TB-303 'Facts' a Myth?

[ENV1]

you're missing the point, and i said that multiple times

No Antto, i dont think im the one who is missing the point. But rather than arguing about who doesnt understand who, why dont we just cut to the chase and make this as easy and simple as possible:


Fact: The TB-303 outputs very unique waveforms.

Question: The distinctive bending of these waveforms is a result of:

A: The Waveshaper

B: The Highpassfiltering


This is ultimately the main question of this thread.

the "303 waveform" especially the square wave, is not something static..

That may well be, but the static or dynamic properties of the Squarewave are not the subject of this thread. Of course this doesnt mean that i dont appreciate the information, but for now the subject is only to find out whether the 303s odd shapes are being generated by the waveshaper or by the highpassing.

go ahead and highpass a sawtooth so it looks like on my picture
when you do, just change the source waveform to a "square" without touching the highpass filters.. you can waste very long.. long time.

May be so, but i wouldnt do that.

With the info i have at this point i would do the basic wiring like in the screenshot below, (no, theres no LPF, VCA or anything else in there because its just to demonstrate the shaping), except that the waveshaper would have to be replaced with something a little better, i.e. less coarse. The next step would be to configure the waveshaper in the correct way.

click for fullsize

[ENV1]

I don't really have much to contribute, just thought I'd throw this up here. This shows the waves from the latest AudioRealism Bass Line 3 for each of three VCO models on square and saw. According to the manual #2 is meant to be the most authentic emulation. To me #3 seems more similar to the other waveform images we've seen in this thread so far.

Yeah, id noticed the differences in Mode 1 and 2 too.

(Mode 3 = ABL2.)

Not sure what to make of it.

[Lineali]

here's a picture.. that's captured from two notes, the second one is low pitched
(that's from the whole audio-output, not the bare oscillator)

Interesting, do you know which frequencies they are?

[Mike Janney]

I don't really have much to contribute, just thought I'd throw this up here. This shows the waves from the latest AudioRealism Bass Line 3 for each of three VCO models on square and saw. According to the manual #2 is meant to be the most authentic emulation. To me #3 seems more similar to the other waveform images we've seen in this thread so far.

Hi,
We actually switched around the meaning of the emulation modes in different versions of ABL3 because we accidentally reversed them in the Rack Extension version compared to the VST. I'm not completely sure right now if the manual is correct in that regards.

But the idea is that Model 3 should be mostly accurate to the 303, while Model 2 is more akin to the VCO model used in ABL2. Some of our users prefer Model 2, some prefer Model 3. We also had a noise bug in Model 3 in the initial 3.0.0 release so after fixing that even Model 3 differs between versions.

A static frequency capture of the ABL3 VCO vs the real 303 should be pretty similar. We have more work to do though, for instance the PW effect that Antto mention is also dependant on the glide from->to frequencies. I.e the PW effect has some lag according to my notes which makes a distinct sound in sliding square waves. But I feel I'm adding to myths rather than debunking them and I'm not sure we did the analysis correctly so don't take my word for it. Yet.

Mike / Audiorealism

[Richard_Synapse]

Fact: The TB-303 outputs very unique waveforms.

Question: The distinctive bending of these waveforms is a result of:

A: The Waveshaper

B: The Highpassfiltering


This is ultimately the main question of this thread.

The answer is simply both, for low notes anyway. That saw->square shaper does not really work properly, and the later high-pass filtering adds plenty of bending on top of that.

Richard