Odp: [sdiy] Re:freq shift allp filter ?

[Roman Sowa]

Hi,

----- Original Message -----
From: jhaible <jhaible at debitel.net>
To: <fdi at ran.es>; <fdi at teleline.es>
Cc: diy <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, January 14, 2003 11:33 PM
Subject: Re: [sdiy] Re:freq shift allp filter ?


>
> The best solution would be a digital implementation
(counter, sin/cos
> lookup table, high resolution DAC). Maybe you can replace
the two
> multipliers
> with multiplying DACs? (But I don't know if there are 12
or even 16bit
> multiplying DACs available.)
>

then why not to use DSP for it. DAC, ADC, DSP, EPROM
should make nice frequency shifter. The only reason not to
make it this
way is that it's not exactly analog (duck!).
It's not much of a hussle either. I made it years ago as one
of excersises with Motorola DSP starter kit AFAIR. It
required
however long Hilbert FIR filter.
About 80 taps gave good suppression of mirror band. I used
DSP56k's internal sin lookup ROM table, which I guess was
only 256 words long and it was good enough.
I think I still have assembler code for it somewhere...

Roman