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Subject: how does an oscillator work

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Original Message 1/17 09-Sep-98 @ 04:12 AM - how does an oscillator work

buggo

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A few questions...how does an analog oscillator work? i know it's some kind of electrical circuit that produces a fundamental tone, but i dont know how it does this....also theoretically why could you not have analog waveforms? if an analog oscillator can do a square or sawtooth wave, why can't it do something more complicated?

also, why the FUCK do companies bother with analog modelling? i can understand real-instrument modelling, for the lifelike realism...but real analog is surely much cheaper than emulating it with a chip! why bother?? seems like a serious case of fixing shite that ain't broke...

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Message 2/17 09-Sep-98 @ 07:03 AM - RE: how does an oscillator work

Sedusa

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I'm not an electronics guy, so I don't really know how oscillators work.. But, it would not be cost effective to mass produce analog instruments nowadays.. Which is why the big companies don't do it.. Really, you'd think it would be cheaper, but it's not.. It's a bunch of pieces that the components aren't available anymore for, electronics manufacturing that has to be done by people and not robots, etc.. Both of the questions were answered within the past couple of months on the Analogue Heaven mailing list, you should go to Hyperreal, and look thru the AH archives..

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Message 3/17 09-Sep-98 @ 09:21 PM - RE: how does an oscillator work

KILO

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WELL THAT IS NOT TRUE, COS THEY DO MASS PRODUCE ANALOG.... NO ANALOG MODELLING ALLOWS THEM TO OFFER THE SMOOTHNESS OF THE ANALOG FOR MANIPULATION, BECAUSE IT BYPASSES THE 'STEPS' THAT ARE INHERENT IN A SAMPLED WAVE TECHNOLOGY , WHILST ALLOWING MULTI-TIMBREL USE BY INTEGRATING IT INTO A DIGITAL CONTROL SYSTEM.... analog waves ... so you are listening to electrical pulses.... by definition they have a limited range of waveshapes.... so the rest of the synth manipulates the electrical waves to get the almost infinate variety..... think about it...everything has a restricted pallete defined by it's physical proporties ...that is the law of the universe ... guitars are guitars.. elephants dont make noises like sparrows etc....

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Message 4/17 10-Sep-98 @ 03:38 AM - RE: how does an oscillator work

kilo

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ok... lookit.... electrical generated waves are very limited in their waveform.... simple electrical wave as you know from AC current is a sine wave...

then you have pulse waves.... a square wave is a pulse emitted all on at once.. held then all-off at once... a sawtooth is fade up and all-off at once (almost).... plus spike waves which are like tiny short on-off bursts... .

a pulse wave has a length called the 'mark' time.. and intervals, called 'space' time..... the mark/space ratio describes the shape of the pulse.... a number of sine waves can be added up to produce a pulse wave with a certain repetition frequency.....one of those frequencies dominates to determine the repetition rate... this is the fundamental frequency..... this accounts for the way the fish can swim undrwater without breathing in the conventional sense as we know it.... er....

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Message 5/17 10-Sep-98 @ 05:13 AM - RE: how does an oscillator work

buggo

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Yeah, but if they can make a sawtooth, with a buildup and immediate dropoff...why not some other kind of single-cycle wave? i know of square, pulse, triangle, saw, and sine waves on synths...an ONLY these waves...seems there ought to be unlimited kinds of waves...after all an oscillator basically just spits out a single-cycle waveform...why not a reverse saw for example, with a sudden "on" and gradual taper out each cycle...or a buildup like a saw wave with a curved droput like a sine wave..whatever..?

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Message 6/17 10-Sep-98 @ 09:56 AM - RE: how does an oscillator work

Richie

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But surely thats the whole reason analogue synths had filters / resonance / more oscilators on in the first place. So they could take a simple waveform and make it more complicated. The pure sine wave is eaten away by the filter to produce the more interesting tone to the ear. I think it's because (as kilo pointed out) that AC current is a sine wave, so the only way they used to be able to produce a sound at all was to convert the AC wave directly into sound (sine osc) or the +- peak voltage (pulse), I'm lost with the saw tho :-) ... Does this sound like crap?

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Message 7/17 10-Sep-98 @ 10:42 AM - RE: how does an oscillator work

Islandman

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Most oscillators have a fundamental frequency that cannot be changed. Crystal oscillators for example are manufactured for this exact purpose. The filter network, made up of capacitors, resistors,
inductors, diodes and other items around an oscillator is what ultimately controls the type of waveform that is produced.

Buggo, the type of waveforms that you are seeking can be done with proper circuit "biasing". With a sine wave, voltage is applied to a certain point then allowed to decay. It does in phase and out of phase thus producing the positive and negative cycle of the sine wave. With waveforms that are being "cut off", you usually have a diode in the circuit that "turns on" when it has a certain amount of voltage on one side of it, thus "cutting off" the waveform. This is biasing. A diode has a negative and a positive side. If you apply +5 volts on the neg. side of a diode, it will not conduct or "turn on". If you apply that same voltage on the positive side, it will conduct. Depending on how intricate the circuit, you can create virtually any type of waveform you desire.

Peace

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Message 8/17 10-Sep-98 @ 03:16 PM - RE: how does an oscillator work

xoxos

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i like my virtual analog stuff.. among other things, the oscillators start where i want them to..

i was mucking about with a tutorial on synthesis a few years back and created a simple program where you add two sinewaves together with different frequencies. try it. as such, you can create a myriad of bizzare waveforms.

try just adding a touch of a detuned 2nd oscillator to 'colour' the timbre of the first. not as intense as some other forms of modulation, but something to explore if you are limited to an analog synth.

xoxos.

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Message 9/17 10-Sep-98 @ 05:02 PM - RE: how does an oscillator work

Sedusa

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Sounds kinda like FM!

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Message 10/17 11-Sep-98 @ 01:23 AM - RE: how does an oscillator work

buggo

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sadly i can't do that...you can't detune the osc's on a juno-106 so I'm limited to having them synced (plus it's a DCO so the waveform is rock-solid, meaning no cool variations...but i usd to do it on Rebirth, making the same pattern on both 303's and detuning one a bit, maybe shifting the slides by a note or 2, creating interesting loops...

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Message 11/17 11-Sep-98 @ 03:37 AM - RE: how does an oscillator work

xoxos

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sadly, i got a nordlead because of it's lovely fm sound, but i've really given up trying to understand exactly how frequency modulation applies to this effect. it's described as 'deep linear' fm but balls all for whatever this means, it just is buzzy. my techie knowledge comes from sporadic delving.

hey buggo, why don't you just use two modules for the same sequence? same effect. unsynced but close envelopes can get some crazylike sounds.

xoxos.

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Message 12/17 11-Sep-98 @ 04:47 AM - RE: how does an oscillator work

buggo

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two modules for the same effect? on a juno? sorry don't have another $400...

on a tx81z one could surely do this though...no?

also, does the tx have individual outs for all 8 voices?

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Message 13/17 11-Sep-98 @ 05:17 AM - RE: how does an oscillator work

xoxos

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well then use a sample of one sound on yer emax for the same sequence as yer juno. just like you layer snares, layer timbres... evil wicked bad badness.

xoxos.

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Message 14/17 11-Sep-98 @ 09:10 AM - RE: how does an oscillator work

bill

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i thought that the tx81z had 8 outputs until i took it off the shelf and looked at it - it may have but they haven't all got jack outs - there's 2 jack outs (labelled I and II(mix) ) and a "cassette" out - which is like the old audio-standard that used leads a bit-like-midi-connections to connect up.....

so unless the cassette out handles 6 other out via a special interface i don't think it has. or else i just completely missed the other 6 outputs.....

anyway, i bought an fb01 in the end - still 8 part multitimbral but just with no onboard editing - have to use sysex.....

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Message 15/17 11-Sep-98 @ 02:30 PM - RE: how does an oscillator work

kilo

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nope....tx has stereo out...

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Message 16/17 11-Sep-98 @ 03:07 PM - RE: how does an oscillator work

bill

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yeah - that's what i figured. in that case, what is the major advantage of buying the tx81z over the fb01 - they're both 8part multitimbral (dunno how much polyphony the tx has - fb has 8 note). i can see that you get front-panel editing on the tx but that seems to be quite difficult to use - and i mostly prefer softeditors for modules (no reaching 6 foot up to a rack to edit stuff).

and the fb01 is half the price roughly....

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Message 17/17 12-Sep-98 @ 02:28 AM - RE: how does an oscillator work

kilo

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well, thats the thing..... when it was released few people used s/w.... plus er... it's a proper rack.... which can make a difference to a gigging setup...

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