[sdiy] the white whale - modular synth patch memory

[Richard Moore]

I think you've hit the softest spot, Paul.  Right now my best thought is to replace the pots on a retrofitted module with a little board containing a pot and a digipot.  The digipot could be controlled by the pot or could receive a value from the CAN bus.  Between the digipots and the analog muxes there could be full patch memory.  I don't like the resolution of switching noise of the digipots, though, so I'm not sold on this concept yet.

-rkmoore





On Wednesday, March 18, 2015 10:50 AM, Paul Maddox <yo at VacoLoco.net> wrote:
problem is, you want to store the parameter values as well as the 
patching to get true patch storage..
suddenly everything get really complex and you start locking our vendors 
of modules if you do something bespoke.




On 18/03/2015 01:48, Richard Moore wrote:
> I couldn't resist.  I'm planning a DIY modular and I haven't yet convinced myself that patch memory is too ambitious.
>
>
> And yes, I did check the archives.  It sounds like different concepts have been kicked around on the list for modular patching busses and patch memory for 20 years.  I probably missed a bunch of good stuff, though.  If you know of someone who has done a good job of this in their system, let me know.  I would very much like to see it.
>
>
> The strategies seem to be:
> 1. Switch matrices.
>
> 2. Sample everything and send lots of data on a digital bus.
>
> 3. Octopus modules (like WMD sequential switch).
>
> 4. Analog signal buses.
> 5. Use a software modular (Pd, MAX/MSP, etc) instead
>
> 6. Why would you want to store patches on a modular?
>
>
> There will always be use cases for #5, but everyone on this list is probably already convinced of the virtues of hardware.  Pin/switch matrices make for very clean modular synth builds, but they're not easily expanded.  Sampling and sharing a digital backplane is a good option, but may beyond my skills/time constraints/budget for a DIY modular.  #3 is limited and inelegant.  Right now I'm thinking about #4.
>
>
> Here's how I think a useful modular patching bus and memory should behave:
> 1. Patch memory - It should be able to route module inputs and outputs.  Hopefully without some patch cable octopus that keeps you from using the jacks normally.
>
> 2. Easy patch storage - You should be able to patch your system with cables and have that configuration stored to be recalled by a bus patching module later.
> 3. Ability to edit - You should be able to load a patch, patch in additional modules, and save an edit.
>
> 4. Portability - You should be able to share patches with people that have similar modules.  Moving your modules around shouldn't break the patch memory.
> 5. Knob position storage - Ideally knob positions could be stored and recalled until edits are made.
> 6. Retrofitting - It would be really nice to be able to retrofit modules from commercial makers to make use of patching buses.
>
>
> Here are my current thoughts:
> 1. Have ~16 signal buses available on the backplane that modules can connect to (like in the ARP 2500)
>
> 2. Give every input and output on each of my modules an analog multiplexer (there are 8 channel ones on Mouser that start at <$1)
>
> 3. Have a single module that stores patches and commands the multiplexers (over SPI or I2C, perhaps).
> 4. Assign some kind of ID to modules or module types to allow for storage of portable patches.
> 5. Have a microcontroller that can "ping" the module inputs/outputs to determine where patch cables are for patch storage.
>
>
> I've got some thoughts for knob position storage and retrofitting, but nothing certain yet.
>
> What else should I be thinking of?  Who else's synth should I be looking at?
>
>
> -rkmoore
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