fig. 5
two types
of overdrive
applied
to a sine
ASYM
5
control
characteristics
The linear input offers linear control, which
means the output amplitude will scale pro-
portionally to the CV (fig. 4). If you have an
exponential envelope, it’s a good idea to use
this input, because it will result in signal am-
plitude that follows the envelope, decaying
towards zero with a natural exponential tail.
Envelopes with amplitude different from 8V
can be easily used here, requiring only a small
adjustment of the knob to compensate.
OVerdrIVe OPerATION
The overdrive circuit in Tallin offers two dis-
tinctive distortion characteristics switchable
via the drive toggles. The upper, symmetric
position activates a bi-polar parabolic distor-
tion curve that equally amplifies and squash-
es both peaks of the waveform (fig. 5), yielding
a spectrum dominated by 3rd order harmonic
overtone. The resulting slightly brightened
sound is modeled after an overdriven push-
pull power amplifier.
The lower asymmetric position of the switch
activates a distortion curve that is more con-
cave in one direction while it is convex in the
opposite direction (fig. 5), yielding a spectrum
dominated by 2nd order harmonic overtone.
The resulting mellow and warm sound is
modeled after a classic single-ended tube am-
plifier. •
8
4
0
-4
-8
Output signal [V]
Time [ms]
0
2
4
6
8
10
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
MIN
MAX
BOOST
7
8
9
1
2
3
4
5
Gain [dB]
Volume knob position
fig. 2
gain vs volume knob
position with
exponential cv
and linear cv at 8v
0
1
2
3
4
5
6
7
8
9
10
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
fig. 3
gain vs exponential
control voltage
with linear control
voltage at 8v
Gain [dB]
Exponential control voltage [V]
fig. 4
gain vs linear control
voltage with centered
volume knob
position
Gain [%]
Linear control voltage [V]
8V
6.5V
expo cv =
7V
140
120
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
expo cv =
expo cv =
SYM
kno
b a
t center
positio
n
kno
b a
t 10 o
’cl
ock
