• Is there anybody has a schematic of Little Phatty or Voyager?
    At least, if anybody has photos of these synths naked? ;)
    I’m curious what electronic parts were used for VCO, VCF, DAC+S&H, etc…

  • I’ve looked inside some of these… Nothing fancy, transistors, LM13700, TL07x. DACs were too small to read :)

  • There’s some photos here of a Voyager stripping.

    The VCF uses a CA3046/3086 for the matched top and bottom transistor pair. Dunno about the VCO or DAC/S&H, but the CPU is a z80 derivative for that ancient and moldy feeling.

  • The voyager has lots of 13700’s TL074’s, CA3046’s, some LM837

    EDIT, beaten to the punch. Nothing fancy.

  • They still cook with water – no magic thingies !

  • oh, and here’s some hi-res photos of the Little Phatty. SMT just doesn’t look nowhere near as sexalicious. And a hi-res photo of the inside of my Voyager OS.

  • Thanks guys!
    Nothing fancy, indeed. Only LM837 seems to be kind of “high-end” part in comparison to TL074.

  • @MaxZorin: You might want to have a need of this most interesting page entitled Op Amps: Myths & Facts


  • Thanks Martin for link!
    I didn’t use the word “high-end” in the sense of an audiophile. LM837 seems to be “better on paper” and it’s only slightly more expensive. It would be interesting to know why they used that instead of the TL074.

  • I read a great post a few years ago about the NE5532, the argument was that they were only cheap due to mass production and they were as good as most of the newer op-amps that are out now that cost 10 times as much. Its a good argument as I suppose the chips all cost as much to make as each other as there is just a square of silicon with some legs, if you make a really good design and then make millions of them after 30 years they end up cheap.

  • +1 for the NE5532. Unless you want to add the LME497x0 which sound great on the Ambika mixed output btw) but then they cost a bit more.

  • I see the point of NE5532s in mixers, preamps, EQs etc where your job is to be as transparent as you can with the signals the user of your product has entrusted you with.

    I don’t see the point in an analog synth where the coloration added by op-amp noise/distortion is negligible compared to all the trash coming from OTAs or VCAs.

  • These days, the whole point of a hardware synth seems to be to color in a way virtual analog still doesn’t seem to manage.

  • years ago I made a simple RIAA pre amp for my record player and tried swapping the op amps around, of the ones I tried the only one that was noticeably bad was a 741, I left 5532s in in the end after trying a few. The 741s are industrial op amps though so it’s not surprising they didn’t sound good. The argument that people want colouration is an interesting one though.

  • Getting back on topic, those through hole component Voyagers look very cool!

  • @Dunk
    If an OpAmp “sounds” bad its the whole circuit that isnt fitted to the OpAmp, not the OpAmp itself. You cant break down a whole design to just one single part and you just cant swap a part in a well thought out whole.

    Just because a rivet is a bad Idea to build a ship that occasionally might hit an Iceberg or a floating Container it doesnt mean rivets are bad – think about this when you next time sit in a Plane.

  • I’m sure there are still “battle-tested” circuits in airplanes using NE555 and 741s :)

  • Actually id rather sit in a Plane that is bolted together with a zillion rivets and relies on 555s and 74Xs rather than in one glued together from carbonfibre epoxy and has LiFe Batteries to power their Win8 computers running on a i7. . . .

  • Oh come on… What could POSSIBLY go wrong?

  • Nothing besides the LiFe battery failing, burning, instantly melting thru the plastic body of the plane thus inducing a pressure drop and structural failure, the win computer not noticing because of a wrong registration key of some vanilla stock .DLL . . . .
    “The Module ‘Plane Crash Countermeasures’ is not certified by Microsoft! Abort/Cancel/Hangup”

  • Pretty sure no aviation engineer alive would ever consider Windows…

  • By the way, if anyone wants the follow-on article to the opamps: Myths & Facts that linked to above, here it is complete with test measurements – Op Amp Measurements

    There’s plenty of useful information in there re real-world practicalities of FET or Bipolar, Gain Bandwidth Product, Open Loop Voltage Gain, Slew Rate, Feedback, Common Mode Rejection Ratio, and Compensation for stability to avoid ultrasonic oscillation.

    Nerds of the world unite!


  • Oh, and here are the ‘favourites’ conclusions in various categories of that well-researched article for those who are frightened of tech talk

    NJM2068 – Cheap and Cheerful
    NE5532 – The reasonably priced objective benchmark
    OPA2134 – A mainstream audiophile favorite
    OPA2227 – Pushing the high-end of the budget with excellent specs
    OPA2277 – For the low power O2 (long battery life version)
    LM4562 – An audiophile favorite (NJM4562 stocked at Mouser)
    TL072 – A former audio benchmark to put the above in perspective

    If anyone wants to lower the output noise levels of the Shruthi, just swap the TL072 used for its output stage for an NJM2068, but don’t expect the same $0.39 price as quoted in the measurement article – they now seem to change hands for a minimum of £2.50 and sometimes £4 + VAT

    Oh, and they won’t work in my SDE either, as you won’t get that desirable output Drive sound


  • If you dislike the “sound” of 5532 that means you must also dislike most of the music available.


  • As long as one stays away from 741’s for audio circuits it should be fine. Then there are some cases where the poor specs of the 741 is a must, but those are usually clearly marked as such.

    I like how some supposedly high-end Buchla 200-series gear designed in the 60’s and 70’s uses the 4136 (quad 741) like the B266, and some other thru zero FM gear by Ian Fritz prefers some fancy OPA opamps…

  • Another example of horses for courses-I built an Aries AR-314 filter circuit a while back, which used ye olde LM301A (with feedforward compensation) buffered by external FETs to integrate the 3080 OTA outputs. I tried replacing them with TL082s and found that at high frequencies they would self-oscillate and effectively stop the filter. The ancient fet-buffered 301s work perfectly at all frequencies…Dennis Colin obviously knew what he was doing when he designed it back in 1973, so why mess with the formula?

    @pichenettes: ....and “battle-tested” stuff in military/space as well. I remember reading in about 1990 that the space shuttle had just replaced its magnetic core memory-based flight computers with the equivalent of a PC XT, and at the time people were joking that the astronauts’ GRID laptop was the most powerful computer in the whole spacecraft!

  • Well one circuit I tried this out is was a very simple buffer I designed, and it was designed for any op amp, I did find that the 5532 spec calls for a minumum gain of about 3 (this is from memory). The 741s do add audible distortion, but I’m not going to start arguing about it. A Texas Instrments 5532 costs 16.9p from the far east, probably less if you buy more than one at a time, so they are not exactly worth replacing with a cheaper component.

  • Many years ago I repaired a Moog Rogue for a friend and I took photocopies of the service manual, including schematics & BOM – Surely enough a clone was soon part of my setup – now long gone. It was a fairly easy strip board build with standard parts ( at the time – late 80’s)
    If anyone fancies a go – or better still if you can make a PCB (then do one for me !! :)) contact me and I’ll email the schematics.

  • OK then…. anyone up for it – inbox me with your email address – I don’t want to clog up the forum with large files.

  • It’s also a great schematic for hacking into – it could be the basis of a mini modular!...

  • Intrigued

  • Oh, another Möög ???

  • @thijs
    I think that the Flight Management System (http://en.wikipedia.org/wiki/Flight_management_system) of the A380 runs on (a version of) Windows. It’s not a ‘primary flight control’ system though, only a ‘super-autopilot’.

  • Just stumbled acros this http://www.gotharman.dk/Voyager_Modular.htm
    Apparently a friend om mine has this machine now.

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