US Audio whirlind Presspower 2 User manual

Thank you for selecting the U.S. Audio Presspower 2 audio
press feed distribution box. The Presspower 2 delivers
broadcast quality audio from 16 mic or line level transformer
isolated outputs. Features include a 20 segment led VU display
for quick visual level setting, a headphone monitoring section, a
tone oscillator for level calibration and a fail safe AC/DC battery
power supply for uninterrupted operation and portable use.
There are two balanced mic or line level inputs and an optional
expander unit, the Presspower 2 Expander is available with 16
additional mic or line level outputs. The Presspower 2 is a four
rack space unit and comes with a padded nylon carrying case for
portability.
INTRODUCTION
SPECIFICATIONS
Frequency Response
Input Impedance
Mic mode
Line mode
Maximum Input Level
Mic mode
Line mode
Output Impedance
Mic mode
Line mode
Maximum Output Level
Mic mode
Line mode
T.H.D.
Phase Shift
Intermodulation Distortion
Range of Level Pot
CMR of Mic Input at 60 Hz
CMR of Line Input at 60 Hz
Range of Headphone Volume Control
Isolation between Mic Outputs
Isolation between Line Outputs
Power draw
AC mode
Battery mode
(All measurements using Mic input driving all outputs)
On with no Led Meter no Headphones
On with Led Meter in Dot mode no Headphones
On with no Led Meter and 30 ohm Headphones
On with Led Meter in Dot mode and 30 ohm Headphones
Size (in Case)
Weight
Rack Unit with no Case
Rack Unit with Case
Shipping Weight Unit in Case
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
-.5 dBm 20 Hz to -2 dBm at 16 kHz
1.5 k ohms
200 k ohms
-5 dBm mic mode
+23 dBm line mode
150 ohms
150 ohms
-5 dBm into 2 k ohms
+23 dBm into 2 k ohms
.075% at 1 kHz at unity gain mic mode
-6 degrees at 1 kHz unity gain
.04% at unity gain mic mode
-60 to +20 dBm
>75 dBm at 60 Hz
>50 dBm
-60 to +20 dBm
>95 dBm
>60 dBm
31 watts maximum
mA DC battery life
40 15 hours
73 9 hours
60 10 hours
94 5 hours
20 X 9.5 X 8.5 inches
12 lbs
17 lbs
20 lbs
99 Ling Road
Rochester, NY 14612
Phone [phone] . Fax [phone]
Email: [email protected]
http://whirlwindusa.com
U.S.Audio
2
U.S. Audio has made every effort to ensure that your
equipment is received in the same perfect condition it was in
when it left the factory. Please inspect your product for any signs
of damage during shipping and report them to your dealer so
that a claim can be presented to the shipper. We recommend
that you save your packaging material for use in the unlikely
event that you need to return your equipment for service.
UNPACKING
In order to deter users from making unauthorized adjustments to the input
gain during use, the input gain controls on the PRESSPOWER 2 have
been changed from knob adjustment to adjustment by screwdriver, coin,
pocketknife etc.
If knob actuation is desired, remove the black bushings and install the
included knobs as follows. Carefully pry the edge of the bushings away
from the front panel and depress the plastic fingers that hold them in place.
The fingers are located behind the printed areas on the face of the
bushing. Rotate the control fully counterclockwise, align the knob’s pointer
with the scale and push it onto the shaft. If repositioning is required, the
knob insert must be removed separately by grabbing the rectangular top
with pliers and pulling it off. Reinstall the insert into the knob by aligning the
ridge of the insert into the knob by aligning the ridge on the insert with the
groove inside the knob behind the pointer.
INPUT CONTROL KNOB CONVERSION

1BATTERY HOLDERS contain the four 9 volt batteries in drawer style
holders. Alkaline or lithium batteries are recommended.
2POWER SWITCH turns both the AC and internal 9 volt battery power on and
off. It does not effect the rear panel DC input.
3AC POWER LED illuminates with AC power present and switched on.
4DC POWER LED illuminates when the 9 volt batteries are good and the
power switch is on, or when 12 volts DC (minimum) is present at the external
DC power input connector.
5HEADPHONE LEVEL CONTROL adjusts the volume at the headphone
jack through a range of -60 to +20 dBm. Under battery power, turn the level off
when not using the phones to prolong battery life.
6HEADPHONE JACK is 1/4“ TRS for connecting stereo headphones but will
also work with mono earpieces.
7METER ON/OFF SWITCH turns the LED display on and off when not
required which will conserve the 9 volt batteries.
8METER BAR/DOT MODE SWITCH selects bar or dot display mode so that
either all LEDs below the actual level are on, or a single LED is on at the actual
level. Use the dot mode with 9 volt battery power.
920 SEGMENT LED METER with 3 dB per segment resolution provides a
wide range display with 1 dB accuracy.
10 PHANTOM POWER SWITCH applies phantom power to both mic inputs.
Voltage is 48 VDC (AC Operation), 36 VDC (9 volt internal battery operation) or
the value of the external DC power supply.
11 TONE SWITCH applies a 1 kHz sine wave to all outputs for level
calibration during setup. The tone level is +4 dBm or 0 VU in line mode and -43
dBm in mic mode.
12 INPUT LEVEL CONTROL varies the amount of signal delivered to the
outputs. The 12 o’clock (U) position yields unity gain in either mic or line mode
with approximately 6 dB of gain adjustment 90 degrees in either direction.
Large increments of adjustment occur at both ends of pot rotation with a total
range of -60 to +20 dBm.
13 LOW CUT SWITCH activates a filter with a 24 dBm per octave slope,
down 3 dBm at 120 Hertz. This filter is recommended for mic use as it
eliminates low frequency handling and wind noise.
14 INPUT MIC/LINE SWITCH selects the appropriate circuit for the applied
signal. The mic circuit is transformer balanced with a maximum input level of -5
dBm. The line circuit is actively balanced with a maximum input level of +35
dBm.
15 INPUT XLR female connector is RF filtered with pin 2 positive.
16 OUTPUT 3.5 MM JACK is wired positive signal to tip and negative to ring.
Do not use this and the XLR output simultaneously.
17 OUTPUT XLR male connectors are transformer isolated and ground lifted
from each other, pin 2 is positive.
18 OUTPUT MIC/LINE SWITCH selects the signal level at each output. Mic
level is 43 dBm below line level.
19 OUTPUT EXPANDER PLUG for connection of the Press 2XP 16 channel
expander module. The unit is connected through a 6 pin right angle
switchcraft R6M.
20 EXTERNAL DC INPUT PLUG allows attachment of batteries or regulated
DC supplies from 12 to 36 VDC to power the unit.
21 EARTH LIFT SWITCH disconnects the AC chassis ground from the audio
common and is sometimes useful in reducing hum.
22 UNIVERSAL AC INLET for attachment of the AC cord.
23 VOLTAGE SELECT SWITCH allows use with 120 VAC 60 Hz or 230 VAC
50 Hz.
CONTROLS AND FUNCTIONS FRONT PANEL
U.S.Audio
PressPower Expander Module
17-32
OUTPUTS
0dB IN = -43dB MIC LEVEL OUT
17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32

The Presspower 2 has two balanced inputs, each switch selectable for mic or line
level signals. In mic mode, a Bauer RE115Kepc mumetal shielded transformer
provides low distortion, impedance gain of 18 dB and high common mode
rejection. Faraday shields in the transformer and RF beads used at the input XLR
offer broadband RF rejection. Capacitors are also used for AM band rejection. A
phantom power switch applies DC power to both mic inputs simultaneously. The
value of the phantom voltage is dependent upon the type of power source
energizing the Presspower 2. In line input mode, the mic preamplifier transformer is
bypassed and an active balanced input is employed. The line input is capable of
receiving signals up to +23 dBm.
From each input circuit the signal is applied to a potentiometer circuit that has an
audio like taper, allowing fine tuning of the level from the 9 o’clock through the 3
o’clock range. The 12 o’clock position yields unity gain in either mic or line mode
with approximately 6 dB of gain adjustment 90 degrees in either direction. Below
the 9 o’clock position, the potentiometer attenuates the signal in larger increments
and fully counter clockwise the attenuation is 65 dBm which will mute the input.
Above the 3 o’clock position, gain increases rapidly up to + 20 dBm with the control
turned fully clockwise. After the gain circuits, the signal passes through a
switchable low cut filter. The filter has a 24 dBm per octave slope, down 3 dBm at
120 Hertz. This filter is recommended for mic use as it eliminates low frequency
handling and wind noise.
The inputs signals are then summed and applied to two separate output busses,
one for mic level outputs and one with an additional 20 dB of gain for line level
outputs. The line level feed also is applied to the headphone monitor section and
the LED level display. The mic and line level busses are routed to the active jack
boards via a balanced cable harness with plug terminations. The Expander
receptacle is also connected at this point in the circuit.
At each of the 16 outputs of the Presspower 2 or its expander module, the
mic/line switch selects the mic level or the line level signal buss and delivers it to a
buffer circuit which drives a whirlwind TRSP-1 balancing transformer. In mic output
mode a resistive H pad is switched into the circuit to attenuate the signal by 20 dB.
The H pad also provides a ground reference relative to pins 2 and 3 of the XLR, but
not connected to any other ground, which minimizes possible ground loop
problems. In line output mode, pin 1 of the output XLR is left floating. A 3.5 mm
mono jack is provided for each output.
The tone oscillator applies a 1 kHz sine wave to all outputs for level calibration
during setup. The tone level is +4 dBm or 0 VU in line mode and -43 dBm in mic
mode.
The headphone driver circuitry provides monitoring of the Presspower 2 output.
Each earpiece is powered by a separate amp circuit ensuring that Tip/Sleeve
headphone connectors (which short the ring) will not short out the entire signal. The
headphone amps are capable of driving 0 dB into 30 ohm headphones, which can
significantly reduce battery life. When only using battery power, turn the
headphone level full counter clockwise or unplug the headphones to conserve the
batteries. The taper of this level control is similar to the control on the inputs.
A 20 segment LED level meter with a 3 dB per segment resolution provides a
wide range of display with 1 dB accuracy. Two switches are provided to help
maximize battery life when using 9 volt battery power. Under battery power only
select dot mode to calibrate levels and use the meter on/off switch to turn the LED
display off when not required. Use the bar mode when the Presspower 2 is under
AC power.
The Presspower 2 has a versatile unipolar power supply allowing the unit to
operate from 120 VAC 60 Hz, 230 VAC 50 Hz, 4 internal 9 volt batteries or any
battery or regulated DC source from 12 to 36 volts. Any combination of the three
types of power can be used simultaneously. The unit will automatically select the
highest voltage, providing fail safe backup and making it easier to power in remote
applications. Under AC power a toroid power transformer is used internally for
superior performance and a voltage switch on the back panel selects 120 or 230
VAC. Nine volt batteries are mounted on the front panel in convenient quick change
holders. An external DC input (screw type) on the back panel will accept 12 to 36
volts DC, from either batteries or a regulated source. This allows use with camera
belt packs, car batteries, etc. At 12 volts DC with a -40 dB mic input and 40 dB of
gain, the Presspower 2 will ouput up to +8 dBm in line mode.
The power on/off switch turns both the AC and the internal 9 volt battery power on
and off. The external DC input on the back panel is unswitched. The AC LED
illuminates when AC power is present and is switched on. The DC power LED
functions as a battery check LED for the 9 volt batteries and illuminates when 12
VDC or more is present at the external DC power input. With no external DC, the DC
LED will light when the batteries are good and the power switch is on. When the total
series voltage drops below 27 volts the DC LED goes out and all four batteries
should be changed.
THEORY OF OPERATION
BLOCK DIAGRAM