2010-06-30 by Guy Drieghe D.
>
> totally impressive work !
Thanks, Dieter !
Coming from you, that's one hell of a compliment.
But hey... thanks for the compliments from the other people as well! A pat on the back is always appreciated. :-)
> You find my comments written inline.
Mine too. º_º
> > It works well, but I still need to tweak a few values here and
> > there... Linear FM is "to deep", VCA goes to overdrive when fully
> > AM'ed (though with a nicely, tubey sounding distortion)
>
> it should be no problem to adjust the behaviour of the linear FM and the VCA
> by changing the values of some resistors. You simply have to add a seriel
> resistor at the corresponding CV input to reduce the sensitivity (or use the
> summing input with another resistor value).
That was the plan, yes.
The VCA Am inputs will be easy. For the Lin FM I'd probably have to try a bit harder.
> > not very happy with the way the Slew Limiter works.
>
> I'm surprised to hear that. The slew limiter works like all slew limiters,
> nothing but a capacitor buffered by an operational amplifier that is charged
> via a variable resistor (potentiometer with logarithmic scale in the range
> 1M...5M recommended). It's exactly the same curcuit as for the upper unit of
> the A-170.
I used a 1M Audio. Might try a higher value...
>
> > Lopass cutoff has a bit of a "knee" in the higher frequencies, though I
> reckon
> > there's nothing I can do about that.
>
> Right. The 12dB VCF is made simply with two VCAs of the SSM2164. There is
> not much that can be changed. Only the quad opamp right from the SSM2164
> (TL074) could be replaced by another compatible opamp with different
> frequency response.
I could try one of the hi-end OPA's, but I reckon it won't make that much of a difference. Probably not worth going for... The knee is only audible under manual control, so as long as one knows this (especially for live situations), it's okay to live with it. This little "deficiency" gets easily compensated by the filter's overall quality and sound. Highly impressive, given that you've accomplished this with such limited means. :-)
> > But overall it sounds very nice. Warm & tender, or gritty & brutal.
>
> Thank's. I like the high pass very much (with moderate resonance).
I agree. The HP is as good as they come.
I'll be having two VCF's in this panel, which will give for some nice LP -> HP Korg MS20'ness...
> > Can't wait to see what Dieter is going to come up with for the
> > expansion module...
>
> in any case noise, random voltage, ring modulator, S&H, VCLFO with reset
> will be included. But we also think about other additions (24dB low pass,
> BBD, wave shaper ...)
All the classics then... :-)
I'd prefer more wave-shaping/multiplying over an additional oh-no-not-again! LP filter.
And extended VCLFO, preferably with PW/M, would be very cool, yes.
Some easy little stuff like Boolean logic, comparators & Schmitt Triggers would be welcome too.
Or replace 70% of all of the above with one VC Slope generator :-)
Thanks for making this possible, Dieter.
_g