[sdiy] Waveform phases and hard sync, sawtooth vs. triangle?

[rsdio at audiobanshee.com]

1) Why do you think that starting from the midpoint will be any less of a discontinuity than starting from a peak?

The discontinuity amplitude would be 6 dB less, on average, but it’s still a discontinuity that can vary from cycle to cycle (at least when modulating pitch of one VCO).

2) Are you looking to create vintage sounds or new and unique sounds?

If you’re shooting for vintage, then the circuit design perspective will cover the most cases.
If you’re looking for new and unique sounds, then I say that it doesn’t matter what the general consensus might be - just offer options between simple circuits and more complex circuits so that more sonic variation is possible.

3) Of the three standard waveforms - square, saw, triangle - two of them have significant discontinuities. Triangle is the exception. It seems to me that discontinuities in the triangle waveform when using sync will simply put the triangle back into the majority category.

For me, the best part of turning on hard sync is the harsh and rich harmonic content. The whole point of subtractive synthesis is to start with a lot of harmonics and then get creative about filtering those harmonics.

Brian

p.s. I’ve never really seen a clear definition of what “soft sync” really means. Could your midpoint triangle sync fall into the soft category while peak triangle sync would fall into the hard category?


On Jun 21, 2018, at 7:07 AM, Mattias Rickardsson wrote:
> is there any general consensus or preferred design choices regarding how the phase of sawtooth waves and triangle waves should align with each other and with oscillator sync?
> I'm sure that there are many sides of it, but for a saw core it feels like:
> 
> - The normal way of syncing/resetting a saw core is to restart the saw from its endpoint
> 
> - The tri/sine waveforms are then created by folding the saw in half
> 
> This results in a synced tri/sine restarting from one of its peaks, leading to maximum discontinuity click which I guess must be considered undesired for the majority of usecases. The attack of a tri/sine-based drum sound or synth sound should probably start from a zero crossing. This could be reached in a couple of ways:
> 
> - Is it really desired (from a usability perspective, not a circuit design perspective) to have the synced sawtooth restart from the endpoint and not the midpoint or quarter points? Does it matter in terms of direct sound or audio-rate modulation?
> An alternative restart point for the sawtooth would facilitate a triangle restart from a zero crossing without having to change the traditional phase alignment of saw & tri.
> 
> - Is it really desired (again from a usability perspective, not a circuit design perspective) to have the triangle peaks phase aligned with the endpoints and midpoints of the sawtooth? Does it make more sense considering the phase of the harmonics in case of waveform mixing? 
> An alternative alignment would be to have the triangle's zero crossings there instead of its peaks. This would mean that the oscillator, when synced, starts the sawtooth from its endpoint (traditional) but the triangle from the middle (new).