TDA1008 (was: Re: LF411 Op-Amp dilemma)

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Thu Jan 30 20:05:00 CET 1997



> -------------------- Tone Generation Scheme ------------------
[...]
> Jim Shearer

Very good description !

> This is, in my
> opinion, what gives the Crumar Performer it's wonderfully rich string
> sound -chords swelling up whilst others fading, unlike the ARP Omni,
> which rudely cut off a fading chord when a new chord is played.

Yes. Another string synth which has individual envelope shaping
for each note is the Korg Lambda. But this one doesn't use 1008's,
but discrete diodes which act as voltage controlled resistors. But the
1008 has a better envelope shape; you always get an unnatural
release "tail" with discrete diodes. They avoided the "tail" in the
Lambda by restricting the release time with a resistor in parallel
to the diodes. I found out about that when I had cut off all these
resistors in an attempt to increase the maximum Release time,
and thenm had to solder them all in again. (&%$%&$& !)
But I disgress.
A funny thing about the Crumar Performer is that is uses a
*mixture* of the both methods individual/global envelope.
If you only select the Strings sound, the 1008's produce the
envelopes. But if you switch on the Brass section as well,
the Attack and Release times of the 1008's are set very short,
and the String sound is routed thru a separate CA3080 VCA
with one global envelope. No more release for the strings
then, and only the first notes have a slow attack, but later ones
just "jump" in, if a chord was held and additional notes are
played.

JH.



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