Monday, November 4, 2019


I have been retiring some circa 2004 DIY modules, but, what to do with them? I could rob them of parts and toss what's left, but instead decided to make a mini modular out of them and use it to test things on the bench like new filters or whatever.

Finished--working! L to R: breakout to amp; power and CV; stripboarded Irwin VCA; crappy mixer; TH ADSR, ASMVCO with 3900 waveform mod

First up, I took an ancient ADSR (read more here, it's a really old Thomas Henry/PAIA design). Stop the presses!  Run, don't walk, and immediately download all the Thomas Henry SDIY reprints here. Anyone doing audio DIY needs to download and at least glance through this PDF!) I think this ADSR was finished in about 2005. Back in the day I hand made the PCB....using press-n-peel, acid and a drill press...I can't believe I used to do that, but the ADSR still works.

To the ancient ADSR I added a much needed buffered LED to get a visual on CV at output; OK how to do that?  Had a very small PCB fab'd up--the IC is SMD:

Punched a hole in the ADSR front panel and mounted it:

Yea I tied wrapped all the wires down after I took this photo.

OK that worked!  Get the Eagle files, PDFs of board, etc., here.

Next built up a buffered CV board, information on my website here:

..and mounted that next to a PAIA power supply relic I had in my junk box in a 1u FRAC panel.  Tight fit....

The 9770 power supply board is from like 2002? I had it in a junk box labeled "Linear power supply".  Don't remember what if anything it was ever used for.  But it works!

Q: will it all fit?

Had some blank alubase panels from lying around--punched more holes to accommodate the power supply and CV board in a 1u Frac.

Ready to test--yes it fits and it worked first time! Bought the wall wart for something like $1.50 USD from the Goldmine
Still need (maybe) to Lazertran the powersupply/CV module? Not sure, so many other things to work on.

OK let's assemble our castaway modules. Almost ready to go, let's rack 'em!

The **not DIY** BGW power amp was purchased on Ebay for $20. A steal! BGW makes great power amps that can be had for next to nothing if you look around.

Wow that was easy.  The whole project start to finish maybe took an evening.

The VCO is a really old ASMVCO but i finished it in 2017, only to replace it with a more stable 3340 VCO, a design I am still working on (next few posts?).

The mixer got pulled out of my main modular racks because I disliked its ergonomics--I put the jacks and knobs too close together, and the lazertran art came out really crappy. But it's fine for a workbench, where it won't get a ton of use.

Good news, everything here, ADSR, mixer, power, VCO, etc. doesn't smoke (it didn't when I pulled it from my modular, and it still doesn't). Good to know 15+ years later there is still a use for this crusty old frac rak crap. I will use this going forward to see how things work with other modules I build. The island of misfit toys? Who cares!

See you next time!

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