[sdiy] Henry Walmsley's page

[Ian Fritz]

At 03:57 PM 12/23/2009, David Ingebretsen wrote:
>I am not seeing how the faders are wired. I presume
>they are wired as a voltage divider and from the data sheets, I assume
>between gnd and +5 volts, right? As a divider, the current draw will drive
>the choice of resistance, correct? So, 100K is OK? There will be effectively
>16 of these in parallel from +5 to ground making about a 6K resistance total
>for a current draw of about 1 mA. (I sure hope I punched my calculator
>right).

According to the text, the faders are connected between +/- 5V.  They feed 
a diff amp with 220k input impedance.  So if you want decent linearity, you 
might want to keep the faders below 50k or so.  You could possibly double 
the four resistors at the amplifier input if you want to use a larger value 
for the faders.


>(Yes, I really like your DoubleDeka Ian. It's just hard to cram it into a
>Frac/Euro space without a lot of effort and "hacking" especially I think to
>the slider board. But, I am looking at the kit Scott offers at
>Bridechamber... :) )

Yes, getting it into Euro is a challenge.  Someone has suggested a unit 
with a single deck of 8 sliders, but that would really limit the performance.

I recently put one into a standalone box (along with a Teezer).  A photo is 
up here:
http://electro-music.com/forum/topic-31618-250.html

This is why I don't like Euro very well -- the panel format dictates the 
circuit design!

   Ian