LFO / Modulation pedal design for Korg

[tomc]

Hi. I need help with a LFO/ modulation pedal for a Korg Trident that was lost years ago.
I have just had my old Korg Trident resurected after years of not working and would like to build an LFO/
modulation pedal to replace the one lost. This pedal was a Korg MS-04
It operated the VCF with a 10v peak to peak of -5 to +5v.
It had 4 wave form selections of triangle, square, random (s&H) and glissando. LFO speed control with led to
show speed and an amplitude level adjustment on the LFO output waveform. Also has a bend adjustment that
controls width to change tone colour of the VCF fcM. It operated with a 9v battery
Any help with a design of similar or even improved nature would be very much appreciated.

[Circuitbenders]

1st result on google gives the schematic

http://users.rio.com/senorris/junk/MS04schematic.gif

[tomc]

Thanks heaps for the link . I have a limited knowlegde of schemtics but was hoping you could tell me what the 
Op amps  that  are used in the circuit ior an alternate. Thanks but I am a novice in electronics design.
Tom

[Gordonjcp]

Whatever old shite Korg had lying around on the day.  You probably won't go far wrong with LM324s.  If you're worried about it, put them all in sockets so you can whip them out and change them.

As an aside, I know people who do this with preamps, because they swear they can hear different tonal differences between different batches of the same chip.  Me, all I can hear is the noisy worn-out sockets crackling.

[jamiewoody]

i assume any component starting with LM is an op amp. (lm741, etc). are these much different? or are they a different number simply because they are manufactured in a different place?

[Gordonjcp]

That's not a good assumption to make ;-)

The LM317 is a voltage regulator IC, for example, The LM2902 is a quad op-amp, the LM2903 is a dual comparator and the LM2904 is a frequency-to-voltage converter.  The LM3903 is an LED flasher ;-)

It's best to look the chips up properly somewhere.

The number indicates what the chip is.  Generally the prefix indicates the type of construction.