[sdiy] frequency shifters...

[Peter Grenader]

Very different.

With frequency mod, a sound and it's harmonics are raised or lowered by an
equal amount, dependant on the amplitude of the signal doing the
controlling, basically a varying voltage.

 With frequency shifting, all the fundemental and harmonicsof any given
sound are not shifted by an equal voltage, but by an equal frequency, oft
times creating dissonanance due to the distruption of the harmonic series of
the input - the mathimatic and/or natural order also being shifted from
their fundemental.  Hard to explain.

Your listening to a Harmoinic waveform of some type in which the base
frequency (fundemental) is 440 Hz and it's first harmonic is and octave up -
880Hz.  If you fm this wave with another signal that's at 440 as well,  you
will hear a richer sound, but all harmonics are being shifted equally so
their relationship to one another stays consistant, they are just all raised
equally. Whatever the net effect of the frequency variation, the fundemental
and ifrst harmonic remain an octave apart.

If you now frequency modulate it with another wave at 440Hz however, the
fundemental goes to 880Hz and the first harmonic goes to 1320Hz (both
shifted by 440 Hz), so the fundemental and 1st harmonic's relationship has
now shifted out of their natural order of an octave.

Hope this helps.

As far as a kit - this would be a toughy.  An aweful lot goes into a
frequency shifter (and please someone step in here if I screw this
explanation up) - but after the shift, the circuit must phase cancel the
harmonics that are only being attenuated by the shifting component (one
example being the national 1496) by means of a 90 degree out of a quadrature
oscillator's output.  Many parts.  Many many parts must be enlisted for this
task.


his is not the same as transposition (in which all of the components of an
audio signal are raised or lowered by an equal interval). With frequency
shifting, all the component harmonics of a sound are shifted not by an equal
musical interval, but by the same frequency.on 7/20/02 7:03 PM,
Nihiliste9 at aol.com at Nihiliste9 at aol.com wrote:

> Hi all. I was wondering if frequency modulation was the same as a frequency
> shifter. Also are there any kits out there for building them?
> 
> thanks
> edward s.