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Re: The VCO vs DCO thread

Posted: Wed Jun 20, 2012 4:05 pm
by GuyaGuy
Stab Frenzy wrote:Not really VCO vs DCO, it's more about 'what is digital?'
I liked my sensationalist title better :D


Stab Frenzy wrote:
GuyaGuy wrote:I just want to find out why a DCO would be considered digital rather than analog since I'd always been under the impression that DCOs are analog with a digitally controlled clock.
DCOs aren't digital, they're a hybrid of a digital part of the circuit and an analogue part. It's an analogue oscillator which is reset by a digital clock rather than being a fully analogue design.

The confusion comes about because we were discussing the Poly 800 and it's commonly believed to be a DCO synth when in fact it's not, it's something quite different to any other synth that I'm aware of. It's a weird microprocessor controlled logic circuit that just puts out square waves, albeit in varying combinations. As the input is purely digital and the output is digital I consider it a digital circuit.
Ohhhh...Now I getchya. You were only discussing the peculiar properties of the Poly800. I thought your description was meant to describe all DCOs. It's clear now that I look back at the posts. Like many here, I was under the impression that the 800 has DCOs. Totally missed this post:
Stab Frenzy wrote:Poly 800 had digital oscs, not DCOs.
That's what I get for reading on my iPhone...Anyhoo...Carry on...

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:10 pm
by samuraipizzacat29
I don't care about how we "got there" right now, I'm just comparing the immediate output. If they both come from transistors, and they both are intended to output as a high state and a low state, then the output is no electrically different other than frequency and amplitude correct?

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:11 pm
by nathanscribe
samuraipizzacat29 wrote:I don't care about how we "got there" right now, I'm just comparing the immediate output. If they both come from transistors, and they both are intended to output as a high state and a low state, then the output is no electrically different other than frequency and amplitude correct?
No.

Please re-read my previous post.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:17 pm
by samuraipizzacat29
Yeah, I did, you didn't address anything that has to do with the output of the physical wave, merely how it was created, which is where were going next.

So, again, if they're both made from the on and off of a transistor, notwithstanding pulse width and spacing of pulses, the only thing that makes them electrically different is frequency and amplitude.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:30 pm
by nathanscribe
Look.

Re-read Stabs' posts.

The difference between analogue and digital waves that LOOK identical is in the implementation.

This is why I quit teaching.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:34 pm
by Sir Nose
Just above this post
samuraipizzacat29 wrote:Can you guys please link to something that agrees with you? Listening to some guy rant on a forum is not a valid authority. Simply saying "this is the way it is" does not qualify as a legitimate source of truth.
was this post.
meatballfulton wrote:As far as a digital circuit, to me as an electrical engineer it's cut and dried. As mentioned before, if the inputs and outputs of the circuit are digital it's a digital circuit.
Not just some guy, but a professional in the field. Words of a true pro = legitimate source, in my book.

He also gave the best description of the bunch.

Also, earlier in the thread, there was some confusion between a processor emulating a digital circuit and an actual hardware digital circuit. For a slow processor there might me some differences (slow relative to the load), but otherwise, at the beginning and in the end it is the same.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:40 pm
by samuraipizzacat29
Relax guys, that's exactly what I'm getting at, that what makes it digital is the intention of what's in front of the transistor and not the physical output. The point I'm making, slowly and concisely, is that for all intents and purposes, the output is exactly the same if the intent to output a square wave. There's no difference, there's no interpolation, it's the same if it's intended to be the same. Analog can be digital and vice versa. Electrically, there's no difference if you don't want there to be.

You can think of an analog square wave as a system of alternating 0s and 1s if you so desire. That's my point.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 4:57 pm
by Sir Nose
Sorry, if I came across as dickish.

Yes and no. There is a difference, because you want it to be.

All digital circuits contain analog voltages and all analog voltages are digital when you get down to the individual electron level.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 5:04 pm
by Sir Nose
samuraipizzacat29 wrote:
You can think of an analog square wave as a system of alternating 0s and 1s if you so desire. That's my point.
The difference is when changing from 0 to 1. There is a small amount of time where the output of an analog square wave oscillator is between 0 and 1. The output of the digital square wave oscillator is either 0 or 1 and never in-between. Even if analog components are producing the square wave inside the digital circuit (as opposed to software on a processor) when the voltage is between 0 and 1 the output is held at zero or pushed up to 1.

Note: a voltage of 0 and 1 can be anything, I do not mean 0 volts and 1 volt.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 5:29 pm
by Stab Frenzy
How's that brick wall feeling on your forehead Nath, nice and comfy?
Sir Nose wrote:Just above this post
samuraipizzacat29 wrote:Can you guys please link to something that agrees with you? Listening to some guy rant on a forum is not a valid authority. Simply saying "this is the way it is" does not qualify as a legitimate source of truth.
was this post.
meatballfulton wrote:As far as a digital circuit, to me as an electrical engineer it's cut and dried. As mentioned before, if the inputs and outputs of the circuit are digital it's a digital circuit.
Not just some guy, but a professional in the field. Words of a true pro = legitimate source, in my book.
If we're whipping out credentials, I worked for a valve preamp company building their units for a couple of years, then after that spent five or so years working at a university building prototype digital artworks, interactive furniture and tutoring design students in electronics. I've given papers at a few conferences on interactive design for artists and musicians. I've designed and built modules for my system, like a M/S encoder decoder and a voltage controlled 8 bit computer. I know what I'm talking about.
samuraipizzacat29 wrote:Relax guys, that's exactly what I'm getting at, that what makes it digital is the intention of what's in front of the transistor and not the physical output. The point I'm making, slowly and concisely, is that for all intents and purposes, the output is exactly the same if the intent to output a square wave. There's no difference, there's no interpolation, it's the same if it's intended to be the same. Analog can be digital and vice versa. Electrically, there's no difference if you don't want there to be.

You can think of an analog square wave as a system of alternating 0s and 1s if you so desire. That's my point.
I'm speechless. How can you be so condescending about this when you only just learnt it?

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 5:38 pm
by samuraipizzacat29
But if transistors make both of the switches, you could logically conclude that there would be a short amount of "travel" in either one, it's just a matter of us disregarding it in our thoughts when we think digital. A pure square wave is always taken to be (in theory) a perfect on and a perfect off. So a good square wave can be taken of as either analog or digital, it merely depends on the application.

Therefore, that's why I said the output of a poly800 can be thought of as analog even though it's a square wave. It's not intended to be a stream of information decoded by something else. It is the actual wave you are hearing. So, the the digital aspect of it (the clock out of the microprocessor ) controls the oscillator circuit which produces a square wave. Just because it's a square wave in and a square wave out does not quality the output as digital. If the output of the oscillator is the analog audio, I think it's fully fair to assess it as a digitally conolled analog oscillator.

OR...... You could say that since its being fed a square wave from a microprocessor and it outputs a square wave, that the output is indeed digital. But since its still a square wave output, i still have the pleasure of saying that its analog :)

What i object to is the misqualification and the idea that its somehow worlds different than the other synths of similar ilk. As previously stated, its very similar to a juno. It was said that a crumar dco stacks pulses, but it wasnt said where those pulses come from. Im willing to bet (im on my phon atm so googling is a pain) that the pulses come from a microprocessor that feeds frequency counters that control a cmos flip flop. This is the way things were done.... just because there were more pulses and then it was fed into a waveshaper doesnt change the fact that the core idea was at least very similar. Thats conjecture on my part, but comes from a knowlege of how things are intended to work.

And no offense meatballfulton, but i was in a music shop last week with a guy that had a degree in eletrical engineering and he was an idiot. I know ALL of you guys are rather intelligent, I just want to readexplanations from scientific sources and/or datasheet rather than what at least sounds like conjecture. I don't like to argue, but I like to read arguments. :)

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 5:56 pm
by Stab Frenzy
Image
samuraipizzacat29 wrote:OR...... You could say that since its being fed a square wave from a microprocessor and it outputs a square wave, that the output is indeed digital. But since its still a square wave output, i still have the pleasure of saying that its analog :)
No, you've misunderstood what people have been patiently trying to explain to you again. The process is a digital one. It's not an analogue oscillator being controlled digitally, it's a digital oscillator. If your statement was correct then you would also be saying that every digital synth was analogue just because you can measure the voltage on the output, and that's clearly not true.
samuraipizzacat29 wrote:And no offense meatballfulton, but i was in a music shop last week with a guy that had a degree in eletrical engineering and he was an idiot. I know ALL of you guys are rather intelligent, I just want to readexplanations from scientific sources and/or datasheet rather than what at least sounds like conjecture. I don't like to argue, but I like to read arguments. :)
Image

OK, perhaps you need to start with a basic electronics course, because you're not understanding what you're reading on data sheets or wikipedia. There's nothing more pitiful than somebody quoting things they don't understand. After you've got your basic electronics under your belt then have a play around with some basic logic chips to see what you can do with them, then learn how to use Arduino and build some analogue and digital circuits, then you can come back and join in the conversation.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 6:02 pm
by nathanscribe
samuraipizzacat29 wrote:As previously stated, its very similar to a juno.
No it fuxxing isn't. Do you actually read, or just gaze at shapes till they look like what you want them to mean?
It was said that a crumar dco stacks pulses, but it wasnt said where those pulses come from
I thought I said quite clearly. Digital control of clocks that drive CMOS counters that put out those square waves you love talking about so much, which are then summed at varying levels and shaped in the analogue realm.

And yes, Stabs, my head has a brick pattern embedded in it from 8 years of working in education. And thanks to this little discussion I missed some nice old synth books on eBay that went for just over a quid.

I need to get out more.

Re: What defines a digital or analogue circuit?

Posted: Wed Jun 20, 2012 11:03 pm
by b3groover
As mentioned earlier, read The Art of Electronics. Then come back to this thread in a few years when you understand it. :)

Re: What defines a digital or analogue circuit?

Posted: Thu Jun 21, 2012 12:09 am
by rschnier
How about this? It's the explanation my college professors used back when I got my degree in electrical and computer engineering (eons ago, it now seems).

A digital circuit is a type of electrical circuit where the voltages inside the circuit are interpreted, by whether they fall into two or more predefined ranges, as a means of representing discrete states. This discrete state representation is needed in order for the state of the circuit to represent a discrete numeric/count-type value (hence the term "digital" - as in the digits on your hands).

All digital circuits are analog(ue), but not all analog circuits are digital. The difference lies in whether or not the circuit is capable of representing discrete states via encoding of voltages or voltage ranges. (Or currents or current ranges -- which is just as valid, but designers usually think in terms of voltage ranges.)

Thus, a pulse/square wave is an analog wave, but if you define the top of the wave as "one" state and the bottom of the wave as "the other" state, then you're using the wave "digitally" -- that the amplitude of the wave is capable of representing one of two different numbers. Same wave in either case; it just depends on how it's being used and interpreted.