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<p>Yep, its all the the algorithm. There is no compression or
anything in the hardware. <br>
</p>
<p>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?</p>
<p>On the algorithm: I know there are the FV-1 algorithms out there,
but I'd be interested in seeing the midiverb code.</p>
<p>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. <br>
</p>
<p>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.</p>
<p>--tr<br>
</p>
<br>
<div class="moz-cite-prefix">On 10/18/2016 8:46 AM, Kenji Garland
wrote:<br>
</div>
<blockquote
cite="mid:CACcCCWynqsvP7Cd_uWqPAZOr6jQ-W63Hm6fdzESsu4oCODvtNw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div dir="ltr" class="gmail_msg">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.</div>
<div dir="ltr" class="gmail_msg">
<div class="gmail_msg"><br class="gmail_msg">
</div>
<div class="gmail_msg">Kenji</div>
<div class="gmail_msg"><br class="gmail_msg">
</div>
<div class="gmail_msg"><br>
</div>
</div>
<div class="gmail_quote gmail_msg">
<div dir="ltr" class="gmail_msg">On Tue, Oct 18, 2016 at 9:33
AM Richie Burnett <<a moz-do-not-send="true"
href="mailto:rburnett@richieburnett.co.uk"
class="gmail_msg" target="_blank">rburnett@richieburnett.co.uk</a>>
wrote:<br class="gmail_msg">
</div>
<blockquote class="gmail_quote gmail_msg" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">As far as
I know it's all in the reverb algorithms. Some of the later<br
class="gmail_msg">
Midiverb used the general purpose micro (that handles MIDI
and the UI) to<br class="gmail_msg">
poke new coefficient values into the DSP part on the fly to
do modulation<br class="gmail_msg">
effects like flange and chorus, and also to add a bit of
movement to break<br class="gmail_msg">
up the metallic ringing in long reverb tails. Keith Barr
has been quite<br class="gmail_msg">
open about the design and algorithms of the Midiverb in
various online<br class="gmail_msg">
forums.<br class="gmail_msg">
<br class="gmail_msg">
As I understand it, the FV-1 is Keith's result of distilling
down the bare<br class="gmail_msg">
essentials of what makes a good reverb, and then designing a
"DSP" chip<br class="gmail_msg">
optimised for this task. For instance it has hardware
sine/cosine LFO's,<br class="gmail_msg">
and can implement things like linear interpolation and
allpass filters using<br class="gmail_msg">
just a pair of special instructions tailored to
chorus/reverb generation.<br class="gmail_msg">
<br class="gmail_msg">
-Richie,<br class="gmail_msg">
<br class="gmail_msg">
<br class="gmail_msg">
-----Original Message-----<br class="gmail_msg">
From: Tom Wiltshire<br class="gmail_msg">
Sent: Tuesday, October 18, 2016 2:02 PM<br class="gmail_msg">
To: Mikko Helin<br class="gmail_msg">
Cc: Synth-Diy<br class="gmail_msg">
Subject: Re: [sdiy] Midiverb reverse engineer project?<br
class="gmail_msg">
<br class="gmail_msg">
<br class="gmail_msg">
On 18 Oct 2016, at 11:56, Mikko Helin <<a
moz-do-not-send="true" href="mailto:maohelin@gmail.com"
class="gmail_msg" target="_blank">maohelin@gmail.com</a>>
wrote:<br class="gmail_msg">
<br class="gmail_msg">
> You don't need to reverse engineer the hardware, the
sound is in the<br class="gmail_msg">
> algorithms I guess.<br class="gmail_msg">
<br class="gmail_msg">
Is that right? Did any of the early units do anything
special on the analog<br class="gmail_msg">
side? Compander or tone filters or anything? I don't know
anything about the<br class="gmail_msg">
Alesis reverb units, and I never owned one.<br
class="gmail_msg">
<br class="gmail_msg">
Aside from that sort of pre/post processing, I agree - you
should be able to<br class="gmail_msg">
take a recent basic DSP and recreate it exactly. Doing it on
an FV-1 would<br class="gmail_msg">
be a nice touch, since Keith Barr designed that chip.<br
class="gmail_msg">
<br class="gmail_msg">
Tom<br class="gmail_msg">
<br class="gmail_msg">
<br class="gmail_msg">
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<br>
<pre class="moz-signature" cols="72">--
--Tim Ressel
Circuit Abbey
<a class="moz-txt-link-abbreviated" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a></pre>
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