# 2 More compressor builds - General Tso's and Convex



## MichaelW (Jul 24, 2022)

So in my last "2 Compressor Builds" thread I mentioned that the General Tso's (Thorpy Fat General) was going to be my last DIY compressor build until a Cali76 project somehow made it's way to existence. 

I "sorta" kept to my word.....even though this is a 2 Compressor build report

I was ordering some MMBF5457's from the AionFX site when I noticed the "Convex Compressor" project and discovered that it's a clone of the pretty rare Dinosaural OTC-201 designed by Dan Coggins. Dan now works as a design engineer for Thorpy and the Fat General is essentially the same circuit with some updates and tweaks. The Convex uses Vactrols and the Tso's uses LDR's, so I thought it would be neat to build both and compare.

Comparing the two schematics it looks like the parallel compression paths are pretty much the same. The Fat General adds a treble control that makes it a bit more flexible. I was chatting in DM with my Chief Pedal Enabler @szukalski and he was saying how the treble control makes it easier to dial in switching between hum buckers and single coils.

These two pedals are the 6th and 7th DIY compressors I've built and I have to say right up front, they are my favorites. (With the MBP Oracle coming in at a close second). 

The two pedals sound "nearly" identical which surprised me slightly. I was expecting to hear a bit more difference between the very controlled Vactrols vs the more variables in the LED/LDR combination. (How the LDR is facing, how far from the LED's they are etc). But I guess that doesn't make much of a difference as long as you're "in the ballpark" with the configuration.

Both are very transparent compressors, even more transparent than my "other favorite" compressor the Constrictor. They can both get pretty squishy at max compression settings but not as much as the Cornish OC-1 (AionFX Oceanid) which so far has the most amount of compression on tap for an optical compressor.
Of course compared to a VCA or Ross, all bets are off. The Oracle (Boss CS-3) has the highest amount of compression out of all the compressors I own both DIY and retail.

Playing them side by side I have a very slight preference for the General Tso's. I'm not sure if it's because I'm hearing a slight bit of coloration (in a good way) or what but it sounds a little fuller than the Convex. But it's really splitting hairs, they are so close. If I were forced to choose one to build it would definitely be the Tso's for the treble control. The Convex has toggle for level cut/boost (+/- 3db or flat) whereas the Tso's has a volume pot. (Oddly called "Balance"). They both share the exposed toggle switch to allow you to choose Blend mode or 100% compressed mode. With the way I like to use compressors, the blend mode works the best with about 60-70% blend. 

I've heard so many people rave about the General Tso's I'm not sure why I put at the back of my build list. I dunno, maybe because I don't like crappy chinese food and there was a subconscious association going on But I am really stoked about the pedal and it's probably going to be my goto Optical compressor and sit right next to the CS-3 on my mini board. 

Smooth build with no major issues except that I only had one green diffused LED so I almost didn't get to box it up this afternoon but Amazon showed up and saved the day! They brought me some 5mm LED's and the Chicken Head knobs I ordered. Love these things! I might get some different colors. 

Both of these pedals have buffered outputs and the AionFx Convex has his usual SPDT slider to select between True and Buffered Bypass on the daughterboard. I installed the slider but probably could just as well have hard wired it in Buffered bypass I never touch those. The Buffered ByPass 3pdt wiring boards from PPCB are out of stock so I wired the 3PDT directly. (which looks messy to me but........whacha gonna do? heh)

The Burnt Orange Tayda enclosure I used for the Convex was not their best example. I love the color but this particular one has extra orange peel and the powder coating chipped when I was center punching. Hence the washers on the toggle switches to cover up the chip and the slightly wonky positioning of the status led. I was pretty annoyed at the prospect of wasting an enclosure but was glad to be able to recover gracefully. The Convex uses a TL072 where the Tso's called for an OPA2134, which I used. (I was finally able to score some OPA2134's from amplifiedparts.com, woohoo!)

Off the top of my head the only other differences I recall are 1N4148's in the Tso's and 1N914's in the Convex and a few different cap and resistor values. But remarkably similar builds.

The AionFX Convex (Dinosaural OTC-201)








PedalPCB General Tso's (Thorpy Fat General)


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## SYLV9ST9R (Jul 24, 2022)

Great builds as usual Michael!


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## Dan0h (Jul 24, 2022)

Man you are a factory lately. Love the enthusiasm and the detail you share. The settings you found on the Tso are pretty much where mine lives as well.


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## MattG (Jul 24, 2022)

Yes, love looking at your killer builds and the write-ups take the build reports to the next level!

Are you really fast at building these, or do you have a lot of time? I’ve never actually timed myself, but I’m guessing it probably takes me at least four hours to do a build.

Anyway, your output is impressive, keep it up!


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## MichaelW (Jul 24, 2022)

MattG said:


> Yes, love looking at your killer builds and the write-ups take the build reports to the next level!
> 
> Are you really fast at building these, or do you have a lot of time? I’ve never actually timed myself, but I’m guessing it probably takes me at least four hours to do a build.
> 
> Anyway, your output is impressive, keep it up!


Because I have no life..............

Actually, I've gotten pretty efficient with my process and builds go pretty fast for me, at the least the ones I'm building. I have in the backlog an MPB DMM clone (Tourbus) and I want to build a Byzantium....because I have extra sets of BBD chips leftover from my Ceasar build, I expect those will take me more time since they're more complex builds.

I tend towards OCD and in all seriousness was diagnosed ADHD about a year ago. (Explains a lot hahah) but I tend to "hyper focus", whether it's building a presentation deck for work or building a pedal. When I'm "in the zone" I can build pretty quickly. 

For me it's all about the prep (I guess it's the same for my cooking too). I pull all the components and put them sorted in plastic a tackle tray box for each pedal. Then I like to drill 3 or 4 enclosures all at one go. (Make all the mess and do all the cleanup). Then I mount the toggles, pots, and 3dpt, dry fit the PCB for each pedal then set the whole thing aside. I'll build them during the week, measure components, stuff, solder, box, rock, post build report (I won't mention that I play a few David Gilmour licks when "rocking" in honor of @thewintersoldier on EVERY build..... I work from home and I can take little breaks during my work day, an hour here, and hour there. Another aspect of my ADHD is that I tend to be better at processing ideas, thoughts, emotions when I'm multi-tasking. So sometimes I'll hit some sort of creative roadblock with work, I can go to my bench and work on a pedal for a bit, and it actually helps free my brain to solve whatever work problem I was working on with the distraction. Of course all of this about me drives my wife absolutely bonkers.....


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## Funnel (Jul 24, 2022)

Looks good! I appreciate your detailed build reports. Compressors aren’t something that I want to build many of, so having so much info on each build is very helpful. I only have the byoc 5 knob but am curious to try the fat general


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## sticky1138 (Sep 12, 2022)

Nice builds! I'm not usually a fan of chicken heads but they're looking really nice here.

Is there a way to control the output level while in blend mode on the Tso's? I assume you are at the mercy of the output level that comes with whatever blend setting you use. That sounds annoying if you get either a volume loss or boost when switching the pedal on and off.

I'm thinking about building one, and if that's true, a useful mod might be to jump the toggle switch so that it's permanently in blend mode (for me that's the draw of the pedal), and then add a volume pot to control the output level in its place.


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## MichaelW (Sep 12, 2022)

No the output is set by the amount of blended signal. And it's pretty strong signal, there's a bit of a default "boost" effect.
In "volume" mode, it's set to 90% blend but you can control the output that way and play with the "Sustain" control to get the desired amount of compression. Playing around with the settings I'm able to get unity with the amount of subtle compression I tend to use.
If I want a real squish I'll use the MBP Oracle (Boss CS-3).


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## Feral Feline (Sep 13, 2022)

Fantastic builds!

I'm so glad this thread got bumped because I'd missed it.

I had the Aion board and because it is so similar to the General Tso, I decided against getting the PPCB version — then in a weak moment during one of the sales, I picked up the PPCB board, too. You've already done the comparison work for me, so I can just sit back and enjoy the builds — but I'm inspired now to at least build them together at the same time. And on that note...



MichaelW said:


> Because I have no life..............
> 
> Actually, I've gotten pretty efficient with my process and builds go pretty fast for me, at the least the ones I'm building. I have in the backlog an MPB DMM clone (Tourbus) and I want to build a Byzantium....because I have extra sets of BBD chips leftover from my Ceasar build, I expect those will take me more time since they're more complex builds.
> 
> ...



Thank you so much for sharing your builds, and particularly in this instance imparting more of your build process. I'm looking to change how I build and was thinking of leaving one at a time behind and doing "mass production" via several levels of build, serially. IE — populating one board at a time, but waiting until I have five (or however many) fully populated before moving on to drilling boxes and then as you've demonstrated, drilling a bunch of enclosures at once, etc.

Your build reports are always enjoyable reading, and always inspiring.


Also, you cook! Indeed, if you cook how you build, I want to come over for dinner!


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## Fingolfen (Sep 13, 2022)

Just out of curiosity, what are you using for your flux remover?


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## MichaelW (Sep 13, 2022)

Fingolfen said:


> Just out of curiosity, what are you using for your flux remover?


IPA


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## MichaelW (Sep 13, 2022)

But I generally don't clean once the board is in the box. And I solder all my pots and off board wiring "in box". Kinda rethinking that whole process.


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## Feral Feline (Sep 13, 2022)

What's for dinner?


Offboard wiring out of box is okay, but pre-soldering pots and switches before they're in the box seems... to invite trouble.


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## MichaelW (Sep 13, 2022)

Feral Feline said:


> What's for dinner?
> 
> 
> Offboard wiring out of box is okay, but pre-soldering pots and switches before they're in the box seems... to invite trouble.


Yah, I did it once....I think it was my first build...heh...


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## Robert (Sep 13, 2022)

Feral Feline said:


> Offboard wiring out of box is okay, but pre-soldering pots and switches before they're in the box seems... to invite trouble.



I solder all of my pots and switches outside of the box, and most wiring once it's in the box.


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## Fingolfen (Sep 13, 2022)

MichaelW said:


> IPA


What purity? I've been using denatured for the bulk and then some of the fancy sh*t for final clean up...


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## Bricksnbeatles (Sep 13, 2022)

Fingolfen said:


> What purity? I've been using denatured for the bulk and then some of the fancy sh*t for final clean up...


99% for me. Got a case of 12 16oz bottles for like $20


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## steviejr92 (Sep 13, 2022)

I use 91% works perfectly fine the higher the better in my opinion it'll dry off faster. I wouldn't go any lower than 90% though.


Fingolfen said:


> What purity? I've been using denatured for the bulk and then some of the fancy sh*t for final clean up...


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## Fingolfen (Sep 13, 2022)

Yeah, alcohols love to pick up water and I don't want it anywhere near my circuits...


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## MichaelW (Sep 13, 2022)

I went through a big bottle of 99% then replaced it with 91%, don't see any difference.


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## Feral Feline (Sep 13, 2022)

Robert said:


> I solder all of my pots and switches outside of the box, and most wiring once it's in the box.


Sure, but you just verify the circuits work, and then throw all those builds in the same one big box.

Some of us have to drill holes in smaller boxes, holes that have to line up with the populated PCBs, and use the pedals after they're built.

Have you forgotten this thrilling drilling thread, or that I won a contest for how bad my drilling is was?


Maybe I'm still doing it wrong. I pop the board, I measure the enclosure and drill the holes, then the hardware is mounted in the enclosure and then I place the board onto the pins and needles of the pots and switches...


I'll try MichaelW's methods, they work for him.


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## Robert (Sep 13, 2022)

Feral Feline said:


> Sure, but you just verify the circuits work, and then throw all those builds in the same one big box.



Well sure, now, but I've boxed up one or two.


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## Mentaltossflycoon (Sep 13, 2022)

Robert said:


> I solder all of my pots and switches outside of the box, and most wiring once it's in the box.


Same. I don't even look at enclosures until it has been rocked.


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