After opening up my Prodigy last night to replace a shot 393 in the 2nd OSC, I was wondering about the LFO. The LFO on the Micro is much more pronounced. The Prodigy never gets that high.
Is there a modification which will allow this? Possibly replacing C21 with a higher value?
Also, has any one ever removed the DPDT release switch and replaced it with 2 SPST switches so the filter and amp can be controlled individually (again, like on the Micro)?
By that do you mean faster? Replacing the rate cap will make the LFO go faster but will also make it “less slow”. And the new cap must be of a lesser value. There´s always the option of selecting various caps with a “scale” switch.
With my Rogue, replacing the original 6.8uF for a 1uF was a safe one. The LFO goes much faster and still allows for more common vibrato modulation.
If by high you mean more ampltude modulation I think you can do it by swapping the mod wheel potentiometer, the value of which I don´t know, but it could decrease the “resolution” and could be difficult to apply more subtle modulation.
Use the search function and you´ll find plenty of information in the forum.
My apologies. I was referring to amplitude, not rate.
The LFO amplitude on my micro goes much higher, which I like. The current pot is 10k, I’m going to look up the micro schematics for the pot value there.
As far as isolating the decay/release switch for the vcf and vca, I didn’t find any thing when searching. It looks like it could be done clean enough. I was just wondering if anyone else had.
Sorry, I was referring to the LFO rate mod only as it had been discussed recently.
Looking at the Prodigy schematic, it seems that by decreasing the value of R103 it´s possible to augment amplitude modulation for the VCOs and the same for R146 for the filter, without the need to change the pot. I´m not sure about this, though. I´d paralel a small value resistor to R103´s pins to check prior to any soldering. And I´d leave the filter modulation as it is.
In case it works you may have to adjust the modulation pot afterwards, to get zero mod at the right point.
It looks like R103 is 205k 1%. It also looks like 101-103 are all 1%. I wonder if its a sip pack.
If so, I’ll probably leave it alone.
And I´d leave the filter modulation as it is.
Why is that? Thats actually the one I wish to change. It looks like R146 604k @1%.
Hmm. I guess the more I look, the more I think I’ll leave it alone. I’ll pop it open just to see what those resistors are though.
[…]to avoid mismatching, BOTH resistor values should be altered. That´s why they´re 1% tolerance! Sorry, I guess I wasn´t thinking right.
I can now confirm this after trying with my Rogue. So that´s the way it works.
All this because there aren´t independent on-board controls for the oscs and the filter. Looking at the schematic of a synth with these features may teach us something.
If I remember correctly the SH-101 has these features. I´ll look at the schematic to see how it´s done.
I´m still having a few issues with my Rogue´s mod pot and just discovered the real value is not 10K as it´s on the schematics, because the amplitude isn´t as radical as before. And boy, there are some bad pots out there 
So in the meanwhile I soldered a little 220R to the pot´s pins to increase its logaritmic factor (or so I believe) and it´s OK for now. It affects both filter and Oscs modulation, of course.
I hope this makes sense. Someone correct me if it doesn´t, as I´m learning too. Thanks.
Like, bump.
Looks like I inadvertently deleted my previous message. Sorry.
The most important bits are quoted, though.
Thanks!
I haven’t had a chance to get back to this. A bunch of stuff fell on my plate…
Sounds just like what I wanted though.
I wonder, on the Rogue, if you put a 3 way switch in place if tri-square lfo switch (or just remove it to test), does it make the mode wheel sweep the osc/filter?
I wonder, on the Rogue, if you put a 3 way switch in place if tri-square lfo switch (or just remove it to test), does it make the mode wheel sweep the osc/filter?
I´m not sure about what do you mean. The LFO switch is 3 way: tri, square and S/H.
But if what you intend is to use U5b as control voltage source to make the mod wheel act as pitch bend up for the oscs and also act as second cutoff slider, instead of cutting traces or removing the switch the best you can do is to lift/cut pin 5 of U5. An IC socket is useful in case things go wrong.
I just did this with a junk 1458 and it seems to work. There are a few bizarre jumps in frequency, but this may be due to the potentiometer I bought for the mod wheel tracks so bad. Perhaps shunting pin 5 to ground is a good idea. Just lift the pin and from there run an isolated wire to the ground side of R46 .