Pass Labs XA100 User Manual

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TM

May 18, 2006

XA100 Owner’s Manual

XA100 Owner’s Manual

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Introduction

Analog designer Nelson Pass has over the years produced some
truly great solid-state amplifiers, each unique in it’s own way. Not
surprisingly, the Pass Laboratories ™ XA100 monoblock amplifier
is no exception. The XA100’s sleek industrial design is a stunning
understatement of artistic form integrated with state of the art
function.

Since the introduction in 1997, the X amplifier series using the
patented Supersymmetry™ circuit topology have been the mainstay
of amplifier offerings from Pass Laboratories™. These amplifiers
are heavily biased Class A/B designs with only two gain stages and
an absolutely minimal component count in the signal path. In spite
of this simplicity and thanks to the unique characteristic of the X
topology, these amplifiers achieve very high power with outstanding
subjective and objective performance.

With the introduction of the XA100 Pass Laboratories™
significantly raises the performance standard of excellence by
introducing an entirely new series of power amplifiers. The new
“XA” series of amplifiers feature a refined and elegantly simple, very
highly biased, pure Class A mode of operation. This is a new and
unique circuit topology that we descriptively characterize as being
Single-ended Class A. This new topology combines the very best
characteristics of Pass Laboratories™ “X” series amplifiers and the
highly rated “Pass Laboratories Aleph™”. The XA series is the
marriage of a highly refined Aleph™ output stage with the patented
Supersymmetry™ “X” front end.

XA100 Owner’s Manual

The emphasis of the XA series is to accentuate performance over
power. The XA series has the characteristic warm midrange and
sweet top end of the Aleph™ product conjoined with the extreme
dynamic range and definitive bass control of the X series amplifiers.

The XA100 is packaged in an artistically refined variant of the
massive chassis previously reserved for the 250 watt X-250.5 stereo
amplifier, but running more than twice the Class A bias current of
our other amplifiers.

The Pass Laboratories™ XA100 will deliver 100 watts rms into
8 ohms of impedance. This is the amplifiers class A limit, driving
the XA100 harder or reducing the impedance of the load will not
convey any additional power. Driving into a short will not convey
any additional power. These are not design oversights or flaws in
the XA100, but rather a condition of the very highly biased Class A
operation. However; as an interesting point of reference, 100 watts
driving a 87dB/1W/1m speaker will deliver in excess of 105 dB
(quite loud) average acoustic signal in a 100 cubic meter room.

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The XA100 has a massive toroidal transformer coupled to a high
current DC reservoir. Recognizing that the XA100’s ability to resolve
microdynamics is best experienced with clean power, the extreme
low-level resolution of the XA-series benefits from a specially
designed power supply that significantly reduces and rejects power
line borne noise.

The XA amps open the sonic soundstage to the very limits of the
recording format. Through the XA100 complex musical passages
reveal themselves in the most dramatic manner. With the XA100
you will hear everything within the upper octaves, which includes any
recording, source or loudspeaker issues. Keep this in mind when
choosing complementary equipment, remembering that recordings
and the other components in the signal chain will strongly dictate
soundstage width and imaging and likely be the limiting factors in
your listening environment. The room itself will also add its acoustic
signature, and should be considered an audio component.

Speaker selection should be strictly a matter of personal taste.
The XA100 is unconditionally stable into any load presented by a
loudspeaker, but will provide less power into other than 8 ohms. The
XA100 accommodates both single ended (RCA) and balanced inputs
(XLR). Input impedance’s are 11 kohm unbalanced and 22 kohm
balanced to permit integration with the widest possible range of
upstream components.

Requirements

You can position this amplifier anywhere you wish, but it must have
ventilation. We do not recommend placing it in enclosed cabinets
or small closets without means for air to circulate freely. Stacking
these power amplifiers directly upon each other is not recommended
for the same reason. This amplifier idles at approximately 300 watts,
the equivalent of a large reading light. At idle most of that energy
is dissipated across the heat sinks, so the heat generated by each
XA100 is likewise equivalent to a large incandescent reading light. To
dissipate this heat the product should have about 6 inches clearance
to the top and sides for adequate air circulation.

Let’s talk about power requirements. The amplifier draws about 2.6
amps (continuous rms) at 120 volts out of the wall during operation,
and this reflects mostly the idle current that we run through the
output stage. When not actually intending to play music the XA100
should be left in standby mode. In standby mode it draws only a few
watts of power, that necessary to keep the capacitors charged.

We have provided a standard IEC power cord that fits into the
standard 15 amp IEC receptacle at the rear of the amplifier chassis.

XA100 Owner’s Manual

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Several XA100’s may be easily run in conjunction with other audio
products on a single 15-amp circuit. This amplifier is equipped for
operation with an earth ground provided by the users AC outlet.
Never defeat this ground connection. The signal ground of this
amplifier is connected to earth through a power thermistor, which
provides a safety ground but provides protection from irritating
ground loops.

As a safety issue we suggest that the power cord should be the last
cable installed on your power-amplifier. You may, if you wish,
substitute a 15-amp aftermarket power cord for the one we have
supplied. Only use power cords, which meet all local safety standards
and carry acceptance marks from the local regulatory authority. The
power cord should be attached to the amplifier prior to plugging
into house power. Place the rear mounted switch in the off (down)
position before plugging in this amplifier.

The amplifier’s voltage and current rating are indicated on the rear
panel. It will be either 240 volts, 220 volts, 120 volts or 100 volts,
all with a restorable type circuit breaker of the appropriate ampacity.
The inclusion of this re-settable circuit breaker does away with the
need for disposable fuses. The frequency rating of the AC line
source is 50 to 60 Hz in all cases. Please verify that the amplifiers
indicated voltage requirements are consistent with the supplied
voltage and current at your location. Transformers are input voltage
specific and their change is not a trivial matter.

Setup

XA100 Owner’s Manual

Looking at the rear panel you will see the AC power cord receptacle,
a power switch / breaker, two pairs of output connectors which
allow for speaker bi-wiring, a single pair of 5 way connectors for
remote turn-on, a single RCA input connector and a single XLR
balanced input connector.

Make sure that the rear panel power switch/breaker is off (down).
Plug the AC cord into the back of the amplifier, and then into the
wall. Then turn the power switch/breaker on (up). The lights in
your house will blink when the power supply charges the capacitors.
(Note: The power switch/breaker is never to be used as a “safety
device” or “emergency disconnect” for this product. This device
provides current limiting which will protect the amplifier, it will not
provide personal shock protection in the event of a reversed hot /
neutral, lack of grounding or other improper wiring in the supplied
mains voltage.)

On the front panel, the “Standby” LED indicator should be glowing
blue, indicating that AC power is available and the capacitor banks

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are charged. The “Power” LED should not be on. If the “Power”
LED is on, don’t get excited, just use the front panel stand-by button
to go to stand-by mode, with the “Standby” LED on and the “Power “
LED off.

OK, so the amplifier is sitting there in stand-by mode with just the
single blue LED lit. No speaker connected yet. You can go ahead
and connect the source and speakers. Make sure you are in standby
mode to protect your speakers from transients. The prudent installer
will unplug the XA100’s power cord from the mains while attaching
speaker cables.

To avoid the possibility of short circuits always connect speaker cables
to the speakers prior to connecting to the amplifier. The output
binding posts will accept either bare wire or spades. (Regulatory
agencies in many countries have banned binding posts that will accept
a banana plug, forcing us to abandon this option.) Make sure that your
speaker wires only attach to the outputs of the amplifier, not to each
other and never to the amplifier case.

Some powered subwoofers require an audio signal ground reference
and their makers may suggest that a black speaker terminal is
where this voltage reference might be found. On complementary
designs, which would be typical of all power amps produced by Pass
Laboratories™, this is an incorrect and unsafe assumption. On all
Pass Laboratories™ power amplifiers a reference of 0 volts will be
found only at pin 1 of the XLR input or at the shell of the RCA input.

XA100 Owner’s Manual

Reference connections for these devices require special consideration
when used with our product. If you have such a device, and wish to
use it with our product, please contact our Foresthill, California factory

for specific instructions.... you have been warned.

The amplifier may be driven single-end or balanced, your choice.
Single-ended input will always occur through the RCA connector
and balanced input will always occur through the XLR connector. If
driving the amplifier single-ended leave the supplied jumpers in place
between pins 1 & 3 on the input XLR. On the XLR connector pin 1 is
ground, pin two is positive input and pin 3 is inverted (negative) input.
Pin numbers are marked on the XLR. If you re-install the jumper
incorrectly or leave it lying about, the amplifier will not work properly.
You must choose either XLR or RCA inputs it is not advised to try and
run both concurrently.

XLR input connector showing proper
placement of jumper pin for use with
single-ended (RCA) input.

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