A better lfo for your xoxbox
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A better lfo for your xoxbox

by mario1089 on Wed Sep 26, 2012 4:26 pm

Dunno exactly, but i guess some here have a vcf input. Think about buying a cheap function Generator at eBay. These devices work perfectly as lfo, do any rate required, do sweeps of rate all the time automatically and so on. Used to have one of them connected to my ms20 before i sold it, and i tell you it was just great.
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Re: A better lfo for your xoxbox

by bmot on Wed Nov 14, 2012 7:57 pm

that's a really great idea. i've never heard of doing this before and am curious, can you answer a few questions?

so to check I understand it, the function generato is an lfo that can be used to control the filter if you have a vcf input? i've got one added to my mc-202 but not the xoxbox. it does have cv & gate out though, so could that be used to sync the lfo? how programmable is the lfo and can you draw your own lfo curves? usually comes with a variety of shapes? i did check ebay but as you know a bit about them would be helpful to hear a bit more, thanks
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Re: A better lfo for your xoxbox

by mario1089 on Thu Nov 15, 2012 5:45 am

Typically you`d look for one called "Sweep Function Generator":

http://www.prime-electronics.com.au/dat ... erator.pdf

http://www.ebay.com/itm/Protek-2-Mhz-Sw ... 2a25e98d8f

http://www.ebay.com/itm/HC-Protek-B-801 ... 1c2d1fa2f6

http://www.ebay.com/itm/Wavetek-FG3B-Sw ... 337d0ec8d6


The will output an oscillator signal within an extremly wide frequency range, like from seconds to highest audio freqs, so they can do sort of FM modulations also, like with the Doepfer MS 404 for example.

If you look for rates of like 30seconds and more, which is reasonable I think, you have to read the manuals before buying. Some of them or maybe most have a minimum rate at 0.2Hz or 0.1 Hz (5s, 10s).

You can`t draw waveforms, but they usually support square, triangle, Saw, Sine.

The nice thing is, with "Sweep" generators, you can set a start-frequeny and an end-frequency, and the time it should take to sweep between those 2, and whether that sweep is performed linearly or logarithmicaly! This is actually an awesome feature.

They are nice to use, as showing their freq on a nice display, and look super-cool-nerdy, haha!

It could be that on an mc-202, which is a digital device, that VCF input may not allow for audio rate modulation, I don`t know - it depends on the sampling frequency of the mc`s VCF input. It may also be you get weird sampling artefacts at high rates, but that may also be a cool feature :) You could try it first by putting some other synth`s-audio signal into that mc input and check if it works, in case audio rate mod is what you`re looking for.

What you should also know:
1) you have to create a cable on your own. I just used a normal audio cable, broke it up at one side, and somehow taped/clamped the wires onto the generators output. But better is to take a cable that matches the gen`s output, break that up and solder an audio cable onto it.
2) It`s a bit unclear to me if it always works, regarding proper groundings, to not have dc offsets for example. But I think it is very likely that it always does. At least on the MS20 is was just perfect.

I don`t think you can use the xoxbox outputs for anything here.

-Mario
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Re: A better lfo for your xoxbox

by bmot on Thu Nov 15, 2012 11:47 am

ok, thanks a lot for the detailed reply, i will look into it.

one point though - the mc-202 is not digital, it's a 1984 analogue bassline synth much along lines of tb-303. sorrym was hard to write that without sounding like a dick. perhaps you mixed it up with the mc-303 or some other PoS.

http://www.vintagesynth.com/roland/mc202.php

on the 202 i had extra cv, gate, filter and portamento inputs added to allow midi control with the kenton pro solo and bypassing the CPU which led to a lag preventing slides/pitch bend. I can use the lfo on the kenton but filter control is only sysex unfortunately, and I don't have any sysex controllers that would do it without manual programming. the 202's LFO is basic with rate and delay but only 1 shape.

i also like the nerdyness of having a machine with lfo waveforms on display, would look nice live

cheers
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