Blah Blah Cafe, the Jean-Michel Jarre forum

[radek tymecki]

I've found this site:

http://homepage.mac.com/synth_seal/html/ds_cs15mod.html

I've made mod in my CS30 - faster LFO speed... anyway?

I know circuit in cs30 is diffrent. anyway i was wonderin howto get 24db lopass?

[JarreYuri]

I don't know... yet.
But I just wanted to say that I would soooo much want to have that synth You have.
Congratulations!

Which version do You have?

[radek tymecki]

I had 3 versions:
- Yamaha CS30L
- Yamaha CS30 with sequencer 6 or 8 steps
- Yamaha CS30 with sequencer 1 to 8 steps

sold first two

[JarreYuri]

Aaahhh.... That's so beautiful!!

Do You have any sound examples of that speedy LFO going to work?

[radek tymecki]

haven't recorded yet... i did same modification in sh101... sounded like ringmod from cs50-80

[JarreYuri]

[synthx]

Perhaps an desireable mod is to clock the sequencer to external gate signal ?

This is easily done by adding a BC547C transistor to the manual step function(button).
If you measure it with a DVM you will see that the way the button works is to
emit voltage to the clock when the button is pushed down, so connect the collector
to the point where you have voltage without button being pushed, and the emitter
to the point where the voltage is lead to while the button is pressed down.
Drill a hole at the back of the CS-30 and install a 1/4 phone jack, put a lead
between Base of BC547C and the inputjack tip, and dont forget to solder the input jack "sleeve gnd" to the ground of the CS-30 or the sequencer will not step forward.

Now set the sequencer in manual mode and feed the new input with +10 gate
signal from a midi>cv converter. now you can externally gate the CS-30 sequencer
with 16 part notes from cubase or whatever.

I´ve done this to a CS-30 and will install the same in my own when I get the time to do so.

[radek tymecki]

oh so maybe you can help me with fixing vca1 problem?

when i set VCF2 to 0 it soulds like it was set to 10. when i set it to 10 it's much more louder than VCF1 volume

what can be wrong?

[synthx]

oh so maybe you can help me with fixing vca1 problem?
when i set VCF2 to 0 it soulds like it was set to 10. when i set it to 10 it's much more louder than VCF1 volume what can be wrong?

Could you try to get hold of a frontpanel print and draw what values the knobs are at
and I can try to help you narow down the problem. The CS-30 is a bit crazy ...

Is it when you turn up the VCF2 knob at the VCA1 section that this problem shows ?

From what I can see you got yamahas own IG00151 IC´s in the VCA section and
Yamaha IG00156 IC´s in the VCF section.

It seems like the VCF1 and VCF2 signals are sumed together in a passive manner
through 2 x 450K Potentiometers, so that would rule out VCA1 (IC2 in VCA section).
Try measuring the pot and see if that is healthy, otherwise if you go further back
you´ve got the VCF2 section with it´s IG00156 IC and a bunch of Capacitors. If you
have a scope look and compare the signals comming out of IC2 pins 10(LP), 13(BP)
and pin 15 (HP) Compare these signal levels with VCF IC1 (Same pins).
If you got higher levels at IC2 then I guess you´ve found the problem.
to be absolutley sure of it compare all pins 1-8 on IC2 (VCF section) to
IC1 pins 1-8, if these signals match within say +-5% then the input side
of the VCF IC´s must be ok.

See if that will help.

Best regards,
/RL

[radek tymecki]

thanx to Yves i've managed to complete another mod called "resonance boost"