Any suggestion about CV and note trigger outputs?

[maxfarnea]

Hi all,

I would like to know if someone has already found a nice solution for a couple of use cases involving my MPA 100k:

1. CV output: I would like to use one digital pot output to generate a standard CV control voltage 1V/1octave. I'm planning to use a transistor for this ... but maybe someone has already expanded the MPA for this and I could save a lot of time. Any schematic available?

2. Note triggering: is there a way to generate a note trigger TTL signal every time a generic note is pressed? I know that I can configure a digital output to raise up when a key note is pressed, but only for THAT note and not for every note. Any ideas?

Thanks a lot to all in advance.

maxfarnea

[John]

Hi all,

I would like to know if someone has already found a nice solution for a couple of use cases involving my MPA 100k:

1. CV output: I would like to use one digital pot output to generate a standard CV control voltage 1V/1octave. I'm planning to use a transistor for this ... but maybe someone has already expanded the MPA for this and I could save a lot of time. Any schematic available?

Since the digipot outputs only have 128 steps of resolution, it's unlikely that you'll be able to use them to get well-tuned output. (but maybe you're going for filter control instead?)

You can get a voltage output by wiring the digipot output as a "voltage divider", as in:

A terminal -> 5V
B terminal -> Ground
W terminal provides an output voltage between 0 and 5V, depending on wiper position.

This may still be problematic, because the "output impedance" will be very high. So you could connect it to something called a "voltage follower" circuit. You can find this on many "introduction to op amps" pages on the web. The output of the voltage follower will be the same as what's provided by the digipot, but it will be able to provide more current while maintaining a steady voltage.

2. Note triggering: is there a way to generate a note trigger TTL signal every time a generic note is pressed? I know that I can configure a digital output to raise up when a key note is pressed, but only for THAT note and not for every note. Any ideas?

This functionality isn't included in the current firmware--sorry. But it's a good idea and it will be considered for a future version.

This functionality is included in firmware version 1.4.

Please let me know if I can provide more information.

[maxfarnea]

Since the digipot outputs only have 128 steps of resolution, it's unlikely that you'll be able to use them to get well-tuned output. (but maybe you're going for filter control instead?)

Yes, I'm already using an output as a voltage divider and it is quite nice for controlling a filter but as you said it is a bit hard to tune a note. Anyway it could be acceptable for me by now because I'm using the MPA with DIY noisy and groovy synths where exact tuning is not the first goal. A standard CV output is in my wish list because I'm planning to buy a couple of modular synth modules where standard CV signals are required. It would be nice using the same MIDI device to control all my gears.

This functionality isn't included in the current firmware--sorry. But it's a good idea and it will be considered for a future version.

Ok thanks! I need a note trigger for a ADSR module but maybe I can get something suitable using the velocity on one pot output.

Anyway, thanks a lot for your support.

bye

max farnea

[John]

The "any note" logic output modes are now included in firmware version 1.4.

[maxfarnea]

The "any note" logic output modes are now included in firmware version 1.4.

that's great! can the board be upgraded by a MIDI dump or I need a new microcontroller?

[John]

that's great! can the board be upgraded by a MIDI dump or I need a new microcontroller?

The only way to upgrade is to replace the micrcontroller IC. Please send an email or private message if you'd like to make arrangements.