| 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
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| 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
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