[sdiy] MIDIVerb reverse engineering

[Eric Brombaugh]

Yes, the power supply on the MV I is a weird one. To the best of my 
understanding it requires a ~12VAC center-tapped wall-wart. The on-board 
supply circuit generates +5V and +/-12V from that using a "unique" 
voltage doubler topology. I ended up building my own with surplus parts 
from MPJA (recently closed down unfortunately) and that worked fine. 
Paul's schematic review video goes over this in some detail (although he 
doesn't specify the transformer voltage).

Eric

On 7/16/25 12:50 PM, Jacob Watters wrote:
> Thank you. I have one of these that I need to repair. Just finding the 
> correct power supply has been a pia.
> 
> *Jacob Watters*
> JacobWatters.com <http://jacobwatters.com/>
> 
> 
> On Wed, Jul 16, 2025 at 3:37 PM Eric Brombaugh via Synth-diy <synth- 
> diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
> 
>     Back in 2021 Paul Schreiber and I reverse engineered the MIDIVerb I and
>     although Paul posted a number of Youtube videos to discuss what we'd
>     learned, we decided at that time to keep the design materials we'd
>     generated from that effort private. Now that Paul is no longer with us
>     I've open-sourced the materials on Github:
> 
>     https://github.com/emeb/MIDIVerb_RE <https://github.com/emeb/
>     MIDIVerb_RE>
> 
>     This repository includes schematics, presentation slides, source code
>     for the disassembler, emulator and compiler, as well as SPICE and
>     Verilog models of the logic. Anyone at all curious about how this
>     product democratized the world of algorithmic reverb is invited to take
>     a look - it's a fascinating glimpse into 1980's minimal TTL design
>     and a
>     testament to the genius of Alesis founder Keith Barr.
> 
>     Eric
> 
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