[sdiy] Ideal polyphonic digital reverb
David Manley
dlmanley at sonic.net
Wed Mar 24 03:15:18 CET 2021
Colin is correct - this box is filled with analog. The delay is
'digital' in that samples are stored in a ram instead of some sort of
charge storing device (like a BBD). Beyond that and the patch storage,
not much is digital.
Check out the service manual for the schematics:
https://www.synthxl.com/korg-sdd-3000/
And to get back to the OP's question: do you mean just reverb or any
delay effect? An ideal reverb (and/or delay) should have a flexible
feedback path and not just flat attenuation. Filtering (and other
modifiers) are very useful in the feedback path.
-Dave
On 3/23/21 3:54 PM, ColinMuirDorward wrote:
> Thanks for sharing these, Michael! I love listening to synth demos and
> music in that field.
>
> Re vintage digital delays and modern implementations, I think the
> challenge would be to recreate the analog signal paths. Many of these
> older units used analog feedback paths with filtering done in that
> domain. As well, it's likely you'd see analog companding. So for a
> modern remake, one would want to consider those aspects. I think it's
> low hanging fruit, though. There is lots to explore. I usually create
> my own exotic delay lines around a console and some budget FX units.
> Shelving filters work especially well in the feedback path, along with
> compressors to reign in unruly escalation. I'd love to try something
> with an above/below type control so I could expand below a certain
> threshold, and limit above a higher one.
>
> On Tue, Mar 23, 2021 at 9:17 PM cheater cheater
> <cheater00social at gmail.com <mailto:cheater00social at gmail.com>> wrote:
>
> Could even add more delay lines and additional I/O for eg inserting an
> analog filter into feedback loops... nothing's stopping you with
> today's hardware...
>
> What sort of feedback processing is there on the SDD-3300? No one
> mentions anything like a filter, or ducking, or compression.
>
> On Wed, Mar 24, 2021 at 2:10 AM cheater cheater
> <cheater00social at gmail.com <mailto:cheater00social at gmail.com>> wrote:
> >
> > Since the SDD-3300 is all digital, it really does not sound like a
> > very sophisticated algorithm - what's stopping someone from making a
> > competent clone on an arduino or a small microcontroller with a few
> > megs of ram?
> >
> > On Tue, Mar 23, 2021 at 6:02 AM Michael E Caloroso
> > <mec.forumreader at gmail.com <mailto:mec.forumreader at gmail.com>>
> wrote:
> > >
> > > SDD-3000 is a single digital delay, no MIDI
> > >
> > > SDD-3300 is three digital delays with MIDI. Complete
> description on my webpage:
> > > http://analoguediehard.com/studio/effects/korg_sdd-3300/index.html
> > >
> > > Both are programmable. Another difference is the LFO: four
> waveshapes
> > > are available on the SDD-3000, while the SDD-3300 is triangle
> > > waveshape only but each delay unit has two LFOs and the LFOs
> between
> > > delay units can be phase offset. That last feature is
> important for
> > > stereo modulated delays that do not cancel in mono.
> > >
> > > MC
> > >
> > > On 3/23/21, cheater cheater <cheater00social at gmail.com
> <mailto:cheater00social at gmail.com>> wrote:
> > > > can you both tell me the difference between an sdd 3300 and
> an sdd 3000?
> > > > thanks.
> > > >
> > > > On Tue, Mar 23, 2021 at 3:41 AM Michael E Caloroso
> > > > <mec.forumreader at gmail.com
> <mailto:mec.forumreader at gmail.com>> wrote:
> > > >>
> > > >> Want more intriguing?
> > > >>
> > > >> MC
> > > >>
> > > >> On 3/22/21, James Coplin <james at ticalun.net
> <mailto:james at ticalun.net>> wrote:
> > > >> > As someone with 3x SDD-3300s sitting here this intrigues
> me mightily.
> > > >> >
> > > >> > James R Coplin
> > > >> >
> > > >> > On Mar 22, 2021, 8:56 PM, at 8:56 PM, Michael E Caloroso
> > > >> > <mec.forumreader at gmail.com
> <mailto:mec.forumreader at gmail.com>> wrote:
> > > >> >>After years of experimentation I have concluded that a
> polyphonic
> > > >> >>synth needs both reverb and at least a pair of delays
> that can be
> > > >> >>modulated.
> > > >> >>
> > > >> >>Reverb alone was never enough.
> > > >> >>Modulated delays alone was never enough.
> > > >> >>
> > > >> >>I had really liked my Korg SDD-3300 triple digital delay
> for synths,
> > > >> >>which can be configured in any series/parallel/cross-coupled
> > > >> >>architecture you can dream of. This gets better modulated
> delays than
> > > >> >>multi-effect boxes. Then I saw a spare output and two
> spare inputs on
> > > >> >>the 3300, so I hooked my Lexicon PCM60 digital reverb up
> to it and
> > > >> >>that was the magic combination I wanted.
> > > >> >>
> > > >> >>Using the 3300 I can route direct signal to reverb, then
> process the
> > > >> >>reverb tales with the 3300. Or reverb in parallel with
> delays. Or
> > > >> >>series. Add predelay to the reverb send. Or multiple
> predelay each
> > > >> >>to different delay times. World of sounds with this
> combination.
> > > >> >>Enough that I built seven sets of these for my synths for
> independent
> > > >> >>processing.
> > > >> >>
> > > >> >>MC
> > > >> >>
> > > >> >>On 3/22/21, cheater cheater <cheater00social at gmail.com
> <mailto:cheater00social at gmail.com>> wrote:
> > > >> >>> let's enumerate some of the possibilities:
> > > >> >>>
> > > >> >>>
> > > >> >>> voice 1: vco1 -> (a1) -> vcf1 -> (b1) -> vca1 -> (c1)
> > > >> >>> voice 2: vco2 -> (a2) -> vcf2 -> (b2) -> vca2 -> (c2)
> > > >> >>> ...
> > > >> >>> voice n: vcon -> (an) -> vcfn -> (bn) -> vcan -> (cn)
> > > >> >>>
> > > >> >>> at a1, you want to have one of a few things:
> > > >> >>>
> > > >> >>> (i) a convolution engine that takes the output of vco1,
> applies an
> > > >> >>IR,
> > > >> >>> and puts it into the input of vcf1
> > > >> >>> (ii) same as (i) but the input is all vcos (1..n) and
> the output is
> > > >> >>vcf1
> > > >> >>> (iii) same as (i) but the output is all vcfs (1..n)
> > > >> >>> (iv) same as (i) but the input is the last few notes
> you played in
> > > >> >>> decreasing order: 1/2 * the vco from the most current
> note + 1/4 *
> > > >> >>the
> > > >> >>> vco from the previous note + 1/8 * the vco from the
> note previous to
> > > >> >>> that etc
> > > >> >>> (v) same as (iv) but you do that with the outputs
> > > >> >>> (vi) same as (i) but there's also input from b1 or c1
> > > >> >>>
> > > >> >>> then you want the same topology at b and c
> > > >> >>>
> > > >> >>> They're all obviously going to have different results
> and different
> > > >> >>> applications.
> > > >> >>>
> > > >> >>> And obviously you can think about all sorts of dsp in
> here, not just
> > > >> >>> convolution, and when it comes to convolution, then not
> just reverb.
> > > >> >>>
> > > >> >>> On Mon, Mar 22, 2021 at 7:03 PM Mike Bryant
> > > >> >><mbryant at futurehorizons.com
> <mailto:mbryant at futurehorizons.com>>
> > > >> >>> wrote:
> > > >> >>>>
> > > >> >>>> Thought I'd change the topic name as we're definitely
> moving away
> > > >> >>from
> > > >> >>>> cheap.
> > > >> >>>>
> > > >> >>>> So given a polyphonic synth with unlimited voices and
> unlimited
> > > >> >>budget,
> > > >> >>>> what should the structure of an ideal reverb system
> look like ?
> > > >> >>>>
> > > >> >>>> Once there's a consensus I'll try coding it into my
> digital synth.
> > > >> >>>>
> > > >> >>>> _______________________________________________
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>
> --
> https://www.instagram.com/colinmuirdorward/
> -
> <https://www.instagram.com/colinmuirdorward/>
> https://www.instagram.com/ssdp_synthesis/
>
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