Analog Filter

So, one of the biggest requests on this forum for WTPA was an analog filter on the output / input.
Are you all serious? You understand that the build complexity would be greater, and the cost would be, too.
It would be totally fun for me to design, but does it really belong in a digital sampler? Should it be a daughterboard? Should it exist at all?


  • DO IT!

    but maybe keep things modular similar to the hardware add on board. that would be the ideal solution, I think.
  • This sampler is already starting to sound like.. A digital modular?! What with all these expansion boards. Hmm, theres an idea?
    A sampling digital modular, albeit with an analog filter bolt-on would be pretty nifty indeed..
  • To me, the WTPA is a sampler, plain and simple. It's great and unique, as it is.
    If you start adding stuff, it becomes generic and a "do it all" sort of machine doesn't interest me.
    Adding an analog filter is akin to attaching one of those X0Xio boards to an X0XB0X; sure it adds tons of features, but it makes the machine sound less and less like a 303 and more like a standard subtractive synth. (There's nothing wrong with that, by the way; the sole reason I had one was to capture that classic tb-303 sound, however.)

    Yeah, and talk about complexity. How will the filter be controlled? Sounds like it'll need an envelope, oh and an LFO, and CV In's, and a trigger button, and...
    I would say, concentrate on the main thing first, perhaps integrating a generic connection bus for audio and data.
  • I personally REALLY like the idea of components that can be added. This reminds me of the akai S3000 where you could add filter modules.
    As far as the filter goes, a multimode with a VCA and either a envelope follower or just a trigger sent on sample start would be fantastic.
  • I definitely wouldn't mind paying some more for an analog filter option, especially if one could patch other stuff through it.
  • Filter pilter. I don't think it's needed.

    Then again, people LOVE filters.

    It would be cool if the WTPA2 had an expansion header, so if you do build a filter, it could be a daughterboard, and same goes for the mentioned "party control" and other such modules.

    I'm not a big fan of modulars in general, but you could basically build the WTPA2 with then option for expansion, then either do it or don't.
  • filter with simple sweep, maybe ctrl via midi, sounds good to me!
  • Or better yet some CV control.
  • I hear what people are saying about keeping it pure sampler and all, but at the same time, the demos I've heard where people run their WTPA through an analog filter sound really sweet. So for me, I would like to see the filter built in - daughterboard or fully built in, I don't care. Sure, I could run the WTPA through analog filters that I already have, but the appeal of having it as an all in one device is most appealing.
  • edited April 2010
    a filter would be JAHMAZING. even if it was a seperate lil board. and you don't need a load of fancy stuff because you could put an LFO on the cutoff from your daw or whatever.

    the cavemen would be happy enough to twiddle knobs...
  • I guess I'll add my two cents. I used to be a filter-scmilter type of guy where for the most part they were "meh" and overdone. However, these days I have to admit that I do like adding filters, especially to digital units. I think it smooths things out nicely, and they usually give you nice control, so if you don't want to use it, don't, but if you want to get into wild, rezzy sounds, you can.

    Also, while it's not a traditional filter, the Flight of Harmony Plague Bearer is quite the nice little FSU module (but can do more than just FSU) that I've really fallen in love with of late. It's got nice CV control, and it's great at adding extra harmonics to a sound source.

    But, yes, a filter would be nice. I would even think a digital filter would be somewhat interesting, just as it's something different.
  • A filter module would be awesome! wtpa was my first project kit and the option to expand the instrument by building different modules would probably make it the greatest learning experience I've ever invested in (I'm definately buying v2). Keeping it as just a sampler is fine, if that's what you want. But being able build a custom instrument suited to your personal tastes gets me pumped! What other kinds of daughter boards are feasible? EQ? DELAY?! I'm sure stuff like that has a higher difficulty level, but if one of the goals of wtpa was to introduce people into the neat-o world of electronics the option to build more complex modules later is within the mission statement.
  • It'd be cool if the daughterboard had a readily available spec. So people can buy their own mini protoboards and make whatever they want on them. So audio/MIDI I/O and power going to the daughterboard header.

    Like that someone can make an analog filter module, and we'd all buy/build it etc..
  • The "expansion slot" idea seems to be getting a lot of props. Everybody seems cool with that, even if they aren't with the filter.
    Is this right?
  • TB@ yeppers over here...
  • Well, with the expansion slots everyone can do whatever everyone wants. As long as the I/O is there, it could be endless.

    Endless might be a bit strong, but it opens up stuff, and in that cool "deal with it later" kind of way.
  • i'll take the filter anyway, a dedicated connector makes it easy i guess
  • Yeah, I like that idea... I guess something like that would be patching a connector before the output op-amp, and after a buffer stage... maybe include some sort of trigger/gate signal if there were an env. generator module or if it were integrated into the filter somehow...
  • Yes! Expansion slots. Getting a bit more out of your gear by adding new functionality is always awesome and less expensive than buying new gear. (analog filter expansion too plz thx)
  • I like the expansion slot idea!
  • A possible problem I have with the expansion slot idea is; will there just be one expansion slot, and will I have to choose between using the analog filter and the permanent data storage system? I think it may be the way to go, but I have fears that this will actually make things less useful and more complicated than necessary. But I have no better suggestion, so carry on. :)
  • They could piggyback?

    If you have access to the I/O that could go to the filter, and for storage, that would address the MCU/ram, so it could do both?

    I guess it depends on how the expansion slot is designed.

    As long as we don't have to hold it between our hands, and ritualistically blow at the expansion to make it work, I'll be happy.
  • Rodrigo, yeah, that's what I was some what assuming. It's just that doesn't seem the most elegant solution to me, especially thinking ahead in that there more than 2 products that can use the expansion slot. I'm just thinking out loud at this point. There's also the problem (?) of how to physically fit the expansion slot on the board. Should it be on the front or back, will multiple ones stack? If so, what type of hardware will be needed to keep these expansions stable, will this greatly increase the vertical footprint and make it harder to fit in a smaller case? etc.

    And it's funny you mentioned the blowing thing, when I first heard the expansion slot idea, that was the first thing I thought of. I thought of the OG Nintendo. I'm actually kind of hoping that I have to blow in the bottom of the analog filter cartridge before plugging it in to get it to work. I think it'll add to the whole 8-bittiness of the thing. It'll make it sound better too!
  • I assumed the expansion slot was more about headers/pintouts than a physical cartridge, though if it was designed around a specific pin width so it could be used with perf/protoboards.

    The Arduino "shield" layout looks really good, so you can stack things, to share the pins/headers. Don't know how many of those you can do before it looks unreliable, but it's something.
  • edited April 2010
    The way I was thinking about the "expansion slot" was as a set of 0.1" holes designed for standard male headers. The connections would include connections for VCC, Gnd, the SPI bus, the 8-bit data bus, the audio input, and the audio output. Modules would likely be soldered and would include holes for mounting screws to take the mechanical stress off the solder connections.

    The permanent memory would have its own connection on the board via the SPI bus. It would look a lot like the "Spare Comm" on the current WTPA boards. Depending on how big the daughterboard was, it might or might not have mounting screws.

    W/r/t infinite expansion -- those busses don't have to be mutually exclusive. There isn't any reason you couldn't use more than one expansion if you could mechanically get all the bits wrapped around whatever enclosure you were trying to fit them into. I agree it merits thinking about this in advance.

    That having been said, realistically, nobody has done anything with the "spare comm" that I know of. Having the problem of choosing between too many awesome WTPA expansions would be a pretty great problem to have. The next time I have the problem of thinking of which pair of hot twins to go home with from the embedded systems conference, I'll briefly and wistfully think of you guys :-)

    Edit: Olivier pointed out that the expansion connector should provide the unregulated vcc as well so as to provide for analog supplies in a higher voltage range. Just noting that here.
  • Yeah, that sounds great, Todd. That way, the user has control over which ancillary functions he wants to install on his WTPA "core" board.
    For the record, I'm not against analog filters, just an analog filter being an integrated part of the WTPA. (Strictly off the record? I'm also against Lemurs. The animals. Don't say a thing to anyone!)
  • Sounds good Todd. But I'm still wistfully hoping for a Nintendo style connection for the expansion.

    "What do you guys want to play with today, the Moog filter or the EMS synthi filter?"

    "I want the Buchla!"

    "Fine, we'll do the Buchla" I pray to the elder gods of electronics and gently blow into the cartridge, then plugging it in, hoping that it will work this time...

    Also, if we can have cheat codes to open up the advanced abilities of the new WTPA, that'd be cool too. I recommend up, up, down, down, B, A, B, A, select, start.

    Or you can go the boring way and god with the typical 0.1" holes for normal headers. That'd probably make a lot more sense.
  • edited April 2010
    @Todd ... I think there is a general consensus amongst WTPA users that the concept of add on components in the form of an open plug-in architecture is a very viable one. You'd be guaranteed to sell them and plenty of users would gladly open their wallets to pay for a more rockin' party! I just think there has to be less of this 'poor man's sampler' mentality and more of an effort towards value-based modular design. You have to understand that not every guy who wants to own WTPA is living off Social Security or out of Brotherhood bins! lol... but seriously... having a distinct lack of features or expandability can actually be a BAD thing for a sampler and I think a move in the direction of add on components and modular expansions is a natural one. Perhaps the expansion cards could be connected via flat ribbon cable, much in the same way as earlier computer peripherals? That would at least keep the slots small and the expansions versatile and easier to install, mount, position, etc. Would make for some crazy modular case designs too!

    An analog filter would be fantastic, but I really don't think it should be included as a standard, built-in feature. Perhaps there is a way of loading a ROM chip with a dozen or so public domain 'one-shot' VST effects (free .DLL's) and being able to render them in real time over the sample output? I'm not sure how that would work, but Mattel have done something similar with their sub-$30 Radica Ucreate Music sampler ... the 8 on-board effects on that little unit are nothing more than .dll files that are loaded directly from a ROM chip and rendered over the sample as it is being played. The circuit bending community thinks that these .dll files might be VST effects, or something very similar. So hackers are currently trying to figure out whether the .dll files actually are VST effects and whether or not custom .dll effects can be created and loaded into the UCreate Music sampler to expand it's feature set. Having VST dynamic link libraries for rendering effects would greatly open up the WTPA to allow for hundreds, if not thousands, of one-shot Cubase plugins (both free and commercial) and would eliminate the need to build any effects from the ground up.

    Would this sort of thing work with WTPA?
  • Alex: You do realize that this device runs on a 8bit uC right?
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