What was the first digital-analog hybrid?

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Re: What was the first digital-analog hybrid?

Post by nathanscribe » Sun Oct 24, 2010 11:09 pm

Then there's stuff like the Bit, which uses an off-the-shelf clock to generate a stepped wave that is then shaped using a simple analogue circuit. I think. I also believe the Synthex works like this but might be wrong.

Speaking of stringers, the Korg Lambda generates its saw waves by combining 4 frequencies of square wave in inversely proprtional amounts. Aliasing can clearly be heard on the lower notes, just like on the Bit.

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Re: What was the first digital-analog hybrid?

Post by steveman » Sun Oct 24, 2010 11:39 pm

rhino wrote: IMHO what you are describing is a divide-down system used in string machines and organs (and a few combo instruments like the Apr Quartet. This is NOT how most polysynths work.
As for CVs while there ARE exception - Most DCO synths use a RC circuit to generate a ramp waveform. Commonly, the CPU and counter(s) send out a 'reset pulse' at the correct time to restart the wave for the next cycle. Trouble is, if the ramp rate is constant, higher frequencies will have lower output levels...the oscillator will be reset longer before it reaches peak voltage. SO, a CV is generated to increase the charge rate of the capacator. The faster 'rise time' allows the cap. to reach the same terminal voltage before the next cycle.
OK, slightly misleading use of the term 'divide down' in my post. But, the counters that are used to reset the RC circuit are derived from the master clock (kind of dividing...). I guess my point was DCO synths do not involve a VCO.

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Re: What was the first digital-analog hybrid?

Post by rhino » Mon Oct 25, 2010 2:59 am

Techie flame war !!!!!

WHO WILL WIN ????

Analog??
Digital ???
Tone wheels ?????
MIDI Cowbells ?????

EDIT: To get back on topic, I vote for the Palm as the first commercial digital/analog hybrid synth.
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Re: What was the first digital-analog hybrid?

Post by moremagic » Mon Oct 25, 2010 8:27 pm

rhino wrote:As for CVs while there ARE exception - Most DCO synths use a RC circuit to generate a ramp waveform. Commonly, the CPU and counter(s) send out a 'reset pulse' at the correct time to restart the wave for the next cycle. Trouble is, if the ramp rate is constant, higher frequencies will have lower output levels...the oscillator will be reset longer before it reaches peak voltage. SO, a CV is generated to increase the charge rate of the capacator. The faster 'rise time' allows the cap. to reach the same terminal voltage before the next cycle.
I think we are getting off topic by not agreeing on a definition of DCO. I stick with "an analog oscillator whos pitch is ultamatly controled by a digital command."
No DCOs use RC circuits to generate any audio, you seem to be getting digital voice assignment as used in analog polysynths confused with actual DCOs. If an osc is fed a CV (even from a computer) it is a VCO. Computers generate CV all the time in polysynths, but that doesnt mean that a Prophet 5 has DCOs.
rhino wrote:EDIT: To get back on topic, I vote for the Palm as the first commercial digital/analog hybrid synth.
EDIT: Would the Synthi AKS count? It had a digital sequencer back in 1971! :shock:

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Re: What was the first digital-analog hybrid?

Post by rhino » Mon Oct 25, 2010 8:44 pm

...taken from Wikipeadia:

Digitally-controlled oscillator
From Wikipedia, the free encyclopediaJump to: navigation, search
A digitally controlled oscillator or DCO is a hybrid digital/analogue electronic oscillator used in synthesizers. The name is an analogy with "voltage-controlled oscillator". DCOs were designed to overcome the tuning stability limitations of early VCO designs.

Contents [hide]
1 Confusion over terminology
2 Relation to earlier VCO designs
3 Historical context
4 Operation
5 Problems with the design
6 See also
7 References

[edit] Confusion over terminology
The term "digitally-controlled oscillator" has been used to describe the combination of a voltage-controlled oscillator driven by a control signal from a digital-to-analog converter, and is also sometimes used to describe numerically-controlled oscillators.

This article refers specifically to the DCOs used in many synthesizers of the 1980s. These include the Roland Juno-60, Juno-106, JX-3P, JX-8P, and JX-10, the Korg Poly-61 and Poly 800, and some instruments by Akai and Kawai.

[edit] Relation to earlier VCO designs
Many voltage-controlled oscillators for electronic music are based on a capacitor charging linearly in an op-amp integrator configuration[1]. When the capacitor charge reaches a certain level, a comparator generates a reset pulse, which discharges the capacitor and the cycle begins again. This produces a rising ramp (or sawtooth) waveform, and this type of oscillator core is known as a ramp core.

The typical DCO design replaces the comparator in the ramp core with reset pulses generated from a counter or microprocessor. This gives the design digital frequency stability, whilst retaining a true analogue waveform output. Aside from the way reset pulses are generated, the typical VCO ramp core and the DCO are identical. Both produce a ramp waveform from which other waves are derived by waveshaping.

[edit] Historical context
In the early 1980s, many manufacturers were beginning to produce polyphonic synthesizers. The VCO designs of the time still left something to be desired in terms of tuning stability[2]. Whilst this was an issue for monophonic synthesizers, the limited number of oscillators (typically 3 or fewer) meant that keeping instruments tuned was a manageable task, often performed using dedicated front panel controls. With the advent of polyphony, tuning problems became worse and costs went up, due to the much larger number of oscillators involved (often 16 in an 8-voice instrument like the Yamaha CS80[3] from 1977 or Roland Jupiter-8[4] from 1981). This created a need for a cheap, reliable, and stable oscillator design. Engineers working on the problem looked to the frequency division technology used in electronic organs of the time and the microprocessors and associated chips that were starting to appear, and developed the DCO.

The DCO was seen at the time as an improvement over the unstable tuning of VCOs. However, it shared the same ramp core, and the same limited range of waveforms. Although sophisticated analogue waveshaping is possible[5], the greater simplicity and arbitrary waveforms of digital systems like direct digital synthesis led to most later instruments adopting entirely digital oscillator designs.

[edit] Operation
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.

[edit] Problems with the design
For a given capacitor charging current, the amplitude of the output waveform will decrease linearly with frequency. In musical terms, this means a waveform an octave higher in pitch is of half the amplitude. In order to produce constant amplitude over the full range of the oscillator, some .
(remainder of Wiki text missing here)
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Re: What was the first digital-analog hybrid?

Post by Automatic Gainsay » Mon Oct 25, 2010 9:01 pm

Obviously, it's great to have that clarification about DCOs, but I have to disagree with the notion that pitch stability on polyphonic synths was the main reason for the creation of DCOs. Granted, pitch stability is important in any synth, especially multiple-osc synths, but somehow plenty of synths (including polyphonics) were able to have stable enough pitch to work.
It's also pretty evidently true based on the fact that most of the DCO polyphonics listed are single-oscillator with limited polyphony.
While pitch stability is helpful in a synth like that, I think it was more about convenience, progress, and cost than about pitch stability.

Ha ha, it's funny to imagine that the Novachord design could also be the grandfather of DCO design.
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Re: What was the first digital-analog hybrid?

Post by rhino » Mon Oct 25, 2010 9:51 pm

My theory is:
1) stable, true-tracking VCOs take top-quality precision componets (1% tolerance), and MUCH design work.
DCOs can use 'sloppier' componets (read:cheaper) and still be kept in tune.

2) since -by this time - nearly every synth had a CPU to provide patch storage, MIDI, read controls, operate a LCD. etc, why not use it for all it's worth and let it contral the DCOs too.
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Re: What was the first digital-analog hybrid?

Post by Automatic Gainsay » Tue Oct 26, 2010 1:13 am

rhino wrote:My theory is:
1) stable, true-tracking VCOs take top-quality precision componets (1% tolerance), and MUCH design work.
DCOs can use 'sloppier' componets (read:cheaper) and still be kept in tune.

2) since -by this time - nearly every synth had a CPU to provide patch storage, MIDI, read controls, operate a LCD. etc, why not use it for all it's worth and let it contral the DCOs too.
Makes sense to me!
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Re: What was the first digital-analog hybrid?

Post by ninja6485 » Tue Oct 26, 2010 1:32 am

welp, that's the end of that chapter - good work team! up next: things heat up as ag and rhino uncover the mystery of why some synths feature self oscilating resonant filters and some don't. stay tuned after a breif rant on the superiority of moog... :D
This looks like a psychotropic reaction. No wonder it's so popular...

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Re: What was the first digital-analog hybrid?

Post by Automatic Gainsay » Tue Oct 26, 2010 2:51 am

ninja6485 wrote:welp, that's the end of that chapter - good work team! up next: things heat up as ag and rhino uncover the mystery of why some synths feature self oscilating resonant filters and some don't. stay tuned after a breif rant on the superiority of moog... :D
Self oscillating filters are for fanboys.

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Re: What was the first digital-analog hybrid?

Post by ninja6485 » Tue Oct 26, 2010 3:01 am

Automatic Gainsay wrote:
ninja6485 wrote:welp, that's the end of that chapter - good work team! up next: things heat up as ag and rhino uncover the mystery of why some synths feature self oscilating resonant filters and some don't. stay tuned after a breif rant on the superiority of moog... :D
Self oscillating filters are for fanboys.

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:lol: i believe it's spelled "fanboi..." :?
This looks like a psychotropic reaction. No wonder it's so popular...

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Re: What was the first digital-analog hybrid?

Post by Automatic Gainsay » Tue Oct 26, 2010 5:36 pm

ninja6485 wrote:
Automatic Gainsay wrote:
ninja6485 wrote:welp, that's the end of that chapter - good work team! up next: things heat up as ag and rhino uncover the mystery of why some synths feature self oscilating resonant filters and some don't. stay tuned after a breif rant on the superiority of moog... :D
Self oscillating filters are for fanboys.

PEWWW PEWWW pew PEWW PEWWWW
:lol: i believe it's spelled "fanboi..." :?
Internet Fanboy spellings of fanboy are for fanboys.
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Re: What was the first digital-analog hybrid?

Post by cornutt » Wed Oct 27, 2010 1:14 am

Automatic Gainsay wrote:Obviously, it's great to have that clarification about DCOs, but I have to disagree with the notion that pitch stability on polyphonic synths was the main reason for the creation of DCOs. [...]
It's also pretty evidently true based on the fact that most of the DCO polyphonics listed are single-oscillator with limited polyphony.
I juxtaposed these two sentences from AG to make a point: I think the main driver for the creation of the Juno DCOs, and for that matter the whole Juno line, was cost. Remember that Roland had already made one effort to design a lower-cost polysynth that didn't work out, namely the Jupiter-6. The first synth in the Juno line, the Juno-6, really went for the low-end price point by eliminating patch memory; it was only after memory and D/A ICs got less expensive that patch memory was added back, in the Juno-60. The DCO eliminated the trickiest bit of engineering in the conventional VCO, namely the expo converter.

Recall, however, that Moog's SL-8 was going to have DCOs. And although Moog undoubtedly wanted it to come in at a lower price point then the Memorymoog, they weren't going as low on the price scale as the Junos were.
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Re: What was the first digital-analog hybrid?

Post by HideawayStudio » Tue Nov 02, 2010 10:32 pm

I can understand why there is so much confusion about how DCO's work.

In short Rhino's descriptions are the most accurate. The Juno-106 is actually a very good example of a DCO based synth. AG is right to bring both price and stability forth as reasons for it's introduction but in it's defence there are many technical advantages too - in the main flexibility and control from embedded micros. The concept was used in some really quite complex polysynths - such as the last line of Roland analogs - and to good effect. One curious analog aspect of the Roland DCO's is that the slew rate of the integrator is adjusted by switching in resistors of different values depending on the selected pitch to ensure that the waveform fills the desired period without leaving gaps. In some ways though, the Roland's do this too well and the what could have been a gloriously distorted analog waveform is actually rather too "mathematical" for my liking.

The Novachord is a very early example of a polysynth based on sawtooth generation but rather than using integrators it simply makes use of RC decay circuits in tube monostables which lead to much more saggy and distorted waveforms due to exponential decay.

As Rhino nicely described, the Roland DCO's work by generating short duty cycle waveforms using a counter timer (PIT) into an analog integrator circuit used to create a falling slope. A transistor is used to short the cap in the integrator and thus reset the ramp every time the counter timer passes 0 on the way down from a preset value depending on the pitch assigned to it. It's beautifully simple and very effective.

The important point here is that in the amplitude domain the signal path is very much analog. What can be argued though, and is mainly down to a certain lack of the programmer's imagination, in the frequency domain the period is synchronised and thus lacks in movement. In the case of the Juno-106 this is made worse by the fact that the sub oscillator is simply a divide down from the main DCO and thus it is phase locked to it. This leads to a rather sterile and thin sound. Even worse is the fact that all 6 oscs hang off the same master clock. This was thankfully not the case in all DCO synths of the era, the Matrix 6 and Matrix 1000, for example, have a number of master oscs driving individual counter timers in order to implement free-running oscillators.

I say this because I'd like to defend the concept of "Ramp Core" DCO's - frankly there is nothing wrong with the idea - it's really down to the technology and firmware used to implement it. As ever, the devil is in the detail and, as we all know, the slightest movement in multiple oscillators - whether it be due to drift in VCO's or clever programming in DCO's makes all the difference.
Last edited by HideawayStudio on Sat Dec 25, 2010 1:43 am, edited 5 times in total.

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Re: What was the first digital-analog hybrid?

Post by intercorni » Wed Nov 03, 2010 6:04 pm

really digital: PPG 340/380 System, the first wavetable synthesizer:
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