# Chop Shop (Fairfield Circuitry Barbershop)



## MichaelW (Jul 27, 2022)

Here's another build that was totally not on my radar until I heard @szukalski talk about how much he likes his.

I have the updated version of this board that has the onboard trimpots. I can't imagine trying to dial in the bias without the trimmers and probably would have installed some if I were using the old board.

Even with the trimmers the biasing is tricky and this circuit seems to be pretty sensitive to the spec's of the J201's. 

I found this thread of course AFTER I had already built it. I usually do a bit of research and look for troubleshooting threads before building a pedal but skipped that this time to my own detriment. I found out that this pedal seems pretty finicky with the JFET's and some sorting is in order.

I actually have a second Chop Shop board (because @PedalPCB seems to have problems counting, hahaha, he sent me an extra board) that I may build out using that thread as a guide.

I decided to use the SMD J201's and this is the first attempt at soldering an SMD besides an FV-1. It was an......interesting experience. 

Not sure I would want to do a whole board this way, but I think I managed ok with only a couple of components. 

I initially biased it by voltage on my bench. I got Q1 to about 5 volts but could not get a consistent reading on Q2. So I said screw it, fired it up and biased it by ear.
I'm still messing with it but I "think" I have it where it sounds like its supposed to. I haven't gone back to check where I landed.
With the bias settings where I have them on Q1 I don't have a lot of output. Unity is around 1 o'clock. If I dial it where there it more output, it's very clean output only and I seem to lose the clipping. So I'm not entirely sure if this is expected behavior, or spec's of my J201's or what. 

Tonally, this has some of the same transistor clipping vibe of the Benson Preamp, although a bit more angular and less smooth.
At higher gain settings it can sound fuzzy and gated.  So far, I've had it with the gain knob set fairly low, and the SAG set pretty low, then boosting it with the Clandestine Preamp, great low gain sounds. Sounds pretty good with my Tele and sounds REALLY good with the P90 Tele.

But definitely still needs some dialing in. 

I decided to go for the same vibe that Fairfield does with their unpainted enclosures. I used a genuine Hammond 1590B and genuine Davies knobs.





Holy crap those things are small!!!!


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## fig (Jul 27, 2022)

Smashing Michael! Now that you’ve gotten a taste for the small stuff, what do you think? More or less of it?


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## MichaelW (Jul 27, 2022)

fig said:


> Smashing Michael! Now that you’ve gotten a taste for the small stuff, what do you think? More or less of it?


Well, I would say that I don’t mind it as much as I mind getting counterfeit or out of spec components How’s that for a political answer?


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## szukalski (Jul 27, 2022)

Looks great. Love the spartan look with the ox-blood knobs. 

What’s with the missing 4k7? Not the led resistor?

I found that it’s similar to the light speed in that it’s very slight colouration or distortion unless I crank it. I usually have the distortion maxed and the level around 13:00, sag depending on mood. Same with the chain placement, I prefer it towards the end of the chain, I’d be tempted to try it in the effects loop if any of my tasty amps had one. 

I enjoy it for a darker, laid back blues tone. Like when you have your neck pickup halfway on vol and tone, playing something moody.


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## MichaelW (Jul 27, 2022)

I just noticed that, wtf was I doing to miss that! I had some extra components left over because the BOM was from the original version and the trim pot replaces some of the resistors in the original BOM. I must have gotten discombobulated.  I’ll install it and report back.


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## MichaelW (Jul 27, 2022)

Ok I installed the missing 4k7 resistor. I "think" it corresponds to R6 of the V1 schematic although I'm not positive. Can't quite tell from the traces without yanking the board out. Installing the resistor has changed the way the Drive knob responds but did not effect the trim bias or the overall tone. My bias settings are still pretty low. With the trimmers maxed out and the SAG knob full CW, I'm only getting 4.5v at the J201's. Where I have them set to sound good by ear is much lower, Q1 = 3.53v, Q2=2.10v. I recall having the same issue when I was biasing my Son of Ben. I was not getting the voltages I was supposed to be when dialed by ear. But I left it where it sounded the best to me.


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## swelchy (Jul 27, 2022)

Your Wiring is beautiful!


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## MichaelW (Jul 27, 2022)

swelchy said:


> Your Wiring is beautiful!


I should put a little sticker in all my builds "Wiring Inspired by @fig"


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## fig (Jul 27, 2022)

Thank you 

…but, it’s not talent it’s just stubbornness that cannot allow my poor eyesight and shaky hands to get the best of my OCD.


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## EGRENIER (Jul 27, 2022)

That's very good work... if I had to guess, you did the left SMD first, I seem to see an improvement just looking at the soldering of the right one !


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## MichaelW (Jul 27, 2022)

EGRENIER said:


> That's very good work... if I had to guess, you did the left SMD first, I seem to see an improvement just looking at the soldering of the right one !


You nailed it. I did do the left one first, I flooded the pads with liquid flux then took so long futzing with the placement and holding the sucker down that the flux dried...HAH. Made an unholy mess. Lots of scrubbing with IPA to clean it all up. Having learned my lesson, when I did the right one I "tacked" it in place dry with a small dollop of solder on the pad first. Then flux, the other two pad and then re-hit the first pad.


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## EGRENIER (Jul 27, 2022)

MichaelW said:


> You nailed it. I did do the left one first, I flooded the pads with liquid flux then took so long futzing with the placement and holding the sucker down that the flux dried...HAH. Made an unholy mess. Lots of scrubbing with IPA to clean it all up. Having learned my lesson, when I did the right one I "tacked" it in place dry with a small dollop of solder on the pad first. Then flux, the other two pad and then re-hit the first pad.


Hey, I'm not one to criticize... I've never solder SMDs, so you're already 2 up on me


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## Feral Feline (Jul 27, 2022)

Stellar build. 
Love Fairfield's circuits. 
The genuine Davies and bare enclosure look great and the little Fresnel lens compliments the whole look — _very_ classy.

Delighted you like it with P-90s, bodes well for my SG Special. Never played it through my Fairfield Barbershop 'cause the two weren't on the same continent, but now that they are...

I built up a Barbershop-ish thing with some EQ on a board not meant for what I was doing, a ROG Mayqueen-based PCB, after I noticed some similarities in the general topology — albeit it required bending some legs around to accommodate a JFET where a BJT should go and vice versa.

I'll build up my Chop Shop stock, when I get to it. 



As always, thanks for the inspiration and especially the kick in the keister to get building.


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## MichaelW (Jul 27, 2022)

Feral Feline said:


> Stellar build.
> Love Fairfield's circuits.
> The genuine Davies and bare enclosure look great and the little Fresnel lens compliments the whole look — _very_ classy.
> 
> ...


Well to be fair I’m having a bit of a “thing” going on with my P90 Tele build, I just absolutely love how that thing plays and sound with just about everything!  The Lollar P90’s definitely live up to their reputation. Having a hard time picking up any of my other guitars at the moment haha.


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## benny_profane (Jul 27, 2022)

Nice work! Would you mind sharing your template / coordinates for top jacks? I don't think the one I'm working from would allow open frame jacks.


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## MichaelW (Jul 27, 2022)

benny_profane said:


> Nice work! Would you mind sharing your template / coordinates for top jacks? I don't think the one I'm working from would allow open frame jacks.


Sure, I’ve been asked a couple times by different people, I’ll try to whip something up.


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## benny_profane (Jul 27, 2022)

MichaelW said:


> Sure, I’ve been asked a couple times by different people, I’ll try to whip something up.


Awesome! Thank you very much!


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## Guilherme Collateral (Jul 27, 2022)

Clean as a whistle!


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## MichaelW (Jul 27, 2022)

benny_profane said:


> Awesome! Thank you very much!


Here you go.


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## benny_profane (Jul 27, 2022)

MichaelW said:


> Here you go.


Thanks!


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