Frequency Shifters

[Grant Richter]

I am in the process of setting up a repair department at Nova Musik in 
Milwaukee. (http://www.novamusik.com)

In the last two weeks, I have serviced Bode Frequency Shifter S/N 1001 and
also a Buchla Model 285 Frequency Shifter. Neither of them is, intrinsic to
the design, particularly good at sideband rejection. The Bode shows carrier
rejection of -40 db and program rejection of -20 db, this is after
calibration of the PDNs and multipliers. These are also VERY early units and
I assume that latter designs have better specifications?

>From a technical point of view, I understand what these do, but what is
their musical context? Is it just for strange modification? They do seem to
destroy the harmonic structure of the sound very well.

I am sort of intrigued by these now and I am wondering if anyone has any
real live stories about using them, playing with one, or any idea what they
are good for? Also, what can a well designed unit expect for results in
terms of sideband rejection? Dan, would you care to comment on the latter
Bode designs?

In both cases, the problem seems to be non-linearity in the multipliers
causing second and third harmonic distortion, which appears as side band
bleed thru and isn't nulled by simple phase cancellation