SSB

[Martin Czech]

> I just purchased 4 AD633 (Low cost analog multiplier) from Newark Electronics for something like $6 each.  (I find Newark good for finding hard-to-find chips but you gotta pay big.)  I got the data sheets with application data from AD's web site.  The chips are well integrated and simple to use.  The offset nulling circuit is a simple resistor/divider type with a pot.  I haven't used them yet but I think 2% max error could be no big deal for musical applications.  
> 
> I wonder how a 2% multiplier error translates into the output (ideal vs. actual) for the freq shifter?

Sources of error could be nonlinearity, that would lead to more harmonics or intermodulation.
Given that you are looking for a strong sound effect, this should be no problem,
a little bit of distortion won't be noticed.
Another source of error could be offset in the differential stages, this would
lead to speakthrough of x or y input, even with the corresponding input is set to
0V. For the ssb this means that a rest of carrier will get through, which will be
modulated back by another multiplier stage to audible frequencies.
This gives a small , but constant output, better trim it away with a
good pot.

When I experimented with ad633, the only thing that got on my nerves was noise.
I used it like an VCA, with dc on one input.
(I expected CD-quality, this was shure not the case, more like tape deck).
Was this due to a defect device ? Nobody seems to complain about noisy 633s.
I blamed the internal zener for the noise, since no pin for shorting the ac
on the reference node via a capacitor is provided. 
If zeners are used in discrete amps, there is always a big cap to remove
noise.
I knew, zeners are used as noise generators.

And than I closed this 633 chapter, maybe too early ?

m.c.