Electro-Voice Precision P1250 User manual

P1250
Precision SeriesTM
Power Amplifier
• Built-in processor ensures
optimum sound quality and
amplifier/speaker matching
• 370 watts per channel
at 8 ohms, 550 watts per
channel at 4 ohms, 650 watts
per channel at 2 ohms
• Compact, two-rack-space chassis
• Neutrik Speakon
®
output
connectors allow use of heavy-
gauge speaker wire for low-
loss connections
• Three-year parts-and-labor
warranty
SPECIFICATIONS
Conditions:
1. 0 dBu = 0.775 V rms.
2. Dual-mode ratings are for each channel,
both operating, unless noted.
3. 120-volt ac line voltage maintained
throughout testing.
Continuous Rated Output Power
(20-20,000 Hz at less than 0.1% THD,
both channels driven per EIA RS-490),
Dual Mode, 2 Ohms:
600 watts
Bridged Mode, 4 Ohms:
1,200 watts
Dual Mode, 4 Ohms:
500 watts
Bridged Mode, 8 Ohms:
1,000 watts
Dual Mode, 8 Ohms:
350 watts
Continuous Rated Output Power (1 kHz,
1% THD, both channels driven per EIA
RS-490),
Dual Mode, 2 Ohms:
650 watts
Bridged Mode, 4 Ohms:
1,300 watts
Dual Mode, 4 Ohms:
550 watts
Bridged Mode, 8 Ohms:
1,100 watts
Dual Mode, 8 Ohms:
370 watts
Power Bandwidth
(+0, –1 dB, reference 1 kHz),
Dual Mode, 4 Ohms:
20-20,000 Hz
Bridged Mode, 8 Ohms:
20-20,000 Hz
Dual Mode, 8 Ohms:
20-20,000 Hz
Frequency Response
(–1 dB, reference 1 kHz/1 watt):
10-30,000 Hz
Voltage Gain, 1 kHz, Input Level Controls
Full Clockwise, Constant-Gain Option:1
26 dB
Input Sensitivity, 1 kHz, Dual Mode for 550
Watts into 4 Ohms:
0 dBu (775 mV)
Maximum Input Level, 1 kHz:
+20 dBu (7.75 V)
Input Impedance (per channel,
20-20,000 Hz), Balanced:
20 kilohms
Phase Response (at rated power, any
mode, 10-30,000 Hz):
±22.5 degrees
THD Plus Noise at 1 kHz (at rated power,
measurement bandwidth 80 kHz):
<0.01%
IMD (SMPTE) (60 Hz/7 kHz, typical, at
rated power; see Figure 2):
<0.01%
Rise Time (10% to 90% at rated power,
any mode):
<2.5 microseconds
Slew Rate, Any Mode:
>30 V/microsecond
Damping Factor, Any Mode:
>300
Amplifier Protection:
Excessive output voltage; shorted loads;
excessive phase shift; rf interference;
overtemperature; excessive back EMF;
In-rush current limiter
Load Protection:
Start-up/shutdown transients; dc fault;
infrasonic signals; low ac line voltage;
nonlinear signal limiter
Output Topology:
True complementary symmetry with
ungrounded collectors (no mica insulators
means better heat transfer)
Output Devices,
Total Number: 20 devices
Pd(max) Rating: 250 watts
Ic(collector current): 16 amps dc
Tj(max): 200 °C (392 °F)
Controls and Switches,
Rear (see Figure 3):
Limiter Time Constant (Fast/Slow);
Processor(LPN/B6/Off); Pole
Frequency—low-pass notch (60 Hz,
43 Hz, 26 Hz); Bridged Mode switch
(Bridged/Normal); Hi-Lo-Cut Filter
(15 Hz/31 Hz/Off); Input Routing
(Parallel Mono/Dual Stereo);Circuit ⊥
To Chassis Switch (Grounded/
Ungrounded);
Front (see Figure 3):
Two calibrated input level controls;
power switch
Front-Panel Indicators:
Six LED’s per channel (12 total) for power
on, input signal; output signal; limiter
on; protection on and processor on
Connections,
Input:
3-pin female XLR-type connectors for
each channel in parallel with a 3-pin
male XLR-type output connector for
easy signal routing; the XLR connec-
tors are wired according to the IEC 268
standard: pin 1 shield, pin 2 positive,
pin 3 negative
Output:
Neutrik Speakon®NL4MP for channels
A, B and for bridged mode
Power:
14-gauge, 3-wire, permanently attached
power cable
_______________
1. Configured for constant-gain option, all Precision SeriesTM
amplifiers, regardless of power rating, have a maximum
voltage gain of 26 dB.

P1250 SPECIFICATION GRAPHICS
FIGURE 1 — P1250 Dimensions
FIGURE 3 — P1250 Front and Rear Panel
FIGURE 2 — P1250 Intermodulation Distortion
(SMPTE 60 Hz/7,000 Hz) vs. Power

Operating Voltage:
120 V, 60 Hz ac
Power Consumption (both channels
operating in dual mode, 1/8power),
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
TheElectro-VoiceP1250PrecisionSeriesTM 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
into2ohmsoverthefullaudiofrequencyrange.
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
powersupply,withitslargetoroidaltransformer,
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
bytwo,three-speed,temperature-sensitivefans.
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-aluminumheatsinkthatisengineered
to minimize thermal gradients and allow the
amplifier to operate safely into low-impedance
loads. The output devices have a maximum
junctiontemperatureof200°C(392°F),sohigh
operationaltemperaturespresentnoproblems.
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 TopologyTM.
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
patentedDynamicSignalProcessingTM circuitry
along with unprecedented speaker matching
and protection. The Dynamic Signal
ProcessingTM circuitry ensures that transient
responseandphasedistortioninthespeakeris
minimized,resultingindynamic, 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, 26Hz). 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
reversefeedingofelectricalenergy(backEMF)
and are switched on via relays to avoid tran-
sients which could damage speakers.
TheP1250hasbuilt-inlimiterstoprotectspeak-
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.
Thelimiter’stimeconstantsareswitchablefast/
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-cutfilters.Thesefiltersattenuateinfrasonic
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
offforuseinapplicationsutilizingfrontendunits
(likecrossoversorequalizers)whichhavethese
filters built-in.
Amultifunctiondisplaykeepstheuserinformed
of the operating status of the amplifier. Sepa-
rateLEDdisplaysforeachchannelshowpower
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-freeconnectionsandsignalrout-
ing.TheP1250 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 SeriesTM 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-
sionalNeutrikSpeakon®connectorswhichpro-
videasturdy,reliableconnectionandallowuse
of heavy wire for loss-free signal transmission.
Thereareseparateoutputconnectorsforchan-
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,detentedpotentiometersonthefront
panelregulatethegainofthe P1250.Thepanel
nomenclatureshowstheamountofattenuation
accurately.
The Electro-Voice P1250 is the choice for seri-
ous, professional amplification applications
which require optimum sound quality, speaker
protection,andthehighestlevelofconstruction
quality and long-term reliability.
ARCHITECTS’ AND ENGINEERS’
SPECIFICATIONS
The power amplifier shall be a dual-channel
model of solid-state design employing high-
poweroutputdevicesinatrue-complementary-
symmetry output circuit . It shall be capable of
operatingfroma120/200/220/240-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
loadsandexcessivephaseshift.Theloadshall
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
transientresponseproblemsoftheloudspeaker.
The built-inprocessorshallbecapableofbeing
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
parallelmonooperation,aswitchforadjustingor
turning off the infrasonic and ultrasonic filters,
and a switch for selecting fast or slow speed for
thebuilt-in limiters. The processor controls shall
includeaswitchforturningtheprocessoroffand
selectingthe enclosuretype(12- or24-dBalign-
ment) and three selectable frequencies for B6
(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-
tentiometersand have accurate markings. The
amplifiershallhaveaconstant-gainoptionthat,
withinputlevelcontrols fullclockwise,provides
a 26-dB voltage gain that is identical to that of
all Electro-Voice Precision SeriesTM 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

ELECTRO-VOICE a MARK IV company 600 Cecil Street, Buchanan, Michigan 49107
MANUFACTURING PLANTS AT BUCHANAN, MI NEWPORT, TN SEVIERVILLE, TN OKLAHOMA CITY, OK GANANOQUE, ONT.
© Electro-Voice, Inc. 1995 Litho in U.S.A. Part Number 532407 — 9531
bridged into 4 ohms; hum and noise, at least
100dB(A-weighted)belowratedoutputpower;
frequency response, 10-30,000 Hz (+0, –1 dB)
at any output power up to rated output power;
damping factor, >300 at any frequency up to 1
kHzinanymodewithan8-ohmload;THD(total
harmonic distortion), <0.05% at 1 kHz at rated
power;transientintermodulationdistortion(DIN
30 or DIN 100), <0.01%; crosstalk, <70 dB
belowratedoutput power. Dimensions shall be
88.1mm(3.5in.)x483mm(19.0in.)x 426 mm
16.8 in.) hwd. Net weight shall be 17 kg (37.5
lb). Color: dark gray.
The power amplifier shall be the Electro-Voice
P1250.
UNIFORM LIMITED WARRANTY
Electro-Voiceproductsareguaranteed against
malfunctionduetodefectsinmaterialsorwork-
manship for a specified period, as noted in the
individualproduct-linestatement(s)below,orin
the individual product data sheet or owner’s
manual, beginning with the date of original
purchase.Ifsuchmalfunctionoccursduringthe
specifiedperiod, the product will be repaired or
replaced (at our option) without charge. The
product will be returned to the customer pre-
paid. Exclusions and Limitations: The Lim-
ited Warranty does not apply to: (a) exterior
finish or appearance; (b) certain specific items
described in the individual product-line
statement(s)below, or in theindividual product
data sheet or owner’s manual; (c) malfunction
resulting from use or operation of the product
other than as specified in the product data
sheet or owner’s manual; (d) malfunction re-
sulting from misuse or abuse of the product; or
(e) malfunction occurring at any time after re-
pairshavebeenmadetotheproductbyanyone
otherthanElectro-Voiceoranyofitsauthorized
service representatives. Obtaining Warranty
Service: To obtain warranty service, a cus-
tomer must deliver the product, prepaid, to
Electro-Voice or any of its authorized service
representativestogetherwithproofofpurchase
of the product in the form of a bill of sale or
receipted invoice. A list of authorized service
representativesisavailablefromElectro-Voice
at 600 Cecil Street, Buchanan, MI 49107 (616/
695-6831 or 800/234-6831). Incidental and
Consequential Damages Excluded: Product
repair or replacement and return to the cus-
tomer are the only remedies provided to the
customer. Electro-Voice shall not be liable for
any incidental or consequential damages in-
cluding, without limitation, injury to persons or
property or loss of use. Some states do not
allow the exclusion or limitation of incidental or
consequentialdamagessotheabovelimitation
orexclusionmaynotapplytoyou.OtherRights:
This warranty gives you specific legal rights,
and you may also have other rights which vary
from state to state.
Electro-Voice Electronics are guaranteed
against malfunction due to defects in materials
or workmanship for a period of three (3) years
from the date of original purchase. Additional
details are included in the Uniform Limited
Warranty statement.
Service and repair address for this product:
Electro-Voice,Inc.,600CecilStreet,Buchanan,
Michigan 49107 (616/695-6831 or 800/234-
6831).
Specifications subject to change without no-
tice.
FIGURE 4 — P1250 Block Diagram