Anybody knows about this unit ? (RCA Spectrum Shifter)

[analogguru]

This one :

http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=2579942228&category=18039

any information appreciated.

analogguru

[Brett Clark]

I'm not familiar with that particular unit, but I do know a bit about spectrum shifters:

A spectrum shifter changes the frequency of its input by a (settable) amount. This is a straight addition or subtraction of  frequency. For example:

With the unit set at ("+100 Hz), an input consisting of 440Hz, 880Hz, and 1320Hz (an A note with its first 2 harmonics), would come out as 540Hz, 980Hz, 1420Hz. This completely destroys the harmonic relationship of the frequencies, creating a sound that is "watery" or "metallic". It's more similar to ring modulation than to a pitch shifter. It is a milder, usually more pleasant effect than ring modulation, though. If you have ever heard a SSB radio drifting off-frequency, that is exactly the effect it produces.

A pitch shifter, on the other hand, maintains the harmonic relationships of the notes, because it multiplies/divides frequencies.

If it works, it's probably way cool. On the other hand, you could make one - it's 2 balanced modulators, some phase shift networks, and a quadrature oscillator. Maybe one of the analog synth sites has some schematics. I believe that one model was made by Buchla.

[Zero the hero]

http://home.swipnet.se/cfmd/synths/companies/moog/
Here you find the schematic of Moog/Bode Frequency Shifter. Since it's quite difficult to build I don't know how much this link could help help you.

[analogguru]

Thanks guys for the infos.

I am familiar with frequency shifters, I made one 20 years ago for feedback elimination with two MC 1495.  The main problem was to construct a filter with a constant 90 degree Phase-Shift over the whole frequency range, necessar for vocal application. I added a frequency between 0,5 and 10 Hz, and the result was up to 12 db less sensitivity against microphone feedback (means 4 times louder before whisteling).  10 Hz is much for good singers, but for speech its a good way, not to use the grateful dead trick with two microphones.

But I´ve never heard that RCA built such a unit, and in the description was written "Phase Shifter", what confused me a little bit.

Thanks for the infos again,

analogguru