AW: [sdiy] Magic little box

[Czech Martin]

btw:

simple CMOS gates like 4066 etc are certainly not recommended 
for precision audio work. This is mainly because of the nonlinearitys
and also low on/off ratio (leakage) and of course input level
limitations (digital rails).

But: this remark is only true for a simple switcher replacement circuit.
If you don't need the bidirectional behaviour, then you can place
it in front of an inverting audio op amp, shorting the inverting
input to ground (not really, you know what I mean). This way
the voltage over the switch is very small, be it on or off.
Cascading two such switches in this manner can give sufficient
atenuation with low distortion and little or none input level problems.

The bidirectional feature could be obtained by having an antiparallel
arrangement of such circuits. The inverting property may be hiden
by another inverting amp, thus giving inverting and noninverting operation
at the same time (as a bonus ;->).

Just found this circuit idea as well as a dozend others while 
scraping onother four years of the "Funkschau" mag.

m.c.

> -----Ursprüngliche Nachricht-----
> Von: Scott Gravenhorst [mailto:music.maker at gte.net]
> Gesendet: Mittwoch, 31. Oktober 2001 08:32
> An: synth-diy at dropmix.xs4all.nl
> Betreff: Re: [sdiy] Magic little box
> 
> 
> Sounds like what you want to do is possible, although
> we don't have truly specific details here.  Low level
> audio signals should work thru an IC like this.  BTW,
> the CD4066 is an improved version of the 4016.  It has
> a lower ON resistance of 80 ohms with a delta of 5 ohms
> between switches in the same package.  It might work
> for control voltages too.  Crosstalk at -50dB, looks OK,
> but not excellent.  40 MHz of frequency response ought 
> to be sufficient for audio.
> 
> "Aku Raski" <aku.raski at welho.com> wrote:
> >
> >
> >
> >Good people of SDYI,
> >
> >Hello all, my name is Aku and I've been subscribing this 
> list for quite some
> >time now. The techinical superiority in the list is usually 
> too overwhelming
> >for me but the good spirit that the list is enjoying makes 
> it still pleasure
> >to read.
> >
> >I was hoping If somebody of you would have ideas or pointers 
> of how I could
> >get the following idea to work:
> >
> >I'd be interested in building multiple very simple cmos spst 
> switches that
> >I'd be able to controll with my midi to cv-gate interface by 
> sending gate
> >signals to the IC. The idea was to have a some kind of a 
> cmos switch circuit
> >(4016?) that I would place in a small enclosure and mount 
> jacks outside the
> >box. Preferably so that it would be powered with a single 9V battery.
> >
> >What I'm hoping this simplified "VCA" would do is to have a 
> signalpath from
> >A to B that would normally be unconnected, but as soon as 
> the trigger input
> >in the IC would receive a positive gate  signal(+5) from the 
> cv-interface it
> >would connect the A and B.
> >
> >The material going thru the pathway is totally uncritical 
> and low in voltage
> >and not expected to fill any hi-fi standards.
> >
> >
> >Best to you all,
> >
> >Aku
> >
> 
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