Interfaces to analog gear

Pehr

I'm really eager to build myself a very simple modular style lunetta synth. First I thought of it like a stand-alone system, with just a audio out to my mixer.

But recently I've been thinking about how to connect my analog modular to a lunetta and I have come up with these ideas:

Analog -> digital:
Analog to digital converters (obviously Rolling Eyes

) - one could use comparator circuits or bare ADC-chips. I have a ADC0804 That I'll experiment with.

Op-Amp comparators - A very good design is the one from CGS39, but instead of the reference resistors one might use a pot to control the pulse width of the digital signal.

Window comparators - built from op-amps ( http://home.cogeco.ca/~rpaisley4/Comparator4Level.GIF ) or perhaps the LM3914 could be used. I'll try a simplified version of Ians 5-pulser for that.

Digital -> Analog:
R2R digital to analog converters- ( http://www.musicfromouterspace.com/analogsynth/D2Aconvert.gif ), as suggested by unkle k in another thread. This may produce wavetable like sounds.

Attenuators (buffered), since a 0-12V square isn't that funny to send into a VCO

Mixers/filters - a good example for this is the WSG filter.

more ideas?

andrewF · Posted: Fri Oct 17, 2008 9:06 pm Post subject:

I tried plugging the outputs of the CGS gated comparator in to CGS DC mixer and got a very CV good sequencer.
so a DC mixer would be a useful D2A section on a Lunetta either for mixing audio freq signals or pulses to get a control voltage

Going the other way, the LM3915/3914 would be interesting

loss1234 · Posted: Sat Oct 18, 2008 5:42 am Post subject:

uh-=oh

did someone say it's dangerous to take 0-12v signals straight out of a cmos chip and plug them into a vco?

i have been plugging my (12v powered) lunetta stuff into my modular for months now....

now i am worried.

am i going to fry something??

thanks

Pehr · Posted: Sat Oct 18, 2008 8:14 am Post subject:

richardc64 · Posted: Sat Oct 18, 2008 9:02 am Post subject:

The danger is in going the other way: plugging +/- signals from a modular into single-supply cmos.

Pehr · Posted: Sat Oct 18, 2008 9:11 am Post subject:

richardc64 · Posted: Sat Oct 18, 2008 9:38 am Post subject:

Pehr · Posted: Sat Oct 18, 2008 9:42 am Post subject:

[quote="richardc64"]

aerogramma · Posted: Sun Oct 19, 2008 1:56 am Post subject:

what about plugging the outs of something like a baby seq into a crude 40106 oscillator array? woud that work?

Wink

Pehr · Posted: Sun Oct 19, 2008 7:15 am Post subject:

aerogramma · Posted: Mon Oct 20, 2008 4:26 am Post subject:

Pehr · Posted: Mon Oct 20, 2008 10:14 am Post subject:

that's easy with gated oscillators of constant frequency.
You could connect the same output stage of the 4017 to several different 'gate in' of those oscillators to activate them. Cool

aerogramma · Posted: Mon Oct 20, 2008 10:25 am Post subject:

and that would be the 'easy' part Wink

what about having fixed tuning for each oscillators... thus achieving chords like you suggested, what could be a good to do that?

Pehr · Posted: Mon Oct 20, 2008 12:46 pm Post subject:

Yes, there could be fixed oscillators with a trimpot to set the frequency for the 12 noted in an octave.

The frequencies could then be divided to fill the whole frequency range desired.

That's how electric organs work. Very Happy

However, I don't know how bad the oscillator drift of a CMOS oscillator is... Confused

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

synthmonger · Posted: Sun Feb 22, 2009 11:10 am Post subject:

That's funny I've been greatly considering making a 2 octave synth using my 40106 vcos and dividers. That would be 8 40106s and 6 4066s though ;x

I need to get working on the pcb for these vco's dangit!