Simple "waveshape-core" question

[Grumblepig]

What does it mean when an osc is described as "triangle-core?" The original Doepfer Dark Energy contains such. The DE II has a "sawtooth core" osc.
Cheers!

[Yekuku]

It means that the first waveform that the oscillator circuit produces is a triangle. All other waveforms ( saw , pulse etc) are produced by waveshaping the triangle.

[cornutt]

To add a bit to that: Most VCOs use a sawtooth core circuit. Other circuitry takes the sawtooth wave output by the core and transforms it into whatever other waveforms the VCO produces. Triangle core VCOs are said to have certain advantages in terms of waveform accuracy, but they are more difficult to design properly and require more components to implement, so they aren't used as often.

[Grumblepig]

Curious! Thanks for the replies. Is there a discernible difference in tone between the different types of oscs?

[Broadwave]

Curious! Thanks for the replies. Is there a discernible difference in tone between the different types of oscs?

Not enough to worry about, although I'm sure some purists here would have something to say about that

Once you start looking at waveforms with a 'scope, you'll notice that Saw/Tri/Square waves are all slightly different when comparing synth manufacturers, but even this varies at different frequencies, so it's not a constant factor.

Another example is that, due to the design of the pulse voltage divider circuitry (5% resistors with no adjustment), the square waves on a Minimoog will NEVER be exactly 50% (more like 48% - It can easily be corrected, but you loose the character), whereas ARP, Roland etc have trimmers to produce an exact 50% duty.

What counts is the end result, not the source waveforms. The Minimoog design unintentionally introduces crosstalk between the VCOs, distortion in the VCF & VCA - all this adds up to produce "that" sound. An ARP 2600 has a much cleaner signal path with far less crosstalk & distortion so it has a totally different character from the MM.

[Bitexion]

I wonder why they left out PWM on the Minimoog.

[Broadwave]

I wonder why they left out PWM on the Minimoog.

I presume, at the time, Moog were going for simplicity - Which sort of worked

PWM can be added to the MM's VCOs, but you'll have to put those extra knobs and switches somewhere - I've done mods in the past which use a break-out box and ribbon cable, as it was the most elegant solution I could think of without drilling holes all over the front panel

[commodorejohn]

I'm kinda curious to hear what that would sound like, as the Minimoog's square/pulse is so distinctive.

[pflosi]

I'm guessing the reason is that the 901 also did not have a CV in for the PW. The 921 that does have it was released after the Model D. AG will come along soon and school us how PWM is not "real" synthesis and just there to "fake" two osc sounds - the Model D has three oscs, so no need for PWM according to that theory Sorry Marc

WRT triangle core, some triangle core oscs in modular land only have a strange sort of "reversing" soft sync, which sounds kinda fun but can be a real pain for synced LFO applications... I guess hard sync is trickier with a tri core? Not entirely sure... Apparently, sine waves are easier to get clean with a tri core (although all Cwejman is saw core and those are the cleanest sines I know), which is somewhat essential for FM. AFAIK, the thru zero FM designs are also all based on tri core oscs.

Cheers

[madtheory]

Maybe MuffWiggler is the place for this kind of, very interesting, debate?

Ya Mark's wrong though. Maybe PWM with an LFO is mostly used to fake a chorusing effect, but being able to adjust the pulse width to change the waveshape is incredibly useful. But that is rarely found on its own, because it is a simple step in most circuits to allow the shape to me LFO modulated.

I really hope there's a debate

[pflosi]

Interestingly, there is a PW control on the 901 - just no CV in.

[madtheory]

Interesting, I did not know that. But hang on, 901 is discrete transistors whereas MIniMoog has 741s instead, so they're not exactly the same are they?

[Broadwave]

Ya Mark's wrong though.

Oh boy, you're in trouble now

I didn't know Mr. Doty was so hung up about PWM. Modulating PW with envelopes, S&H and even Keyboard CV is vital to me - It's not all about the LFO

[pflosi]

Yeah the Mini oscs are not exactly like the 901. But definitely based on it.

A 901 modded for PWM can be heard here: https://soundcloud.com/q-uazimodo02/mod ... ulse-width

[meatballfulton]

I didn't know Mr. Doty was so hung up about PWM

This is an unsubstantiated rumor...