Doepfer A-152 Voltage Addressed Track&Hold / Switch (Multiplexer) / Digital Outputs - Manual (Page 9)

doepfer System A - 100
Voltage Addressed T&H/Switch A-152
9
trigger the advance to the next address of the A-152.
The trigger delay connected between the gate source
and the clock input of the A-152 is required because of
the timing between the positive transition of the gate
signal and the CV change. The T&H has to take over
and store the CV not before the CV is stable. Otherwise
the result will not meet the expectations. As the time
correlation between the gate transition and the CV
change may vary the A-162 is used to solve problems
that may arise from this. Ideally the gate transition and
CV change happens exactly simultaneously, but "simul-
taneously" is a problem in the real world as there are
always some delays in the micro/millisecond range that
may cause problems (e.g. the MIDI-to-CV interface or
sequencer of manufacturer #1 generates the gate transi-
tion 200us before the CV change but for manufacturer
#2 the behaviour is reverse and the delay is 500 us). To
avoid such problems the A-162 is used. First the trigger
length is adjusted so that the A-152 triggers correctly. If
the width is too short the A-152 may not trigger or the
step advances are uneven. After that the delay time is
adjusted so that the CV values appear sequentially at
the T&H outputs of the A-152 as expected. Usually the
A-162 settings will be close to the left-most positions of
the controls for delay and length.
In the example the digital output five is connected to the
reset input of the A-152 to limit the number of outputs to
four.
The four VCO outputs can be mixed in an A-138 before
the subsequent signal processing (VCF,VCA,ADSR ...).
But even each VCO outputs can be processed separa-
tely. In this case the digital outputs of the A-152 may be
used to trigger the envelope generators that are assi-
gned to the corresponding VCO.
The number of outputs can be decreased or increased
by connecting the reset input to another digital output.
A special case is the limitation to two outputs. This leads
to the function of the toggling S&H unit of the Buchla
module 266 Source of Uncertainty. The only difference
is that the Buchla module contains two S&H instead of
two T&H. If an A-148 S&H is connected between the CV
source and the A-152 the functions are identically.
Another solution is to modify the A-152 so that the T&H
section works as S&H. For details please refer to the
DIY page on our web site www.doepfer.com.