Ambika - troubleshooting timing behaviour

I’ve stumped myself, and gave it few days, but now I’ll ask for help.

I have an Ambika with 1 SMR4 voicecard built from a kit, working nicely, responds to MIDI, everything else seems to be function as expected (which is awesome btw, merci Olivier!).
But, when the arpeggiator is set to internal (or external clock for that matter), the grid setting seem to be running at half its expected value, i.e. 1/16 plays 1/8th notes.
The clock output is at the correct BPM (checked with MidiPal). Pattern is set to 1 ( straight divisions, no pattern), len1, len2, lenp are all 16 (I believe, whatever the default INIT setting is).

I’m guessing I’m either overlooking some simple setting somewhere, or I’ve soldering something of an odd value somewhere else (quartz related?).

Any help or slaps to my forehead would be appreciated.



An additional note of stupidity, I soldered the LCD in upside-down, slapped myself, then desoldered, and resoldered in the correct orientation.
That’s what I get for working late at night and being too confident.

First: a hardware bug will never, ever cause something that specific to happen. With a wrong quartz value the synth might boot; but it will not receive MIDI (serial data needs to be parsed at an accurate rate).

There’s no problem here indeed. I think you are misunderstanding the meaning of the “grid” setting. This sets the duration of a “step” in the arpeggiator pattern (visualize the buttons/LEDs of a 808). But what is played is determined by the sequence of on/off steps in the arpeggiator pattern. For example, even if “grid” setting is set to 1/16th, the following pattern:

x - - - x - - - x - - - x - - -

will play quarter notes.

The arpeggiator pattern 1 is:

x - x - x - x - x - x - x - x -

So it will play eighth notes.

Arpeggiator patterns

Thanks, pichenettes. I figured it was something I misunderstood. I didn’t think it was hardware related, but good to get confirmation.

Thanks, FP