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MB808 from the begining, sources of info


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It's a simple DOUT based DAC, the ASCII based schematic can be found in the setup_* files (e.g. http://svnmios.midibox.org/filedetails.php?repname=svn.mios&path=%2Ftrunk%2Fapps%2Fsequencers%2Fmidibox_808%2Fsetup_seq_dr_default.asm )

 

;; CV values can also be output via DOUT shift registers
;; This option is sufficient to control the "velocity" of drum instruments, and it's cheap as well!
;; We expect following connections:
;; 
;;   DOUT         160k
;;    D7 ---o---/\/\/\---*
;;               80.6k   |
;;    D6 ---o---/\/\/\---*
;;               40.2k   |
;;    D5 ---o---/\/\/\---*
;;               20.0k   |
;;    D4 ---o---/\/\/\---*
;;               10.0k   |
;;    D3 ---o---/\/\/\---*
;;                5.1k   |
;;    D2 ---o---/\/\/\---*----o CV Out
;;              220 Ohm
;;    D1 ---o---/\/\/\--------o free assignable trigger
;;              220 Ohm
;;    D0 ---o---/\/\/\--------o another free assignable trigger
;; 
;; The DOUTx channels are matching with the AOUT channels as specified in the DEFAULT_TRKINFO table above.
;; Allowed values: 1-16 (selects DOUT shift register) or 0 to disable
;; Ensure that DEFAULT_NUMBER_SR is high enough so that all DOUTs are updated.
#define DEFAULT_CV_DOUT_SR1  4
#define DEFAULT_CV_DOUT_SR2  5
#define DEFAULT_CV_DOUT_SR3  6
#define DEFAULT_CV_DOUT_SR4  7
#define DEFAULT_CV_DOUT_SR5  8
#define DEFAULT_CV_DOUT_SR6  9
#define DEFAULT_CV_DOUT_SR7  10
#define DEFAULT_CV_DOUT_SR8  11
#define DEFAULT_CV_DOUT_SR9  12
#define DEFAULT_CV_DOUT_SR10 13
#define DEFAULT_CV_DOUT_SR11 14
#define DEFAULT_CV_DOUT_SR12 15
#define DEFAULT_CV_DOUT_SR13 16
#define DEFAULT_CV_DOUT_SR14 0
#define DEFAULT_CV_DOUT_SR15 0
#define DEFAULT_CV_DOUT_SR16 0

 

Best Regards, Thorsten.

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  • 2 months later...

Thanks Throsten for this!

Dout to CV!

 

A question for this..

The output voltage is between 0v and +5V right??

 

If yes is there a way to make this work between 0v and +15?

 

Or far away better for TR-808: Accent = Trigger pulse between +5v and +15v

My target is to make a Dout Trigger pulse of 1ms width between +5v and +15v ( This will be the accent for 808 voices )

 

Update:

I know i need a shift register that will be operateable at 15 volts..

I found that http://www.ti.com/product/cd4094b can operate at those voltages but this is not a 3-state output register.. Is this a problem?

 

Regards, Tilemachos

Edited by Navicat
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