Operating Voltage:
120 V, 60 Hz ac
Power Consumption (both channels
operating in dual mode,
1
/
8
power),
4 Ohms:
550 VA
Dimensions, (see Figure 1)
Height:
88.1 mm (3.5 in.)
Width:
483 mm (19.0 in.)
Depth:
426 mm (16.8 in.)
Color:
Dark gray
Net Weight:
17.0 kg (37.5 lb)
Shipping Weight:
17.8 kg (39.3 lb)
DESCRIPTION
The Electro-Voice P1250 Precision Series
TM
am-
plifier is a very-high-quality power amplifier
designed to elicit maximum performance and
sound quality from any speaker system. Its
ultralow distortion, powerful amplifiers and
unique processor section ensure that any
speaker system will sound its very best.
Each channel of the P1250 delivers more than
350 watts continuous average power into
8 ohms, 500 watts into 4 ohms and 600 watts
into 2 ohms over the full audio frequency range.
In the bridge mode, the amplifier can deliver
more than 740 watts into 8 ohms and 1,300
watts into 4 ohms at less than 1% THD. The
power supply, with its large toroidal transformer,
gives the amplifier impressive headroom and
current output.
The P1250 contains 20 high-power output de-
vices with 5,000 watts of dissipation capability.
These devices are protected from overheating
by two, three-speed, temperature-sensitive fans.
The fans are quiet enough to permit use of the
P1250 in noise-sensitive applications such as
recording studios and houses of worship.
The output devices are mounted to a massive,
extruded-aluminum heat sink that is engineered
to minimize thermal gradients and allow the
amplifier to operate safely into low-impedance
loads. The output devices have a maximum
junction temperature of 200 °C (392 °F), so high
operational temperatures present no problems.
The output devices are mounted directly to the
heat sink without mica insulators to ensure
better dissipation of heat.
Many electronic circuit innovations exist in the
P1250. Among the most novel of these circuits
is the Dual Differential Discrete Topology
TM
.
This circuit is part of the front end of the ampli-
fier, uses discrete electrical components in-
stead of integrated circuits, and is fully sym-
metrical for both polarities.
The built-in processor utilizes Electro-Voice’s
patented Dynamic Signal Processing
TM
circuitry
along with unprecedented speaker matching
and protection. The Dynamic Signal
Processing
TM
circuitry ensures that transient
response and phase distortion in the speaker is
minimized, resulting in dynamic, powerful bass
and clear, three-dimensional highs. The pro-
cessor controls allow you to select the enclo-
sure tuning (12 or 24 dB per octave) as well as
adjust the “notch” frequency which closely cor-
responds to the 3-dB-down point of the enclo-
sure (60 Hz, 43 Hz, 26 Hz). The processor also
has circuits that help prevent severe amplifier
clipping and can limit peak power fed to the
loudspeaker if high power levels are main-
tained for an extended period.
The P1250 has sophisticated protection cir-
cuits that guard it and the load from problems.
Protection circuits guard against overload,
overtemperature, shorted outputs, radio-fre-
quency interference and dc faults. The output
devices are protected against damage from
reverse feeding of electrical energy (back EMF)
and are switched on via relays to avoid tran-
sients which could damage speakers.
The P1250 has built-in limiters to protect speak-
ers from the deleterious effects of amplifier
clipping. The limiter’s action is governed by
very sophisticated input/output comparators
which have acoustically optimized time con-
stants to preserve the integrity of the source.
The limiter’s time constants are switchable fast/
slow, so the limiter may be matched to the
application for which the amplifier is being
used.
The P1250 has built-in switchable high- and
low-cut filters. These filters attenuate infrasonic
and ultrahigh-frequency signals, preventing
them from being amplified; this allows more
effective use of the amplifier’s power and adds
a measure of load protection. These filters are
adjustable (15 Hz or 31 Hz) and may be turned
off for use in applications utilizing frontend units
(like crossovers or equalizers) which have these
filters built-in.
A multifunction display keeps the user informed
of the operating status of the amplifier. Sepa-
rate LED displays for each channel show power
on, input signal present, output signal, limiter
on, protection active and processor on.
The P1250 has electronically balanced XLR-
type input and output connectors that allow
easy, problem-free connections and signal rout-
ing. The P1250 has an input routing switch that
allows selection of either normal dual-channel
operation, or parallel mono operation, which
routes an input to both channels but still allows
for independent level control. The P1250 also
has a constant-gain option which, with input
level controls full clockwise, provides a 26-dB
voltage gain that is identical to that of all
Electro-Voice Precision Series
TM
amplifiers in
the constant-gain option, regardless of power
rating. This makes it possible to exchange
amplifiers of different power ratings without
upsetting delivered sound pressure levels or
spectral balances.
The P1250’s output connectors are profes-
sional Neutrik Speakon
®
connectors which pro-
vide a sturdy, reliable connection and allow use
of heavy wire for loss-free signal transmission.
There are separate output connectors for chan-
nels A and B, and for the bridge mode. The
bridge-mode connector is sealed with a plastic
cover to prevent connection errors.
To prevent ground loops from occurring, the
P1250 is equipped with a ground-lift switch.
When the amplifier is operated in a rack with
units of different ground potential, the switch
may be adjusted to eliminate hum.
Calibrated, detented potentiometers on the front
panel regulate the gain of the P1250. The panel
nomenclature shows the amount of attenuation
accurately.
The Electro-Voice P1250 is the choice for seri-
ous, professional amplification applications
which require optimum sound quality, speaker
protection, and the highest level of construction
quality and long-term reliability.
ARCHITECTS’ AND ENGINEERS’
SPECIFICATIONS
The power amplifier shall be a dual-channel
model of solid-state design employing high-
power output devices in a true-complementary-
symmetry output circuit . It shall be capable of
operating from a 120/200/220/240-V, 50/60-Hz
ac line. The power amplifier shall contain a
modern limiter circuit with switchable time con-
stants to protect the load from damage by
amplifier clipping.
The amplifier shall contain sensing circuitry to
provide protection for the output transistors
against overtemperature, excessive output
voltage, radio-frequency interference, shorted
loads and excessive phase shift. The load shall
be similarly protected against infrasonic sig-
nals, start-up/shutdown transients, low ac line
voltage and dc.
The power amplifier shall contain processing
circuitry that will ameliorize the phase and
transient response problems of the loudspeaker.
The built-in processor shall be capable of being
adjusted for the enclosure type and low-
frequency characteristics of the connected
speaker.
Rear-mounted panel controls shall include an
input routing switch for selecting dual/stereo or
parallel mono operation, a switch for adjusting or
turning off the infrasonic and ultrasonic filters,
and a switch for selecting fast or slow speed for
the built-in limiters. The processor controls shall
include a switch for turning the processor off and
selecting the enclosure type (12- or 24-dB align-
ment) and three selectable frequencies for B
6
(24 dB) alignment of 60 Hz, 43 Hz and 26 Hz.
Front-panel indicators shall include power on,
input present, output, limit, protect and proces-
sor on LEDs for each channel. Front-panel
controls shall include a power switch and level
controls that shall be calibrated, detented po-
tentiometers and have accurate markings. The
amplifier shall have a constant-gain option that,
with input level controls full clockwise, provides
a 26-dB voltage gain that is identical to that of
all Electro-Voice Precision Series
TM
power am-
plifiers.
The power amplifier shall meet the following
performance specifications: maximum input
voltage, 7.75 V rms; rated output power from
20-20,000 Hz at less than 0.1% THD, each
channel, >350 watts into 8 ohms, >500 watts
into 4 ohms, >600 watts into 2 ohms, >1,000
watts bridged into 8 ohms and >1,300 watts
