Whirlwind PA1 User manual
CIRCUIT DESCRIPTION
MPLIFICATION SYSTEMPERSONAL A
The whirlwind PA-1 is a high quality, portable stereo headphone
amplifier designed to deliver superior sonic accuracy in any audio
monitoring application. High output level combined with very low
distortion make the PA-1 suitable for critically listening to all
professional audio sources in any environment. The PA-1 accepts
both balanced and unbalanced stereo line level signals through
paralleled XLR and 1/4” TRS inputs. A switch changes the input
configuration from separate balanced stereo inputs to unbalanced
TRS (ring-right/tip-left) for sources such as headphone jack outputs.
Power is supplied by two nine volt batteries that load into easy access
drawers or an external AC supply which is included.
®
RIGHT
LEFT
INPUT MODE
BALANCED L/R
T=PIN 2=+
R=PIN 3=
UNBAL STEREO
T=PIN 2=L
R=PIN 3=R
ALL JACKS
PARALLEL
20 dB PAD SWITCH
STEREO
LEVEL
CONTROL
PAN
STEREO/
MONO
HEADPHONE
1/4” TRS
1/8” MINI
The PA-1 accepts line level inputs and will monitor both separate
balanced left and right feeds and unbalanced stereo signals on a
single connector. Each channel has a female XLR and a 1/4” TRS jack
that are parallel wired with pin 2 wired to tip, pin 3 wired to ring and pin
1 connected to shield. This feature allows for loop through operation
with commonly available adapter cables. The input mode select switch
changes the input wiring from balanced left and right to unbalanced
stereo. The XLR and 1/4” jacks are all paralleled together in
unbalanced stereo mode. After the input hardware the audio can be
attenuated by 20 dB by applying the pad. Signals are then routed to
balanced buffers and the stereo gain circuit. Volume is controlled by a
dual gang potentiometer, which provides a gain range of -60 to +15
dBm of gain. The volume control has an audio type taper from the 9
o’clock to 3 o’clock positions with larger amounts of gain and cut at
the extremes (above 3 o’clock and below 9 o’clock). The stereo signals
then go through a standard audio taper pan potentiometer, for
balancing the signal in the two earpieces. The stereo/mono switch,
when in mono, allows the PA-1 to be used as a two mix monitor. In
mono mode, the pan pot serves as a mix control adjusting the blend of
the two input sources in both ears. The output drivers of the PA-1 are
capable of delivering high sound pressure levels with low impedance
headphones. Turn the volume control down before putting on
headphones to prevent accidental ear damage. Both 1/4” and 1/8”
jacks are available on the PA-1 for use with all types of headphones.
The PA-1 is powered by 2 nine volt batteries or the supplied PS-24 wall
power supply. When using the PS-24, the batteries are automatically
disconnected.
WARRANTY
This product is guaranteed to be free from defects in materials and
workmanship to the original purchaser for a period of (2) years from
the date of purchase. Should service be required, return the unit
postage prepaid along with the original sales receipt to:
whirlwind
Attention - Repair
99 Ling Road
Rochester, New York 14612
The warranty on this product shall not apply to defects or damage
resulting from abuse, abnormal use or from repairs or modifications
performed by anyone other than whirlwind. If it is determined a
manufacturing defect has occurred, whirlwind will repair or replace the
unit at our option and pay the postage back to you.
WARNING
THIS UNIT IS CAPABLE OF DELIVERING
HIGH SOUND PRESSURE LEVELS.
PERMANENT HEARING LOSS CAN RESULT
FROM EXPOSURE TO VERY LOUD SIGNALS.
MAKE SURE TO TURN THE VOLUME DOWN
BEFORE CONNECTING HEADPHONES.
SPECIFICATIONS
CONTROLS AND FUNCTIONS
Frequency Response
Input Impedance
Maximum Input Level
Output Impedance
Maximum Output Level
Rise Time
Headphone Impedance
Noise
Stereo Separation
Range of Gain Controls
T.H.D. +N
Power Consumption AC
Adapter
Power Consumption Batteries
Stereo Tracking
C.M.R.R. of Inputs
Weight
Size
-2.5 dBm at 20 Hz
-.4 dBm at 20K Hz
+3 dBm 17-61K Hz
20K ohm with PAD off
200K ohm with PAD on
+20 dBm with PAD off
+40 dBm with PAD on
10 ohms (headphone)
+10 dBm into 30 ohm
headphones
+18 dBm into 10K load
5.6 u S
30 ohm minimum
Battery power -84 dBm full up 100 dBm full down
PS24 power -88 dBm full down
-83 dBm full up
68 dBm at 1K Hz / 45 dBm at
20K Hz
-60 to +15 dBm
.006% at 1K Hz
<.055% 20-20K Hz
35 mADC idle, 105 mA full
clean in 30 ohms, 148 mA full
clip
25 mADC idle / 60 mA full clean
in 30 ohms, 80 mA full clip
1 dBm from 9 o’clock position
to full CW
74 dBm at 60 Hz
1.22 lbs. with batteries
6” x 3 7/8” x 2 1/8”
1. MONO/STEREO SWITCH allows selection of either stereo or mono
operation. In mono mode two separate inputs can be mixed in
conjunction with the balance control.
2. PAD SWITCH attenuates the input -20dB when applied to the
circuit.
3. VOLUME controls the amount of signal that is delivered to the
headphones.
4. POWER LED when lit, indicates that the unit is functioning and has
enough power.
5. POWER SWITCH when activated, illuminates the LED, indicating
that the unit is receiving power from either two nine volt batteries or the
included AC power adapter.
6. BALANCE adjusts the relative levels of the right and left channels in
stereo mode or two separate channels in mono.
7. PHONES provides connection for headphones with 1/4” or 1/8”
plugs. Both jacks can be used simultaneously, but total minimum
headphone impedance is 30 ohms.
8. TRS INPUTS are left and right 1/4” jacks parallel wired to the XLRs
for looping, pin 2=tip, pin 3=ring.
9. DC IN applies DC current from the included wall supply or other 1824v DC power supplies that are wired tip positive and sleeve negative.
10. INPUT MODE SELECT SWITCH allows the choice of balanced
left and right inputs or unbalanced stereo inputs. In unbalanced stereo
mode all four input jacks are paralleled together.
11. XLR INPUTS for balanced left and right signals or the input of two
separate sources when used in mono mode.
FRONT
1 3 4 5 6
STEREO
MONO
5
6
4
3
2
1
PAD
0
VOLUME
10
7
8
9
POWER
L
BALANCE
2
R
7
PHONES
BACK
+
TIP
SLEEVE
DC IN
L
BALANCED L/R
R
UNBAL STEREO
LEFT
8 9 11
10
RIGHT
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