KVR Audio

yul · Post by **yul** » Fri Jun 29, 2012 2:46 am

Hello,

can it be done? I am having a hard time finding ANY intelligible information on FM basic algo's.

I know these waveforms are supplied in the operators but I would lioe to know how to build it from scratch. Currently, capable of building square and saw.

Thanks!!

Yan

dalor · Post by **dalor** » Fri Jun 29, 2012 2:55 am

Hm NI FM8 has Triangle as a basic waveform included.
Not sure if its possible to create a Triangle from pure sines.. With phase distortion maybe.

yul · Post by **yul** » Fri Jun 29, 2012 3:21 am

That's what I have been reading so far too. I do own FM8 but wanted to understand how to build a basic triangle but I cant' figure it out.

GeckoYamori · Post by **GeckoYamori** » Fri Jun 29, 2012 4:58 pm

I just went ahead and tried on a whim in FM8 and got results surprisingly fast. Used 2 sine operators, simple modulator>carrier setup. The modulator has a feedback loop around 40 and an amplitude between 10 to 15 to the carrier. It sounds close enough to me anyway.

yul · Post by **yul** » Fri Jun 29, 2012 5:59 pm

Ok got it. Actually, the modulator>carrier ratio is 2:1. Reverse phase the modulator, feedback at around 33 and amp at around 14. Almost perfect!! Thanks!

phreaque · Post by **phreaque** » Fri Jun 29, 2012 6:47 pm

Following the basic waveform concept, the Triangle waveform includes odd harmonics similar to the Square waveform, so that Operator 1 pitch (coarse) should be set to 1:00 & Operator 2 @ 2:00, let Op2 slightly modulate Op1, now you're getting a sine inside sine figure, to melt the peaks & get a smooth slope you have to shape Op2 by increasing its Feedback. And this is it:

BTW. Invert the phase of Op2

GeckoYamori · Post by **GeckoYamori** » Fri Jun 29, 2012 10:32 pm

Now here's a tougher one I haven't figured out... How about recreating squares at different pulse widths using sines?

dalor · Post by **dalor** » Fri Jun 29, 2012 11:03 pm

GeckoYamori: Now that I'd like to see too..

phreaque · Post by **phreaque** » Fri Jun 29, 2012 11:29 pm

GeckoYamori wrote:Now here's a tougher one I haven't figured out... How about recreating squares at different pulse widths using sines?

My idea is to make the Square waveform simulation then by adding a third operator that works as a notch (pulse maker or shaper). The op3 coarse is 1.00 as the same basic fundamental tone, then by adding some phase adjustment (%25) so that the notch (pulse shaper) shifts & intersects with the square waveform producing a pulse.

GeckoYamori · Post by **GeckoYamori** » Fri Jun 29, 2012 11:46 pm

There's no direct phase feature in FM8. Can it be achieved via the offset somehow?

I don't have nearly as much pure theoretical grasp on synthesis, I mostly just go by ear when tweaking stuff.

This little tune has the typical PWM sounds, but it's all done through FM. OPL3 on a Sound Blaster 16 to be precise, which could also use sines cut in half, squares and saws so it's possible or probable that those were utilized.

phreaque · Post by **phreaque** » Sat Jun 30, 2012 7:44 am

GeckoYamori wrote:There's no direct phase feature in FM8. Can it be achieved via the offset somehow?

Hmmm, I'm not quite sure as I don't have FM8, But offsetting works different than phase shifting... I'll try doing another method without applying phasing & will let you know, although I doubt it

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Update:

Solved, here's the concept:
In order to obtain a basic Pulse Waveform, we have to mix 1 sawtooth with an inverted sawtooth, as shown here:

To achieve this:
Op2 modulates Op1, both at same frequency, the Op2 must be phase shifted (inverted), trying to get a simple (Saw-Square) combination, then by shaping the waveform using the feedback loops for both Op1 & Op2 you get the required shape.

I have FM7 which can't simulate such thing as it doesn't have phase inversion. What about FM8?

yul · Post by **yul** » Sun Jul 01, 2012 1:41 am

WOW Great responses! I also like to use Smartelectronix S(m)exoscope to visualize my results. Such great tool and hobby!!

GeckoYamori · Post by **GeckoYamori** » Sun Jul 01, 2012 1:58 pm

I tried with an inverted saw like you said, it sounds more like I'm changing the pitch on a sync sound rather than changing the pulse width.

phreaque · Post by **phreaque** » Sun Jul 01, 2012 3:26 pm

GeckoYamori wrote:I tried with an inverted saw like you said, it sounds more like I'm changing the pitch on a sync sound rather than changing the pulse width.

Hi.
No don't use saw waveform, instead simulate the sawtooth from two sines one modulates e other with little feedback.
But as i told, there must be differences in result as we used different FM emulators.

If you have IL Sytrus i could send you the preset to study it.

phreaque · Post by **phreaque** » Tue Jul 03, 2012 11:13 am

Gecko Yamori Hey wait a minute you're the genius music maker of SOR-Remake! My honor to know you & talk to you! Please let's keep in touch I'm pleased to know you

how to make FM triangle wave from sines ?