Hwr, Fwr and more

[Wim Verheyen]

Hello DIYers,

I was reading Musical Applications of Microprocessors by Hal Chamberlin again.
Figure 2-2C illustrates half-wave rectification.
A circuit for a HWR is described in the IC Op-Amp Cookbook by Walter Jung, 
figure 5-1 (precision diode circuits). I want to use this both for control and
audio signals. Jung says that the limitations of the circuit are defined by
the
slew rate of the op-amp used and that a 101 operates up to 1 kHz. This is
obviously not very high, I wonder how high a TL084 or similar would go.
Another aspect is that the op-amp must not be a low differential-input-voltage
type. Again what about a TL084 ? Any advice on other op-amps more suitable for
this circuit ?

I'm thinking about integrating this idea in a more flexible module.
Jung describes the linear OR in figure 5-3. With a Vref of OV this is a HWR
again. But making Vref available outside makes a voltage controlled clipper.

Figure 2-2D in Chamberlin describes HWR with offset. The previous circuit can
be extended with a level shifter before the input, this would of course be
a voltage controlled level shifter.

Figure 2-2D and 2-2E describe full-wave rectification.
Rather than building a FWR, I would take two HWRs as I described above, one
with positive and the other with negative rectification.

Throw in two inverters and four summers and you can make the following :
HWR(+) - HWR(-) = FWR
HWR(-) - HWR(+) = FWR inverted
HWR(+) + HWR(-) = original input signal
-HWR(+) - HWR(-) = inverted input signal
This is true for Vref = OV and no level shifting, things get more interesting
with VC offset and level shifting of course.

All this circuitry can be made with a handful of (quad) opamps.
Each individual building block can be made available on the front panel and
some connections can be pre-patched.

I think this could be a cheap module with lots of sonic and control 
possibilities. What do you think ?
Has someone built such a circuit ?

Unfortunately, I don't have a schematic drawing program, otherwise I could
illustrate these ideas more clearly. I just hope that many of you have the
Chamberlin and Jung books to make this clear.

Greetings,

-------------------------------------------------
 Wim Verheyen, Hasselt, Belgium, catwim at innet.be
 The Aemit modular analog home :
 http://www.club.innet.be/~year0828/wim.html
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