Aphex
Thermionics
- Division of Aphex Systems Ltd.
very well in any studio wiring scheme because its
output is impedance balanced. However, should
you experience chronic hum problems around
your studio, you may want to consider rewiring
with our recommended grounding practice.
4.6 Using Purchased Adapters & Cables
You may sometimes have trouble using the vari-
ety of connector adapters available through audio
pro shops, though
most of the time
they will work
extremely well.
If you get hum
or no signal, use
an ohmmeter or continuity tester to be sure they
are wired according to the diagrams of this sec-
tion. Some adapters are built with the outdated
“pin-3 hot” practice which will not always work
with the Model 1100, especially when converting
to an unbalanced output. If you are in the prac-
tice of using standard mic cords (which are wired
according to 4.1) for general purpose intercon-
necting of equipment, then the shield ground
will flow through connecting both pin 1’s. That
will violate the rules we have been outlining here,
but don’t despair. You probably won’t experi-
ence any problems. If hum or interference does
appear, simply try cutting the shield wire from
the sending end of the cable.
4.7 Checking For Output
If, for some reason, you think there is no output
from the Model 1100 MkII even though signal
is indicated on the Headroom Meter, check the
insert jacks. If they are not used, then the signal
should pass through. If the Return jack has a
plug inserted, be sure a signal is getting back to
the 1100 MkII from the external equipment. In
the event all of this seems ok, then be sure the
output cable is correctly wired. There should be
no troubles using balanced lines, but if you are
feeding an unbalanced input, then be sure you
have the 1100 MkII’s output wired as pin-2 hot,
not pin-3.
4.8 Matching The Levels
Audio equipment interface
levels can vary within the
same room. The Model 1100
MkII
accommodates
both
pro and consumer operat-
ing levels by providing a
normal level switch on the back panel.
4.9 Mute Function Wiring
The rear panel mute jack accepts either a mono
or stereo phone jack. Refer to section 2 on Back
Panel Features for wiring diagrams and instruc-
tions for use.
4.10 Insert Jacks
The 1100 MkII’s rear panel send and return jacks
are intended to allow you to insert a compres-
sor or other processing device between the mic
preamp and the A/D converter and line output
stage.
The send output is impedance balanced and
can therefore be readily wired out as balanced
or unbalanced. The operating level is typically
around 0dBm but may run hotter if you are run-
ning the preamp gain high enough to consistently
push MicLim. If you desperately need an auxilliary
audio output, you can plug into the send jack
without breaking the 1100’s signal path. Just be
aware that you can potentially introduce noise or
distortion into the A/D converter and the main
analog output if your interception is not clean
and free of loading.
Inserting a plug into the return jack breaks the
1100 MkII’s internal signal path and gives you
the entry point to the A/D converter and line
output stage. The return input is semi-balanced,
meaning it accepts a balanced input but is not
fully balanced electronically. Usually, outboard
equipment used with the 1100 MkII’s insert will
be located nearby, so hum or buzz will never
become a problem.
It is imperative that you adjust your external
equipment’s output level to return an acceptable
level to the 1100 MkII. The worst problem you
can encounter is overdriving the A/D converter
with too much level. You can use the 1100 MkII’s
headroom meter to verify. It monitors the signal
received at the return jack whether from the
normal circuit or external equipment. Make sure
you never drive the peak headroom meter all the
way up to 0 from external equipment. When run-
ning without an insert, the 1100 MkII automati-
cally protects the A/D converter from overdrive
and hitting 0 on the meter will cause no harm
other than potential distortion.
Page 4-2
Interfacing & Cables
