Eurorack fever continues to spread. The ease of making musical electronics fit the standard, pioneered by Germany’s Dieter Doepfer, and the growing appetite from a small but passionate audience, seems to make producing new modules irresistible. The entire design equation is different: a single task or handful of tasks can become a product.

Dave Smith Instruments is the latest entry. And the product is the perfect choice for DSI. It’s a module built around on the Curtis filter, the signature filter found on everything from the 1980s Prophets (back when Dave’s company was Sequential Circuits) to the latest Mopho and Prophet 12 – as well as instruments like the Oberheim Xpander and Rhodes Chroma.

Putting the Curtis filter in a module gives you a range of features:

  • Switchable 2/4-pole, resonant low-pass filter
  • -12 dB, -24 dB switchable filter slopes
  • Dedicated voltage-controlled amplifier (VCA)
  • Audio input jack, filtered audio output jack (well, of course, though you can choose signal from either before or after the VCA)
  • Control voltage inputs for frequency, resonance, and amplitude
  • Self-oscillation in 24 dB mode

Street (MAP) US$179.

And yes, it’s actually as far as I know the first time in quite some that Dave Smith, known as the father of MIDI, had his name on something without MIDI built in. But that’s not in and of itself news; a module is by definition different from a standalone synthesizer.

What I think is worth discussing is what the value proposition is. In the context of a modular system, having a Curtis module makes perfect sense. On the other hand, modular isn’t a format that makes sense for every application. You can get this same filter in a DSI Evolver for not much more than the module costs (on the used market) – and sort of get an entire synthesizer free in the process. So if you’re just looking to route your sound through a filter, that remains an option. Apples to oranges? Absolutely. Sometimes you want an apple; sometimes you want an orange. (Sometimes you want both. Or a juicer. I’m off topic.)

The other question I have is how the DSI module fits in with the DSI lineup, whether we’ll see more from the maker. Maybe just a one-off filter module is enough, because of the abundance of great modules now in the Eurorack ecosystem. We’ll have to watch to see if Dave Smith is just testing the waters, with more to come.

But as this ships, I’ve no doubt it’ll please a lot of Eurorack lovers. And it should make a great addition to modular setups – I could see it even in a fairly small suitcase rig. Full details:




1 CV In – Frequency (3.5 mm jack) Range: 0 to 10V
1 CV In – Resonance (3.5 mm jack) Range: 0 to 10V
1 CV In – VCA (3.5 mm jack) Range: 0 to 10 V
1 Audio In (3.5 mm jack) +/-5V or 10V p-p
1 VCF Out – pre-VCA (3.5 mm jack)
1 VCA Out – post-VCA (3.5 mm jack)
Self oscillation in -24 dB/octave mode, tracks at 1V/octave

Internal power connector (ribbon cable included)
Current draw: +12V @ 36mA, -12V @ 25mA

Physical Specs
1.59″ W x 5.06″ H (40.3 mm x 128.5 mm)
Depth (measured from back of panel with power cable installed): 1.06″ (27 mm)
Mounting screws included

Compact, too – 8 HP.

DSM01 Curtis Filter [Dave Smith Instruments]

  • pixelmechanic

    DSI aren’t the only ones testing the water… Here’s something from Monome to swim in Euro:


    • http://pkirn.com/ Peter Kirn

      Ooh, cool. Will keep my eyes peeled.

  • Derek Morton

    I am one of those very passionate eurorack fans and its very telling that DSI can sell this classic Curtis VCF (which includes a VCA) for that price without the need to cash in on their name. For those that have not been watching closely, eurorack is becoming more affordable (still not cheap) and boutique manufacturers are now starting to think about the price point. Kind of curious if/when Korg, Moog jumps in to the “Lake Eurorack.”

    Peter – if you can find me a used DSI Evolver for around $200. Hook me up! : )

    • http://pkirn.com/ Peter Kirn

      Sorry, not *much* more — I’ve seen them going routinely around $250-350. Depends on where you’re buying. Not for $179, of course.

  • lala

    I dont understand the cult behind the curtis filter chips
    I have an SCI multitrack and its rotting away, I never use it
    Its not like old roland Filters or the moog cascade …

    • Popo Bawa

      Any synth chip is only as good as its implementation. The budget Sequential synths were fairly limited by use of all-in-one VCO+VCF+VCA chips and slow digital envelopes. The Max, SixTrack, Split8 and MultiTrack all suffer in this regard. But they can be fun, if you don’t push them too hard.

      IMO once can’t directly compare these CEM 3394 chips with their one function per chip ICs such as the CEM3340, CEM3320, CEM3372, etc. Sure, they might not ooze character, but this is important with a poly because each voice sits in a mix. I think the Curtis filters do compare quite favorably with Roland and Korg 24db low-pass VCFs, sounding like slightly rubbery butter.

      Anyway, I was not aware that regarding them well constituted a “cult” of any kind, whatever that may mean. Not being like another kind of filter can also be something of a bonus, rather than a flaw.

    • lala

      With cult I mean why is he still using them?
      Because they are cheap?

    • lala

      What do u mean with sits well in a mix?
      I had to eq the dammed thing like crazy …

    • lala

      In fact I had the multitrack directly plugged into a 30 band graphic eq and that into the mixer …

    • Popo Bawa

      I meant that with a polyphonic, each *voice* sits in the internal mix. Unless your MultiTrack had six individual outs to your mixing desk.

    • Popo Bawa

      Putting a whole circuit on a chip is cheap. It also makes them small, consistent, and temperature stable. These are all reasons why CEM and SSM chips were popular in polysynths and samplers of the 1980s. If you are making 6-8 voices, you typically want them each to tune and sound the same.

      For example, the TB303 is famous for being a cheap discrete synth where no two units sounded alike. Now imagine six of them in a poly303 where no two *voices* sound alike! What sounds like “a bit of character” for one voice could sound like “a big mess” when duplicated with a few similar voices.

      Smith isn’t still using the same chips. For the Evolver, he had apparently worked with OnChip to get new, surface-mount synth ICs. But they make sense because he is solving a similar design problem to what people encountered in the 1980s. How to make a computer-controlled analog synth which is small, cheap, and stable? If each voice was discrete parts on its own little PCB, the final product would be bulkier and twice the price.

    • Aaron

      Roland doesnt even have good filters really. Filters aren’t exactly what old Roland gear is known for aside from the decade later lucky mistake that was the 303. In fact, one of their most reputed filters was coupled with Curtis VCO/VCAs. You’re funny.
      Also, its not the “moog cascade”.. several one-pole cascades make up the Moog Ladder filter. Also, also.. citing the Moog filter everytime someone mentions the word “filter” = rub a dub nub,

    • lala

      Jada jada jada
      I do not care for the tec specs, all I care about is sound

      The old Roland filters sound great (100m )
      So do the moogs
      Who knows why?
      What ever Dave Smith does with does chips, it doesn’t sound good to me

  • http://vrpr.org/ Henry

    Well, it is true that many a synth these days has external audio in, CV/Gate in/out and whatnot, which makes it possible to integrate modular racks with your synths. But I still find it perfectly valid to have a dedicated rack module of a certain thing available, because fitting your Evolver (or Pro 2!) into your modular rack is not possible, so it would always be a busy desk…

    I would like to see the new Pro 2 oscillator as a standalone module!

  • Jellyroll

    “… the Curtis filter, the signature filter found on everything from the original 1978 Prophet-5”
    Peter, I don’t want to appear pedantic, but it’s worth noting that the Prophet-5s built between 1978 and early 1980 featured VCO and VCF chips made by SSM, not Curtis. This is a key element of the Prophet mythos, and it’s why Rev.1 and Rev.2 P-5s are so sought-after.

    • http://pkirn.com/ Peter Kirn

      No, sorry, major correction – all *but* the ’78-80 models, yes.

  • regend

    Interesting, all of a sudden I am getting Eurorack device promo emails from Sweetwater, Zzounds, and other retailers.

  • Popo Bawa

    One nice feature of these is that Smith actually has *new* Curtis chips made by OnChip Systems, the successor to Doug Curtis’ company. Every other Curtis VCF module I have seen to date has been made from the dwindling supply of original stock from the 1980s. These older ICs are scarce and needed for repair of vintage synths. Smith getting new chips made makes for more reliable and affordable modules than would be had using rare parts.

  • poopoo

    It is a perfunctory module. Why not add a few attenuverting inputs and some mixers?

  • m.

    Hold on, doesn’t the Doepfer Dark Energy (mk I) and A-111-5 module version sport the same filter?