Doepfer – Doepfer A-100(~ 40 MB) User Manual

Page 633

DOEPFER

System A-100

BBD Module A-188-1

The position of the polarity switch 9 defines if the normal or
the inverted BBD signal is mixed to the original signal
(please refer to page 6 concerning this function). Especially
for short delay times the position of this switch leads to
clearly audible different sounds. In the middle position of the
switch the BBD share of the mixed signal is off and only the
original signal is heard. Consequently the switch can be
used to turn on/off the BBD effect at the mix output $.

(

Ext.FB In:

external feedback input

Feedback:

feedback level control

Polarity:

feedback/BBD Out polarity

This group of elements is responsible for the feedback
functions of the module. Socket ( Ext.FB In is the input of
the feedback loop and is normalled to socket ) BBD Out. If
an external module is used to control the feedback loop
(e.g. a VCA or VC polarizer) the module has to be inserted
between socket ) BBD Out and socket ( Ext.FB In. The
polarity switch 8 controls the polarity of the signal appearing
at the socket ) BBD Out and consequently the polarity of
the feedback signal. In the center position of switch 8 the
signal at socket ) BBD Out is off and no feedback is active.
Consequently the switch can be used to turn on/off the
feedback effect. The polarity of the feedback signal leads to
clearly audible different sounds at short delay times. For
longer delay times ("analog delay" application) the sound
differences are much smaller (for details please refer to
page 6).

Knob 4 Feedback adjusts the feedback level. In the left/ccw
position of the knob no feedback (or resonance/emphasis) is
added. As the knob is turned right/clockwise feedback
occurs. In the fully right/cw position the module goes into
self-oscillation. As already mentioned in chapter 2 the result
in the self-oscillation state depends upon the "audio history"
(for details please refer to page 6). Both the self-oscillation
behaviour and the "smoothness" of the feedback also
depend upon the BBD circuit used in the module (128/256
... 4096 stages).