Would it be much difficult to redesign Ambika?

I have an SMR4 ambika, I was fantasizing about VCOs in it the other day. Would it be possible to redo it to use VCOs? Or at least DCOs with an analog master clock exactly like the Juno 60?

Try and find out.

I think you’re mistaken about the Juno 60 DCOs; you might want to read up on that.

There’s probably no reason you couldn’t do VCO or DCO card, however it would be a choice between VCO or the digital oscillator card. Doing both would be more complicated, you would need a way to set which are VCO and which are digital.

Software would need major changes and you would still need the ATMEGA on the voice cards for communication purposes and control.

The big issues will be stability, noise, PCB space (SMD required) software control of each oscillator and so on.

You’d effectively be building something like a Korg Prologue or Prophet 6 on a budget, with less UI.

Mmm, I may not have time in my life to take on that project right now. Just curious! And about the Juno DCOs, I read they were indeed different DCOs than the 106, that’s why they sound fatter, something about an analog clock vs quartz. I may be wrong, but the 60 definitely sounds nicer

The master clock in the Juno 60 runs slower than the master clock in the Juno 106.

The frequencies that drive the DCOs are derived by dividing from this master clock based on which note is played, and on the Juno 60 this results in a more uneven tuning between the notes than on the Juno 106 as the result of bigger rounding errors.

That’s it, really.

… and probably causing more beating when playing chords. Hence more “thickness”.

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Probably at that point it would make sense to make a new synth with a different architecture, wouldn’t it?

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Yes, exactly. And more “organic”…

Ah I see, is it more costly to make DCOs in the fashion of the Juno 60, rather than a Dsi tetra? I know this depends on the type of oscillator, but do you guys know the ballpark price difference to produce a synth, between 1 VCO in a poly, 1 DCO in a poly, or 1 digital oscillator (cost per voice)? Being more exposed to modern synths, I never really had to deal with synths going out of tune much. In fact, the first time I had a synth go out of tune, it took me a bit of time to figure out what was going on because I thought I had a parameter set incorrectly. My sub phatty has never gone out of tune, but still has a very rich sound.

I’m not sure what you mean here because it’s just the same principle.

The Juno 60 uses old-fashioned logic chips, the Tetra does everything with a microcontroller, but this has no impact on sound; and with a microcontroller you could actually round the frequency to get Juno-60 style temperament.

From more complex to less complex: VCO, DCO, digital oscillator. It cannot be summarized in a single number: we’re talking about development time, software complexity, reliability, size…

Also, it should be noted that some modern VCO designs use digital signal processing to keep them in tune. I haven’t looked into the details, but it’s my understanding from an interview with Dave Smith that that’s what they’re doing in the Prophet-6 and OB-6.

Of course, this means that they had to bring back the tuning drift from those original VCO designs by adding a “Slop” knob that controls the level of drifting that’s simulated by the DSP that controls the tuning…

Hmm that’s interesting. You know that slope function on some synths, I have it on the Tetra, it changes the tone by like 1% while all the way up. It’s barely noticeable, perhaps on some other synths that feature makes it sound more like VCO’s. I think an easier way to get the sound in a box would be if I built 6 Shruthis and fed 6 analog oscillators into the External input, and put everything into 1 box. It may be a hassle to setup though.

What makes you think VCOs are the source of the “sound” you’re after?

It’s got to be the VCOs, every synth with VCOs I have sound nicer when the filter is fully open. I also gave a moog freqbox which is 1 VCO and that sounds great. The VCO on the SEM is also phenomenonal. I also like the Minilogue oscillators, filter fully open, compared to my tetra. And with mono, Sub phatty over Pulse 2.

What I like is an oscillator that sounds thick on its own, and lively (almost like a lightsaber), where you can hear tiny unstable changes in the sound, and a pretty raw “buzz” on top with the sawtooth, but very heavy weight. Much more euphoric, as if the frequencies I don’t want to hear are never present.

Ideally, with the filter fully open, an OBXa is perfect. That is my dream synth, I’ve been desiring one for so long. The JUNO 60, is an odd bird. Those are the nicest DCOs I ever heard. Very thick compared to others.

They have to be thru hole VCOs as well :smiley:

Using old stock 5% tolerance resistors!

A lot of other technological changes occurred at the time synth designers moved away from VCOs:

  • Power supplies got better. No pitch “wobbling” or subtle intermodulations caused by blinking LEDs.
  • Better and cheaper circuit board manufacturing techniques: less wires, straps, better grounding, causing circuits to behave closer to their ideal characteristics.
  • Op-amps got much cheaper, allowing designers to use them everywhere. The end of single transistor mixers with a lot of, ahem, character!
  • Op-amps getting better. The end of those 741s rounding the highs.
  • Components got better, with narrower tolerances.

Well, there you have your solution. If the OBXa is what sounds best to you, then you need to get a OBXa. No other synth will sound like that because other synths aren’t the OBXa. If you try to redesign something existing to be an OBXa, you’ll probably only be disappointed.

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That’ll be why old synths sound more exciting, much like vocals being auto-tuned makes for bland music, having really stable designs and rock solid tuning makes an analogue synth a bit lifeless.

When DSI did the OB6 they had to back off the CPU controlled tuning a little to make it a bit more interesting.

Of course, nobody wants hum, buzz and lots of background noise :slight_smile:

Ah, perhaps I shall get an OBXa one day if my wallet allows me. Yeah stability and functionality is very important for workflow. That is one thing I must say I take for granted when being surrounded by the synths of today.