Telex: Teletype expanders


That’s in line with some other measurements I’ve made.


Thanks for your efforts everyone!


Hi, I’ve finished building two TXO with Teensy 3.6, Europower Helper and 110p caps instead of 180p.
I’m testing them on my work bench before installing them in the main case and connecting them to the Teletype. The voltages are correct but the modules don’t show a sign of life yet but maybe that’s normal (?) Are the LEDs supposed to light up or something ? There’s no LED on the Teensy either. Thanks.


There is no “blink on” behavior for the module - so you wouldn’t necessarily see anything unless you sent it a command.

On closer read - it is clear that you built the Europower helper. I’ve removed my notes about that.

So…have you connected it to a Teletype and sent it commands? Knowing more about what you have tried would make it easier to troubleshoot. :slight_smile:


Thanks for your reply ! Yes, the euro power helpers are in place. I was imagining a LED routine on boot, that’s why I was in doubt but now I guess I just have to test it with the Teletype :slight_smile:


No it’s not connected to the Teletype, I wanted to be sure the module works before plugging it in the main Eurorack case, but I’ll try tomorrow (I need to make DuPont cables) and I’ll post with details if anything goes wrong. Thanks again :wink:


Yeah - i had it in there once, but the Teletype starts so quickly that it just didn’t make sense to do anything but be ready to accept commands (especially the init commands). That is why you need to “hack” your Teensyduino installation to reduce the start time if you compile the firmware yourself (as mentioned up on the GitHub Repo).


I understand. I used the hex file provided on GitHub. Will it work with the latest Teletype firmware or not at all ? I think I saw somewhere that the firmware 2.? is recommended


You will want the latest Teletype firmware. It is awesome. TELEX integration hasn’t changed in a while. :slight_smile:

If you were getting 0V on the CV outputs, that is a good sign. As long as your power section is working, it means that your DAC is connecting and being initialized. If the DAC was “dead” you would be getting +10V on the CV outs.

ASIDE: The DAC output is inverted to save on components. OV coming out of the DAC thus becomes +10V. When you get 0V on a CV output, that means that the DAC has initialized and centered the voltage at zero.


If you play with envelopes and/or oscillators, know that they are dependent on the CV voltage for the output being non-zero. Oscillators/LFO’s vibrate between the current CV value and its polar opposite (with shifting behavior when offsets are applied). Envelopes zero out the output (or set it to the offset value if that is set) and use the current voltage as the peak when the envelope is triggered.

Those two things hang a lot of folks up until they get it. Leads them to think something is broken. Once they do, I hope they realize how powerful the implementation is and how many cool things you can do playing with combinations of the various commands. :slight_smile: :slight_smile:


Great ! I’m mesuring exactly 0.0000v on each cv output. I can’t wait to start experimenting with these expanders. Yes, playing with the oscillators and envelopes is the main reason I decided to build them. Thanks for the valuable informations, for the the detailed instructions on GitHub and for creating these modules of course :wink:


I’m testing the oscillators today, really happy with the results. I have a question about the TXo+, and especially about TO.OSC.WAVE, it’s supposed to have more waveforms than the normal TXo but is the range the same (0 to 4999) ? Edit: (I thought I could emit “white noise” with the TXo but obviously I misunderstood the term “noise” in the documentation :grimacing:)


Range is somewhat expanded for the TXo+. I kinda went nuts.

There are 327 waveforms spaced 100 steps apart for morphing (the TXo only has 46). So, values range between 0 and 32699. Every 100 you get another “pure” waveform. 32600 should be random noise, if I remember correctly.

The additional waveforms are from the Adventure Kid set. They are annotated in the source code. WARNING: huge file:

I should point out, the oscillators are more precise for the TXo+. In addition to the improved sampling rate, we are using some native computation for the triangle wave and polyblep band limiting for the square and saw waves. You will still need to put a filter on the outputs if you want to clear up some of the aliasing (set it to just under 12.5k and make it steep as hell). Why? Well, the TXo circuit’s filter alone just isn’t steep enough as it wasn’t designed for audio.


Thank you for this detailed answer ! Good to know that it’s possible to output random noise. I will try 32600 tomorrow because at 4999 I was getting a waveform close to a sine wave :thinking:. I think I uploaded the correct firmware but maybe I should verify and upload it again . I’m also having problems with the OSC.scale that doesn’t seem to have an effect when I switch to a different scale…
I will investigate, maybe I have to read the user manual again. Thanks again :slight_smile:


Did I miss something? Is this a different hardware build or a newer firmware? I did not know there was such a thing as TXo+ :thinking:


Just requires a different teensy!
More info in the post earlier in this thread.


A Teensy 3.6 and a small PCB called Teensy eurohelper.


I’ve found the noise at 32600 :wink: I’m experimenting with the envelopes and various waves, I can get good kicks and percussions with these expanders, that’s really cool !


I was wondering if anyone had a link to the components (or a BOM) for the i2c backpack (got 3 pcbs coming from oshpark). also… if anyone has a bom registered with mouser or digikey for the backpack or the telexi/o that would be :100: :smiling_face_with_three_hearts:

excited to extend!!!


Sorry I don’t have a readymade cart for the txo but here’s the BOM for the small Teensy helper.

Project BOM:


has anyone tried to mount the telex modules in a 1u row?

A teletype is the last piece I’m waiting on to fit in to a single row 84hp sequencer skiff that I’ve got. My aim is to keep the skiff small and portable so I can connect it to various voice oriented racks while keeping the sequencing approach familiar, and it occurred to me that with an alternate faceplate a pair of telex modules could potentially sit horizontally in a 1u row and be quite ergonomic, perhaps with quadratt or a couple of other utilities (depending on what 1u standard is being used)…