[sdiy] chaotic midi to dynsync conversion with a tb303

[Philippe Schelté]

Hello,

hope it is not too much OT...
after about 4 months of struggling in building the Colin Fraser midi to
dyn sync converter (m2dc) http://www.colinfraser.com/m2d/m2d.htm
(programming the 12F629 was very difficult especialy with the fact that
I wanted to do it on Linux with a home made PIC programmer ;)) I come to
a mitigated result :

I can start the TB303 with the computer, but the TB303 stops whenever it
wants, it is chaotic, sometimes It doesn't start anymore...etc. 

let me explain my setup :

first, I have simplified the schema in order to have only the midi to
dyn conversion, because I want to use it with a TB303.
http://dubphil.free.fr/scheme2.png

I'm working exclusively on Linux, I have a Terratec PHASE 26 USB sound
card with 1 midi in and 1 midi out, I have also an Edirol UM2 midi
interface that provides 2 midi in and 2 midi out. Externaly I have the
sliders KENTON control FREAK connected to the midi in 1 and the midi out
1 of the UM2 midi interface.
I use seq24 http://www.filter24.org/seq24/ to send the midi clock to any
midi port of my choice.

Something interesting : when I connect the m2dc to the midi out of the
PHASE 26, the voltage in the circuitry is not higher than 2.5V. 
When I connect the m2dc to the midi thru of the control FREAK, the
voltage in the circuitry is around 5V (between 4.8V and 5.2V).
but I can start the TB303 with both setups and none seems to give better
result than another.

I'm very lost because of all the parameters to verify, but intuitively,
I suspect my TB303 to be the faulty. It is a second hand synth that I
found having a sort of bug : when I apply a slide between the last step
and the first step, the last step seems not to be played (perhaps it is
the normal behavior, I don't know...).

In order to help me, I would like to have some confirmation on thought I
have :

- The 12F629 has been burnt succesfully because I can start the TB303.
true ?

- The m2dc schematic simplification has been well done. true ?

- The midi clock sent by a software via a computer is enough reliable to
synchronize a TB303 using the m2dc, true ?

if all those assertion are true, so the faulty is my TB303 in this case
any tb303 pros remember this kind of issue ?

Thanks in advance for your kind help.

Philippe

-- 
http://dubphil.free.fr