[sdiy] Oi vay. The trials and troublations of sequencer design. ;)

[Rykhaard D.A.M.I.A.N.]

Well - after 10 years of development (with only a 9 year, 11 month, 30 day
and 20 hr. break in between ;) LOL ) of my sequencer, some progress has
finally been made. :)

Using the 'keyboard interface' constant current source, to drive my 12 step
rotary switch, from Barry Klein's book - I spent well over 2 hours trying to
figure out WHY, I was getting a continuous 10.21VDC across my trimmer; my
tuning control and at the beginning as well as end of the 12 x 121R 1%
resistors, around the 12 step rotary switch.
I tried switching the trimmer for a pot; switching pots; switching the
2N3906.  I KNEW the LF353 dual opamp was running fine.

Almost 3 hours into bug searching, looking at Barry's schematic - I realized
I didn't have the Tuning pot, GROUNDED.

Ummm.  DUH?  :D  LOL

I'm still having a minor trouble though.  After switching the 10k/4k7
resistor divider to the 1st opamp, to give 5V from 15V instead of 10V, I
found that I STILL have to have the Tuning pot, as well as the Trimmer, set
to NO resistance, to get what I originally THOUGHT was 1 octave, between
steps 1 and 12.

Running my LFO (driving the ADSRs to the VCF and VCA), so that I could
switch the rotary TWO steps at a time (to go my Whole tone - I figured), I
found that THEN - I was going by semitone!
So originally - my 12 step rotary was giving me 1/4 scale tuning!  Haha. :D

Now - I just have to figure out the proper resistance in the entire chain,
to give me 1/12th of a V/octave per step, rather than a 1/24th. ;)

Finally though - once again after 10 years - development of my sequencer
(named Woody ;) - 10 years ago) has begun. :)

Once he's up and running, the full schematic will be posted to the webpage.

But - for anyone that has Barry's book out there - looking at the single bus
keyboard interface - could you possibly point out ANYthing that I'm doing
wrong - with minimum resistance, giving me a 1/4 octave tuning scale rather
than a normal equal temperment scale??  (Increasing resistance on the
trimmer, from 0 resistance DECREASES the amount of voltage between steps,
rather than increasing.  I'm on a break for the moment - just stumped. :( )
Help?  :)


--
Take care,
Warmth and Peace,
Ryk

http://deathlehem.bravehost.com/damian.html - D.A.M.I.A.N.;s webpage - Dec
0805 updated
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