Arc Resolution

  • So I just read the following info about Arc

    "256 steps per revolution, with integrated push button"

    Am I interpreting that wrong somehow? I was expecting higher resolution than that from the way it's being marketed, is there some way of getting higher resolution?

  • this has been covered in other posts, but the short of it is, a single step of that resolution translates to something like .01" movement of the knob.

    "256 steps per revolution" distinctly does NOT mean that the arc outputs a number between 0 and 255.

  • I did search but couldn't find anything, any tips on threads?

    So you can definitely get sub-degree accuracy?

  • no, the smallest resolution is 1/256, which works out to be 360/256 = 1.40625 degree steps.

  • Quote from Brian in response to the question -
    **How are those messages sent via OSC?**
    "there’s a simple format similar to other monome devices. we’re about to release a new serial-osc server (called serialosc) which will make for a much more plug-and-play experience.
    encoders send out delta values: +1, -1, -2 for example. they don’t have an absolute position, so it’s up to the software to count and transpose these values. it makes for much more interesting translation of what knob movement means– for example you could map a single “tick” to be 1 normally but 0.1 when holding the button down– coarse/fine movement.
    the led ring has a flexible and detailed set of messages. set a single led, set all leds to one value, set a range of leds to a value, or send a whole array of 64 led values in one OSC packet. these optimizations allow for incredibly fast refresh rates, resulting in very smooth animation.
    the leds support variable brightness with 16 values per led. i see a lot of potential here– layers, waveform mapping, background vs. foreground, reactive metering…"

    from
    http://createdigitalmusic.com/2011/01/arc-new-music-controller-in-video-detailed-qa-with-monome-creator-brian-crabtree/

  • hmm ok. Dissapointing.

    I used CAD systems 20 years ago with encoders for axis manipulation that had 320 steps per revolution (for obvious reasons).

    Was kinda expecting something a bit more up to date!

    Guess my monome will sit alone.

  • hey griotspeak, yes I understand the difference between an encoder and a potentiometer.

  • Sorry then

    But i would add that 256 doesn't seem that bad and cost is probably also a concern.

  • No, not bad. Just not high resolution. As a monome user I appreciate why the decoupled nature of the encoder plus leds is very powerful though.

  • perhaps high resolution in the context of music/video whatnot? double the typical 'resolution' by brute comparison, no?

  • Well, even for music standards, 256 steps isnt exactly highres. Better than standard midi, but certainly less resolution than you get out of a dedicated scratch platter (like the vci-100, the v7 or the otus) Out of curiosity, does anyone know how the whole hd midi methods work? As i understand it, there are a number of differnt approaches. I've heard of some scratch wheels that send out two midi signals, and somehow transform those two into a single 14-bit value...

  • But doesn't size come into the matter? I am guessing that you mean a record sized encoder or at least cd size versus the 3-4 inches.

    I sound a bit like a shill right now don't i? I don't even own one.

  • most music gear encoders are 16-32 step.

  • the powermate is 90.

  • USDigital makes encoders that are 2500 CPR. they're also over $60 for an OEM part.

    for practical purposes, 256 steps allows the most minute gesture to be articulated and detected.

    everything is relative. there's always "more" but often "more" isn't what you need.

  • yeah 256 is definitely a good res for fast scrubbing.

  • if you did mount an encoder on a platter or cd, you'd definitely want higher res, as stated before-- you're looking for degree-movement.

  • on a bit of a tangent, did you come across any encoders with two encoders on a single axis? i.e. a bit like those pots that have a coarse at the bottom and fine up top.

  • no, but i'm not sure how that'd be useful. couldn't you just use software to scale the input? it definitely makes sense for pots, and i love those old mechanical units.

  • lokey they use a 'most significant bit-least significant bit' system

    basically one range is coarse control the other is fine control within each step of that.

  • i wrote a patch that does that with the pushbutton...

  • yeah I was replying to lokeys post, not about the dual encoder.

    For the dual encoder I had a project in mind where I'd need to do something analogous to being able to read the position of the minute & hour hands of a clock.

  • @monobass,

    Your application sounds less like dual encoders so much as needing two rows of LEDs. But with variable LED brightness, you've probably got a way or two around that as well.

  • You can write a patch that requires 1 rotation to make an led do a 360 rotation, it'll take 256 steps to to a circuit.

    Then you could tweak that patch to take 100 rotations to make an led do a single 360, suddenly you've got 25,600 steps.

    I don't think a finer encoder would help.

  • the resolution comes into play when, for example, trying to mimic a turntable scratch through a buffer. With only 256 steps, you're not going to be able to get a fine scribble scratch that sounds the same as if you used a record, or a high res scratch platter. Not that the arc is designed with that in mind...plenty of neatness to be had with steps...

  • @lokey

    that sounds like a challenge to me ;).

  • if you can output displacement information as fast as the computer can receive it... I don't see what the difference is

  • dudes! it's gonna be fine.

    it's half about the software too

  • @lokey: this is true, but i think the resolution is sufficient that with some programming (ramping between values) you'll get the sound you're expecting and it'd match your action tightly.

    at lower resolution, the tiny movement wouldn't be detected. here, it will be, albeit grainy, but the program interpolation will compensate.

    i'm excited to see some of these ideas implemented, that'll be the test.

  • also! since there was a comparison to 14-bit controllers back there somewhere-- these encoders are optical. they have no noise. they do not jitter like pots, ever. they're also don't require debounce times like mechanical pots, so the upper limit to detectable rotation speed is far beyond what you can do with your hand.

  • @lokey - but since the arc sends deltas you can treat its single step as anything you like. You can decide that it takes 1000 arc single steps to correlate to 10 samples in a buffer, for example.

  • well, i don't know many turntablists there are about here, but the tiny movements really are at the heart of a lot of the expression you get out of scratching. I agree, for beat juggling and larger, choppy scratches, no problem with sufficient interpolation. But for scribble-style scratches, where you basically hold the platter still, and send very tight vibrations through your fingers by tensing your forearm, there are noticeable artifacts if you can't consistently detect movement, as well as the most dreaded aspect, slippage, where the sample and the platter lose their correlation (and so you can't reliably return to the same spot and hear the same point in the buffer). If all your movements occur within an area smaller than 1.4 degrees, then i don't think you'll be sending any delta signals at all, correct? I know, it's a quibble and for the bulk of uses, 1.4 degrees is more than ample, but for this one specific application, it's a concern. Pax amigos...

  • 1.4 degrees is a very very different distance on a 12" record than on a 1.5" knob. the equivalent motion performed on a turntable, transposed to a comparatively small knob, will have a good amount of data to play with.

    i fully understand your skepticism... and it's never going to feel like analog. but the resolution conversation has gotten unfortunately murky.

  • Again, spatial resolution is relative to circumference. Keep your hand on top of the dial - as you position it closer to center, the distance necessary for detection decreases exponentially.

    A large free-spinning disc with ultra-high resolution would indeed be nice. But I don't think arc's trying to emulate Vinyl any more than the monome was trying to emulate the Zen Drum. Different tools for different needs...

  • completely agree with everything said, and certainly not intending skepticism at all, just helping to define and discuss the functioning of the device...the utility of this thing is so broad as it is, best to define what its best suited for! Looking forward to hearing what you folks produce with these!

  • you bring up a very good point-- the arc isn't good for everything. nor is a grid good for everything.

    i think a good designer will discern the best use of a tool, and know when to use a different tool, even though there is curiosity in making a tool do the job of another, etc. tool tool tool.

  • willingness for this new tool to be, well, exactly that, is key. if you want the nuances of a turntable..... if you want to see what is possible of an entirely new device that is completely open to application/experimentation... let it BE

  • ^ Words of wisdom. ;]

  • Just came back to this thread.

    All that being said, really enjoyed reading this discourse. Especially between people that have a finer knowledge of the materials and techniques at hand, than I...

  • i reckon 256 steps will be well more than enough when hooking up the arc to the clip launcher in ableton to get some sick loops/sequences goin!

  • little offtopic:
    If anyone is interested in arduino midi/osc/hid turntable project, contact me or open a new tread.

    I'm working on it (and learning arduino) for two reasons:

    arduinome.

    Scratch encoder.

    Back in topic: Arc doesn't seems to scratch it but there is more room to play!

    ;)