MF-102 LFO mod?

[Tibbon]

Has anyone messed around with increasing the range of the LFO to a wider range, or even up to the same range as the oscilators on the Voyager? I got the impression in talking to Amos the other day that it might be possible. Tomorrow I plan to pull out the scope and the iron and see what I can get going... I'll post pics/sound examples if anything good comes of it (or if I'm having to make another trip to Ashville to get my MF-102 fixed...).

[GregAE]

Has anyone messed around with increasing the range of the LFO to a wider range, or even up to the same range as the oscilators on the Voyager? I got the impression in talking to Amos the other day that it might be possible. Tomorrow I plan to pull out the scope and the iron and see what I can get going... I'll post pics/sound examples if anything good comes of it (or if I'm having to make another trip to Ashville to get my MF-102 fixed...).

By applying an external voltage to the LFO Rate input, you can increase the LFO Rate, but not by a significant amount - certainly not anything approaching the Voyager's oscillator range. There may be something you can do by changing component values on the inside (do you have a schematic?), but I wouldn't recommend it.

What I would suggest is that you read the SquareWave article "Lord of the Ring Mod" to learn how you can scale the MF-102's Carrier Oscillator to track the Voyager's Pitch CV (a very cool trick that gives you a tracking ring modulator, or an extra oscillator for your Voyager!), along with some other neat things you can do with the Ring Modulator.

It might make you forget all about cracking the cover and performing surgery on your '102!


- G

[haiku-ish]

Yes, i would be great to have the lfo in the audio range too,
anybody have the lfo schematic ? i did this to the small stone lfo, great (just swap between two capacitors).

best
hk

[OysterRock]

Yes, i would be great to have the lfo in the audio range too,
anybody have the lfo schematic ? i did this to the small stone lfo, great (just swap between two capacitors).

best
hk

I don't have a schematic, but I have opened the 102 up and taken a peak. There are quite a few LM13700s in there and, while I didn't do any probing or anything, if i had to guess I'd say that the LFO is based on that chip. Check out the datasheet for the LM13700, there is a design for a tri/square VCO right in the datasheet.

I don't really know what the 102's LFO is based on, but it might be worth checking out if you have some circuit know-how.

WARNING: Make sure you know what you are doing, though. Its pretty easy to fry an LM13700 by applying to much control current (No more than 2mA, I believe).

http://cache.national.com/ds/LM/LM13700.pdf

[haiku-ish]

thanks a lot, i'll look this way.