# LFO sine wave?

@pichenettes

The Shruthi is packed with very interesting and very well thought out features form a sound design point of vue, so I’m wondering why there is no sine wave for the LFOs ? The LFOs have a triangle wave, but that doesn’t give quite the same result in terms of modulation.

Would you consider adding such a sine wave ?

I haven’t checked but isn’t it there in one of the 16 “wavetable” shapes?

Yes, there is a sine wave in the wavetable as described in the manual. To confirm this I have sampled a patch made with an unmodulated oscillator with Sha = wav (for the oscillator) and I have checked the waveform displayed on my sampler (V-Synth XT). The 5th waveform (Prm = 32) and the 10th (Prm = 96) are indeed sine waves.

BUT : I believe there is a problem with the LFO using the wavetable.

When you modulate, say, Osc1 pitch with an LFO, the closest to a sine wave is Sha ~10 (*), but it’s not quite a sine wave : you can hear the modulation reach a maximum = A for 2 cycles then a maximum = A’ > A for the 3rd cycle, then back again to A, A, A’ etc.

(*) with Sha = ~5 or another waveform, the LFO modulation is not a sine wave at all.

What I have noticed with my ears when modulating the pitch is confirmed by the display of my sampler when modulating the VCA : the overall amplitude envelope consists in 3 consecutive sine-ish cycles with maximum = A, A, A’ (A’>A).

Could the wave pointer be a bit off when the wavetable is used by the LFO ?

I checked again and the “fancy” waveforms used for the LFO are not from the “sha = wav” wavetable. They are taken from the positions 16 : 32 of the wave memory and correspond to resonant/formant-y shapes, so there’s no sine wave at all in them.

I have tried to send this file to my Shruthi, but nothing happens.

I use MidiOx to send/receive sysex files and my V-Synth XT as a MIDI interface. That configuration works fine to send patches I have downloaded from this forum to my Shruthi.

Thank you very much !

Try this

~1 is now a sine wave.

I’ll redirect the people complaining about broken patches to you

From the manual: To update the Shruthi firmware, hold the S6 switch while the synth is being powered on. Instead of being greeted by the splash screen or the filter page, the screen remains empty, and the LEDs L1, L3, L5 and L7 are lit. The Shruthi is now waiting for SysEx data containing firmware update commands.

EDIT: oooh, that’s nice! Good call Georges. I tell’s ya, The Shruthi is the synth that keeps on giving!

I’m assuming that Olivier has only changed the LFO ~1 waveform to a sinewave, and left the remaining ~2 to ~16 as they were.

If so, I’ve just had a quick check through the factory presets, and NONE use ~1, so they sound identical with this custom firmware.

Martin

But anyone that created a custom patch using ~1 may be in for a “wha the?”

Only one of mine uses this, and I suspect I can tweak it

Or let it ride man.

Actually, ~2 isn’t THAT different from the old ~1

I’ve saved my preset with ~2, and it’s worth it to get a proper sinewave into the LFO collection

Martin