Chop Shop is more than I expected

[Alan W]

Build Rating

5.00 star(s)

My plan was not to post build reports until I had a "finished" pedal to document, but I just can't let my delight in this simple design stay contained. Granted, it's a very honeymoonish fling, since I just finished the wiring yesterday. So—first a brief review, then I'll give a build report.

I had high expectations for this, after having owned a few Fairfield Circuitry pedals. They are all very distinct from the mass of circuit borrowed merchandise out there—designed with a fairly specific goal in mind, I think. This is a lowish gain drive pedal, with no tone controls, and the gimmick of having a sag control to under-supply the transistors. I don't get along with most drive pedals. I like a good, very clean gain stage, and the Transcendence Boost has made me very, very happy. (Holy Fire stayed on my board for 15 or more years, 48V wall wart and all, so the fact that the Trans. largely has the same sound as the HF made me happy—but I sort of expected this.) Even as a clean only drive (ie, no Sag or Drive added) the Chopshop sounds great—not truly clean, but clean enough, and with a fairly neutral, but slightly weakened bass and lower midrange. (So far have only played single coils into it, and only into a brown/black Fender style amp.) The breakup is entirely natural, in ways that a diode breakup just isn't.

Adding in a small amount of Drive brings the lower bass and midrange back to balance. Adding more drive doesn't smear distortion over everything. It still REALLY follows your playing dynamics. Much to my surprise, I spend quite a while last night with the Drive dimed! The Sag also works in a pretty natural sounding way. The amp I played with (and still own) until the "clean Fender" bug bit me a few years ago, a Top Hat Club Royale, has a switchable rectifier in it, with hard and soft settings—the sag in an exaggerated version of that (but can be used subtly).

Basically, what amazes (yes, not too strong a word about this pedal) me is that everywhere I had the knobs, it sounded great. I don't think I've ever run across this before. My Baritone Tele is a good testbed, especially for lower frequencies. If this pedal had tone controls, I'd just leave them as close to being out of the circuit as possible. I'm going to play P-90s through it later today; I've got pretty good sense of how sensational that weill sound.

Until final assembly, the build went easy. I've learned that I need to double check all my soldering, parts placement, etc. I do this all along the way. When I plugged the pedal in, I got no sound. Well, if I cranked drive and volume up all the way, I got greatly attenuated sound. I could still tell that the sag was working too—but all at a good 60 or 70 db below what it should be. This made me suspect the 2N2222A I had used. It tested fine, but I had been confused about pin-outs, having misread a post that included bias instructions, thinking that the 2222 and 2222A had reversed pinouts (it was the P version of each that is reversed...) so I began second guessing that, because since everything seemed to be working, I thought that final output was being strangled there. But, even after replacement, and more checking with my 75A tester, it was a no go. Leaving having to pull the board as a final option, I got out my 8X binocular loupe, and a bright lamp, and just looked at everything. There is was, a cold solder joint on the stomp switch, at the output. (This made me think about how I check and recheck everything so carefully, but generally just solder the stomp in and trim it, no further inspection.) In any case, that was the issue, and a quick reflow took care of it. Oh—IDSS for Q1 was 720uA and 540uA for Q2, and I was able to dial in 6.00V on the drains easily. First time using a Gorva stomp, which I think will replace the Alphas I've been using.

Here's a front and gut shot, along with my current plan for the painted design. Just non metallic glossy white and red, with black lettering. I'm holding off on doing painting until I have designs for about 10 or 12 pedals finished, and will then order the transfer lettering I like to use. (It's too expensive unless I gang up a bunch of pedals.) I may not include the dots around the knobs...

QUESTION ABOUT VOLTAGE: Fairfield says 9 or 12 volts. At least one person on TGP that I have come to respect says he runs his at 18V—and I want to try this; nothing I used has less than a 35V rating, so while I don't see any potential problems, I'm also just a bit leery. Does anyone here have experience with running this at 18V? (And, when biasing for 9 volts, I checked at 12V, and the bias drifted to just below 8V—if I can run this at 18V, should I leave bias where it is (set while at 9V, or should I set it to 12.00V? (I'm expecting it to be close enough to 12, but I love nice round numbers.)

 

[leeinthesprings]

Sweet build! My chop shop should be in the mail box tomorrow : ) How many J201's did you have to go through to get the IDSS you wanted? Also what's the drain? How did you test it for voltage? Sorry I'm new with this stuff...

 

[Alan W]

Thanks! I had about a dozen old J201s in my “collection” and measured them to try for the IDSS levels that are listed in one of the longer posts about the Chop Shop. They were almost all in the 600s, but I was able to get two that were in the right range. The drain is one of the three leads coming off the J201 (the others are the source and the gate). If you touch the negative probe onto a connector sleeve (ground) and the positive probe onto the small round pad that is just above the trimmers, that will give you the drain voltage. (That pad is attached to the drain lead, just to make measuring it easier.)

I also have a tendency to socket transistors, so it makes it easy to experiment.

So, the drain should be 2/3 of whatever your supply voltage is. I have now tested the pedal at 18 volts, and it’s absolutely worth trying it at that voltage (as long as all your caps are rated for 25V minimum—and I’d feel more comfortable with 35v ratings).

 

[leeinthesprings]

Thanks! I had about a dozen old J201s in my “collection” and measured them to try for the IDSS levels that are listed in one of the longer posts about the Chop Shop. They were almost all in the 600s, but I was able to get two that were in the right range. The drain is one of the three leads coming off the J201 (the others are the source and the gate). If you touch the negative probe onto a connector sleeve (ground) and the positive probe onto the small round pad that is just above the trimmers, that will give you the drain voltage. (That pad is attached to the drain lead, just to make measuring it easier.)

I also have a tendency to socket transistors, so it makes it easy to experiment.

So, the drain should be 2/3 of whatever your supply voltage is. I have now tested the pedal at 18 volts, and it’s absolutely worth trying it at that voltage (as long as all your caps are rated for 25V minimum—and I’d feel more comfortable with 35v ratings).

Awesome!! Thank you for explaining everything. Looking forward to this build.

 

[szukalski]

This is one of my favourite pedals. How do you like 18v? More headroom?

 

[Alan W]

I really need to go back to 9 v and compare. That’s certainly what I usually expect—both more headroom and typically a finer “grain” to the breakup. I planned on trying out a guitar with P90s, to see how it reacted to more output, but since I also bumped it up to 18v, thought I would start with my Strat, since that’s the last thing I played the day before, and also the sound I’m most used to (although my baritone gets about as much play lately). But then, I just got lost in playing… .

I did grow to understand the interaction of the two upper knobs though. (And 9v works the same, and may be just as obvious; when I go back to test that, I’ll know)—the level control starts to break up some at 1 o’clock. So the cleanest sound is with it there, and the drive somewhere between 9 and 10 o’clock. This is being fed with med. output single coils (Wilde Alnico Microcoils).

I haven’t even tried stacking it yet, but I have been nudging the knobs to see how close I can get it to my favorite “set” drive sounds. (with drive pedals, once I get them sort of figured out, I tend to leave them in what I think of as their sweet spot, and tend to not change that too much, beyond tweeks to match different guitars. I know this is lazy and unfortunate, but that’s how it is). If I really like that sound, the pedal stays; if not, I keep it for “that sound” or give it away. This pedal is different though, (and may replace 2 or 3 drives!)—between a quarter turn of the sag, or a slight change in drive, and the harmonic bloom and envelope of the notes changes in a very predictable way, so I really can see changing settings on this. (The missing tone knobs are not missed in the least, so far with both guitars I’ve played through it, it’s exactly where I’d want those knobs, if they were there.)

I‘ve learned that it takes me a while to get to know the sound of something. I spent decades tweaking stereos, listening to different resistors, etc. I’m much better with slow realizations, recognizing what is no longer there, than first impressions. And most drives I’ve tried leave me uninterested. I’ve been building more drives than anything else the past half year (since actively restarting this hobby) but limit how fast I finish them, to give me a chance to get to know them better. Most drives sound plasticky to me, mainly in how the harmonics get pruned.* Some of this may be the op amp used (I just got in a small stash of OPA 2134s in to try in a few 072 positions on various pedals, since this chip seems more natural sounding to me.) The most recent drive built before this was the Aion Nordland deluxe board, which I was surprisingly pleased by, (it does have a bit of that plastic quality, but also keeps everything very tidy, and if I’m pushing a heavier mod (say the Ceasar with the blend at noon) I get better note to note separation with that than with the Transcendence, which still reigns as the cleanest, most harmonically neutral pedal I’ve played through. The next two drives I’ll be testing are the Snouse (Pot and Kettle) and the Cattle Driver. But before that, I have a Mercurial and the Aion Harmonic Percolator that I’ve been super curious about. But I’ve come to not expect too much from pedals with purposeful clipping sections in them.

Sorry for the TL;DR reply, especially with the crux of all of this being, ”I’m not sure of the differences at 18v yet—but I keep thinking how much like a really good tweed amp, both in sound AND FEEL, this pedal can be.” (Sometime in the early 90s I sold a Gibson GA3 and still do think about that sound (especially with the ‘62 ES330 I typically played through it back then). Not much clean volume to be had, (in all fairness, it was a tiny amp, pretty much Champ sized), but so rich…

*note: if it’s not obvious, I typically walk away from high gain. I’ve had Muffs, Rats, etc. over the years, and unless I need to match a sound, I just find them uninteresting, beyond how much of my sloppy playing they can obscure.

 

[MichaelW]

My plan was not to post build reports until I had a "finished" pedal to document, but I just can't let my delight in this simple design stay contained. Granted, it's a very honeymoonish fling, since I just finished the wiring yesterday. So—first a brief review, then I'll give a build report.

I had high expectations for this, after having owned a few Fairfield Circuitry pedals. They are all very distinct from the mass of circuit borrowed merchandise out there—designed with a fairly specific goal in mind, I think. This is a lowish gain drive pedal, with no tone controls, and the gimmick of having a sag control to under-supply the transistors. I don't get along with most drive pedals. I like a good, very clean gain stage, and the Transcendence Boost has made me very, very happy. (Holy Fire stayed on my board for 15 or more years, 48V wall wart and all, so the fact that the Trans. largely has the same sound as the HF made me happy—but I sort of expected this.) Even as a clean only drive (ie, no Sag or Drive added) the Chopshop sounds great—not truly clean, but clean enough, and with a fairly neutral, but slightly weakened bass and lower midrange. (So far have only played single coils into it, and only into a brown/black Fender style amp.) The breakup is entirely natural, in ways that a diode breakup just isn't.

Adding in a small amount of Drive brings the lower bass and midrange back to balance. Adding more drive doesn't smear distortion over everything. It still REALLY follows your playing dynamics. Much to my surprise, I spend quite a while last night with the Drive dimed! The Sag also works in a pretty natural sounding way. The amp I played with (and still own) until the "clean Fender" bug bit me a few years ago, a Top Hat Club Royale, has a switchable rectifier in it, with hard and soft settings—the sag in an exaggerated version of that (but can be used subtly).

Basically, what amazes (yes, not too strong a word about this pedal) me is that everywhere I had the knobs, it sounded great. I don't think I've ever run across this before. My Baritone Tele is a good testbed, especially for lower frequencies. If this pedal had tone controls, I'd just leave them as close to being out of the circuit as possible. I'm going to play P-90s through it later today; I've got pretty good sense of how sensational that weill sound.

Until final assembly, the build went easy. I've learned that I need to double check all my soldering, parts placement, etc. I do this all along the way. When I plugged the pedal in, I got no sound. Well, if I cranked drive and volume up all the way, I got greatly attenuated sound. I could still tell that the sag was working too—but all at a good 60 or 70 db below what it should be. This made me suspect the 2N2222A I had used. It tested fine, but I had been confused about pin-outs, having misread a post that included bias instructions, thinking that the 2222 and 2222A had reversed pinouts (it was the P version of each that is reversed...) so I began second guessing that, because since everything seemed to be working, I thought that final output was being strangled there. But, even after replacement, and more checking with my 75A tester, it was a no go. Leaving having to pull the board as a final option, I got out my 8X binocular loupe, and a bright lamp, and just looked at everything. There is was, a cold solder joint on the stomp switch, at the output. (This made me think about how I check and recheck everything so carefully, but generally just solder the stomp in and trim it, no further inspection.) In any case, that was the issue, and a quick reflow took care of it. Oh—IDSS for Q1 was 720uA and 540uA for Q2, and I was able to dial in 6.00V on the drains easily. First time using a Gorva stomp, which I think will replace the Alphas I've been using.

Here's a front and gut shot, along with my current plan for the painted design. Just non metallic glossy white and red, with black lettering. I'm holding off on doing painting until I have designs for about 10 or 12 pedals finished, and will then order the transfer lettering I like to use. (It's too expensive unless I gang up a bunch of pedals.) I may not include the dots around the knobs...

QUESTION ABOUT VOLTAGE: Fairfield says 9 or 12 volts. At least one person on TGP that I have come to respect says he runs his at 18V—and I want to try this; nothing I used has less than a 35V rating, so while I don't see any potential problems, I'm also just a bit leery. Does anyone here have experience with running this at 18V? (And, when biasing for 9 volts, I checked at 12V, and the bias drifted to just below 8V—if I can run this at 18V, should I leave bias where it is (set while at 9V, or should I set it to 12.00V? (I'm expecting it to be close enough to 12, but I love nice round numbers.)

View attachment 37303View attachment 37304View attachment 37305

Man, I feel the same way about the Chop Shop, I really need to dig it out and play it more!

 

[Feral Feline]

I really need to go back to 9 v and compare. That’s certainly what I usually expect—both more headroom and typically a finer “grain” to the breakup. I planned on trying out a guitar with P90s, to see how it reacted to more output, but since I also bumped it up to 18v, thought I would start with my Strat, since that’s the last thing I played the day before, and also the sound I’m most used to (although my baritone gets about as much play lately). But then, I just got lost in playing… .

I did grow to understand the interaction of the two upper knobs though. (And 9v works the same, and may be just as obvious; when I go back to test that, I’ll know)—the level control starts to break up some at 1 o’clock. So the cleanest sound is with it there, and the drive somewhere between 9 and 10 o’clock. This is being fed with med. output single coils (Wilde Alnico Microcoils).

I haven’t even tried stacking it yet, but I have been nudging the knobs to see how close I can get it to my favorite “set” drive sounds. (with drive pedals, once I get them sort of figured out, I tend to leave them in what I think of as their sweet spot, and tend to not change that too much, beyond tweeks to match different guitars. I know this is lazy and unfortunate, but that’s how it is). If I really like that sound, the pedal stays; if not, I keep it for “that sound” or give it away. This pedal is different though, (and may replace 2 or 3 drives!)—between a quarter turn of the sag, or a slight change in drive, and the harmonic bloom and envelope of the notes changes in a very predictable way, so I really can see changing settings on this. (The missing tone knobs are not missed in the least, so far with both guitars I’ve played through it, it’s exactly where I’d want those knobs, if they were there.)

I‘ve learned that it takes me a while to get to know the sound of something. I spent decades tweaking stereos, listening to different resistors, etc. I’m much better with slow realizations, recognizing what is no longer there, than first impressions. And most drives I’ve tried leave me uninterested. I’ve been building more drives than anything else the past half year (since actively restarting this hobby) but limit how fast I finish them, to give me a chance to get to know them better. Most drives sound plasticky to me, mainly in how the harmonics get pruned.* Some of this may be the op amp used (I just got in a small stash of OPA 2134s in to try in a few 072 positions on various pedals, since this chip seems more natural sounding to me.) The most recent drive built before this was the Aion Nordland deluxe board, which I was surprisingly pleased by, (it does have a bit of that plastic quality, but also keeps everything very tidy, and if I’m pushing a heavier mod (say the Ceasar with the blend at noon) I get better note to note separation with that than with the Transcendence, which still reigns as the cleanest, most harmonically neutral pedal I’ve played through. The next two drives I’ll be testing are the Snouse (Pot and Kettle) and the Cattle Driver. But before that, I have a Mercurial and the Aion Harmonic Percolator that I’ve been super curious about. But I’ve come to not expect too much from pedals with purposeful clipping sections in them.

Sorry for the TL;DR reply, especially with the crux of all of this being, ”I’m not sure of the differences at 18v yet—but I keep thinking how much like a really good tweed amp, both in sound AND FEEL, this pedal can be.” (Sometime in the early 90s I sold a Gibson GA3 and still do think about that sound (especially with the ‘62 ES330 I typically played through it back then). Not much clean volume to be had, (in all fairness, it was a tiny amp, pretty much Champ sized), but so rich…

*note: if it’s not obvious, I typically walk away from high gain. I’ve had Muffs, Rats, etc. over the years, and unless I need to match a sound, I just find them uninteresting, beyond how much of my sloppy playing they can obscure.

Great post added to already great thread.

 

[Alan W]

I’m writing a build report on the Mercurial Boost, and (after some minor mods, to be explained in the build report), I’ve got to change one of my praises of the Chop Shop.

With the Mercurial at unity gain, feeding it with just a notch to either side, the harmonic structure of the Chopshop can be slightly (and in a very meaningful way!) pushed fatter or thinner, without loosing its integrity. (I apologize if this reads as a rant. But to me, it’s huge. If I ever wanted a dual boost pedal, it would be the Mercurial into the Chopshop.)