VCO or VCF

[Mark Pulver]

>Reading some of the notes in the archive, it seems to me that some people
>think that its the VCF that determines the overall sound of the
instrument.
>Do the oscillators actually make a difference? One person said a
squarewave
>is a squarewave whatever the VCO design. Surely, this is not true. Slew
>rate and HF performance of the semis will have an effect, won't they? And
>sawtooth outputs, well, some sawtooths can have terrible flyback times.
For
>instance, my old Rogue (which I sold for 40 UKP about 5 years ago, what a
>plonker! ), had a sawtooth with a flat top, like it had been clipped at
>12volts.

This discussion comes up every-so-often on various lists, and while there
is in fact a lot of banter about VCFs ("Hey man, I got one of them Moog
filters in my 303!") the fact is that most every piece of the audio chain
from the VCOs to the 1/4" jacks used on the backplane of the synth will
have an effect on the tone of the instrument.

The VCO is incredibly critical in the sound of a synth. The 921's in my
Moog modular are much different sounding than the design in my Fatman (talk
about different levels of the foodhchain!). As you say, slew, linearity,
the age of any decoupling caps, everything.



>And what about VCAs, all my modular stuff uses LM13600 or 3080s, does a
>AD633 really make a difference that can be heard? Or does it only make a
>difference when you try to modulate with AF rather than slow EG outputs?

VCA's are a HUGE part of the signal path! I can radically change the sound
of an instrument around here just by patching it through one of the
modulars. Along this path, there are also the CV response of the VCA's in
regard to the EGs that are controlling it. Exponential or Linear? For those
folks looking for the ultimate WHHHHHAAAPPPP out of a synth, exponential
leads the way.


>I will agree that VCF types really make a difference, but for my next
>project, I'm going to be working on oscillator waveforms. I am going to
use
>a 3340 running at a very high frequency driving a Walsh generator bank.

This sounds like an awesome project Tony!  Have fun!


Mark

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 Mark Pulver - http://shoga.wwa.com/~mpulver    The "Son of The MIDI Wall"
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