a-188-2 tapped bbd module
price : $290.00
a-188-2 is another module that is based on a so-called bucket brigade device (bbd). if you are not familiar with bbds please refer to the
a-188-1. there you can find some details about this special type of circuits.
the main difference between a-188-1 and a-188-2 is the type of bbd circuit that leads to completely different
module principles and sounds. the a-188-1 uses different single bbd chips with one signal input and one signal
output only. in contrast the a-188-2 uses as so-called tapped bbd that has available six outputs - the so-called taps after the bbd stages
396, 662, 1194, 1726, 2790 and 3328. in the a-188-2 we use this special bbd circuit (mn3011) to obtain these module features:
the module has available two separate mixing sub-units. for both mixers the levels and polarities of each bbd output can be adjusted to
obtain two different mixtures of the bbd outputs. a new type of potentiometers with center detent and center terminal is used for the bbd
mixing controls to have a better feel for the neutral position. each mixer has a wet/dry control at its output that allows choosing between
the pure input signal (original), the bbd mix or anything in between. the two outputs can be treated as stereo outputs but it is also
possible to use one of the outputs for other applications (details in the next paragraph).
the a-188-2 has a feedback section available that is very similar to the one in the a-188-1. but as we now have 6 different bbd outputs
available 6 different feedback types are possible. the feedback input socket is normalled to the "396" output (not to "1194" as shown in
the scheme, the front panel is correct). but by patching the feedback socket to any of the single output sockets another bbd tap can be
used for the feedback to obtain different sounds. even external feedback processing is possible (e.g. with a vca for voltage controlled
feedback). the feedback control has polarizer function, i.e. the neutral position is at the center. left from the center the feedback
signal is subtracted from the input signal, right from the center it's added (negative/positive feedback). even for this potentiometer the
new version with center detent is used.
a special feedback can be obtained if one of the mix outputs is used for the feedback function. in this case for each tap the positive or
negative feedback share can be adjusted. this leads to multiple peaks and/or notches in the frequency response of the module.
for each tap of the bbd a separate output socket is available. these sockets can be used for changing the feedback loop - as mentioned
above -, for voltage controlled mixing of the taps - e.g. with the voltage controlled mixer a-135 or other
applications that require access to each single tap.
the a-188-2 uses the same high speed vco (hsvco) for the bbd clock as the a-188-1. the clock and consequently the
delay time can be controlled manually (delay control) and by the two control voltage inputs cv1 and cv2. the sensitivity of cv1 is
approximately 1v/oct. cv2 is equipped with a polarizer (the new type of potentiometers with center detent too). the hsvco has a clock
output available that is normalled to the clock input socket. these sockets can be used to link different bbd modules and to run them with
the same clock. but even other applications with frequency dividers (e.g. a-163) or pll (e.g. a-196) are conceivable. a voltage composed of the manual delay control, cv1 and cv2 is available at the cv out socket,
e.g. to control an external clock suppression filter as the a-188-2 is not equipped with such a filter (same as for the a-188-1).
this module has a maximum current draw of 120ma. it requires 30 hp/te worth of space to fit in a eurorack frame.