CVx - CV Expander compatible with the MIDI 1U

Already shipping since announcement last week. Quite limited quantity in first batch but we already have second batch underway.

re:I2C. If someone from the Teletype community would dedicate the time we would be happy to provide them details. CVx should be able to connect to a lot of different things, not just MIDI 1U.

Sure, here’s the info. Each CVX consists of two two I2C devices, one EEPROM and one DAC. The DAC is an LTC2605, so you can find the necessary commands in its datasheet. The EEPROM just uses the standard I2C eeprom command set. Addresses for each based on the CVx address jumper settings are:


Device Address
Exp 0 0x53
Exp 1 0x51
Exp 2 0x52
Exp 3 0x50

DAC (LTC2605)

Device Address
Exp 0 0x30
Exp 1 0x12
Exp 2 0x22
Exp 3 0x10

The EEPROM contains the calibration information for each channel of the DAC. It’s stored as an array of consecutive 16-bit unsigned integers. The first 8 are the DAC codes required to produce a 0V output. The next 8 are the DAC codes required to produce a 1V output.

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One thing that didn’t fit together for me - the LTC2609 is a quad DAC; is it multiplexed somehow, or is that a typo for the LTC2605 octal DAC?

Yes is it should be the LTC2605 octal DAC

Well it took a while, But I sold my FH-2 five months ago, anticipating that MIDI 1U + CVx would be the holy grail for my needs, and save me 8HP of 3U space.
Got the CVx this week to add to the MIDI 1U - and I can confirm. It is the holy grail. With these two 1U modules, I can go up to 6 individual voices (CV+Gate), two with Velocity, and the master clock from Ableton… or…
use those 8 CVx outputs for high-resolution sequencer control of anything.
The bonus, when compared to FH-2, is that the Control panel is a gorgeous, user-friendly app!
Thanks for delivering another solid product @Danjel, @kamil and team!!!


Great! Let us know how it works out for you. It’s still a pretty new system so we haven’t received a ton of feedback on the expander yet.

Btw I just posted a firmware update you will likely want to apply:

Will there be an expander (3u) for the uMidi? Or will there be a new 3u midisolution with extra configurable CV-outs in the near future?

Unfortunately the original 3U µMIDI does not have an I2C port so we can’t make an expander for it.

OK. Any plans for a new 3u midimodule with lots of (CC)-CV out?

Hi! I had a question about how CVx - does it handle polyphonic aftertouch, or other per-note parameters besides velocity? Say, could I set a CVx to do two-voice polyphony (4 outs per voice) with pitch, velocity, gate and aftertouch out? I see in the manual where it describes polyphonic pitch/gate combos using CVx, but just wonder how it works for other arrangements.

I have not implemented polyphonic aftertouch, in my experience with MIDI it’s rarely, if ever used. You could configure the MIDI 1U / CVx in a channel-per-voice setup similar to MPE and use channel aftertouch though.

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I have a feeling a segment of the market out there is going to be embracing MPE a lot more now that Ableton Live and Push2 support it, All the Arturia virtual synths support it, and various others are jumping in. I recently started experimenting with it because I have those tools - but also because I keep seeing (aka “Drooling over”) what Buchla folks are doing with the 222e/223e, aka Thunder, aka Multi-Dimensional Kinesthtic Tactile Input thing. I was considering Sensel Morph/Thunder Overlay for this. I’ve been approximating the Buchla thunder experience using Tetê/Tetrapad and the pressure functionality you have developed.
I think more artists are thinking about multi-touch/tactile performance. I would agree that one could do a custom MIDI setup to feed CVx with a channel per voice to get a similar effect, but round-robin poly functionality with channel pressure would be a nice feature.

I’m not sure how round-robin poly factors into MPE mode? MPE is basically just channel per note, with the sending device deciding on the allocation. What more do you think needs to be added to the MIDI 1U?

Currently if I set MIDI1U to have a polyphonic synth, I can create a round robin set of voices like this:
Output 1x1 and 1X2: both set to pitch.
Output 1x3 and 1x4: both set to gate.
This will give me a two voice polysynth.
But if I set 1X5 and 1X6 to aftertouch, both will only output mono aftertouch, as expected.
PolyAT in theory should behave much the same way as pitch and gate, in a round-robin cycle.
If I press the first note: 1x1 sets the pitch, 1x3 has a gate, and 1x5 will modulate based on pressure…
If I then lightly hold another note, 1x2 has pitch, 1x4 has a gate, and 1x6 will have different modulation, based on how much pressure I apply. If, I let go of the first note, 1x1,1x3 and 1x5 are released to handle the next note and so on…
If you had this working on MIDI1U - you would need all four CVx’s added to do an 8-voice synth, with poly AT and velocity - and A LOT OF MODULES!

Quick article here: How does the MIDI data for polyphonic aftertouch differ from "normal" aftertouch? - Sound Design Stack Exchange

One thing I noticed lately - when I have ableton open (not running), Intellijel Config will not recognize MIDI 1U unless I reset/interupt the USB cable, or quit Ableton. Not sure if this is a problem with Ableton “hogging” access to MIDI1U or not… but once I reset the USB cable, both Ableton and Intellijel Config can function simultaneously - just making sure not to make changes to the config while Ableton is playing/running/sending data.

Yes, but MPE does not use polyphonic aftertouch at all, it only uses channel aftertouch.

If you want to use the MIDI 1U with an MPE device, you don’t want to set it up in Poly mode. Instead you need to create as many mono synths as you will have voices, and put each one on its own channel. Then configure your MPE controller to use that set of channels. I do this with my Linnstrument and it works well. The controller will handle the voice allocation itself.

That’s right - I’m confusing MPE with PolyAT…
Keith McMillen QuNexus also does MPE. But that wont work with Ableton Live 11 and Push 2 natively.

So if I wanted to get the cv expander I could use that as additional outputs for the monome teletype, without the midi 1U?

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The Tetetype would need to support it, but the info is out there so they could add support. It’s also never been tested.

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It’s electrically plausible (but not AFAIK tested) and the physical layer protocols are compatible (I2C is I2C), but the way that Teletype uses I2C logically is going to be tricky.

Here’s the docs for how Teletype uses I2C, called just II

The biggest difference is granularity:

  • a whole Ansible module uses a SINGLE address (one of 0x20-0x23) to receive commands
  • a CVx module uses two addresses (one for the DAC and one for the EEPROM)

There’s also an issue of address conflicts - the II documentation links to the pre-assigned list, and some of the existing assignments overlap with the addresses used by CVx. (they have reserved a range for Tetrapad, tho)