[sdiy] Delays and companders

Tim Ressel timr at circuitabbey.com
Mon Mar 4 20:37:44 CET 2019

This is an adjustable delay design with a pretty long delay. This is why 
I think a separate expander section is needed.


On 3/4/2019 11:19 AM, Gordonjcp wrote:
> On Mon, Mar 04, 2019 at 10:07:27AM -0800, Tim Ressel wrote:
>> Hi,
>> In making a BBD delay often a compander is used to reduce noise. One
>> schematic had a clever circuit that used one rms-dc block to run
>> both the compressor and expander VCAs. This would make sense in a
>> non-delay circuit. But in a delay where the output is not time
>> aligned with the input, is it the right thing to do? It seems to me
>> you want completely separate compressor and expander circuits with
>> their own rms-dc blocks. Say a pair of 4305s from That Semi. Or am I
>> in the weeds here?
> Depends on how long a delay you're talking about.  For the
> handful-of-millisecond delays you get from BBDs, you'd probably be okay
> with using the same level for input and output since it would still be
> within the envelope detector's "reaction time".
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

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