Metal: the JX-3P's ramp reset against a phase that keeps running #125

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opened 2026-10-05 23:46:12 +00:00 by bcox · 0 comments

bcox commented

2026-10-05 23:46:12 +00:00

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bcox asked on 2026-10-05 for a ticket for each engine gap in his moregaps.md feature table that no existing ticket covers. Engine claims are from reading the tree at f6aa8eba on main. Instrument claims are from that day's research, read mostly as archive.org OCR of the manuals by research agents and not re-checked; the sources are listed in that document. Nothing here is built, measured or listened to.

Summary

The JX-3P's (and MKS-30's) cross-modulation switch is off, sync or metal. Electric Druid, from the MKS-30 schematics and through a summarizing fetch: a DCO is a counter that sets the pitch and a ramp integrator it resets; sync resets both the counter and the integrator from the other DCO, and metal resets the integrator alone and leaves the counter running. So under metal the ramp is reset by two trains of pulses, its own counter's and the other DCO's, and the result is inharmonic. The owner's manual describes it only as DCO-2 controlling DCO-1 for a "ring modulation style sound", with DCO-2 forced to sawtooth.

Here, sync resets the slave's accumulator and the waveform is a function of that accumulator (dsp/va_layer.h:1721-1745); nothing resets a shaped ramp against a phase that keeps running.

The work, as a sketch

Metal is a third phase: a ramp advancing at the slave's increment that resets on the slave's own wrap and on the master's wrap, while the slave's accumulator goes on untouched. The saw read from that ramp is the metal output; the slave's other shapes are unaffected.
That is one more Q0.32 accumulator per slave, reset by two events, and a PolyBLEP step at each reset, which the saw's edge correction already handles for a step.
It is a sync mode, so it belongs beside #124, as a fourth value.

Open

The manual and Electric Druid describe the direction differently (DCO-2 controlling DCO-1 against an integrator-only reset in the slave); the schematic reading is the stronger one but was not read against the page.
Whether the JX-8P's "Sync 2" (sync and cross-mod together) is related.

bcox asked on 2026-10-05 for a ticket for each engine gap in his `moregaps.md` feature table that no existing ticket covers. Engine claims are from reading the tree at `f6aa8eba` on `main`. Instrument claims are from that day's research, read mostly as archive.org OCR of the manuals by research agents and not re-checked; the sources are listed in that document. **Nothing here is built, measured or listened to.** ## Summary The JX-3P's (and MKS-30's) cross-modulation switch is off, sync or metal. Electric Druid, from the MKS-30 schematics and through a summarizing fetch: a DCO is a counter that sets the pitch and a ramp integrator it resets; sync resets both the counter and the integrator from the other DCO, and metal resets the integrator alone and leaves the counter running. So under metal the ramp is reset by two trains of pulses, its own counter's and the other DCO's, and the result is inharmonic. The owner's manual describes it only as DCO-2 controlling DCO-1 for a "ring modulation style sound", with DCO-2 forced to sawtooth. Here, sync resets the slave's accumulator and the waveform is a function of that accumulator (`dsp/va_layer.h:1721-1745`); nothing resets a shaped ramp against a phase that keeps running. ## The work, as a sketch - Metal is a third phase: a ramp advancing at the slave's increment that resets on the slave's own wrap and on the master's wrap, while the slave's accumulator goes on untouched. The saw read from that ramp is the metal output; the slave's other shapes are unaffected. - That is one more Q0.32 accumulator per slave, reset by two events, and a PolyBLEP step at each reset, which the saw's edge correction already handles for a step. - It is a sync mode, so it belongs beside #124, as a fourth value. ## Open - The manual and Electric Druid describe the direction differently (DCO-2 controlling DCO-1 against an integrator-only reset in the slave); the schematic reading is the stronger one but was not read against the page. - Whether the JX-8P's "Sync 2" (sync and cross-mod together) is related.