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Durwood75

DCO vs. VCO

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Yet another newb question here.

 

Can someone explain the pros and cons of these different types of oscillators? I'm specifically curious about analog oscillators that are digitally controlled rather than voltage controlled and how that may affect their stability and sound. Also, can this difference in control also apply to filters, LFO's, and amplifiers? If so, what the pros and cons within those applications?

 

Thanks.

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As far as I know, DCO means a digital circuit monitors the frequency output by the oscillators and adjusts the tuning on the fly to keep it within range. My Dave Smith Instruments Prophet '08 has DCO's on it and there is an "oscillator slop" parameter that allows you to adjust fine drift of the oscillators. I am not sure what the exact control loop mechanism is, but I would guess that it is voltage control with a gain (value) adjusted by the digital control system. Without DCO, you just set a tuning pot that adjusts the oscillator frequency. There is a greater sensitivity to changes in tuning due to say, temperature changes (especially while the instrument warms up to a steady state temperature). Voltage control in general refers to a conversion from a control voltage value to a control signal, either directly as a voltage value, or digitally as a number using a something like a voltage-to-frequency conversion IC.

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google is your friend. this topic has been hashed over and over again to the point where its not even like beating a dead hoarse any more. more like beating some smelly dirt with whats left of your arm-stump.

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What are online forums for if not to beat a dead horse into smelly pulp? I did try the seach before posting and was surprised to find no hits - maybe it's not working correctly.

 

The info I found using google wasn't all that clear (wiki, technical sites, other forums, etc.) but thanks for the advice. I was just looking for some feedback from the informed folks here in the HC forums.

 

The Prophet 08 is a perfect example of what I had in mind when I asked the question. It's apparently a 100% analog audio signal but I was curious about how digital control affects the sound / functionality.

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What are online forums for if not to beat a dead horse into smelly pulp? I did try the seach before posting and was surprised to find no hits - maybe it's not working correctly.

 

welcome to harmony central, my friend. Their search has always sucked.

 

Google it

 

Tony

 

p.s. this topic has a tendency to descend into a very bloody fight between different forms of synth nerds. beware.

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We had something like 2-3 huge threads regarding VCO vs DCO with all the details you need.

 

We? Who? Why don't you just ignore the thread if you have enough of this subject?

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Can someone explain the pros and cons of these different types of oscillators? I'm specifically curious about analog oscillators that are digitally controlled rather than voltage controlled and how that may affect their stability and sound. Also, can this difference in control also apply to filters, LFO's, and amplifiers? If so, what the pros and cons within those applications?

 

The DCO vs. VCO debate allows certain purists to puff up their wings and state that if your synthesizer has a little itty bitty bit of digital in it, its tone completely sucks and your music will be complete shyte. :D

 

Reality is, when you start adding any element of digital control to a synthesizer (which you need for any practical patch memory), there are quite a number of ways you can implement that. I'm glad that VintageSynth post came out, because it clearly pointed out that the issue is more than "VCO vs. DCO".

 

In general you trade a bit of warmth for greater tuning stability (and potentially tightness) the more digitally controlled you go, but it's not a hard and fast rule. I personally avoid esoterics and tend to look more at the overall sound of a synthesizer. There are some pretty crappy-sounding pure analog synthesizers, and some very good sounding digitally controlled ones. As an example, I think it says a lot that the Waldorf Pulse DCO (which wasn't labeled specifically as such) was able to fool many people for quite a long time.

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This isn't really answering your question but I find this interesting. Here's some classifications of oscillators made by Haible Juergen on Analogue Heaven circa 1995. There's probably a few more variations of oscillators he didn't mention.

 

search the analogue heaven archives too. www.retrosynth.com

 

 


(1) free running analogue oscillator, controlled by analogue voltage divider

keyboard. (Minimoog, ...)


(2) free running analogue oscillator, controlled by digital via a D/A

converter

without correction, and analogue modulation (Oberheim n-voice (?) )


(3) free running analogue oscillator, controlled by digital via a D/A

converter,

with autotune, scale correction and stuff, but still analogue modulation

(Sequencial Circuits Prophet5 rev. 3)


(4) free running analogue oscillator, controlled by digital via a D/A

converter,

with autotune, scale correction and digital LFO / Sample&Hold / Glide

modulation, but with analogue ADSR->VCO modulation (Oberheim OB-8).


(5) free running analogue oscillator, controlled by digital via a D/A

converter,

with autotune, scale correction, and all modulations including ADSR via

DAC (Sequential Prophet 600).


(6) free running analogue oscillator, controlled by digital via a D/A

converter,

with autotune, scale correction, and all modulations including ADSR via

DAC, plus automatic autotune in the background from time to time

(Oberheim Matrix12 (?)).


(7) Simple Ramp-Oscillator that is synced by a counter every cycle, but

with different clock/divider tree for both DCO's in a voice (Oberheim Matrix

6,

EDP Wasp)


(8) Simple Ramp-Oscillator, that is synced by a counter every cycle, but

with one single clock/divider tree for both DCO's in a voice (Oberheim

Matrix 1000)


(9) Staircase Waveform stuff (as described in different recent mails)


(10) Wavetable stuff (also as described in recent mails)


These are the different types I know of. Maybe there are still others in

between.

Speaking in the word's original sense, (2) - (6) would be something like

"DCVCOs" ("digital controlled VCOs") in the sense of a digital word forms

an analogue voltage that controls an oscillator. (7) and (8) would be real

"DCOs", cause they are still oscillators, only under the iron grip of

digital

clock, which makes them sound thin and lifeless. (9) and (10) shouldn't

be called "controlled oscillators" anymore, perhaps just call them "DOs"

("digital oscillators") or even closer to the point, "DDs" (digital

dividers)

or "DS's" (digital scanners). Well, but that would go too far then.


Oh, I forgot another interesting variation:

Analogue oscillators with digital dividers / waveforms:


(11) analogue VCO with dividers (some ARP-synths - thank You Joachim,

for the schematics! - and of course the Suboscillators in various VCO-

based synths)


(12) 12 analogue VCOs for the 12 top-octave-semitones and digital

dividers (Farfisa VIP 245, Korg PS-3x00 series)


JH.

 

-Larry

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We had something like 2-3 huge threads regarding VCO vs DCO with all the details you need.

 

so? This is a synth forum and he asked a GOOD question. It wasnt one of those "help! what KB should I get!!!!?" that we all get sick of.

 

heaven help the person that wants to learn about synths. You all should know by now that this forums only purpose is to talk about nonsense and post random pictures over and over and OVER again.

 

and where are these HUGE threads? I dont remember seeing them? Break out the search feature and find them.

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I like stuff that makes noises and sometimes music comes out.

 

I like math and calculating stuff with math on computers, too.

 

If someone asks a question about math and calculating stuff with computers, I answer to the best of my ability. Then I try to point out books and possibly articles or research papers for further info. If there is a reliable website for info, I might give that, too. I never give a "search it" answer, even if it is a question that has been asked a thousand times before and discussed in every intro to numerical analysis book worth reading.

 

So why do that with questions about stuff that makes noises and sometimes music comes out? Especially if the question is a good question like Durwood's? If there are discussions about it elsewhere with useful info, how about putting links to those discussions here? Leitner6's quote of Haible Juergen was very informative and interesting (and I thank you for that!).

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so? This is a synth forum and he asked a GOOD question. It wasnt one of those "help! what KB should I get!!!!?" that we all get sick of.


heaven help the person that wants to learn about synths. You all should know by now that this forums only purpose is to talk about nonsense and post random pictures over and over and OVER again.


and where are these HUGE threads? I dont remember seeing them? Break out the search feature and find them.

myteeGTi, as much as i like your humorous posts, right now you're like that little guy in the kung fu movies who shows up to say 'hey boss! you're kung fu is pretty good!!'. -ms

 

Makes one wonder is it harder to click one button and type two words, than typing the whole page full of questions? Click the search function and type something like "digitally controlled" or whatever.... Benefits are:

 

  • you don't need to wait for an answer

  • you find out much more information than asking question after questios, as all possible subquestions are probably already answered too

  • you don't need to waste time writing posts that have already been written

In fact, i just used the FSC - the {censored}ing search command a let's see what have i found:

http://acapella.harmony-central.com/forums/showthread.php?t=1308282

http://acapella.harmony-central.com/forums/showthread.php?t=1551129

http://acapella.harmony-central.com/forums/showthread.php?t=1639595

 

See? It works! And there is much more, even larger threads, etc... The only question is: does the search sux, or the searcher?

 

Cheers!

 

:wave:

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Makes one wonder is it harder to click one button and type two words, than typing the whole page full of questions? Click the search function and type something like "digitally controlled" or whatever.... Benefits are:

 

Im not saying people shouldnt use the search feature. They SHOULD!!

 

but there is a difference between saying "its been covered, try the search" and being a dick and saying something like "OMG!!! WTF YOU MORON!!!!? Please dont bring this up! ITS BEEN COVERED!!!" like you did, and for some reason you deleted that response. :confused:

 

I guess you took a page out of ADSRs book :idea:

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:idea:

 

What if all the :deadhorse: threads were linked into a thread, and that thread was stickied. It would be like our synth demos thread except it would be it's evil twin. Anybody who wanted to watch people debate could go in there and get lost for hours. :blah::blah::blah::blah::blah::lol:

 

Oh btw I like DCO's.

 

VCO's too. ;)

 

Jerry

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Got 57 DCOs and 15 VCOs at home. 2 VCOs (in black case with a lot of 1/4 jacks and knobs) are on the way and another VCO (in grey case with knobs) soon to be sent to me. :D

 

 

P.S. LFOs excluded

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Got 57
DCOs
and 15
VCOs
at home. 2 VCOs (in black case with a lot of 1/4 jacks and knobs) are on the way and another VCO (in grey case with knobs) soon to be sent to me.
:D

I'd love to hear a mega-unison patch in your house. ;) Or 75-note analog polyphony (depending on the architecture of the boxes all those oscillators reside in) ;)

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Also, can this difference in control also apply to filters, LFO's, and amplifiers? If so, what the pros and cons within those applications?

 

To answer some of your questions from a different angle (leaving out the VCO/DCO debate stuff).... filters, amps, EGs and LFOs can also be affected soundwise by the advent of 'digital creep', however these followed different paths and timelines from that of oscillators in synth evolution, and the extent to which they affect the sound differs from a lot to very little.

 

LFOs and EGs, as they are modulators - not sound carriers - were the first to go all-digital (i.e. software) around the same time that hybrid oscillators (DCOs) were first being developed. The most noticeable difference were slower envelopes due to CPU speed issues on early processors. LFOs didn't seem to suffer too much.

 

Filters and amps (sound carriers) were the last to go digital, as they were difficult to develop into the digital domain with such slow processors that existed at the time. These affect the sound a great deal, hence the very large batch of hybrid synths and sampling synths released between 1984-1987 which had generally a warmer sound than those of all-digital synths. A warmer sound due to analog signal processing, not just 0's and 1's being processed in software by a computer.

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