Aphex
Thermionics
- Division of Aphex Systems Ltd.
Model 1100 MkII Mic Preamp - Owner’s Manual
or from a matched impedance master clocking
distribution. Please refer to the appendix for a
thorough discussion of clock wiring and distribu-
tion systems.
When the Model 1100 MkII is operating in exter-
nal clock mode, the Clock In jack is tied directly
to the Clock Out jack through a metal relay
contact. The input impedance is high enough to
daisy-chain up to eight units by looping straight
through. The final unit should have a 50 or
75 ohm (as dictated by your distribution cable
impedance) BNC terminator plug inserted in its
Clock Out jack to properly terminate the trans-
mission line. If only one unit is connected, then
simply place the terminator plug on the single
unit’s Clock Out jack.
When the Model 1100 MkII is operating in the
internal clock mode, the Clock In jack is isolated
and unterminated. Be aware of this in case you
intend to operate in both internal and external
clock modes. You may need to terminate your
distribution cable using a tee adapter up front
instead of using the last Clock Out jack for that
purpose. Refer to figure 2-3 for illustrations of
the two most commonly used daisy-chaining
options.
2.4.2 Clock Out
As previously described, this jack is directly tied to
the Clock In jack to facilitate daisy-chaining mul-
tiple units to a master clock source when the unit
is operating in external clock mode.
When the Model 1100 MkII is operating in
internal clock mode, the Clock Out jack is discon-
nected from Clock In and instead is connected to
the unit’s internal clock source. Thus, any Model
1100 MkII operating in internal clock mode can
serve as a master clock source when required. The
internal clock is derived from a low jitter crystal
oscillator and is fully competent as a master
clock.
2.4.3 Local Clock Mastering
In the absence of a suitable external clock
source, you can use one Model 1100 MkII as a
clock master and slave everything else to it. For
example, to synchronize a group of Model 1100
MkII’s, simply set the first unit to internal clock
mode and all the others to external. Daisy-chain
the Clock Out of the first unit through the clock
ins and outs of the remaining units. This way all
digital audio outputs will be locked together to
the first unit’s clock reference. You can also loop
the clock output of the last unit in line to your
digital recorder or workstation, but remember to
terminate the last unit in line.
2.5 Audio I/O
Both preamplifier channels comprise a similar
back panel arrangement. We’ll describe channel
1 in detail then you can apply that to channel 2
as well.
2.5.1 Line Output
The phase of the Model 1100 MkII is matched
from input to output, i.e., pin 2 of the output
is of the same signal polarity as pin 2 of the mic
input jack.
Figure 2-3 Daisy Chaining the External Master Clock
Clock Source
Tee
&
Terminator
Unit 1
Unit 2
Unit 3
Unit 4
In
Out
In
Out
In
Out
In
Out
Clock Source
Terminator
Unit 1
Unit 2
Unit 3
Unit 4
In
Out
In
Out
In
Out
In
Out
Page 2-2
Back Panel Features
