6
01010111
00111110
00110101
00101011
00111001
01011100
10000000
fig. 3: the principle of a/d conversion
(offset). To achieve a bipolar output signal,
set the offset slider to a lower position, sub-
tracting some voltage from the positive-only
output of the D/A converter and making it
swing around 0V.
The D/A converter is calibrated and offers
precise 1/12V steps when the gain slider is at
maximum. A range of 256 semitones is equiv-
alent to over 20 octaves or over 20Vpp, which
may sometimes be impractical. The dac range
miniature switch
12
selects between this full
range and a narrower 10+ octave range (128
semitones) by ignoring the lowest significant
bit and scaling everything down by 1/2.
The illuminated link button
13
connects the
data arriving at the Leibniz in header at the
back as normalization signals for the bit in-
puts. Patching any cable into any DAC binary
input breaks its normalization and overrides
it with the external signal. However, with no
signals patched to the inputs, the converter re-
ceives either the bits from the Leibniz data ca-
ble (when link is engaged) or just 00000000
(when link is off). This arrangement allows
you to replace only a few bits from the in-
coming data or disconnect the DAC from the
Leibniz source entirely and use only the front
panel jacks.
THE PRINCIPLE OF OPERATION
The ADC section of Drezno II converts analog
signals to digital numbers. This process con-
sists of sampling the voltage at each clock
cycle followed by quantization of the sampled
value (fig. 3). During quantization, the value
is compared to a set of discrete levels, which
are numbered from 0 to 255. For example, if
10001111
10010110
10101101
10011011
10001010
10010011
Voltage
Code
Time
Time
the principle
of operation
quantizer
sample &
hold
Input signal
Output data
ADC clock
