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XR-LFO
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author XR-LFO
Dragonslair
I had built a few other LFO's, but I wanted one with a fairly clean sine wave output, every time I needed a sine wave, I had to dedicate one of my main oscillators to the task. I was looking at building Thomas Henry's vco with the XR2206, and while perusing the data sheet, I thought, "this would make a great LFO", so I went and designed one, it works perfectly, the sine wave output is almost perfect, the square wave out is a bit distorted, but not to bad.
It also has controls for the frequency (3 ranges) and amplitude so, for instance, you can set up some tremolo on a patch and dial in the speed to your liking, and set the amplitude (amount) to be barely discernible to almost overpowering.

I am now working on version 2 of the board, and will be adding voltage control for the frequency and amplitude.
parasitk
Does it go into audio range? I'm guessing yes, but I want to be sure.

With Freq and Amp control, and decent 1v/oct tracking, this thing would be a cool utility VCO - with a nice sine, maybe an FM modulator - is this realistic?
Dragonslair
Frequency range is approx 1 cycle every 15 seconds to 1 KHZ.
Thomas Henry already did a nice VCO with the 2206, I'm actually looking at a VCO based around the 8038.
I've never done a VCO design before, so I'll have to do some more experimenting on the 1v/octave scaling.
flight
Whoah, were you able to find a good source for the ICL8038 or are you using the NTE version?

I like how you get more outputs with the 8038, but the range is better on the 2206. One of these days I want to dink around with the 2206 and see what can be done about the number of waveforms at a time...
Dragonslair
Well scrap the idea of the 8038, I have a dozen or so here, but when I checked with my supplier, the price has gone up to 4 times what I paid for these, and don't even think about the NTE version, even the 2206 has more than tripled in price, I have about 100 of those, but when they run out, that's probably going to be it for them to.
So I've gone back to my old oscillator design, it uses 3080's (which are also starting to get harder to find), it only has square and pulse waves out, but I built an add on module that outputs sine and triangle waves.
flight
It's such a shame, isn't it, how all the useful components keep disappearing?
I see you have the same opinion of NTE as I; does anyone know who they really are or where/who actually manufactures their chips? I know that their pots are made by Precision. I don't think they actually do any manufacturing... hmmm.....
I keep wanting to play around with the (now Texas Instruments) OPA 86x OTAs and see if they have any use in synths at all, but the price is rather prohibitive.
Rych
I successfully built 2 'precision' 1V/oct triangle VCOs around the CA3080 from Thomas Henry's 3080 book. I've got them tuned fair enough to operate at 1V/octave through 3 or 4 bass range octaves.

Outside of that, my original intent was to use them as VCLFOs. They're working quite well as bass VCOs too.

Once I run out of CA3080's (about 20 left), I'll see about changing the core to the LM13700. I'm sure there's a decent Triangle to Sine converter listed somewhere on the electro-music site. I prolly have one somewhere in my archives, as well.
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