#62

What would be the uses of a -5/+5v output ?
I mean, TT doesn’t seem good for audio or LFOs, for instance.

1 Like
#63

multiple cv inputs in the mannequins line have a -5v to 5v range, not 0v to 10v. iirc this includes settings like formant, barrel, span, quality, and survey. that’s at least five bi-polar inputs right there. :slight_smile:

#64

what’s the reason? is there an advantage or benefit to using bipolar voltages?

#65

edit: actually, you know what, I think I’m wrong on this. too early and not enough coffee. I’ll chalk it up to wanting more options.

#66

In some respects there is no difference, it’s easy enough to convert between -5V to 5V and 0V to 10V, perhaps not so easy when dealing with pitch as you need to make sure that the scaling doesn’t change when you offset.

In many cases it’s a human interface issue, some people would rather tune their oscillators to middle C or A440 and then use a bipolar CV to control it, you can’t do that with 0-10V, instead you have to tune up to the lowest note you’d want. Both methods have their pros and cons.

The place where you notice it the most is with filters, if you’ve got 0-10V envelope + 0-10V pitch going in you can often find yourself with not enough CCW turn on the frequency knob to get the cutoff down to where you want it.

Eurorack is like New World wine, innovative and mould breaking, but the lack of rules means you don’t always know what you’re getting :wine_glass:

3 Likes
#67

Happy New Year!

Phase 2 is starting - I’ve pulled out my OshPark Teensy 3.2 and am going to start playing around with getting a workable CV signal using the extended PCM functionality of the platform. It is iffy that this will be possible - but I’m feeling that some experimentation is needed with the additional bit-depth and variable clocking that the Teensy provides. If it is a bust, we can certainly go the DAC route … but I’m not one to throw in the towel so early.

oshpark-teensy.jpg2902×1633 845 KB

As for bipolar voltages, I like the idea. My inclination would be to have this be software-switchable as opposed to something that is hardware based - but this will make the circuit a bit more complex and deviate the behavior of the expander’s outputs from those of the Teletype. I’m not so keen on making a separate module for this behavior nor am I keen on making the behavior switchable via a hardware switch - that seems to be against the whole philosophy of the Teletype. Any thoughts? How important does this feel to folks?

As for MIDI, there are a lot of good MIDI modules on the market that support this functionality today. There are also lots of DIY projects out there that walk you through how to do this. It feels to me that unless something really different was planned, it makes more sense to just get a great MIDI to CV/Trigger module, patch it into the Teletype and go to town. On the other hand, it also feels to me that a Teletype-like module that exists for the sole purpose of providing complex, lower-level MIDI processing could be very interesting. One that utilized a specialized syntax to do things with the MIDI data that you just can’t do today in standalone hardware modules. Sigh. Let’s see how these expanders go. : )

I’ll keep everyone updated as I progress - but, just to warn you, it will be slow for at least the month of January.

b

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#68

Yes, there are lots of modules to do this. There are a much smaller number of modules available that go in the opposite direction, especially if you consider CV-modulation-to-MIDI (not just triggers). I’ve had it on my TODO list to explore this area for a while now, but unfortunately there are a few other projects higher on the list at the moment.

2 Likes
#69

Agree. I’ve been daydreaming about a module for going CV/Trigger to OSC over serial. It felt more right to me than trying to shoehorn the signals into MIDI.

#70

I’m greedy and want both (and the general purpose MIDI mangler that you also described). But there may be limits to time, space, matter, and energy. :wink:

#71

Thanks,
i was more wondering what would you do with Teletype and bipolar voltages. But you’re right, there are lots of potential uses. Even if TT doesn’t produces audio signal and is not good at making LFOs.
All in all, i think it should be accessed with
CV.OFF 1 -5

1 Like
#72

check this out

2 Likes
#73

I’m super curious about the Open Sound Module. Curious how accurate it is, depending on what you throw at it.

#74

Yeah me too actually. It could be a dream to use with max/MSP, or Lemur on ipad.

2 Likes
#75

I have to admit, I kinda wish it had about 8x the I/O. Mostly because I’ve been having too much fun with MPE (multidimensional polyphonic expression) devices that generate a lot of simultaneous data. That being said, it’s a ridiculous desire because it’s so difficult to create polyphonic voice setups in modular synths. Still, 2x2 is a bit limited.

1 Like
#76

@chapelierfou - love using the offset command. One of the ways i was thinking of achieving this is to have the capacity and resolution to render a wide range of voltage our of the Teensy (say +/-10) and then map the Teletype range initially to 0-10. Rather than having a software switch for bipolar/unipolar, i love the idea of being able to shift the offset by any desired value. This would rule out +/- 10 as the resolution/range would only be half that, but you could do -10 to 0 if you wanted.

I have also been watching the OSM from RebelTech. These guys are very interesting - though I’ve been waiting for forever for an OWL to arrive at AnalogueHaven here in LA. Anyway, the thing that made me nervous about the OSM is that they are relying on WiFi - which has the potential to be disastrous in a live, interference-heavy environment. I’ve worked on some WiFi-heavy projects in some of the country’s larger venues and it has always been a hair-pulling, get the Cisco engineers in here kind of problem due to the absolute chaos that is the 802.11 spec. This can even be a problem in smaller venues due to all of the wild RF flying around. For my $ - I’ll take serial.

b

#77

Totally. But their open source hardware may provide some inspiration.

1 Like
#78

Happy new year! Great news, cant wait for the telex-O… Any chance we can get them up on modular grid?

#79

IMHO, DACs generally is the wrong thing to be cheap about, especially if this is expander is to be used for pitch/sequencing. PWM, I suppose, can be made to work decent enough, but why go through all that hassle; and it’ll still be inferior. Also considering that the K20 is probably vastly overpowered for just being an i2c slave putting out CV, my personal preference would be using, say, a Teensy LC and invest the difference (+/- 10 $) in a proper quad DAC.

That might also solve the bipolar/unipolar thing; ie there’s DACs such as the AD5724R (that’s the 12 bit version), which have a programmable output range (+5v, +10v, +/-5v, +/-10v) and run off dual supplies (ie +/- 12V). These are a bit pricey but not terribly pricey.

3 Likes
#80

Hey @gloom_and_glare - totally hear you and agree. I’m not being cheap, I’m just curious how well it will perform with the additional capabilities of the teensy (adjustable bit depth and frequency). Hence, some experiments. : ) But, yeah, most likely will go DAC unless this little thing impresses me.

I’m planning to approach the project in the following phases (and share everything along the way here and up in a Git Repo when appropriate):

Phase One: Requirement Gathering, High-Level Specification and Front Panel Plan [completed]
Phase Two: R&D + Prototyping on Each Pathway for I and O (in no particular order):

  • PWM / DAC CV Out [in process]
  • Trigger Out
  • CV In
  • Encoder In
  • II Communication

Phase Three: Design Circuit Boards, ||: Print Test Run, Modify :||
Phase Four: Finalize Source Code for Modules and Publish to Git Repo
Phase Five: Finalize Panel Design and Print Test Run
Phase Six: Finalize Documentation

Finally, just to reiterate it for those who are following along, I don’t have the time to make this an urgent project. I have a lot on my plate - so it will most likely take a little time to go through all of these steps. I am really enjoying the conversation with everyone and looking forward to making this together.

Thanks!

b

3 Likes
#81

Well, it’ll probably work well enough; certainly there are modules that use PWM for CV (“Trans Europa”, for example); but 4 x all that filter circuitry and so on … I guess I was just saying a DAC will make things a lot easier (code, layout etc).

On the other hand, PWM probably will make fewer people freak out than TSSOP… : )