Electronotes Summary?

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Fri Jan 26 20:00:00 CET 1996


Thanks for the list, especially the comments from Your
experience with different circuits !

A few things for me to add and to ask:

>     VCA-3      3080-based linear         Really simple, works fine

In ENs, there is this strange control current circuit for 3080's almost
everywhere. I see the advantages (vs. the usual opamp + pnp circuit):
(1) slightly cheaper, with stress on "slightly", and (2) it avoids the 1/hfe
error of the pnp circuit.
But what about security? In the usual circuit I can easily add a 15k 
resistor
between the pnp and pin 5 of the 3080. In the EN's circuit, the OTA is
directly in the feedback loop of the opamp; so if something goes wrong
with the input voltage, the opamp might start limiting currents as late as
at 20mA. And how does the circuit behave when one of the supply
voltages breaks down, and the other one is still there?
These thoughts have kept me from using it, so far. Didn't You have any
problems with that?


>     VCF-5      Variable-slope            Never tried

I've built a combination of Variable slope and switchable all pass /
lowpass stages filter. The Variable Slope part by itself gives some
interesting nuances, but it's not earth shaking different from other
ota filters.

>     EG-6       Ringing ASR               Never tried

Just finished mine (slightly different design). Very nice!

JH.



More information about the Synth-diy mailing list