Hayling Island

Hayling Island

Sunday, November 10, 2013

And so it begins ..

Well what with having the puppies pretty much sold now, and light at the end of the tunnel from the work life I find my mind turning back to the modular synth. I dug out the linear power supply I made for the purpose 15 years ago, found out what was wrong with it;

It's a 15-0-15 power supply based on linear regulators with external bypass transistors. The circuit, originally published with the Formant synth from Elektor relies on having two separate windings on the transformer. Turns out the potted one I was using didn't - I must have done an incomplete job of probing with Rita (the digital multimeter is called Rita the Meter. Actually they all are to avoid confusion, with the exception of the tiny little 4.5 digit autoranging one which came all the way from China for a stupidly low price, and she is called Lita)

So, one new transformer later it's up and running. The first device I have powered with it is a mixer - Soundcraft Compact 10 from *bay - only cost me a tenner or so. As with many lower end professional audio products, the power supply had gone to Silicon Heaven in dramatic style. I've since disconnected the original PSU, feeding from the Formant PSU and all happy. Being a heavy load for the PSU it's also given me the chance to see if the performance under load is OK. It is ..
I will probably attach the mixer to the synth anyway, since you always need to integrate audio sources and sinks together. It also looks pretty with lots of colored knobs.

I have decided that the second step on the way is to make the MIDI-CV converter. I have decided to use an FPGA board I have, coupled to a new daughter board with the MIDI interface on, a touch LCD display and an AD5668, so I have eight channels of CV coming out. I'll probably use ZPUino as a soft processor. I already have a VGA interface on there, so I can use a small retail color display from IBM as a general purpose monitor. I remember working on text mode color display adapters for IBM many years ago, and what took months then to code up and have assembled in TTL took me about four hours to get going with a Xilinx FPGA and their free tools.

Ah, will need a 5v PSU. Well, I have many of those around the place - I wonder if I use a switcher, will that break through into the audio path?

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