Studio Technologies M233-01151 User Manual

User Guide

Mic-PreEminence

Microphone Preamplifier

Issue 5, April 1994

© 1994 Studio Technologies, Inc.

5520 West Touhy Avenue

Skokie, Illinois 60077 U.S.A.

Telephone [phone]

Fax [phone]

www.studio-tech.com

50101-494, Issue 5

Table of Contents

Quick Guide to Using the Mic-PreEminence ............................... 5

Introduction.................................................................................. 6

Installation.................................................................................... 7

Operation..................................................................................... 8

Technical Notes...........................................................................10

Circuit Description........................................................................11

Troubleshooting...........................................................................13

Appendices
Appendix A

Specifications .........................................................................16

Appendix B

Enabling the Output Coupling Capacitors ..............................1 7

Appendix C

Replacing the 0.33uf Coupling Capacitors .............................17

Appendix D

Solutions for RF Problems .....................................................18

Studio Technologies Limited Warranty........................................19

Schematic Diagrams.........................................Not included in PDF

Mic-PreEminence User Guide Issue 5, April 1994
Studio Technologies, Inc. Page 3

Quick Guide to Using the
Mic-PreEminence

Connect your selected Mic-Pre-Emi­nence line outputs to the line inputs of
the next device.

All of us get in a hurry to use a new device.
Studio Technologies, Inc. wants you to fully
understand how best to use the Mic-Pre­Eminence. First we’d like you to read this
long and highly exciting manual. If you’ve
already read the manual and want to re­fresh your memory, here’s a quick run
through on how to get things going:

1) Check the back panel to see if the AC
mains voltage selected is correct for
you, 115V or 230V. A 0.5A fuse should
be in place for 115V; 0.25A for 230V.

2) Plug in the power cord and turn on the
power switch, located on the front
panel.

3) On front panel: Turn phantom power
switch to the ON position if +48V phan­tom voltage is required. Set the phase
reverse switch to NORMAL, and set
gain control to MIN gain (fully counter­clockwise). Do this for each channel.

4) Using shielded, low capacitance micro­phone cable, connect a microphone to
the microphone input connector on the
back panel. Do this for each channel.

5) Each channel contains two line outputs,
balanced and unbalanced, which are
located on the back panel. The bal­anced outputs use 3-pin, XLR-type
connectors with pin 2 high and a nomi­nal output level of +4dBu. The unbal­anced outputs use monaural ¼-inch,
2-conductor jacks (tip and sleeve), and
have a nominal output level of –10dBv.

6) Careful! Turning the phantom power
switch on or off, or the power switch
on or off, can produce a large amplitude
spike in the line outputs. Protect your
ears, speakers, and equipment by
being careful while the Mic-Pre-Emi­nence line output is connected to an­other piece of equipment.

7) With signal going into the microphone,
adjust the Mic-PreEminence gain con­trol to give the desired output level. The
LED meter can provide assistance in
setting the level. The meter is designed
to have characteristics somewhere
between that of a VU meter and a peak
(PPM) meter. It is strictly a reference
and shouldn’t force you into setting the
gain to give a “standard” reading on the
meter. Even if the red LED is lighting on
peak signals, you are most likely still far
from the Mic-PreEminence’s clipping
point; the red LED lights approximately
18dB below clipping!

8) Watch the gain setting! Most equip­ment connected to a Mic-PreEminence
line output will clip well before the Mic­PreEminence will. Example: your tape
recorder may be distorting on peak
signals even though the Mic-Pre-Emi­nence isn’t. This is because the tape
recorder input is being overloaded with
too much signal. Turn down the Mic­PreEminence gain control until the
distortion stops.

9) Enjoy the great sound!

Mic-PreEminence User Guide Issue 5, April 1994
Studio Technologies, Inc. Page 5

Introduction

General Description

The Mic-PreEminence is a high­performance, two-channel microphone
preamplifier. The Mic-PreEminence, with
its low noise, low distortion, and high
speed design provides a level of technical
and sonic performance that is virtually
unmatched. As a complete, stand-alone
unit, the Mic-PreEminence is applicable
for studio and location recording, digital
sampling, live broadcasts, and sound
reinforcement.

Features

• Two independent preamplifier channels

• +48Vdc phantom power, switchable
on/off

gain, unlike the characteristics of most
console mic preamplifiers. We use superior,
high-performance circuits not found in other
audio equipment. By building a dedicated
microphone preamplifier, we were not
hampered by the cost restrictions that
console manufacturers have. We think that
the result is an incredibly great sound and
excellent specifications.

Additional Note From the Designers

This issue of the Mic-PreEminence instruc­tion manual covers a new and improved
version, the Mic-PreEminence Second
Edition. We are gratified with the response
we’ve received about the original unit over
the past few years. We’ve heard some
fabulous recordings that were made by
excellent engineers, along with assistance
from the Mic-PreEminence. Keep up the
good work!

• Dual, 5-segment LED level metering

• Output phase reverse switch

• Selectable balanced or unbalanced
outputs

• Adjustable gain range, +12dB to +68dB

• Electronically balanced input and output
circuitry

Note From the Designers

The Mic-PreEminence was designed by
James Cunningham with help from Gordon
Kapes, Mitch Budniak, and Phil Sutterlin.
When designing the Mic-PreEminence, our
goal was to produce a transparent, clean
sound. We were not shooting for specs, but
rather for great sound. We knew that if we
achieved the sound, the specs would be
there. We wanted nothing added to or
subtracted from the original signal besides

Changes were made for three reasons:
improve reliability, enhance unbalanced
operation, and provide better level meter­ing. For reliability, zener diodes were added
to the input circuitry to prevent overvoltage
spikes from damaging the circuitry. These
diodes do not hurt the sound in any way.
They only kick in at very high signal levels,
levels that are not present in any normal
microphone input signal. They are espe­cially helpful in minimizing the spikes that
are created when the phantom power
switch is turned on or off.

To make using the Mic-PreEminence’s line
outputs more convenient when interfacing
with unbalanced “–10” equipment, a sepa­rate unbalanced output with nominal signal
level of –10dBv has been added to each
channel. The unbalance switches have
been replaced with output select switches.

Issue 5, April 1994 Mic-PreEminence User Guide
Page 6 Studio Technologies, Inc.

They select if signal will be present on the
balanced outputs (XLR connectors), or on
the unbalanced outputs (¼-inch, 2-conductor
monaural jacks). The nominal level of the
balanced outputs is +4dBu, unbalanced is
–10dBv.

Level monitoring has been improved by
going to 5-segment level meters, instead
of the original signal present and clipping
LEDs. The meter ballistics are designed
to give a combination of VU and peak
performance.

We hope you like the improvements!

Installation

Mounting

The Mic-PreEminence is rack-mountable,
requiring one 1.75-inch (4.5cm) rack space.
It weighs a bit over four pounds (1.9kg),
and operates on AC mains power of either
nominal 115Vac or 230Vac.

Locating the Unit

It is a good idea to keep the
Mic-PreEminence physically separated
from other electronic devices that produce
electrical fields. As a high gain device,
hum and noise pickup is possible through
the chassis and associated cabling. Locating
the unit away from power amplifiers, power
transformers, lighting controls, etc., will
help to avoid pickup of unwanted signals.
If the Mic-PreEminence is mounted in a
rack, be sure that sonic “garbage” is not
being picked up from nearby equipment.

Connecting the Unit to Power

The Mic-PreEminence may be operated
from mains power of either nominal 115Vac
or 230Vac, 50/60Hz. Units shipped to North
America are factory selected for 115V
operation and are supplied with a 0.5A 3AG
fuse and a power cord. Units shipped out­side North America are factory selected for
230V operation and are supplied with a

0.25A 5x20mm fuse. No power cord is
supplied with those units. Your dealer or
distributor will provide an AC mains cord.
Before connecting the Mic-PreEminence
to power, determine the actual line voltage
and check to see that the voltage selector
switch (located on the back panel of the
unit) is set to the appropriate voltage.
Please note that an incorrect setting could
seriously damage the unit. Should it be
necessary to change the voltage selection,
ensure that the correct fuse value is used:

0.5A for 115V, 0.25A for 230V.
The Mic-PreEminence uses an IEC

standard connector to mate with the AC
mains cord. The wire colors in the AC mains
cord should conform to the internationally
recognized CEE color code and must be
wired accordingly:

Connection Wire Color
Neutral (N) Light Blue

Live (L) Brown
Protective Earth (E) Green/Yellow

Signal Connections

All signal connections on the
Mic-PreEminence are made via 3-pin,
XLR-type male and female connectors, and
¼-inch, 2-conductor monaural jacks stan­dard to the audio industry. The microphone
input connectors are female, the balanced

Mic-PreEminence User Guide Issue 5, April 1994
Studio Technologies, Inc. Page 7

line output connectors are male, and the
unbalanced output connectors are female.
The Mic-PreEminence conforms to the
world standard for 3-pin audio connectors:
pin 1 shield, pin 2 signal high, pin 3 signal
low. This standard is especially applicable
for the Mic-PreEminence as most recording
studio quality microphones conform to this
standard. Pin 1 on the four XLR-type audio
connectors and the sleeves of the two
¼-inch, 2-conductor jacks are connected in
common with power supply common, chas­sis ground, and power cord ground.

Operation

Using the Controls and Meters

There are five switches and two gain
controls on the front panel of the Mic-Pre­Eminence. There are two switches on the
back panel.

Power Switch

The power switch controls the AC mains
to the unit. Power can be applied to the
Mic-PreEminence continuously without
adverse effects. Energy conservation
practices dictate applying power only as
required; think green! When power is
switched on or off, high level audio “pops”
on the output connectors are likely. This is
a function of the DC power sources turning
on or off to the Mic-PreEminence circuitry.
Care must be taken to ensure that these
“pops” do not damage equipment or ears
associated with the Mic-PreEminence
outputs.

Phantom Power Switches

Each channel contains a phantom power
switch. When this switch is in the ON
position, +48Vdc is applied via 6.81k ohm
resistors to pins 2 and 3 of the associated
microphone input connector. This +48Vdc
power should allow virtually all phantom
powered microphones to work correctly.
Microphones that require high start-up
current, such as the Neumann TLM 170,
will operate correctly. When using micro­phones that do not require phantom power,
the phantom power switch should be left in
the OFF position. When phantom power is
switched on or off, high level audio “pops,”
several seconds of hissing noise, or other
strange sonic gyrations on the line outputs
are possible. Care must be taken to ensure
that these noises do not damage equip­ment or ears associated with the Mic-Pre­Eminence line outputs. The level meter
LEDs will light for a few seconds when
applying or removing phantom power. This
is due to leakage current coupled through
the input capacitors to the input semicon­ductors. This is completely normal and does
not indicate any Mic-PreEminence prob­lems. After the current dissipates, the lights
resume their normal function and the nor­mal sonic cleanliness returns.

Output Phase Switches

The output phase switch associated with
each channel reverses the relative phase
(input versus output) of both the balanced
and unbalanced outputs. For the balanced
output the switch reverses the connections
to pins 2 and 3 of the output connector.
For the unbalanced output the switch
changes the point in the circuitry where the
unbalanced output obtains its signal. In the

Issue 5, April 1994 Mic-PreEminence User Guide
Page 8 Studio Technologies, Inc.