Peavey DPC 1400X Overview

Soundroom
Soundroom
Bi-colored Input sensitivity knob
LED (31 detent positions)
STATUS
Peavey DPC 1400X Power Amp
By Terry Buddingh
Construction: 4
Back in the '80s Peavey began
experimenting with "switch-
mode" power-amp designs, which
use digital technology to supply
large amounts of power without
the huge transformers and capac-
itors required by conventional
amps. The flagship DPC 1400X
uses the company's patented
phase-modulated circuitry to pro-
vide unprecedented power in a
single-rackspace package. Its
austere exterior is no indication
of the sophisticated design work
hidden inside.
A large glass-epoxy printed cir-
cuitboard board spans the full
width of the rugged steel chassis,
housing the power supply and
extensive filtering components
required by a switch-mode amp.
Each channel's output offers a set of binding posts and a pair of
1
or / " plugs; they also accept
4 TRS
68
B A S S P L A Y E R
Bi-colored
level
SIGNAL
LED
A smaller PC board holds an abun-
dance of ICs and modern surface-
mount components. Silicone
adhesive secures the large toroidal
inductors, while the smaller induc-
tors are soldered directly to the
board. A low-profile cooling fan
draws air through the back panel
and forces it through a channel-
shaped heatsink, exhausting it
through a front-panel vent.
Electronics: 4.5
With today's proliferation of
5-strings and low alternate
tunings, power has never been
more important—extra power is
required to faithfully reproduce
extra-low notes. Solid-state class
AB amps have been the standard
for many years; these must use a
large power-supply transformer to
provide the high current needed
to run its output devices, as well
1
/
1
/ " mono plugs for unbalanced operation.
4
O C T O B E R 2 0 0 0
Output
MODE
button
as large capacitors for current
storage and filtering. This explains
the large size and weight of high-
powered conventional amplifiers.
An alternative is to raise the 120-
volt, 60Hz line to a much higher
frequency. The class D 1400X uses
a switching power supply to run
at 280kHz, where a smaller trans-
former and capacitors can do the
same work as class AB amps' heavy
components.
Most class D amps use pulse-
width modulation to control the
output stage. Since the output
devices are constantly being turned
on and off at different rates, the
amp's performance is ultimately
limited by the speed, or rise time,
of the devices used. Peavey avoided
this problem by using two non-
changing pulses that vary in their
phase relationship rather than their
width. This elegant solution also
" jacks. The inputs use a combo connector to accommodate balanced
4
1
/ " jacks allow easy connection of additional amplifiers.
4 THRU
DDT
/
DEFEAT ENABLE
button
enables the DPC 1400X's output
MOSFETs to be driven with a sim-
pler circuit. The audio signal gets
amplified with the switching sig-
nal; then the high-frequency
switching signal gets filtered out
before it reaches the amp's output.
The result is unheard-of power in
a smaller and lighter package.
The DPC 1400X also includes
Peavey's DDT (Distortion Detec-
tion Technique) protection cir-
cuitry, which compares the amp's
output with its input and reduces
the internal gain when clipping or
current limiting occurs. You can
defeat the DDT via a front-panel
button.
Ease of use: 5
Peavey specializes in user-friendly
products, and despite the DPC
1400X's sophisticated design, it's
no exception. All the controls and
XLR