[sdiy] Cheapest good sounding digital reverb?

cheater cheater cheater00social at gmail.com
Wed Mar 24 04:54:11 CET 2021


On Mon, Mar 22, 2021 at 3:47 PM Richie Burnett via Synth-diy
<synth-diy at synth-diy.org> wrote:
>
> A few general comments:
>
> 1. High quality reverb requires a decent chunk of MIPS and RAM.
> 2. Convincing small rooms with short reverb times are the hardest to do
> algorithmically.
> 3. Different reverb algorithms needed for different sources.  (More/less
> diffusion for percussive/pad sounds to trade off density & flutter against
> metallic ringing.)
> 4. 16-channels (or 64 !?) is a _LOT_ of data bandwidth.  Use DMA for the
> ADC/DAC/CODEC.
>
> You also need a decent size word-length for the storage and calculations.
> Early 16-bit reverbs were very noisy due to build up of quantisation noise
> within the algorithm due to feedback.  Use at least 20-bit storage or that
> funky floating-point RAM that Keith Barr used for the delay memory.  Or you
> might get away with noisy reverbs if you're gonna put a VCA (noise gate!)
> after it, but there will always be sounds like a deep mellow bass sound that
> will reveal "fizzy" quantisation noise because there's no HF content to mask
> it.
>
> -Richie,

Thinking about this...

I understand you'd want high fidelity in the reverb algorithm itself,
and that's a valid point, might as well use 32-bits here. But what
about the AD/DA? Do you really need that much more than 12, maybe 14
"real" bit linear PCM? (eg a "16 bit" ad/da path with effective 14 bit
dynamics). Remember we're talking about a full-scale oscillator signal
with a filter on it but no volume envelope - how much fidelity do you
need here?


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