Compatibility: JV-1080 and up
Audio example: PWM.mp3
The super JV series features two saw waves that have inverted amplitude to each other. A little bit of math shows us if we play them both, we will get silence at the output, but if we detune one of them, we will get Pulse Width Modulation. Basic procedure:
- Initialize the sound.
- Turn on T1 and T2.
- Go to WG1, and select ‘Synth Saw 2’
- Go to WG2, and select ‘Syn Saw 2inv’
Ok, now we got the basic setup. Next thing is to create detune. To avoid the modulation sound exactly the same each time we play the note, we will create detune by using Random Pitch.
- Set Random Pitch on WG2 to: 1
Now we must be careful here, because random means sometimes 0 at the output, and that would result in no detune = silence. To prevent this we will add Fine Tune which must be at least +2. Why? Because there are two possible cases. In case a) random gives 0 at output, Fine Tune of +2 preserves non zero value (it will be +2). In case b) random gives -1 at the output, Fine Tune of +2 again preserves non zero value (total fine tune will be +1).
- Set Fine Tune on WG2 to: +2
I assume most people would use PWM for the bass, therefore:
- Set Coarse Tune of WG1 and WG2 to: -12
You will notice the sound plays very slow pulse width modulation. To give more expression we will add one controller to modify the pitch of one oscillator. Please be careful here. You can’t assign this modulator to ‘any’ Tone you desire. It must be the tone that we applied detune function. In our case, this would be the Tone 2.
- Go to PATCH LFO&Ctrl #1 (Matrix Control)
- Matrix Control 1 Source set to CC01: MODULATION
- As Destination set PITCH, and put +6 to Sns (sensitivity)
- Disable Tone1 within matrix to make it look like this: PITCH : +6 -> _ooo
- Set TVA as necessary
Now when you move Modulation Wheel up, you will fasten the Pulse Width Modulation. If you want faster PWM by default, put higher values at WG2 ”Fine Tune”. And that’s about it!
By three methods we may learn wisdom: First, by reflection, which is noblest; Second, by imitation, which is easiest; and third by experience, which is the bitterest. – Confucius
Amazing website! Thanks for all the beautifully provided information!
Hm. Since I found no useful information on the internet yet, I might just ask the pro: the two waveforms “Synth Saw 2″”Syn Saw 2inv” seem to be missing on the MC-909 (incl. SRX-05). Do you have an idea where I could get them from? – Strangely one always and immediately stumbles over the one thing which is not available, hehe. First patch I wanted to recreate on the 909 – of course – included PWM. 🙂
I don’t know where are they hiding.
Don, trying to recreate thw polymoog vox humana preset and string preset, nees to synthesize PWM on the JD990. Any help or pointers you could woukd be greatly appreciated. Nicholas Faith
The only trick I’m aware of here btw is setting both to square/pulse enabling osc sync and moulating one of the osc’s. I know you know the JD series really well, and thought if their were any other methods that were viable you’d know.
Yeah, the good old saw+ramp trick. 😉 It’s nice but there are two disadvantages over real PWM.
First the modulation speed depends on the beat frequency of the detuning which is relative to the played note. You can compensate this a bit with by assigning control2 to keyfollow and carefully set the destination of tone2 to pitch with a low negative value.
Next issue is that the sound always starts with a pulsewidth of zero because on PCM synths oscillators always keysync their waveforms which is nice for a piano or guitar sample but totally uncool for single cycle waveforms like a saw or square. Thats the reason why e.g. two detuned saws on a PCM synth sound cheesy and digital by default instead of fat and warm on a analog synth with its free running oscillators.
Luckily the JV has that tone delay parameter. If you set this to 1 on tone2 (works only with structure 1) the second wave has a delay of a just few ms and the delay time is quite below sample accuracy. This gives you a bit random phase between the two waves with sounds quite cool with the saw+inv saw trick.
Bonus: with the JV structures you can get even more PWM-ish sounds by using structure 4 (one of the two booster stucts) and setting W1 to DC, w2 to triangle and play with booster and gain settings. the volume of W1 (DC) now controls the pulsewidth and you can modulate it either by tva or lfo (offset to -100, tva to pos. value), keysnced or not. Happy PWMing 😉
These Structures are what makes the JVs and XVs so much more than just a rompler. You can even trick the JVs to fake hardsync with these! Eat this, Motif 😉
Tell me about the hard sync trick ? Cheers