Thursday, May 12, 2011

PAiA 2720/4700 Quick Help

So you bought an old PAiA system. It looks cool but now what do you do with it? It seems like I've answered this question countless times on the nerd forums. Therefore, I decided to post some of my stock answers and suggestions here:

You bought it. Now what?

- Inspect the power module. How does the board look? Are there any shorts or other problems? Replace all of those capacitors (aka a "cap"). Isolate the power module and test the voltages before firing up other modules. Another option is to get a new, clean, power supply. Many people run their systems happily on the oldschool power. The system does run quieter and smoother on a nice modern PSU. I'm running my machine off of a modern medical power supply that I have tapped into the 4771 so I can still tap it for a bias. Just a tip, the system runs fine at 15V instead of 18V.

- When I get a "new" module the first things I do is recap it and check for errors. There were a lot of builders back in the day and not all of them had skills. As far the caps, some of them are pushing 40 years old. Isolate each module before testing it for the first time.

- As you see, the 4700/2720 systems use pinjacks (which I kind of loathe). I use bananas elsewhere so this is a better option for me. The extra unused pin holes also leaves spaces for mods if you'd like that sort of thing. Bananas fit in the existing holes with any additional drilling.

- Remember, the PAiA 2720/4700 has linear VCOs similar to the early Korg and Yamaha machines. This linear response is based on the Hz/Volt system and not the Volt/Octave, or exponential system used by Moog, ARP, MOTM, modern PAiA 4700 synths, etc..

- Again, these systems can be great, especially when tweaked a bit.


- Links to all the PAiA tutorials and build documents. John Simonton wrote some great tutorials that are definitely worth looking through.

- Info about exponential versus linear responses in context of the PAiA 2720/4700, look here.

- Module current draw info.

- Scott over at PAiA talk can be a lot of help as well.

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