Been using the sawtooth out of VU009 to sync my Castle VCOs with the front panel sync input, so I can use them in my HD system, need to play with the offset of the sawtooth in the high frequencies, but it works decently, even though it would work better with a pulse/square waveform I guess.
Then it feels a bit wasteful to use VU009 as a kind of RCA sync extractor, so a dedicated module as in this thread would be super neat Sync extraction circuit in order to free the “master” VCO for something else.
Castle VCO would probably benefit from changing the timing caps to reach higher frequencies, as I often use it to clock Castle Shift Register and obviously, it doesn’t do as small/fast “sampling” in HD as in SD. Haven’t tried replacing the caps yet, but since VU009 is derived from Castle VCO, pretty sure it can go faster.