Lich inputs and outputs - specifications

Is there anywhere I can find full specs for all thr Lich inputs, outputs and displays?
If not, would here be a good place?

Questions i have.

  1. Are the regular outputs, and cv outputs the same? if not, how different.
  2. to what extent are the switches, gate inputs
    and leds hard wired together?
    3, for completeness, would be nice to have voltage levels for the gate ins and out…not essential.
  3. how much current can the midi host port supply?

I can answer at least part of this.

First of all, audio channels are connected to codec and naturally it’s sampled at sample rate. CV and gate are connected to microcontroller’s ADC/DAC/GPIO pins and are sample at block rate (which means 1/64th of sample rate currently).

LEDs on gate inputs are controlled in software and are independent from the input voltages (i.e. you can use them to implement either momentary switches or latches in your patch), while output LED is hardwired to gate output. You can have a look at Lich UI.

I’m not sure about voltages (I think it’s just ±5V for audio and 0-10V for CV, but it might be different). However I know that you can get up to 500 mA on USB host.

Thanks, that makes sense.
Is there any smoothing on the CV outs?

I’m still wondering if the gate ins and the switches are hard wired…going to look at the scematic if poss.

Voltages: audio ±10V, CV out 0-10V.

Is there any smoothing on the CV outs?

Yes there’s a low pass filter with a high cutoff at ~ 20kHz to prevent digital hiss/noise bleeding through to the CV.

I’m still wondering if the gate ins and the switches are hard wired…

You could say they are ‘soft-wired’: they use separate microcontroller pins, but the events are merged in the firmware so that both gate and switch generate the same BUTTON_1 and BUTTON_2 events.

going to look at the scematic if poss.

Here it is:

ta. I had a look at the schematic. Looks like an additional low pass (shelf) included in the output buffer for any potential zipper noise. cool.

Am I right in guessing that the cv outputs aren’t going to be usable for accurate 1V/oct?

I also saw in the code where that ‘soft wire’ is.
Might come in useful, although Midi control will be my go-to for additional switches.

I would say that it’s not impossible to use CV outs for V/Oct, but:

  • it’s just 12 bits of precision vs 24 bits that you have with codec
  • you’re restricted to block rate vs sample rate (so 64 times lower SR)
  • you can’t output negative voltage (this is the case for Lich, not necessary true for other devices)
  • can’t use calibration patch (but it’s probably possible to have a similar calibration patch that uses DAC output instead of codec)

Many thanks.
So that’s an update of 750Hz, or every 1.33mS.
That ties in with the filter on the output. (although I may shove a 1u cap right across the output if I hear the higher frequency residues from zippering…that extra filter is shelving, as it’s a non-inverting op amp config).

That’s correct. And I guess another number to consider here is 10 Volts giving us 100 cents * 12 semitones * 10 octaves = 12000 cents spread over 4096 DAC samples, so we have 2.9296875 cents as DAC resolution.