[sdiy] Question how to improve rotary encoder feel

[rburnett at richieburnett.co.uk]

The Ion pots are available from Alesis as replacement parts for repair 
work.  Perhaps you could buy one to play with, then see if there is any 
manufacturer's info on it to suggest if it's made by one of the usual 
suspects like Bourns, Alps, Alpha, etc...

I don't have an Alesis Ion, but an engineer friend who has one explained 
the operation of the pots to me like this:

Dual track potentiometers, except one track is rotated 180 degrees 
relative to the other track, and no mechanical end-stops so they can 
rotate continuously.  When the wiper for one track goes over the 
discontinuity in its track, the other wiper is in the middle of its 
track.  Some clever software is then used to read the voltages from both 
wipers and "hide" the discontinuities in each track by using data from 
the other track at that time.  You then get smooth high-resolution 
parameter adjustment with endless rotary control, and free from any 
glitches or mechanical detents.  That's the theory anyway, perhaps some 
Ion users can comment on how well it works in practice?  They've been 
around for a while now, so it would be interesting to know how well the 
well-used pots are holding up!

I hope that explanation made sense.

-Richie,



On 2017-06-09 12:26, Julian Schmidt wrote:
> I found 2 pics of the ION parts
> http://studiorepair.com/gallery/Alesis/Ion/slides/Alesis_Ion_Potentiometer__STUDIOREPAIR_04032501_1510157530.JPG
> http://studiorepair.com/gallery/Alesis/Ion/slides/Alesis_Ion_Panel_PCB__STUDIOREPAIR_04032501_1510087626.JPG
> 
> julian
> 
> Am 09.06.2017 um 13:17 schrieb Julian Schmidt:
>> I'm all ears if you know a part number or source for affordable 
>> endless pots.
>> All I can find are expensive industrial ones in the >10€/piece range 
>> and although being 360° endless rotation parts, the resistive taper 
>> spans only 340°
>> The Ion pots look more like the normal, cheap 1-2€ pots but my 
>> research turned nothing up, yet.
>> 
>> julian
>> 
>> Am 09.06.2017 um 12:53 schrieb rburnett at richieburnett.co.uk:
>>> You could look at using continuous rotation pots like the Alesis Ion 
>>> supposedly uses.
>>> 
>>> -Richie,
>>> 
>>> 
>>> 
>>> On 2017-06-09 11:30, Julian Schmidt wrote:
>>>> Hello All,
>>>> 
>>>> I have a current idea that could vastly benefit from using encoders
>>>> instead of pots.
>>>> My only gripe is that I never had an encoder where I liked the feel.
>>>> With the standard 24PPR encoders you have to make way too many turns
>>>> to get to a higher value.
>>>> Rotationspeed based value speedups made the feeling even worse on 
>>>> the
>>>> machines I tried. Also a lot of people complain about encoders on
>>>> synths for the same reason.
>>>> Best solution so far is something like on the midibox or AN1X where
>>>> you push the encoder for fine resolution.
>>>> 
>>>> The only one people seem to like are the Nord ones with the LED 
>>>> rings.
>>>> I never had a nord machine in my hands, but Forum research suggests
>>>> that they somehow managed to line up the LED movement on the ring 
>>>> with
>>>> the encoder travel. So if you turn the encoder half a rotation, the
>>>> value LED is at half, too.
>>>> 
>>>> Any idea how they've done this? looking up the specs it seems like
>>>> they are using Bourns ECW1D-C24-SE0049L encoders
>>>> (http://electro-music.com/forum/topic-50251.html).
>>>> 49L is not specified in the datasheet, but my guess would be 48L =>
>>>> 48PPR which would still be too little resolution to even bring a 7 
>>>> bit
>>>> value up to full range in one revolution.
>>>> Is the front panel resolution just reduced and interpolated on the
>>>> nords?
>>>> 
>>>> So if anybody has some hints how to give an encoder a more
>>>> potentiometer like feeling I'm all ears. Especially if we talk 12 
>>>> bit
>>>> instead of 7 bit parameter resolution.
>>>> 
>>>> For practical reasons encoders would be great for layered UIs to 
>>>> share
>>>> a set of controls between multiple LFOs or preset saving. LED rings
>>>> are sexy as hell, too. But whenever I use encoders for something 
>>>> other
>>>> than menu diving and editing settings I wish for a pot in my hands 
>>>> ;)
>>>> 
>>>> Cheers,
>>>> Julian
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