Analogue Synths with Nonstandard Waveforms Pt.3

US What the Hell is Metal-Sync, Anyway? 18/03/25

One of the joys of my (admittedly rather late!) System 8 ownership has been exploring all of the ways Roland implemented "XMOD/Cross-mod" throughout it's analogue lineage. Depending upon the synth you might get Exponential FM, AM or a mixture of Sync & AM when you turn up that XMOD. On the System 8, where 5OP Yamaha-style "FM" also exists, this results in a wonderful variety of nuanced, clangorous tones.

But there's one type of XMOD that I always wanted to play with - the JX3p's Metal Sync, available to me via the Plug Out version. Just what did this involve, what did it sound like? I dialed up a sound and held some keys - what sprung forth was a rather captivating tone, kinda like hard sync, with some of the nonlinearities of AM or Ringmod, but not as extreme, harmonious.

If one were expecting forbidden planet soundscapes, they might feel underwhelmed - yet, I feel that it has it's own thing going on, something definitely usable. So how does it work? Electric Druid has a great article which explains:

"Hard Sync" slave waveforms are reset to zero everytime the master resets. They never complete the full wave cycle they would have done (shown dotted for a couple of examples).

The "Metal Sync" effect which Roland invented for the JX-3P is similar but subtly different, and depends on the different technology used – it's a DCO effect, not a VCO effect.

In a VCO, there is only a ramp integrator keeping track of the frequency, so when the master resets the slave's integrator, the slave is completely reset to zero. In a DCO, there are two parts; a digital counter keeping track of the frequency and generating reset pulses, and a ramp integrator generating the waveform. To completely reset the DCO, you need to reset both the counter and the integrator. This is what the normal "Sync" mode does on the JX-3P and the subsequent instruments, and it produces waveforms exactly like those above.

But what would happen if you only reset the integrator? The counter would still carry on as if nothing had happened, and would cause the DCO's ramp to reset at the time it would have done anyway, as if nothing had happened. The master frequency's reset pulses no longer entirely determine the frequency of the output. Rather, they just provide "additional" reset pulses scattered across the waveform at the master frequency. The effect of this is complex, but it's not entirely unlike ring modulation and can give similar non-harmonic sounds, hence the "Metal" name.

Metal Sync

There we have it then. Some clever, thrifty DCO magic. To hear Metal Sync, and more JX3p magic in general, check out this video by Mathew Jonson, and see you next time for more odd Analogue waveforms!

Posted by MagicalSynthAdventure an expert in synthesis technology from last Century and Amiga enthusiast.

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