Mic-PreEminence User Guide
Issue 5, April 1994
Studio Technologies, Inc.
Page 11
to output circuit offset. This should not pose
a problem for most devices connected to
the Mic-PreEminence line outputs. In the
unlikely case that capacitor coupling of
an output stage is required, the two 0 ohm
resistors can easily be removed, placing
the coupling capacitors in the circuit.
Detailed instructions for enabling the output
capacitors can be found in Appendix B.
Replacing the 0.33uf Capacitors
The coupling 100uf electrolytic capacitors,
as previously mentioned, are paralleled with
0.33uf stacked, metallized film type capaci-
tors. We feel that this provides an excellent
coupling characteristic. Other people in
the audio industry feel that polypropylene
capacitors “sound” better than other types,
including the film type we chose for the
Mic-PreEminence. Our egos are not tied
to the parts we chose so we welcome you
to select the parts you feel most confident
about. We have no problem with qualified
technicians replacing the stock film type.
Refer to Appendix C for detailed instructions
on replacing the 0.33uf capacitors.
RF Problems and Solutions
Because the Mic-PreEminence is a wide
bandwidth device, there may be cases
where radio frequency signals can get into
its circuitry via the microphone input. So
as not to penalize the many for the few,
the Mic-PreEminence does not include any
overt RF suppression circuitry. We want as
little done to the input signal as is required.
It is possible to implement a low pass filter
by adding inductors in series with the input
signal. Only if there is an RF problem
should this action be taken. Refer to
Appendix D for detailed instructions.
Level Designators
Studio Technologies, Inc. has opted to use
the dBu designation as it seems to be quite
rational. Using dBm was fine when all audio
line outputs were terminated with 600 ohm
loads. In this way it was easy to say that
0dBm is 1 milliwatt dissipated in the known
load (i.e., 0dBm across 600 ohms will
measure 0.7746V). In contemporary
applications, an output is rarely terminated
in 600 ohms. Generally, 5k ohms or higher
is used. The dBu designation is a better
reference because it refers to dB refer-
enced to 0.7746V, with no reference to load
impedance. This takes into account the
current audio scene with load impedances
varying greatly. When the Mic-PreEminence
specifications refer to the clipping output
level in dBu, this would translate to dBm
only when the output is terminated with
600 ohms.
The unbalanced line output level is
specified in dBv, as is common with “–10”
equipment. The dBv refers to dB refer-
enced to 1V, in contrast with dBu that is
referenced to 0.7746V. So if you measure
+4dBu on the balanced output you will
measure –7.8dBu on the unbalanced out-
put. This –7.8dBu corresponds to –10dBv.
Got it?!
Circuit Description
General Information
The following paragraphs describe the
circuitry of the Mic-PreEminence. This
information will help you understand how
the unit works and, if required, help identify
