Hardware Desgin, Differences between V1 and V2

So I've started messing around with designing the new version of WTPA.
I _could_ just re-release the old version, but I'd prefer to make some design changes, since there are plenty of things that aren't perfect about WTPA v1.
And, since I'm at it....

So, here are the things that will definitely change:

1.) WTPA 2 will have 8 controller buttons and not six (the very first one had 5 I think). This will allow us to avoid the dreaded 3-button combo when accessing functions.
However, this means two more buttons, and one more shift register IC and socket. This costs more.

2.) There will be a through hole RAM chip. This means the whole kit will be through hole (no smt). This will probably cost about the same, but the board will need to get a little bigger.

3.) The analog sample clock will be based on a 4046 and not an op-amp relaxation oscillator. I can do this because I don't need the extra op-amp section for overdubbing. This will cost a little less and will also allow CV input to the clock.

4.) The control pot will be replaced with an endless rotary encoder. This will help in all kinds of subtle ways. This may cost a hair more. Given enough pins, I may add a second encoder.

5.) The MCU will be either an Atmega644p or 324p, simply because I want the freedom to add new functions and we're pretty much out of flash memory on the 164. This will also give us more RAM which may help some of the granularizing functions, and may be able to help with ISR speed if I'm smart about buffering. Those chips are still a 40-pin dip. They cost more.

6.) Some of the values in the analog section will change, which will result in slightly more headroom. This will probably cost about the same.

7.) The bus which is just hanging out doing nothing on the v1 WTPA will be used to access permanent memory. There will be an optional daughterboard which will contain a flash memory chip and will be able to store either 8, 16, or 32 samples depending on how some pricing and availability works out for me. I _might_ implement a sample loader via MIDI. Maybe. The daughterboard will come assembled (all that stuff is small smt biz) and will cost more than $20. Not sure how much more. So permanent storage will be optional.

8.) Instead of a hardware goodie bag, there will be another optional board which will have PCB mounted jacks for MIDI, Audio, and DC. Second to the RAM chip, most build problems in V1 were in the wiring. This should eliminate that problem. This board will mount under the main board. This will _probably_ be more expensive than the goodie bag, but may not be depending on some of the jack pricing.

9.) The routing from the input amp to the AVR will change A LOT. This should lower the noise floor a little.

10.) Because of all these changes, the board will be bigger. Probably not a lot bigger, though. My guess is the price will go up a little too.

Let me know what you think! Now is a great time to hit me with suggestions.
There's another thread for feature requests, too.
Also, anybody who says ANALOG FILTER gets the gas face :-)
Hell, I might as well just go ahead and start a new thread for that too....



  • Optional 2 or 3 line display...maybe on a daughterboard add-on as well.
  • hmm...

    todd, does the new ram alow for permanent sample storage? it would be cool to have a (switchable) option to store samples permanent.
    will there be a kit at all, or will it be plain pcb to buy?

    regarding strangeAgent proposistion of the 2 or 3 line display - you can alread do that no? I remember someone on here used a display on their wtpa. it takes away from the oldskool flavor though...
  • d'oh, just read point #7....

    DO IT!
  • Consider adding a .1" header (SIL or DIL) with all of the front-panel pot/led connections on it... That would possibly decrease the chances of miswired WTPA's, surely for ones with off-board mounted controls. also I believe I remember seeing a photo of an early WTPA board that had a little proto section on it -- you may not have room in the end but I thought that was clever...

    In general, it'd be nice to see it a little more hackable. Instead of vias everywhere it might be nice to have holes with pads.
    And this leaves more room for error, but jumper points between circuit sections would be cool. To make it a little more modular/patchable. For example, if the output of your input buffer/gain stage was connected to a jumper that could be removed if you wanted to put a different gain stage in its place (say if you were interested in interfacing with 10Vp-p signals)

    I know that this wouldn't appeal to TOO MANY but it's a feature I'd be interested in. thought I'd throw it out there.

    Also, if you're doing 8 buttons it may be worthwhile to consider using a push-button rotary encoder as one of the buttons. I've found it's a very handy + tactile approach. Not sure how that would work its way into the UI.

    Probably would require a few more IC's but you could add exponential CV scaling for proper pitch-tracking with 1v/oct gear...
  • More knobs the better! Would make it kinda 'analogue' to use too.. Which no other sampler of the past really did. You know it makes sense (even if I don't :p )
    Seriously though, more knobs with less button presses would be neat. Or perhaps combine the 2 in a neat way, like the matrix systems that the Waldorf Pulse etc used.
  • That all sounds awesome. I really stoked about it.

    8 buttons is nice, particularly if user definable. As is a rotary encoder. As mentioned, a pushbutton one would be nice. Two encoders is better.

    I like the expandable idea. I probably wouldn't use permanent storage much, but I'd probably buy it to know I could.

    The PCB mounted I/O is awesome.

    Overall, it would be nice to have it be easier to set it up in a more 'pro' manner. I like the little buttons/pots onboard, but it's a lot of wiring to set it up in a bigger/sturdier case and all.

    All noise reduction/headroom stuff would be awesome.

    I also second the hackability. Granted, I didn't try bending mine much (at all really), but if there was a particularly "juicy" area for bends, it'd be sweet if it was organized/labeled/grouped as such.
  • permanent storage would be awesome, really. maybe even data dump via midi so one could record sample data with a sequencer (e.g. the old Atari Notator) and play it back in.
    i also think a dedicated bending area like you had it on the
  • Would you consider a case and faceplate? I was/am still a newbie at DIY stuff, and I remember being a little apprehensive at first when looking at the WTPA because of lack of an enclosure, faceplate, etc... I can see other people who might be on the fence about DIY, and who are eager to try, but might end up avoiding the WTPA unless the kit was "complete". Sure, they could purchase the assembled unit from you as you have hinted that you will do, but I think there a lots of people who *want* to get into the DIY route, but who will only do so if they have the whole shebang included...
  • @dnigrin
    Done. I totally agree with you. There will be a case sold separately too. Basically there will be everything you need to put together something stand alone, and the assembled unit will just be all the possible bits put together by some hipster in my basement (taking applications for said hipster, by the way...)

    @smrl and rosch
    I like the proto area. But I get the impression nobody used it. Lord knows I never did.
    I also like the idea of breaking out the connections you might use for a front panel in case somebody wants to make their own.
  • has an LCD screen been mentioned? 8 buttons, more features than you can shake a stick at, sounds hectic. it would be nice to know exactly where the party is at, if you know what i mean.

  • @oootini--
    Now, for a non-caveman like yourself you should have no problem keeping track of those features on your MIDI controller or DAW, right?

    It's a good idea. An LCD would be great, but there's a special kind of can of worms associated with it. For sure it means more code (either really boring code for a character LCD, or not-insignificant code for a graphical one) and more memory for strings and character maps and shit, RAM if you're doing a blit, all of a sudden there's this annoying English language thing going on, then menus start to happen, and most importantly it means sourcing an LCD which is either expensive and emasculating for some sparkfun-y serial LCD style module or more irritating and less expensive for a normal samsung-compatible LCD. Then you have to worry about mounting it.

    [I went down this road for a second a long time ago. On a version of WTPA that never saw the light of day (a much more powerful version) I'd spec'd an LCD with a touchscreen, and since I wrote this bangin' pong game awhile back for the AVR, it could play Pong. That will probably never happen, though the taste in my mouth remains]

    Still, I'm all for usability, and the current UI system leaves something to be desired. How about a better silkscreen legend on the PCB as a compromise?
    Since it seems like people are geeked about bringing out a generic bus for communications, I guess an LCD could always get added on later, if somebody really took one for the team.
  • A better UI could definitely improve things, since more and more is being added, and it's already pretty complicated/confusing.

    How about the sampling/looping/bank stuff only ever does that. Period.

    Then the "leftover buttons" handle all the function/effect/edit stuff. Maybe another set of LEDs to scroll through FX, so you only need 1 button to pick what's going to happen, then the other buttons to control how it happens. Might get confusing with multiple things happening at once, but it could go towards streamlining the UI.
  • @Rodrigo--
    Not a bad idea. If I can think of a way to do that cleanly, it's on.
    Thanks again, everybody!
  • edited April 2010
    could backlit led buttons/encoders/combined with silk screen legend be used in a pinch for a rudimentary UI?


  • actually i just want those fancy led encoders :) they look hawt.
  • Holy shit, who cares if those are useful! Those are AWESOME. I'm getting a quote right now.
  • SPAM!
  • edited April 2010
  • With that encoder, I could play Simon on my WTPA2, too!

    Yeah, I could imagine that single encoder being the hub of information for the user. It'll still take some programming, however. An LCD would certainly make it the Cadillac of lo-fi samplers, but would be overkill, considering the type of information a user would need to know.
    How about a couple standard 7-segment LED's? Shoot, you'd need a driver chip too, eh? You could get really creative with UI stuff.

    Anyway, some hardware thoughts:

    -->Will the WTPA2 be two channels or more?
    -->Separate audio channels for each sample channel.
    -->"Stereo mode" which would link two (input/output) channels. (Perhaps, that's a software thing.)

    That's all I got for now.
  • Those LED encoder ring gadget things sure do look neat! I hope a good excuse is found to incorporate them somehow. And to make them useful too of course! I confess, I am a sucker for ze pretty flashing lights..
  • Man, that looks amazing!

    I think a completely redone UI, built around a rotary encoder like that one, and maybe another one with no fancy LEDs for other stuff, and dedicated transport/bank controls would be amazing.
  • I guess slightly less fancy single colour led rings would be damn nearly as nice, and plenty sufficient though.. And likely cheaper?
  • like these?

  • Yes :) Although for a rotary encoder, im thinking a 360 degree one has to be more suitable. Im sure they must exist, as quite a few synths and hardware controllers use this kind of thing these days.
    If I remember rightly, some of the early digital mixing desks didn't have the convenience of these ready made LED rings. Instead there were individual surface mount LED's placed around the encoder on the main mobo. Perhaps that is still an option for the WTPA too? Although that would be a chore to solder!
  • the kenton killamix mini has individual lieds for this purpose (or so it looks like)...
  • http://cdn.mos.musicradar.com/images/Computer%20Music/Issue%20111/CMU111revkillkilla-460-80.jpg
  • Ok, Ok. I'm getting prices on pretty encoders. But what else?
  • As much as I'm always dissing the MIDI maybe a USB->MIDI option, so you could plug one of those korg nanokontrols directly into it without having mess with midi/power cables. Or just have the Party Control type thing.

    If it had usb, perhaps it could be programmable via that too? For the "finished product" purchasers.

    Multiple parallel input/outputs for people interfacing with a bunch of bits of gear. Not stereo, just 2 ins feeding the same circuit, and 2 outputs coming out of it on the other end.
  • It's fun to have started working on this thing. I forget sometimes that the really awesome part about all this crap is the engineering. I mean, and getting your leg humped.
    Thanks again.
  • whhhat about a conductive pad that you could get all finger wiggly on. like that manta controller. you could select an effect, and have a good wiggle on the pad amazing everyone with your moves.


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