Moog Music Forum

EMwhite wrote:Synths like the Roland Juno 106 and the Oberheim Matrix 6 each had DCOs; the Moog products are VCOs, however in the case of the Sub37 (and I believe, the SubPhatty before it), there is much improved tracking in the modern Moog VCOs than what was in my Little Phatty Tribute near zero warm up, etc. Both are still analog but the frequency clocking is controlled digitally on DCOs

If this is the case then the Sub line is DCO based. The thing is that there are lots of different DCO designs, some clearly better than others. This is a digitally controlled oscillator in which the frequency is kept under digital control, although the waveform generation is 100% analog, but the frequency is perfect. VCOs have imperfect tuning by definition, mostly temperature-influenced. So yeah, technically the Sub Phatty and Sub 37 have DCOs, as unfair as it may sound.

autoy wrote:

EMwhite wrote:the Moog products are VCOs, however in the case of the Sub37 (and I believe, the SubPhatty before it), there is much improved tracking in the modern Moog VCOs than what was in my Little Phatty Tribute near zero warm up, etc.

If this is the case then the Sub line is DCO based.

All Moog synths, Sub line included, have VCOs. Nobody is saying that the oscillator is locked directly to some kind of digital frequency control. It's a free-running VCO controlled by a pitch CV. It's just that the pitch CV is generated by a DAC (digital to analog converter) and the oscillator responds predictably to that voltage, so the tuning can be very precise.

Amos wrote:All Moog synths, Sub line included, have VCOs.

"Rahhbrahh!!!" - Gabby Johnson

Amos wrote:

autoy wrote:

EMwhite wrote:the Moog products are VCOs, however in the case of the Sub37 (and I believe, the SubPhatty before it), there is much improved tracking in the modern Moog VCOs than what was in my Little Phatty Tribute near zero warm up, etc.

If this is the case then the Sub line is DCO based.

All Moog synths, Sub line included, have VCOs. Nobody is saying that the oscillator is locked directly to some kind of digital frequency control. It's a free-running VCO controlled by a pitch CV. It's just that the pitch CV is generated by a DAC (digital to analog converter) and the oscillator responds predictably to that voltage, so the tuning can be very precise.

Thanks for chiming in Amos, and clear things up. My bad, then. I completely misunderstood how this worked perhaps on the basis of what's said in other forums. Glad to see Moog found a smart workaround without having to rely on pure DCOs and compromise on sound quality. Hope this concept can grow into polyphony in the future.

_DemonDan_ wrote: "Rahhbrahh!!!" - Gabby Johnson

THAT'S some authentic frontier gtibberish!

ive always been told that a VCO controlled by a digital pitch CV is the very definition of a DCO....an analogue oscillator that is controlled digitally (to help with pitch problems). A DCO in a juno 106 is obviously still a real, electronic circuit, with resistors and capacitors, so you can call it "analogue" compared with modern-day digital synths that run code to generate their waveforms, for instance, Amos are you from Moog? i would like to hear the official word on this...

Blackout wrote:ive always been told that a VCO controlled by a digital pitch CV is the very definition of a DCO....an analogue oscillator that is controlled digitally (to help with pitch problems). A DCO in a juno 106 is obviously still a real, electronic circuit, with resistors and capacitors, so you can call it "analogue" compared with modern-day digital synths that run code to generate their waveforms, for instance, Amos are you from Moog? i would like to hear the official word on this...

It is admittedly a little confusing, which is why there have been so many discussions of this subject online over the years.

The most common form of DCO such as you find on a Juno 106 has its frequency determined by a high-speed numerical counter that is synchronized to the processor; this is not the same thing as a pitch CV. With a traditional VCO, you don't need any kind of processor running at all and the oscillator will still oscillate. In the case of a standard DCO, if there are no reset pulses coming from the processor, there's no oscillation.

More info (which is still potentially confusing but has some good details) at Wikipedia:
http://en.wikipedia.org/wiki/Digitally_ ... oscillator

wikipedia wrote:A DCO can be considered as a VCO that is synchronised to an external frequency reference. The reference in this case is the reset pulses. These are produced by a digital counter such as the 82C53 chip. The counter acts as a frequency divider, counting pulses from a high frequency master clock (typically several MHz) and toggling the state of its output when the count reaches some predetermined value. The frequency of the counter's output can thus be defined by the number of pulses counted, and this generates a square wave at the required frequency. The leading edge of this square wave is used to derive a reset pulse to discharge the capacitor in the oscillator's ramp core. This ensures that the ramp waveform produced is of the same frequency as the counter output.

More of a Digitally Tuned Oscillator than a Digitally Controlled Oscillator then


R.

Rufus the Dog wrote:More of a Digitally Tuned Oscillator than a Digitally Controlled Oscillator then.

The voltage that's going to the OSC *is* analog.

It'd be like saying that a speaker is digital because the analog voltage that goes to that speaker was digitally controlled by an audio CD.
(But that, when you play a vinyl record instead, the speaker then becomes analog.)

_DemonDan_ wrote:

Rufus the Dog wrote:More of a Digitally Tuned Oscillator than a Digitally Controlled Oscillator then.

The voltage that's going to the OSC *is* analog.

It'd be like saying that a speaker is digital because the voltage that goes to that speaker was digitally controlled by an audio CD.

I know Dan, was just chucking in my 2 pence worth… the DAC that drives the VCO starts digital and ends up analogue.

As far as I am concerned the Sub37 is an analogue synth…. full stop/period (delete where applicable)


R.

what particially has grinded in my crotch recently was the marketing spin around the Dave Smith Prophet 12, where the phrase "analogue synth" was used just one too many times. And indeed it turned out it had digital oscillators. and then later they said "oh when we said analogue we were just referring to the filter...' personally i felt lied to.

for example if you watch this video here of the Prophet 12 being explained by Dave Smith all you here is the word "analogue" repeated...no mention of the oscillators being Digital....purposely not explained fully.

https://www.youtube.com/watch?v=1s5AiueF5og

even read the description of the youtube video... "This 61-key analog beast...."...a straight-out Lie (granted it is a Sweetwater post but where do you think they got that information from).

i think it is important for Moog to "fess up" about what is exactly going on here with the Sub37 and the oscillators. I dont want to be lied to again. i feel a repeat situation as the Prophet 12. i have faaaar to much respect for Moog, wayy above and beyond DS stuff. Moog should clear this up now in a statement or official email or something. Especially as the SOS interview has come out, and what has been said is apparently "wrong" now it seems? where did the SOS reviewer get his information from then? he has certainly thrown a spanner in the works. is the next issue of SOS going to retract this explanation then?

Blackout wrote: i think it is important for Moog to "fess up" about what is exactly going on here with the Sub37 and the oscillators. I dont want to be lied to again. i feel a repeat situation as the Prophet 12. i have faaaar to much respect for Moog, wayy above and beyond DS stuff. Moog should clear this up now in a statement or official email or something.

Amos' statement (2 posts further down than this one) should be considered as coming from the horse's mouth.

Blackout wrote:if you watch this video here of the Prophet 12 being explained by Dave Smith all you here is the word "analogue" repeated...no mention of the oscillators being Digital....purposely not explained fully. https://www.youtube.com/watch?v=1s5AiueF5og
even read the description of the youtube video... "This 61-key analog beast...."...a straight-out Lie (granted it is a Sweetwater post but where do you think they got that information from).

Hi Blackout,
I agree that, when you see the YouTube video outside of the Sweetwater page, you don't get accurate enough information. I wasn't part of the Prophet 12 review, but I'll ask if the description text can be updated. When you see that video on the Sweetwater page though, it's directly under a large-type headline that says:

Digital Precision on Top of Analog Filters and VCAs

And the Tech Specs section on the same page clearly states:
Sound Engine Type(s) Digitally-controlled oscillators

http://www.sweetwater.com/store/detail/Prophet12

Blackout wrote:ive always been told that a VCO controlled by a digital pitch CV is the very definition of a DCO. [...] Amos are you from Moog? i would like to hear the official word on this...

I really am from Moog. I've worked here for over ten years; when I started, Bob Moog still came in to work every day.

The short story is that you've been told the wrong definition of a DCO.

The simplest description I can give of a DCO is that it involves a processor generating a simple on/off signal (like a square wave) which is then shaped into other waveforms using analog circuits. If the processor stops, the oscillator stops.

With a saw-core VCO, a processor is completely not needed... if there is one, then it's just turning up and down a voltage that controls how fast the oscillator is oscillating. This is what the Voyager uses, also the Little Phatty, also the Minitaur and Sub Phatty and Sub 37.

The fact that a "digital" processor was involved in setting what voltage the pitch CV should be, does not turn a VCO into a DCO.

I hope this helps. There is no need for any hand-waving or spin when it comes to Moog oscillators; they are classic VCOs in the tradition of Bob Moog, with the same basic kind of pitch control that has been in use since the days of the Source and the Memorymoog, only with better resolution and tuning accuracy.

cheers,

Amos

Hi Amos,

Please shed some light on how external CVs are handled in Sub37 -- are they mixed into CV after the main CPU DAC, or they are ADC'ed first, and then added to a calculated value before it is sent to DAC. If the latter, what's the digitization frequency?

Thank you,
/Peter