4016, switching audio and VCO signals

[BJ]

Tony Allgood wrote:
> 
> Hi,

HiHo! 

> I would not want to pass the final mix out through one, or a 4066
> directly. Why?
> 1. Distortion is too high

In singel switch mode usage at high voltage and at CD quality audio
allmost YES!

> 2. Limited output swing +7V5 to -7V5 is your max. This will also make

Usually YES, but there is a +18Volt version of 4066,4016.

> your control signal rather tricky. You could bias the audio up to half
> of 15V before switching.

Take a NPN and let it sving between rails.

> 3. You have to use two. One series pass, the other shunt. NOT control
> required.

YES, improves tremendously, now CD quality and better are achived.

> 4. They do thump a bit, you will hear it.

Many sources of this phenomen , one is leek currents, a cure is switch
when amplitude is low or at zero crossing, but usually not a problem.

> 5. Some better parts exist. SSM used to do a click less audio one. I do
> not know whether they still do. The DG2xx series are quite good, but
> again should be used with an op-amp. DBX vca's are good too, but pricey.

Hmm!

> 6. Op amp and two fets are better. No click. Controlled on times. And
> less bleedthrough. If used near the virtual earth they are switching
> current not voltage (except for Rds on), output swing limited by the
> op-amp.

Right.
 
> If anyone needs the circuit for this, mail me and I will do a copy in a
> few days. I don't feel up to ascii drawing at the moment. My baby
> daughter's teeth are deciding to come down today.

Nice! Dont use a 4066 for switch off baby crying!! 
 
BJ