[sdiy] digital delay, was ...

[Ingo Debus]

Am Montag, 15.09.03 um 09:53 Uhr schrieb Glen:

>
>> So you want to use a pitch shifter (among other things) to improve the
>> sound quality of a BBD delay. But how is this pitch shifter built?
>
> Okay, I'm not sure if I was using the proper phrase now. There are two
> devices that do similar things. I think I was referring to one device,
> while you were thinking of the other.
>

As I understand it, a pitch shifter shifts the pitch by a certain 
musical interval, for instance an octave down, or a fourth up or 
something like that. Musical intervals in the signal remain intact, 
musically speaking, the signal is "transposed". This is equivalent to 
multiplying the frequencies with a certain factor.

Opposed to that, a frequency shifter shifts the frequencies by a 
certain amount of Hz. Musical intervals don't remain intact in this 
case. If you shift a 100Hz sine up by 100Hz, it's an octave up (200 
Hz); but if you do the same thing with a 200Hz sine it yields 300Hz, 
much less than an octave.

> The device I am thinking of is similar to technology used in SSB radio
> communications. It involves balanced modulators, demodulators, precise
> filtering, and generation of a carrier signal well above audio 
> frequencies.
> Basically, it's a self-contained SSB transmitter and receiver all in 
> one
> module.

This would keep frequency differences (but not frequency ratios), 
correct? So according to the above it would be a frequency shifter.

> Was "pitch shifter" the wrong term? If so, what's the correct term? It
> might even be called something different in your country than here in 
> the USA.
>

Don't know... I know there are people in Germany who use these terms 
differently too.

Ingo