MOTM

I spent a few months trying out different ribbon controller designs 
earlier this year. Here are some of the results I came up with.

1. A pure analogue design will always droop, and that's bad. There 
are schemes to have several sample and hold circuits in succession, 
each with a larger cap, to minimize droop, but they won't eliminate 
it completely. You must have an ADC/DAC in there somewhere to do 
sample and infinite hold.

2. I tried the PAiA circuit, it's analogue and so it droops. It also 
doesn't have the ability to hold the last voltage when you release 
the ribbon unless you specifically tap on the "Hold it Now" button 
just before you let go. The dual output sounds like a great idea, but 
unfortunately there is always some interaction between the two 
because your finger does not have zero width.

3. The D*epfer R2M is not as bad as you think. I was skeptical at 
first too, but in the end I chose it as the basis for my ribbon 
controller. I have not yet heard any zipper action as a result of 
using it. Yes, it is limited to 0 to +5V, that's one of the reasons 
why I built my add-on board (to get bipolar output). It doesn't have 
the "zero-point" feature of the CS-80, and it never will because it's 
limited to 0 to +5V. Had they designed it with bipolar outputs in the 
first place, it would have been trivial for them to do the 
"zero-point" in firmware. It is possible to add a "zero-point" 
feature using an add-on board, but in order to avoid droop, you have 
to go through a ADC/DAC which adds a lot more circuitry (ADCs aren't 
cheap either). I tried this but was not satisifed with the results. 
After accounting for processing time in the R2M, the "zero-point" 
feature added more delay and often resulted in glitching and sluggish 
performance. It hardly seemed worth the effort. I chose a simpler 
design that merely adds an offset voltage and allows setting a dead 
band zone. It's so simple and it gets me 90% of the way there. I am 
content.



At 12:49 PM -0700 2005/07/29, Dino Leone wrote:
>I can only agree with Michael! I too would be very
>much interested in a ribbon controller.
>
>I was just (again) drooling over Old Crow's Yamaha
>CS-80 page (http://www.cs80.com/) and he emphasizes
>the fantastic implementation of the ribbon with the
>"zero-point" wherever the ribbon was touch initially -
>wouldn't that be great for a MOTM-ribbon. I have no
>idea if the Doepfer ribbon could be modified or
>programmed this way?
>
>Best Wishes,
>
>Dino
>
>
>
>--- tontaub <egroups@...> wrote:
>
>>  Hi All,
>>  after yesterdays rehearsal I'm pretty sure that a
>>  nice ribbon
>>  controller is a necessary addition to my setup.
>>  I did a quick archive search and found Larry's
>>  message on this subject.
>>  Also Scott J. offers some 3rd-party product
>>  "motmized".
>>  http://www.tellun.com/motm/diy/tln854/TLN-854.html
>>  While the ribbon of the Doepfer product itself at
>>  least looks nice
>>  (and some reviews on the Net say it's good to play
>>  too) I'm not
>>  convinced by either of their available controllers.
>>  The analog one only has few features and the R2M
>>  suffers from the
>>  traditional 12bit/5V dilemma which results in a
>>  rather bad resolution.
>>  (I don't favor Doepfer anyway for some reasons).
>>
>>  I also printed the PAiA article about their ribbon
>>  controller in order
>>  to read it at home ( http://www.paia.com/LabNotes/ )
>>  and get informed.
>>
>>  So what would you recommend? Who's succesfully using
>>  such a ribbon
>>  controller and what product(s)?
>>
>>  Thanks a lot, Michael.
>>
>>
>>  --- In motm@yahoogroups.com, "J. Larry Hendry"
>>  <jlarryh@i...> wrote:
>>  > Ribbon controller:  I'm using the Doepfer Ribbon.
>>  The ribbon is
>>  > great, the module sucks.  I have the new PAiA
>>  ribbon controller
>>  > module on order.  The circuit description sounds
>>  exactly like
>>  > something I was planning myself.
>>  > So, I am looking forward to its arrival. Much more
>>  on that later. 
>>  > Be certain there will be a Stooge panel
>>  implementation Ribbon
>  > > controller based on the PAiA kit and the Doepfer
>>  ribbon element.
>>
>>
>  >
>>