done.

[Borderline]

yes , I understand. I guess i was kinda hoping the circuit was so formulaic someone could just second guess roughly the signal path and determine from the capacitor values alone which was causing the darkness.

Cheers anyway , I'm gonna start reading some guides and get some basics done to make things easier here in the future.

[Groovenut]

Without better pics there's no definitive way to know, but at a guess I would say it's a two Jfet overdrive. The input feeds the gate of first fet through a resistor which in turn uses a trimmer to set the bias and has a bypassed resistor (value blocked by the cap label) attached to the source. There is a cap from the drain feeding a 470k bypassed by a 500p feeding the gain pot which is bypassed input to wiper by a cap. The gain pot feeds the gate of the second fet which uses the other trimmer for bias, has a bypassed resistor attached to its source, and a cap from its drain to the tone pot. The tone pot filters highs through a cap to ground and passes the signal to the level pot, which in turn sends signal to the output jack. So by all appearances its a jfet version of a plexi preamp minus the cathode follower and tone stack. If you wish to make it brighter there are several things to try. Reduce the cap from the drain of Q1 to the gain pot,or reduce the cap bypassing the 470k, or reduce the cap on the gain control, or reduce the cap on the drain of Q2, or reduce the source resistor bypass cap on Q1 or Q2, or do all of the above.

[Borderline]

Thanks for that - although i had to read it about a million times to make any remote sense to me ( !!I'm one of those idiots with a solder iron and no technical knowledge and so far have just replaced caps with higher quality ones like for like)

but i am getting somewhere here - I've realised I've been using the wrong word all along, its not so much brighter but more transparent is what I'm going for - I want to hear more of my guitar underneath the overdrive, exactly if possible.

To confuse matters more, I do find myself using the tone knob ( it sounds to me like it only cuts a very specific frequency and not like a guitar tone knob ) so that tells me maybe Its something to do with something very early on in the stages, before it even hits the tone stack.

what would you recommend with these new clues limiting ourselves before the tone stage ? if you could pls literally gives me cap by number and a specific value to try based on your experience.

for example would reducing C2 to 2.2uf do anything. ( i'm only going by what I've learnt with guitar tone knobs 0.47uf = darker etc. )

Thanks for your time.

[Borderline]

That didnt really make any sense did it ? It made sense in my head !!!

I guess what i mean is that even if you have the gain on low tone to full and volume high , most drive pedals come close to being a clean boost - this doesant, it sounds muffled from the get go.

maybe i'm trying to coax something from it that the design does not permit, which is odd as for some reason ive associated FET based pedals as being bright clear and almost bell like.

[karul]

tell us what are the markings on the transistors, so we can be sure it's jfet overdirive - we're just guessing right now.
in case it's jfet overdive it could be that fets are biased for more gritty overdriven sound, and you want a cleaner sound you could try with the trimmers to bias the fets for max headroom, that is cleanest sound - if that's what you're aiming at

before messing around with trimmers, mark the current position, so you can reverse it the way it was

[Groovenut]

For the cleanest sound, I would bias the fet drains at half B+ voltage. If the B+ is 9, bias the drains at 4.5. Next, I believe there's a bypass cap on the gain pot. This makes the gain pot more of an adjustable high pass filter than a gain pot. Try lifting one leg of the cap that bypasses the gain pot (.0047u I believe) and see if this allows the pedal to clean up more.

[lead2203]

For the cleanest sound, I would bias the fet drains at half B+ voltage. If the B+ is 9, bias the drains at 4.5. Next, I believe there's a bypass cap on the gain pot. This makes the gain pot more of an adjustable high pass filter than a gain pot. Try lifting one leg of the cap that bypasses the gain pot (.0047u I believe) and see if this allows the pedal to clean up more.

The .0047 is on the output of the tone control.... but it is to ground before the volume..so you could still mass with that.

[lead2203]

Its FET. If you could post a pic of the traces under the pots.....The quality of the pics are good enough ....just need to see under there.

[Borderline]

tell us what are the markings on the transistors, so we can be sure it's jfet overdirive - we're just guessing right now.
in case it's jfet overdive it could be that fets are biased for more gritty overdriven sound, and you want a cleaner sound you could try with the trimmers to bias the fets for max headroom, that is cleanest sound - if that's what you're aiming at

before messing around with trimmers, mark the current position, so you can reverse it the way it was

That was literally the last thought I had in my mind before i slept !! even in my layman term thinking it seemed like the only logical reason, this pedal is designed to simulates two halves of a 12AX7 tube gain stage using fets - it must of been bias slightly overdriven.

I did mention the transistors in a earlier post - The transistors both are - Fba19 J201

Thanks Groovenut - I will try the things you mentioned, I'm gonna study every technical point you've made to me and understand it.

lead2203 - The pots are soldered onto the board i think, maybe the best I can do is draw them by hand and superimpose it - I'll see what I can do.

[Borderline]

agh , just deleted my post instead of edit.

Just to let you guys know lifting the leg of C6 did the trick. Thanks everyone for your help.

in the end it just a matter of voicing, it sounds great now - he would proberly do well adding a switch for " modern " and going from the stock 0.0047uf and something lower.

although usable now i will proberly try a 0.0022uf rather then leaving it wide open and hopefully get more range out the tone knob as at the moment it does sound a bit harsh after a certain point.

Thanks again - virtual beers all round.

[karul]

cheers

[poorlittlefingers]

Resurrecting this long-dead thread. I landed here because I have a J&J and was looking to do the same thing - open up the very muffled high end of the sound.

The suggestion of removing/substituting C6 works great. I used a .001 and got good results. This is a killer sounding gain pedal that's thick, and very touch responsive, and with the mod has good clarity and harmonics.