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Re: Electro Harmonix Freeze - Sound Retainer



>Charles Zwicky wrote:
>
>>The delays used in an allpass filter are typically very  short, and 
>>measured in samples rather than mS...
>
>At least in Bidule the delay parameter for Allpass is measured in mS.
>In freeverb the range is from 5 to 15mS.


Certainly not within the range where you would hear them as a discreet 
delay...

>
>As I understand it, it's intended to be a way of having a delay
>with feedback, but arranged so that there's no comb effect on
>sustained notes.


No, not at all.. it's effect is diffuse an impulse.  Try putting one 
in  the feedback loop of a delay line with a coefficient of about 0.5 
and you'll hear what I mean...

>
>
>>I'm not sure that you meant to write "phase dispersion"...
>
>Just meant that different frequencies are delayed by different amounts.
>(Allpass is also used in a phase fx.)


It's an entirely different implementation than what you'd typically 
find in an analog "phase shifter".


>
>
>>Try to think about the topolgy in a different way.   If the allpass 
>>network is located after the loop,
>
>sorry, I took your description below to mean that there
>was a "loop of allpass filters".
>
>>
>>>Charles said
>>>>in fact most digital reverbs consist of  a loop of allpass filters*


This comment is referring to a non "constant density" reverb, for 
example as in a Lexicon and Ensoniq reverb.
As I pointed out above there are several ways to do it. It's likely 
that the EH "Freeze" uses a series of allpass filters before and 
after a fixed delay line.

>
>;-)
>andy

Yep... |-O



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