Vintage Synth Explorer Forums

Doing some research I found that with regards to FM synthesis, unless I've misunderstood, in purely mechanical terms, there is no difference between the actual hardware one uses in something like a DX7 and a computer running something like FM8 (or Operator etc etc). That's to say these programs aren't actually emulators, they are "the real deal".

http://www.soundshock.se/phpBB2/viewtopic.php?t=188

But for instance I *also* know that my beloved "Analogue" Matrix-1000 also uses DCO (digital) chips and that "Almost everything, an amazing lot!, happens in software" within it.

http://wolzow.mindworks.ee/analog/m1k.htm

I was wondering if anyone was able to explain how the actual circuitry architecture differed between hard (especially Analogue) and soft synths and whether there were fundamental technical differences between the processes with which they make sounds. I suppose that the very question of "emulation" is what is at the heart of this question. To my mind "emulation", in the place of some technically "authentic" process is bad.

Oh, ye gods. Well...

In a nutshell, "analogue" means that the sound is generated via electrical signals that mimic the pattern of the sound - that is, the signal is analogous to the end result. Digital (including FM, VA, software) uses bits, ie. 1 and 0, in quantities, to represent numbers that are then arithmetically worked on till eventually they're sent into the outside world as sound, through a digital-analogue converter.

FM synths, VAs, etc - hardware synths - are custom bits of software running on chips in a system. Software in your computer is basically the same thing, but hardware synths are custom systems, not generic ones like a PC. But the processing and generation of sound is done 'virtually', for want of a better term.

So analogue synths are working on voltage that fluctuates smoothly as an audio waveform would, digital are working on binary and it's converted at some point in the system to analogue for output.

There are combinations - the Korg DW8000 has digital oscs but analogue filters, so the signal is converted between them. The Ensoniq Mirage is a sampler with analogue filters - ditto. FM synths have no filters to speak of, so the signal is only analogue once it's headed for the outside world at the end of the path.

Does that help?

Oh, and by the way, a DCO is a Digitally Controlled Oscillator, but is commonly an analogue ciruit - that is, a circuit that generates and works in the analogue realm, but is clocked or driven by digital circuits.

Plenty of synths are a combination of things - DCOs, analogue filters, software envelopes, for example.

One final point for reference, though I know you didn't bring this up - a square wave is not in itself digital. Nor is a clock, in itself, necessarily digital. They might provide binary output (ie high and low, on or off), but they're not generating digital numbers.

So, for example, the sub-osc in the Juno (6, etc) is generated by sending the regular analogue waveform into a CMOS flip-flop, which puts out a sqaure wave (though from what I recall there is also digital control over the clocking of this, as the Juno has DCOs - there has been an in-depth description of the Juno's oscs before, and it might still be lingering in the depths). That wave is sent to the filter just as the other waveforms are. Even though we might think of CMOS ICs as digital, or logic chips, the signal in this chain is basically treated just the same as the smoothly varying voltages of any other analogue signal.

Thanks Nathan. I think I'm right in seeing that the distinction you're making is essentially between "virtual" instruments and non-virtual, though I see the distinction is not hard and fast.

Slightly tired with Analogue snobbery, which seems to founder on the idea of real and tangible processes, (whereby the sound of an oscillator is shaped by subtractive synthesis) so I'm sort of enchanted by the whole FM thing which seems (if you see what I mean) like "an authentic process" in its own right- has some purity of process.

If I might ask another embarrassing question, what other processes in soft synths are so clearly defined/are not a mulch of different calculations striving towards some kind of emulation?

Thanks.

Hollow Earth wrote:the distinction you're making is essentially between "virtual" instruments and non-virtual

Well, yes and no. I don't count digital hardware synths as 'virtual' exactly, but the way the sound is generated has its roots in mathematical manipulation of digital numbers, rather than the more 'physical' process of directly manipulating an electrical waveform. In a way, an analogue synth is also a kind of computer, generating and processing information, and outputting a signal that can be transformed by an amp/speaker into audio. Analogue processes (generating waves, filtering) are mathematical processes too, but are not being carried out on numbers. They're being carried out on quantities.

I'm in danger of getting bogged down in theoretical stuff that I don't know too much about here. But when I said 'virtual' earlier, that's all I meant.

Slightly tired with Analogue snobbery...

Yeah. That's another issue.

...which seems to founder on the idea of real and tangible processes, (whereby the sound of an oscillator is shaped by subtractive synthesis)

Tangible in the sense that there's a direct relationship between the measurable quantity at any stage (eg osc wave output, filter output, etc) and the output (as an audio waveform). As opposed to the value of a couple of bytes that might be being XORed or something, which in no way directly resembles the movement of air. This, as you rightly say, does not reduce its validity as a method of sound creation.

FM ... seems (if you see what I mean) like "an authentic process" in its own right- has some purity of process ... what other processes in soft synths are so clearly defined/are not a mulch of different calculations striving towards some kind of emulation?

I think I know what you're getting at... that FM is its own type of synthesis, rather than attempting to mimic another form of sound generation (which is what VAs do - try to emulate a genuine analogue method, digitally). The answer, I don't know. Others will. There are several types of synthesis, some achieved analogue-ly (!), some digitally, some in a combination. All digital forms will be "a mulch of calculation" - that's digital. But no, they're not all aimed at emulating other types.

Any fully digital synth can in theory be reproduced in software, since a digital synth is really just a specialized computer. Algorithmic synths such as the DX7 are the simplest to implement in software, as only the algorithms need to be recoded, no need to pull samples, etc. PCM-based synths can also be recreated in software, provided that the sample sets are available.

That still doesn't guarantee that the software version of a digital synth will sound like the original. Every digital synth has one analog section: the D/A converter and the output gain section (which drives the outputs, provides the master volume control, etc.) And that section can sound unique in a certain synth. The D-50 comes readily to mind, the quality (or lack thereof) of its converters gives the D-50 a lot of its character. If one were to clone the D-50's code into a softsynth, it won't sound like a D-50 unless VA code is written to emulate the character of the D-50's DAC.

Software versions of analog synths, require that the analog characteristics of the synth be emulated digitally. This is done in a manner similar to VA synths, by algorithmically generating the waveforms and running them through a software emulation of the original analog filters, etc. Conceptually it's fairly simple but most of the work is in recreating the character/sound quality of the original synth.