MOTM

The audiophile* version: make it 24 bit and give it a fairly high 
base sampling rate (96 kHz?), so you could sweep down to half 
the base SR and up to double (with 192 kHz capable parts) and 
still use a fixed full audio bandwidth anti-alias filter? Linear 
voltage control and/or exponential for the for the physmo stuff? 
Manual selection of taps would be excellent. You could have 
multiple taps by digital mixing and/or multiple DACs. The same 
basic module could be optimized for longer or shorter delay 
times. Problems: expense,  jitter, RFI - but, could it work?

*From my understanding and experience, this is what it would 
take to get close to high end analog (MOTM quality?) with digital.

Barry

--- In motm@y..., "paulhaneberg" <phaneber@o...> wrote:
> I've been playing around with ideas for delay modules for 
some time.
> I would use a ADC of presumably 16 bits or better on the input 
with 
> a fixed filter at around 20 kHz.  The converted data would go 
into 
> RAM of a fixed length then come back out through a DAC and 
another 
> filter.  Most delay lines vary the point at which the data comes 
out 
> of RAM.  This is why you get zipper noise when varying the 
delay 
> time on most digital delays.  In order to do away with the zipper 
> noise you have to vary the clock speed.  You would want to do 
this 
> with voltage control.  I'm not sure if you'd want the frequency 
> response of the clock to respond linearly or exponentially or 
> logarithmically to the control voltage.  A selection of all three 
> would be interesting.  The problem is (and I don't know the 
answer 
> yet) Over what range can you vary the clock rate of the 
converters 
> and RAM?  This is something I'll be playing with in the future if I 
> ever get caught up on module building and get started on 
some of my 
> own ideas.  It doesn't sound cheap though.
> I agree that you can do a lot of interesting things with short 
delay 
> times.  Although most delays do not go below 1mS you can do 
some 
> great stuff in the 50uS to 1mS range.  One of my favorites is to 
> split a mono signal and delay 1 side my a sub ms amount.  
Great for 
> really strong stereo imaging.
> I think you would want the feedback as well.  Ideally, I'd make 
the 
> feedback amount Voltage Controlled with a VCA.
> Interesting Stuff.