[sdiy] Midiverb reverse engineer project?

[Giles Ward]

Here's a page where someone has done the Midiverb/Midifex switching and 
has also racked it:

http://m.bareille.free.fr/goodies/midiverb/midiverb.htm

On 18/10/2016 19:58, Tim Ressel wrote:
> Yep, its all the the algorithm. There is no compression or anything in
> the hardware.
>
> To switch between midiverb and midifex: I wonder if you could solder one
> eeprom on top of the other and simply break out the chip select and
> output enable pins?
>
> On the algorithm: I know there are the FV-1 algorithms out there, but
> I'd be interested in seeing the midiverb code.
>
> On the hardware: yes I know we don't actually need the hardware to
> figure out the algorithm. But Mr. Barr's accomplishment is amazing
> enough to warrant the effort.
>
> Personal note: I worked at Alesis for a short period during the midiverb
> days. So this is a bit of a nostalgia trip for me.
>
> --tr
>
>
> On 10/18/2016 8:46 AM, Kenji Garland wrote:
>> On the hardware side, I'd be interested to learn whether there's
>> anything very special about the Midiverb line's A/D converters. I love
>> sampling synths through a Midiverb II with its input sensitivity
>> cranked, and I've never been sure if the Midiverb did any distinctive
>> clipping to make that arrangement sound so good, or if it was just the
>> magic algorithms as others have suggested.
>>
>> Kenji
>>
>>
>> On Tue, Oct 18, 2016 at 9:33 AM Richie Burnett
>> <rburnett at richieburnett.co.uk <mailto:rburnett at richieburnett.co.uk>>
>> wrote:
>>
>>     As far as I know it's all in the reverb algorithms.  Some of the later
>>     Midiverb used the general purpose micro (that handles MIDI and the
>>     UI) to
>>     poke new coefficient values into the DSP part on the fly to do
>>     modulation
>>     effects like flange and chorus, and also to add a bit of movement
>>     to break
>>     up the metallic ringing in long reverb tails.  Keith Barr has been
>>     quite
>>     open about the design and algorithms of the Midiverb in various online
>>     forums.
>>
>>     As I understand it, the FV-1 is Keith's result of distilling down
>>     the bare
>>     essentials of what makes a good reverb, and then designing a "DSP"
>>     chip
>>     optimised for this task.  For instance it has hardware sine/cosine
>>     LFO's,
>>     and can implement things like linear interpolation and allpass
>>     filters using
>>     just a pair of special instructions tailored to chorus/reverb
>>     generation.
>>
>>     -Richie,
>>
>>
>>     -----Original Message-----
>>     From: Tom Wiltshire
>>     Sent: Tuesday, October 18, 2016 2:02 PM
>>     To: Mikko Helin
>>     Cc: Synth-Diy
>>     Subject: Re: [sdiy] Midiverb reverse engineer project?
>>
>>
>>     On 18 Oct 2016, at 11:56, Mikko Helin <maohelin at gmail.com
>>     <mailto:maohelin at gmail.com>> wrote:
>>
>>     > You don't need to reverse engineer the hardware, the sound is in the
>>     > algorithms I guess.
>>
>>     Is that right? Did any of the early units do anything special on
>>     the analog
>>     side? Compander or tone filters or anything? I don't know anything
>>     about the
>>     Alesis reverb units, and I never owned one.
>>
>>     Aside from that sort of pre/post processing, I agree - you should
>>     be able to
>>     take a recent basic DSP and recreate it exactly. Doing it on an
>>     FV-1 would
>>     be a nice touch, since Keith Barr designed that chip.
>>
>>     Tom
>>
>>
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>
> --
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
>
>
>
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