AOUT_LC specification for Midibox SID

[e-toy]

As I am planing to make a Filter extension for my MidiBox SID, I have a few question about the use of AOUT_LC in the MIDibox SID project.

I like to have a small (2 channel) AOUT module like the AOUT_LC, but I'm not really happy with the fact that Filter resonance will only have 4 bit (16 steps), so my question regards mostly this problem.

Since I read that the Filter cutoff parameter of the SID SW can be interpolated, I think Filter resonance will still have max 128 steps (no interpolation). Right ?

How much steps (or in other words, bits) have the smoothed cutoff signal ?

Currently 12/4 Bit is the only supported output format of the AOUT_LC (for MB_SID). But it seems that theoretical all combinations of max 16 bit could be possible (eg. 9/7 bit). Right ?

Is it just a matter of HW configuration and the driver ?

Wich CV format will the AOUT_LC (controlled by the SID SW) provide ? V/Oct or Hz/V ?

e-toy

[TK.]

Hi,

yes, the resonance cannot be interpolated. Internally it works with 7bit resolution (128 steps) as you assumed. The SID itself has only a 4bit register for resonance.

CutOff has internally 16bit resolution (65536 steps), the SID provides a 11bit register for CutOff.

Currently 12/4 Bit is the only supported output format of the AOUT_LC (for MB_SID). But it seems that theoretical all combinations of max 16 bit could be possible (eg. 9/7 bit). Right ?

Is it just a matter of HW configuration and the driver ?

yes, you could even combine 3 shift registers instead of 2 to output 16/8 bit resolution, the changes have to be made in sid_aout_lc.inc

Wich CV format will the AOUT_LC (controlled by the SID SW) provide ? V/Oct or Hz/V ?

the output curve is linear, don't know if we can speak about V/Oct when no oscillator frequency is controlled by the CV

Best Regards, Thorsten.