[sdiy] Delays and companders

Gordonjcp gordonjcp at gjcp.net
Mon Mar 4 20:19:33 CET 2019

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".


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