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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

1027.0. "Yamaha SPX90 - Triggering Loops In FX Unit" by PLDVAX::JANZEN (Tom LMO2/O23 DTN296-5421) Tue Nov 24 1987 18:20

    Hi.
    If you wanted to trigger an SPX-90 so that it could have
    variable loop lengths (it's fixed) what would you use?
    a drum machine; a cz101 playing a clock; a sequencer;
    a threatening gesture.
    
    I'll have to read the midi part of the manual to make better
    guesses.
    Tom
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1027.1solvecPLDVAX::JANZENTom LMO2/O23 DTN296-5421Mon Nov 30 1987 17:2824
No one replied with an answer on making the SPX-90 do variable length
loops. 
Well, I made it work with gear on hand and not using MIDI.
I used the first sample program.  Now, using "trigger in", and triggering the
foot pedal input will start the sample, which
is now 2 seconds with the memory upgrade.  So, I could just hit the
pedal periodically to restart the sample and get variable loops.
Better, I could build a 555 timer-based oscillator with potentiometer-
controlled period down to about .5 Hertz, and open-collector buffer. 
What I actually did was a kluge, until I build the oscillator next weekend.

My little electronic metronome has an earphone jack.  I cabled this into the
PAiA multi-filter, tweaked for low pass to pick out the lower metronome tone
(in 2/4 time, the metronome has two pitches of tones alternating).
The reason I picked of alternate tones was that the metronome only goes down
to 40 and I needed 30.  So by setting it to 60 I got 30.
Anyway, the lowpass output of the filter was sent to the PAiA envelope follower.
(a precision rectifier just like the one in the National Semi Linear Handbook).
The fast pulse output of the envelope follower was sent directly into the 
SPX90.  It worked.  The SPX90 now played its sample to a variable
xtal-controlled metronome.  If I deselected "trigger in" the metronome made 
the spx cycle through all of its programs.  So I had to remember to stop
the metronome during sampling or program changes.
Tom Janzen Digital Equipment 111 Locke Marlboro MA 01752
1027.2onward and offwardANGORA::JANZENTom LMO2/O23 DTN296-5421Mon Dec 28 1987 16:457
    Last night I built a little circuit with a 556 (dual 555)
    timer that triggers the spx90 regularly, but the timing isn't
    variable, so I'll try to make that work tonight.
    The purpose of this was to make the spx90 have a variable repeat
    loop duration.
    I imagine it's publishable somewhere EM or KB.
Tom
1027.3success, eliminate PAiA h/w hackPLDVAX::JANZENto cogitate and to solveTue Dec 29 1987 11:545
    It works.  My 556-based low frequency oscillator (.5 Hz to 10 Hz)
    plugs into the foot pedal jack and triggers the sample program
    on regular intervals.  This makes a variable loop duration,
    which the spx90 doesn't intrinsically have.
    Tom