Oscillator sync: identical oscillator

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ByteMe666
Posts: 1
Joined: 01 May 2020

Post 01 May 2020

Hi,
My understanding of Oscillator sync conflicts with my experimentation.
If I reset Thor, make osc 1 and 2 identical, let only osc 2 through and turn sync on and off, I get a darker sound when sync is on.
However I chose identical oscillators, so osc1 resetting osc2 should have no effect.
What's going on ?

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Jagwah
Posts: 1687
Joined: 16 Jan 2015

Post 20 May 2020

ByteMe666 wrote:
01 May 2020
Hi,
My understanding of Oscillator sync conflicts with my experimentation.
If I reset Thor, make osc 1 and 2 identical, let only osc 2 through and turn sync on and off, I get a darker sound when sync is on.
However I chose identical oscillators, so osc1 resetting osc2 should have no effect.
What's going on ?
Good observation, when sync is off there are more harmonics in the very top of the spectrum when using saw waves, I wonder if someone in the know can chime in on this...

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Loque
Posts: 7260
Joined: 28 Dec 2015

Post 20 May 2020

Interesting observation. AFAIU the syncing is based on some math here, where the peak of Osc1 resets Osc2. Not sure if this is compareable to modern "sync" modes. But you are right, it creates indeed a slightly odd saw in the direction to triangle which results in a bit darker sound with less harmonics.
notfullsaw.jpg
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:reason: 11, Win10 64Bit.

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Benedict
Posts: 2176
Joined: 16 Jan 2015
Location: Gold Coast, Australia

Post 21 May 2020

OSC Sync is when you use one OSC (OSC 1 in this case) to reset the phase of the waveform on another OSC (OSC 2).

This means that if both OSC are Sine waves, the resulting wave is going to be fragments of Sine with the hard chopped edges of a Pulse as OSC 1 resets the OSC 2 waveform when it crosses its own threshold. That constant re-start of OSC 2 generally creates a harder sound. This works best with two different pitches for the OSC. You get that really gnarly sound when OSC 1 is moving as it makes the wave keep restarting as changing intervals as the rate of OSC 1 keeps changing.

Thor's Analog OSC are free-running (unlike Sub or Europa w. Phase set to On) so they are statistically unlikely to be perfectly aligned at any given key strike. But if they are the same shape and pitch, the restart of the wave on OSC 2 is going to be less dramatic on any of the more complex waveforms like Pulse or Saw.

:-)

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Jagwah
Posts: 1687
Joined: 16 Jan 2015

Post 22 May 2020

Benedict wrote:
21 May 2020
OSC Sync is when you use one OSC (OSC 1 in this case) to reset the phase of the waveform on another OSC (OSC 2).

This means that if both OSC are Sine waves, the resulting wave is going to be fragments of Sine with the hard chopped edges of a Pulse as OSC 1 resets the OSC 2 waveform when it crosses its own threshold. That constant re-start of OSC 2 generally creates a harder sound. This works best with two different pitches for the OSC. You get that really gnarly sound when OSC 1 is moving as it makes the wave keep restarting as changing intervals as the rate of OSC 1 keeps changing.

Thor's Analog OSC are free-running (unlike Sub or Europa w. Phase set to On) so they are statistically unlikely to be perfectly aligned at any given key strike. But if they are the same shape and pitch, the restart of the wave on OSC 2 is going to be less dramatic on any of the more complex waveforms like Pulse or Saw.

:-)
I knew there would be some logical explanation behind it!! :geek:

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Benedict
Posts: 2176
Joined: 16 Jan 2015
Location: Gold Coast, Australia

Post 22 May 2020

I just have Thor open right now trying this very thing.

Yes with a pair of Saws in Analog OSCs, the resulting OSC 2 is definitely less bright. I am assuming that is because as I have said above, the phases are not the same so OSC gets shortened in its period which essentially rounds off the height & dramatic-fall of the Saw.

As soon as I start changing the tuning of OSC 2, that typical Sync sound starts appearing.

:-)

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