Analog Oscillator Board?
  • All the great filter board options available now makes me kind of wish for an analog oscillator. Don't get me wrong, the two digital ones that we have are extremely useful and fun, but they have so much character on their own that I sometimes feel that the nuances of an interesting filter can get lost, or perhaps superfluous. As we have it now, I can get lost in wavetables and modulations, and easily forget about the filter.
    It would be quite possible, I'm guessing, to make an analog oscillator board to replace the functions of the digital board. It could maybe even use the same layout of knobs, switches, and screen, to make use of the existing cases. Or maybe a simplified layout. It could be two simple saw/pulse oscillators, or maybe a single more advanced oscillator with a sub, and maybe a noise generator.

    Or would this be too boring? Do we already have too many machines on the market to fill that sonic niche?
  • If it was that simple it would have been done :)

    You would still need host processor so you can’t get rid of that. Then you need to find analog oscillator chips or use bulky components to build it up. I think an analog oscillator board would be as big if not bigger than the analog filter boards.

    You would need three oscillators to match the current sound architecture, 2 + 1 sub.

    You would only really get simple waveforms too, saw, square, sine, tri.

  • An analog oscillator with good temperature stability and a waveshaper has roughly the same space / part count as a filter + VCA (We’re talking here about 5 DIP14/16 chips surrounded by parts). There won’t be much space to house that + MIDI interface + Controls on a control board. Not to mention that proper DACs would have to be used for accurate pitch reproduction.

  • I like the idea…

  • A nice idea but there’s plenty of analog stuff out there now. It’s all very fixed, you can’t add new oscillators or tweak them much. Plus if you’re using the same IC chips as other units then you’re not really going to sound all that much different.

  • Yeah, I think it’s a nice idea, but, but there are other synths out there with analogue oscillators, and personally, I prefer the greater flexibility of the digital oscillators. There’s nothing stopping you only using the basic synth waveforms.


  • But I would keep the controller board and make a “filter board” with three “discrete” VCOs, a mixer, a VCA and a VCF. I get that it has to be bigger but paired with at Shruthi XT enclosure that would possibly not be a problem. What you get is a DIY synth with memories and VCOs, and those are far between…

  • The actual Digital board isn’t capable of controlling 3 VCOs so you’ll need to redesign this one as well….

  • Your “filter board” would then be 2.5 the size of the control board. Those oscillators require space and 2 CVs each (pitch, at least 12-bits or 2x8-bits if you don’t want crappy stepping when pitch-bending ; and PWM). This also means that an extra MCU would be required to receive data from the main MCU and for talking to DACs.

  • It definitely is a new product almost by the time you’ve done all of that.

    Plus if you use discrete VCO VCA chips you can’t really do much in the way of different waves. You would have to mangle them up later down the signal path.

    Then there’s the issue of controls and if you bother with modularity, with a synth that is a circuit you have a fixed signal path which means inflexibility. Having patch leads and connectors means you can re-route, but then for complex modulation you need a hell of a lot of wires and such patching can’t be “stored” in the patch (easily).

    Even Vince Clarke says he uses soft synths for some sounds because to do complex modulation with modular synths requires a mile of cable.

  • imo it’s much easier for the user to decide for an existing VCO, Waveshaper, VCF, VCA design and then add what you need in terms of modulation sources and/or, if you like it programmable build a midibox CV. besides Olivier’s approach to the digital FX there are existing designs for filters that work with the chips, with some differences. also there are differences in what you can do with this or that oscillator. but i guess the main reason for wishing something like this for the Shruthi would be the programming / MIDI access to the waveform generation, which i guess is not that easy to do, at least not with just one routine.

  • When you do signal generation (oscillators + mixing) in the analog domain, it is quite straightforward to stick pots and switches everywhere in the circuit to control things. Want a waveform selector? Bring the signals of the waveshapers to a rotary selector and that’s it. Want a waveform mixer? Bring 3 pots or sliders to an op-amp. Want a glissando control? Add a pot and a cap at the output of the pitch DAC.

    Now, if you want to have patch recall or MIDI control over this, you’ll have to replace the waveform selector by a 405x ; the waveform mixer by an array of VCAs ; and the RC filter by a 1-pole VCF.

    This is pretty much why all analog synths have a “knob per function” interface. It’s the easy way to do it. Once you want MIDI / CV / patch memory control over all this mess everything gets 2 or 3 times more complex.

  • I guess that’s why the Minibrute is so much cheaper than any equivalent- no MIDI parameter control or patch memories.


  • If it were possible to do, it would be neat to have a non-midi, no patch memory, non-digital, 1 knob per function analog oscillator board that would work with the existing analog filters. I would buy it…

  • Or maybe just midi for keyboard/gate like the Minibrute (having MIDI is awfully nice)?

    The ShruthiBrute board?

    The Bruthi?

  • A relatively easy way to do a somewhat analog VCO would be to use the CEM3396 with a MCU-derived clock, but the downside of that is that it would require lots of necro to get hold of those chips – making a workalike isn’t easy either.

  • The first synths with “patch” memory were massively stripped down. The memory moog etc.

    There’s exceptions, the Prophet 5 and so on. But in 2012 (34 years later) do you really want to keep regurgitating 70s sounds? while bouncing on your space hopper and wearing flared trousers.

    It is time to move on :)

  • I have a CEM3396. Free to a good home, if you can prove you’re going to be able to use it.


  • Ah ah, I stopped with the 3379, 2044 and 3109, and it’s certainly not to start again with another member of the gang :D

  • A wise choice! It would be too complicated to ask people to once again source some rare old chips :D

  • I'd love to give it a try -- what kind of proof you're looking for?

    I used to have Matrix 1000 and loved it, now I have Cheetah MS6 and also like the sound -- this is why i'm thinking about building a single voice CEM3396 based synth.
  • You have to admit, regardless of how impossible it might be, that a mix-n-match system would be f***ing amazing. Hmm, I’d like a 303 osc with a Dual SVF filter. Or maybe an Arp osc with the poly filter. I guess this is what modular is for…

    @6581punk, the piano has been around for about 300 years, should we move on from that? :) There’s still a ton of music to be made with those 70s sounds IMO.

  • Agreed @ pichenettes. It’s what you want to get away from, and with good reason.
    I really think this whole analogue oscillator thing is a red herring. If you want a synth with analogue oscillators, your best bet is to buy a vintage synth, start building a modular system, or go for something like the Minibrute. The Shruthi-1 is a hybrid system, and that’s what makes it interesting- the warmth of an analogue filter, with the flexibility of digital control and oscillators.


  • What started my thoughts about an analog oscillator board was that I was looking at the Sidekick, and thinking "I don't know what I'd use this for. This needs an oscillator!"

    I wasn't thinking of three oscillators with complex wave shaping, I was more thinking in the line of of an SH101, or even TB303. I know it's been done to death, but not with this kind of selection of filters. That we can assemble ourselves!
    I'd personally be very happy with a non-programmable knob-per-function approach (but a MIDI in would be nice), but you'd quickly run out of surface space. Maybe a basic (MIDI Pal size) menu system for MIDI, some envelopes and LFOs, and 8-12 hardwired VCO/VCF controls? Of course, this would require a different case, at least the top section.
  • Now to the Real Point of all the Discussion: would an VCO generated Waveform sound different than an DO generated – after you treated the Signal with the beautiful SMR-4. If not theres no Gain in having a VCO. Tu put it another way: only because its pure Analog it must not sound better.

    So please, if anyone has a Modular Synth, make a recording routing an Analog Waveform (Pulse, Square, Saw) thru an SMR-4 and do the same (maybe on the 2nd stereo channel) with Shurthis DO.

    I bet the discussion instantly stops if we all can hear ourselves theres no audible difference.

  • My opinion on this:

    For the saw & square with param = 0, I doubt it.

    For square with param > 0, I think there’ll be a difference, because I generate the signal at sr = 20kHz so it lacks highs.

    The VCO “liveliness” is joke. If you design a VCO to stay in tune and track correctly, well, there’s not much room for liveliness. If you cut corners and don’t bother with temperature compensation, you have very lively and capricious unplayable thing. Don’t know which side is better…

  • Personally i like to evoke any kind of liveliness by myself – thats the reason god gave the Shruthi a ModMatrix.

  • My last comment is that it wouldn’t necessarily have to sound better to be desirable, just different. But I defer to the gurus here who know a lot more about this than I do.

  • VCOs generate surprisingly boring waveforms. I’ve got a Doepfer A-110, and it sounds like test equipment :D Sawtooth waves look like sawtooth waves, square waves look like square waves, sine wave look and sound horrible. In vintage synth, there’s plenty of stuff in other places that add the coloration (stabilization caps in mixer stages ; bypass caps before the filter ; and then the distortion induced by the filter).

  • So if the new moogs have analog oscs that are digitally tuned, does that now make them a DCO?
  • Depends on the time constants in the feedback loop that is used to control the pitch of the VCOs. If it’s super tight, to the point that the digital controller micromanages the VCO, it won’t be that different from a DCO. If it’s very sloppy, the VCO will keep a bit of character. Maybe they provide an option to adjust this?

  • From playing the Shruthi back-to-back with my analogs (juno-106, mg-1) I can say that the analogs do get quite a bit brighter. Probably if I didn’t do any back-to-back I wouldn’t have noticed, but after doing it I really want the Shruthi to get brighter. This should be solvable without going analog though right? Beefier MCU?

  • Just for definition Purposes:

    VCO: Analog Oscillator controlled by analog CVs
    DCO: Analog Oscillator digitally controlled (presumably by digitaly generate analog CVs ;-) )
    DO: Digital Oscillator, Waveforms generated mostly by D/A Converters or the Shruthi Way by PWM

    Analog Oscillators drift with Temperature so this must be compensated, in an VCO mostly by measuring the Temperature and compensating by a CV or the Cheap Doepfer way by just heating the Oscillator to a defined Temperature.

    DCOs can either be compensated like an VCO or be measured by the Processor and compensated by the computer generated controls.

    The liveliness of a VCO comes mostly from the Chain that follows (Mixer, Filter, Amplifier) – if you listen to pure VCO signals they sound mostly plain boring – best example is the EMS Synthi A.

    Yups, if the COntrol signals are generated by an computer its a DCO by the above definition

    what you hear might be just to the fact that the Filters in The Shruthi are limited to about 15khz (if i get tho right) whereas you Goodies might let thru higher frequencies (when filter open). Thats part of the Magic of the PPG for example, these high Frequency Hiss and Noise that the Waldorf PPG 2.x Plugins simply lack. Sadly the MicroWave partly as well.

  • There’s a difference between pianos and synths. They still make traditional pianos new, there’s a huge second hand market. Just like guitars are easy to obtain.

    Subtractive is popular as it is simple to operate, people just couldn’t get their head around FM even though FM can create much more advanced tones.

    I think it is no wonder music hasn’t really changed that much for a while as there’s been very little development in the instruments. Just big developments in production and recording instead. Even the vocoder is an old device and that was big a while ago.

    The interesting oscillators in the Shruthi-1 are what got my interest and I think losing some of that to get some “vintage” warmth seems a shame.

    So many people are looking for that warm sound of the 70s and 80s when recordings were done on reel to reel with outboard gear. They also didn’t compress (dynamics not data compress) the hell out of the sound back then either. If you want vintage sound then loose the computer recording techniques. The obsession with noise and loudness has also given us this clinical over compressed sound.

    Have a read of this:

    Alan Wilder on compression

  • @6581punk +1 for the recording techniques. My first recordings with Logic went terribly fucking wrong as i was too excited to have a compressor on every channel and 4 different SpaceDesigners + myriads of Modulation FXs + and delays everywhere. I now have a single Compressor to patch to different Channels, a Stereo Compressor for Subgroups, a SPX-90, a Virtualizer Pro and a MX200 (i can’t live without a LEXICON!) and thats it. What helps is a small neutral near Field Monitor. And Study some of the great recording from the 80ies.

  • Yea who needs a compressor when you have is a bunch of midi synths and no half drunk drummer to worry about.
  • @6581punk, I would never suggest we lose the existing digital board in favor of one with analog, only add to the list. Think of the combinatorial explosion that happens with 9 filters! :) If you added 2 more control boards Frank would have to own 27 Shruthi’s! Anyway, I don’t mean to start an argument, I just cringe when someone talks about “moving on” because I think anything that makes a cool sound is a worthy instrument of making music with until the end of time. There were so many artists making amazing electronic music in the 90’s (with equipment from the 80’s) that turned to shit in the 00’s because they wanted to keep up with the new technologies and switched to computers.

  • i always had more problems with a guitarist taking odd substances and cranking up his Marshall Double Stack to 11. Sometime he didn’t show up anymore and a few weeks later we found out he was in Jail. He was replaced by a Slick looking Guy playing a Mark 3 – which was better for all of us in terms of overall level and musicality. BTW, our Bass Player hat an Orange Stack, the Amp custom modified with a Cigarette Lighter from an old BMW... That was the 90ies. Today you are the Blinkenlight Hero if you bring a Launchpad to accompany your MacBook. I always wonder if an APC-40 would help with the girls ;-)

    And my final contribution:

    If you want 80ies sound its easiest using 80ies Equipment.

  • Indeed, a very interesting discussion…

  • Filter wide open, the Shruthi is less bright than analog synths for the following reasons:

    • Its sample rate is 39kHz, so it doesn’t generate anything musically useful above 20kHz. You’re lucky, though, if you can hear that high.
    • It uses band-limited wavetables for the saw and square oscillators. Due to the crossfading between wavetables, there’s a small “grey zone” on some notes in which we crossfade the band-limited signal from the previous octave with that from the next one ; and this causes the half of the upper octave of the spectrum to be lost (anything above 14kHz).
    • There’s a 22kHz 1-pole low-pass on most filter boards to attenuate the 39kHz PWM carrier.

  • FYI, a DCO is not a VCO with a digitally generated CV or a VCO with a digital tuner in a feedback loop.

    It works this way… A MCU or programmable timer generates a pulse at the target frequency. This pulse is hooked to a BJT that resets to 0 an integrator. As a result we get a sawtooth wave whose “discontinuity” is synchronized with the pulse from the timer. From there, it’s the same thing as an analog saw-core VCO. The charging rate of the integrator has no influence on pitch ; just on amplitude.

    So the hierarchy would be:

    • VCO (the CV is fed to an exponential converter, which generates a current charging a cap ; a comparator monitors the cap charging and switch on a BJT that resets the integrator 0 when it exceeds a threshold -> sawtooth wave ; then comparators and shapers to get the rest).
    • Digitally controlled VCO in open loop. Same as a VCO, but CV generated by a DAC.
    • Digitally controlled VCO in closed loop. Same as above, but the output signal edges trigger the start/stop of a counter so the MCU is aware of the VCO pitch and can correct the CV accordingly.
    • DCO. Little control is done on the charging rate ; the discharge pulse comes from a timer, not from a comparator.
    • Digital Oscillator.
  • > You’re lucky, though, if you can hear that high.

    Am I crazy for saying even though I can't hear that high, I can definitely SENSE high frequencies that I can't hear? Drives me nuts.
  • Well there are harmonics. But you do have to be careful when you talk about things not being there and “vibe” and “feel”. It’s not long after that you start keeping your CDs in the freezer and start buying $1000 speaker cables :)

  • >I just cringe when someone talks about “moving on” because I think anything that makes a cool sound is a worthy instrument of making music with until the end of time

    Nobody is saying they need to be exterminated and thrown away. People are still making analog subtractive synths, you can buy them now.

    I just don’t feel that a big beast of an analog synth is the best thing for a small company to develop and it would need to be a beast or offer something really unique to stand out. Look at all the features people are asking for on a daily basis, you can’t do that with analog without ripping things out of the board.

    The last big beast of an analog synth IMHO was the Alesis Andromeda and that was released 12 years ago. Why haven’t many others followed suit on that scale? simple, the masses use VA or soft synths now because they are affordable and in the case of software they can download dodgy copies of it.

  • @herrprof
    What you hear is just the same Pricniple that generates Freakwaves ;-)
    Honestly: Same here. If testing with an Oscillator i can’t hear much above 15,5kHz (and i am lucky to hear that high with 40…) but if i cut the Heights at above 17kHz on my Console its well a difference. Oh, strictly analog for shure, Signals from a old School CD-Player. BTW there Is a difference between Apple Lossless and 16 BIT from a CD – and i am far from freezing CDs or painting their edges with a 39€ Pen….

  • All the audiophiles have moved onto blu-ray and TVs now :)

  • how can a Flat-Screen be audiophile?

  • Multimediaphile then :P

    They obsess about their surround experience.

  • >People are still making analog subtractive synths, you can buy them now.

    I think there is a lot more room in the market for more good analog monosynths. Sure, poly’s are too big and expensive, especially for a small operation like this. But I bet if Oliver decided to make an all-analog synth it would be badass. I don’t necessarily buy the “analog oscs are boring” argument. Look at the Minibrute. Most of the coolness of that thing comes from the amazing oscillator section. Can you make a digital synth with oscs that sound like that? Sure I could just go buy a minibrute but where’s the fun in that? I want to build one myself! :)

  • Don’t get started on the surround thing! I got a Denon 4310 (somewhat, no really expensive) surround receiver. It did cost a fair bit, but sometimes I think that a decent stereo amp from the good old days is as good sounding since no money was spent on licensing all kinds of DSP gizmos, decoding, HDMI etc… Still, that and my B&W plus Monitor Audio gear and a couple of small-ish subs (I live in a condo – otherwise I’d rock Sunfires) sound very nice. But, it’s always a good thing to listen to good-quality BD/DVD Audio/SACD/CD or FLAC music instead of just watching movies.

    Anywho, a nice VCO is always nice, but I’m not running out there to buy an Andy, a Jupiter, a CS80, a Sunsyn or some Studio Electronic Omega/Code 8. Of course I’d like to, but there’s a reality as well. Not everyone drives a supercar either :p Hmm, I don’t want to know how expensive that modular hobby is either…

    I totally see why there is no M-I Analog (yet?). You can always get an old underrated analog or DCO poly without breaking the bank.

  • You want to build analog?

    Everything under the sun :)


    Where it gets really hard is controlling this all using digital. You can get all manner of quirks, clicks and pops. It takes a long time to iron all these things out.

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