[sdiy] Klangumwandler freq shifter

[Fernando de Izuzquiza]

     Hi Henry/all,

     Following the 1977 diagrams I have, this type of frequency shifting is called
     Klangumwandler, and was used in radio systems in Germany. The results of the phase-type
     freq shifter (Bode/Moog) are much better, but this one is factible with usual synth
     modules, providing you can get a HP filter with a slope better than 30 dB/oct (best with
     48 dB/oct or more, 60?) Of course, cascading many HP filters you can get that slope.

Klangumwandler

1. For the Klangumwandler freq shifter we need two ring modulators (two four quadrant mults,
balanced mods), two oscillators capable of 20 kHz or higher, a HighPass filter array capable of 30
dB/oct or more. It's good to have also a CV buffered distributor and a CV mixer.
2. The circuit: modulatorA - HPfilter - modulatorB.
3. Signal to be processed to Mod-A X input, reference oscilator to Mod-A Y input.
4. Output of Mod-A to HP filter/array.
5. Output of HP filter/array to Mod-B X input, shifting oscillator to Mod-B Y input.
6. Mod-B output is the processed signal (freq shifted signal)
7. Control ref. osc, HP filter and shift. osc with the same CV (--->reference freq of 20 kHz or
higher) I would use a CV buffered distributor to do this instead of a simple multiple.
8. Apply the CV to shift freq up or down to shifting oscilator (summing it to the ref CV). You can
do this by using another control input of the oscilator or by using a CV mixer on the same input and
sum the reference freq with your shifting control voltage. Of course this voltage can be constant or
as crazy as you like. You should try first with little displacement to test all is working.
9. I think it worked like this...!    =:)


     Hope this helps,

     Fernando



f
*

> De: "Henry" <henry01 at ntlworld.com>
> Fecha: Fri, 7 Feb 2003 19:01:23 -0000
> Para: <synth-diy at dropmix.xs4all.nl>
> Asunto: [sdiy] Through-zero FM oscillator
>
> I reckon I can make a through zero linear FM oscillator, without going to
> extremes....
>
> Make a 20KHz sine oscillator which has quadrature outputs. This is easy,
> you can use a state variable design and use the BP and LP outputs.
>
> Make another quadrature sine oscillator which is voltage controlled - just
> use OTAs in the state variable design.  Arrange the currents so that a
> control voltage of say 5V runs the voltage controlled oscillator at 20kHz,
> 10V runs it at 40kHz and 0V runs it at 0Hz.  Feed the quadrature outputs of
> both oscillators into the four inputs of two four quadrant multipliers with
> a sum at the outputs.
>
> Now, your modulating signal varies the 5V CV from 0 to 10V, your output from
> the multiplier is 0Hz at 5V CV and it is 20kHz at both 0V CV and 10V CV.
> The through zero point is at 5V CV and if my intuition is correct, the phase
> will all take care of itself, as the multiplier can do little else than get
> it right.
>
> OK, so I haven't built it yet, but surely this will do the job? Very
> similar to the "SSB style" frequency shifters, only easier to do cos you
> don't need a wideband phase shift for the input signal.
>
> Henry. Farnborough, UK.
>


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