Sub Phatty non continuous waveshape oscillators

[Raizerpiano]

Hello all,
I have just got a brand new SP here in Brazil! After some time discovering my new synth I noticed a strange thing. I could hear a small rough "step" while turning the wave button. This happens just before the triangle turns into saw. I have tried both oscillators and they sound exactly the same, with this little step on this particular spot. I then turned on my osciloscope and found out that the morphing between waves are not continuous, on this point a small negative peak appears on the waveform and the sound changes abruptly (not to evident though, but noticeable). I've tried to run a full oscillator calibration, but they still remain the same. I did not have any modulation, nor filtering or other circuit engaged, such as the multidrive, just the plain oscillator with a classical sustained ADSR. When I modulate the Waveamount with the LFO I can hear this "problem" also. Is this normal? please take a look at the picture below...

Triangular


Saw


The "peaked" waveform just a tiny bit before the saw


Square

[Raizerpiano]

If you would like to compare, there is also a video on Youtube of a persons analyzing the SP oscillator with an osciloscope (1:44) and this peak does not show up on his.

the link for the video: http://www.youtube.com/watch?v=ZBJUmAL2R30

[IgorCristo]

Fala companheiro brasileiro!!
Responderei em inglês apenas para manter o restante do fórum no assunto.

I have this with my Sub Phatty. Actually, this is one of the things to criticize about it... my Little Phatty doesn't behave like this and the reason is that the oscillators are different. The Sub Phatty has new oscillators, more stable and everything, but have this problem. It's very easy to hear this on the change from saw to a mix saw/square. The effect is more subtle when using LFO, but still there, as you've posted.

I don't believe that this is actually a true problem, although it's a problem with the development of the synth itself. I don't think we've both been prized with a problematic Sub Phatty.

Só de curiosidade, pagou quanto nele?

Abraço!

[bgirl]

Did you try with a real oscilloscope on the SP main out ? Audio interface and converters can give you weird results ...

[Amos]

this discontinuity is a normal part of the variable-waveshape circuit. They all do it; even the Voyager has this little spike as you transition from the saw to square/pulse wave. You might be getting a crispier version of it with more high harmonics on the Sub Phatty, so it's more noticeable... it's just a part of the character of the oscillator though.

[bucephalus]

I don't here any "step" when turning the know really slowly. Is this a pure graphical issue or do you guys hear it and are really disturbed by it?

[bgirl]

I had the same result from an analog 4. Doesn't matter really if you like the character of its sound

[Raizerpiano]

hello all,
thanks for sharing all your thoughts! I am really glad to here from such knowledged people.
I am getting used to this thing, specially after Igor said that this is a little nothing, and that it is due to the synth construction itself. Since Amos has confirmed this also, I can not argue anymore. Nevertheless, I still find this subject a bit odd since there are other sub phattys around the planet that has a smooth wave variation (that video..). This makes me think that there are some "golden" units around and some other ones a little less shiny, mine is somewhere around the #3200.

I have used MOTU Cuemix FX to analyse the waveform, but even if it had a not so real reading, my ears could not lie, and this "fx" is still noticeable.

It is not common to modulate the waveshape of saw waves anyway, being this a square/pulse width thing tradition, but, maybe I could use this saw spike to serve me on its particular way. Maybe this is the real deal with a hand built jewelery. Maybe mine is a golden one.

I am not sad afterall with it because there are a whole bunch of other things taht makes this synth such a joy to play and head, but, as I work for a computer music distributor, I will try out another one, and...

Replying to Igor, who has asked in Potuguese: I have paid around US$2500,00 with all taxes included, the common Brazilian government ripp off. Imagine how much a Voyager costs here?

Thanks, and all the best to you all!

[mmarsh100]

You can hear it quite clearly transitioning from triangle to saw with the knob *almost* at saw. the little bump in brightness is not obnoxious and even sounds great as part of a patch. Also, it is like a audio detente for finding the best saw

[Raizerpiano]

Hi everyone, just to let you people know that I have tested another Sub today, and the result is: It was different. I could have not realized until now that each moog synth could have such its own personality and was some sort of a living thing. Do I prefer mine? Yes of course, because I have already made some sort of mental connection with it that I can't explain, but for sure it is a normal thing among moog owners and you might know what I am talking about...I will keep this one for being so singular. Happy ending.

[kingfriday]

Ok wait so... other Sub Phatties don't have this issue? Mine certainly does, and I don't care for it. So confused.

[kingfriday]

Just watched the youtube video and I'm shocked. There is no spike on his Sub Phatty, yet I have one on mine.

I would say this qualifies for a repair, no?

[kingfriday]

Another thing I noticed is that the Pulse wave does not achieve the extreme end of the duty cycle without using the modulation/ wheel. In other words, it only goes to about 75% before the knob runs out of room, but you can get it to go 99% or silent with modulation.

[Amos]

This thing you're talking about has been a part of the character of the waveshaping circuit since the Voyager. It's the same there also. It's not a defect or something unusual to one or another instrument. The same discontinuity exists just past the sawtooth setting on Voyager, Little Phatty, and Sub Phatty. I don't remember Voyager users complaining about it; maybe they did 10 years ago when it was new, or maybe not. In any case, it's inherent in the design and has been there from the Voyager onward. It's possible that there are more upper harmonics audible from the Sub Phatty oscillators, which are accentuating the sound of this particular waveshape in a new way...

as for the skinniest pulse width available from the waveform knob, yes that can be calibrated in software.

[kingfriday]

I think I know what you mean about the high harmonics accentuating the switch. I took the osc down to 3 on the mixer and killed all multidrive and could only hear the switch if I did a very slow sweep. It doesn't really make itself apparent when doing PWM type effects. No worries, just being a picky sound nerd at this point.

Great news about the PW being adjustable through software. I'd like to formally request that for a future OS update. I love the sound of taking a pulse wave osc to near silence and sweeping it in under another wave form.