passTM
XA200 Owner’s Manual
May 18, 2006
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The XA200 has a massive toroidal transformer coupled to a high
current DC reservoir. Recognizing that the XA200’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 re-
cording format. Through the XA200 complex musical passages reveal
themselves in the most dramatic manner. With the XA200 you will
hear everything within the upper octaves, which includes any record-
ing, 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
XA200 is unconditionally stable into any load presented by a loud-
speaker, but will provide less power into other than 8 ohms. The
XA200 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 up-
stream 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 650 watts, the
equivalent of a small hand held hair dryer. At idle most of that en-
ergy is dissipated across the heat sinks, so the heat generated by each
XA200 is equivalent to a small hair dryer. 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 5-1/2
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 XA200 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 stan-
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dard 15 amp IEC receptacle at the rear of the amplifier chassis. Two
XA200’s may be run 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, substi-
tute 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 plug-
ging 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
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 “emer-
gency disconnect” for this product. This device provides current limit-
ing 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 are
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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 con-
nect the source and speakers. Make sure you are in standby mode to
protect your speakers from transients. The prudent installer will unplug
the XA200’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 bind-
ing 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 volt-
age 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.
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 am-
plifier single-ended leave the supplied jumper in place between pins 1 &
3 on the input XLR. On the XLR connectors 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 concur-
rently.
XLR input connector showing proper
placement of jumper pin for use with
single-ended (RCA) input.
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Now that the source component is connected, make sure there is no
signal coming from it, probably by turning the volume all the way
down.
With the speakers connected, make sure the power cord is attached
and plugged into mains power; push the front panel button to activate
the amplifier. The “Power” LED will come on.
Do everybody a favor and try not to have shorted output cables. It
happens accidentally all the time, and the amplifier is designed to sur-
vive, but why tempt fate. If you accidentally cause the breaker to trip,
it can be reset by first cycling the breaker handle to the off position
(down) and then on (up). The fault, which caused the “trip”, will need
to be corrected prior to resetting this breaker.
You are ready to play music
Of course it’s always possible that something may go wrong. If so,
don’t get excited. It’s really aggravating when a product doesn’t work,
we understand, but it will get fixed. We go to a lot of trouble to make
products reliable, and the failure rate of our amplifiers is very low.
This is small comfort to the few, but take it easy and give us a call if
you have problems.
People are interested in how long it takes for these amplifiers to break
in. Depending on the resolution of the rest of your audio chain, you
may or may not notice any break in of the XA200 beyond the first 50
hours of operation. You will likely notice the difference in sonic char-
acter between cold and normal operating temperature, so we recom-
mend letting these amplifiers warm up before any serious listening.
It takes about an hour for them to warm up, and this is where we ad-
just them first. Then we adjust them again and again over a couple of
days, keeping the bias and offset in the sweet spot. Our environment
is about 23 degrees Centigrade, room temperature, and the heat sinks
will rise to about 25 degrees C. above that, for a heat sink temperature
of about 48 degrees C. This is where they operate best.
In your setup the heatsink temperature may vary a bit due to line volt-
age and ventilation, but it is not a big deal. You should be able to put
your hands on the heat sinks without discomfort for 10 seconds or
so.
The amplifier has a thermal cutout that will disconnect AC power if
the temperature exceeds 75 degrees Centigrade. This thermal cutout
should never occur in real life.
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More things to know
You may remotely operate the stand-by mode by applying 12 volts DC
to the single pair of 5 way connectors on the rear of the amplifier.
The positive of the 12 volts DC goes to the red connector, negative
to the black. This connection has an actual operating range of about
9 volts to 15 volts. This switching feature will override the front panel
button, only when the front panel button is in the standby position.
The XA200 is optimized for 8-ohm speaker loads. Having said that; we
are not aware of any speaker on the market that presents an unusual or
difficult load for these amplifiers.
Speaker Interface
The XA amplifiers do not care particularly about the reactivity of the
load. Reactive loads typically will have slightly less distortion at a given
voltage/current level than resistive loads. The XA circuit was designed
to be quite happy driving electrostatic speakers and any other esoteric
loads we know of.
Interconnects and Speaker
Cables
We have a general recommendation about interconnects, and speaker
cables; which is that they should cost less than the amplifier, and con-
tain at least some conductive material. We have tried a lot of products
and most work well, but as a practical matter we cannot make blanket
recommendations.
The amplifier is not sensitive to source interconnects. It is also not sen-
sitive to radio frequency pickup, which allows some flexibility in choos-
ing source interconnects without shields, though shields are always in
good taste. For long runs balanced cables are highly recommended for
their inherent rejection of common mode noise.
We prefer speaker cables that are short and stout, oxygen free copper
and silver are the suggested materials. If you find any really exceptional
cable made of gold, please gift us a couple hundred feet.
Fortunately this amplifier is not sensitive to the capacitive/inductive
character of some of the specialty speaker cables, so feel free to experi-
ment.
We have found that about 90 per cent of bad sounding cables are really
bad sounding connections, and we recommend that attention be paid to
cleanliness of electrical contact surfaces and proper connector fit.
Speaker cables should be firmly tightened down at the speaker output
terminals, but not with a wrench. Output terminals will not withstand
the levels of torque that may be easily applied by wrench. Hand tighten-
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ing without excessive force is plenty. Cleaning contact surfaces with one
of the commercially available electronic contact cleaners should be part
of your annual system maintenance.
Fun Hardware Facts
The XA200 has a single large power transformer, under actual condi-
tions in the amplifier, it supplies but a fraction of its rated power. This
very conservative rating contributes to exceptional voltage regulation
figures and low noise figures at the loudspeaker.
The XA200 has a significant number of power supply filter capacitors.
These caps are used to create the unregulated output stage rails at plus
and minus 60 volts at 9 amps. RC filtering is used to passively remove
ripple from the supply rails.
All the power transistors in the product are hyper-matched parts, with
gate voltages matched to 0.5% and all devices taken from the same
manufacturing lot codes (made on the same wafer).
So how long will this hardware last? It is our experience that, barring
abuse or the odd failure of a component, the first things to go will
be the power supply capacitors, and from experience, they will last
15 to 30 years. Fortunately they die gracefully and are easily replaced
by a good technician. After that, the longevity will depend upon the
number of operating thermal cycles, but we can say that we have had
amplifiers operating in the field in excess of 20 years with no particu-
lar mortality, and we don’t have good information beyond that. More
to the point, you should not worry about it. This is a conservatively
built industrial design, not a frail tube circuit run on the brink of cata-
strophic failure. If it breaks, we will simply get it fixed, so sleep well.
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XA200 Specifications
All figures obtained after 1 hour warm-up, with regulated 120 VAC
power line. See manual notes about AC power line regulation.
Gain
26 dB
Freq. Response
Power Output
-3 dB at 1.5 Hz, -3 dB at 100 kHz
200 watts max @ 1% THD,
1 kHz, 8 ohms
Maximum Output Voltage
Maximum Output Current
Input Impedance
plus, minus approx. 60 volts
plus, minus approx. 9 amps
22 kohm balanced
11 kohm unbalanced
30 ref @ 8 ohms nominal
plus, minus 50 V/uS
300 uV unweighted 20-20 kHz
approx. -60 dB @ 1 kHz
< 100 mv
Damping factor
Slew rate
Output Noise
Balanced CMRR
DC offset
Power Consumption
Temperature
Dimensions
approx. 650 watts
25 degrees C. above ambient at idle
19 “ W x 11.25” H x 28” D
180 lbs.
Shipping Weight
For more information please contact:
Pass Laboratories Inc.
P.O. Box 219,
24449 Foresthill Rd.,
Foresthill, CA 95631
Tel: 530.367.3690
Fax: 530.369.2193
www.passlabs.com
© 2006, Pass Laboratories Inc.
“Pass”, “pass”, “Pass Labs”, “Pass Laboratories”, Supersymmetery”,
“Aleph”, and “Zen” and are all registered trademarks of Pass
Laboratories, Inc., and all rights thereto are protected by law.
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Please check with the factory-authorized distributor in the country you are
purchasing this product for specific warranty information.
Warranty Information
All Pass Laboratories products purchased from an authorized Pass Labora-
tories dealer in North America are covered by a transferable, limited 3-year
warranty. This warrantee includes all parts and labor charges incurred at the
repair facility in addition to return shipping to the domestic customer, exclu-
sive of subsequent damages. Damage due to physical abuse is specifically
not covered under this warranty.
For this warranty to apply the customer is responsible for returning the
product unmodified to the factory within the warranty period. The customer
assumes all responsibility for shipping and insurance to the factory or a fac-
tory specified repair facility. The conditions and stipulations of this Pass
Laboratories warranty only applies to units sold new in North America.
Non-North America customers should consult with their original Pass Labs
dealer or distributor for warrantee repair instruction prior to contacting the
factory or shipping product for repair.
Non-North American product must be returned to the country of origin for
warrantee service. Foreign distributors are only required to offer warranty
service on Pass Laboratories product that they have imported.
Please note: Conditions of warranty service and customer rights for product
purchased outside the United States may vary depending upon the distribu-
tor and local laws. Please check with your local distributor for specific rights
and details.
Any modifications to Pass Laboratories products that have not received
written factory approval nullify all claims and void the warrantee. Should a
modified product be returned to the factory for repair the owner will be re-
quired to pay all necessary charges for the repair in addition to those charges
required to return the product to it’s original configuration.
In the case of safety issues, no product shall be returned to the customer
without those safety issues being corrected to the most recent accepted
standards.
Removal or alteration of original Pass Labs serial numbers voids the factory
warranty. Product with altered or missing serial numbers will be suspected
as counterfeit product.
Pass Laboratories will not repair or in any way indemnify any counterfeit or
cloned product.
Pass Laboratories does not offer products in voltages intended for inter-
national markets either to authorized Pass Labs dealers or to third parties
located in the United States or Canada.
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For your protection please
read the following:
Water and moisture: Electrical devices should not be used near
water ( as per example, near a bathtub, washbasin, kitchen sink,
laundry tub, wet basement or swimming pool ). Care should be
taken such that objects do not have the opportunity to fall, and that
liquid is never spilled onto or into the device enclosure through
openings.
Power Sources: An electrical device must be connected to a mains
power source in strict accordance with the supplied product owner’s
manual. Please verify that the AC mains voltage specified in the
product manual matches those requirements indicated on the unit
and the AC voltage provided to your location by the power company.
Grounding: Adequate precautions should be taken so that the
grounding provisions built into an electrical product are never
defeated.
Power Cords: Pass Laboratories provides a power supply cord that
meets all legislated requirements for the market in which the product
was originally sold. If you choose to substitute an after-market
product we urge you to choose one that is fully safety rated by the
necessary local authority.
Power Cord Protection: Power supply cords should be routed so
that they are not likely to be walked on, abraded, or pinched by items
placed on or against them, paying particular attention to cords where
they enter plugs or exit from a device. Never under any circumstance
insert a cut or damaged power cord into a mains power socket.
Power and Signal: Cables should never be connected /
disconnected with equipment powered up. Failure to heed this
warning may damage or destroy equipment.
Ventilation: Power-amplifiers run hot, but you should be able to
place your hands on them without discomfort. You must allow for
this heat in installation, by providing for free air circulation around
the product. Electronics should not be subjected to sources of
excessive radiant heat. Excessive heat can shorten the life of the
product and may cause the electronics to self-protect and shut down.
Servicing: To reduce the risk of fire, electrical shock or other
injuries, the user should not attempt to service the device beyond
that which is described in the operating instructions. All other
servicing must be referred to qualified service personnel.
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XA White Paper:
Like Peanut Butter and
Chocolate
Sometimes two designs complement each other so well that you are
surprised when you learn they weren’t invented together. So it is with
the X Supersymmetery™ amplifier and the Aleph single-ended Class A
output circuit.
© Nelson Pass
The Supersymmetery™ “X” amplifier repeatedly demonstrates the pos-
sibilities for very high power, dramatic dynamic contrast, and effortless
control by a simple circuit utilizing absolutely minimal feedback. As
with the art of Aikido, the X circuit works with the intrinsic character
of a balanced circuit and deftly turns that character toward perfection.
This has been the basis for a very successful Pass Laboratories™ prod-
uct series, which has won numerous prestigious awards and garnered
critical acclaim worldwide.
For over ten years, the Aleph™ series of single-ended Class A ampli-
fiers have received praise for their outstanding sonic definition, warmth,
and smoothness; and have often been compared favorably with the very
best tube amplifiers. The Aleph™ topology achieves state-of-the-art
performance with a very simple linear design, and is additionally one of
the most stable and reliable audio amplifiers in existence.
A considerable number of audiophiles have found themselves bi-amp-
ing their loudspeakers, putting Pass Laboratories™ X amplifiers on the
bottom for power and control, conjoined with Alephs™ on the top
for that smooth warm midrange and top end. We well appreciate these
complementary differences, and for the past few years Pass Laborato-
ries™ has been at work marrying these two design concepts into a single
amplifier topology. The trick was to create an amplifier, which carries
the best of both designs, and not otherwise.
X Supersymmetry™
The Supersymmetry™ X amplifier uses a new radical approach to
achieving high performance from a simple 2-stage circuit. The design
exploits the symmetry of a matched balanced amplifier so that distor-
tion and noise are cancelled at the output to the loudspeaker, then uses
a small dose of a unique new form of feedback to make that symmetry
more perfect.
US Patent # 5,376,899 describes our topology, which takes advantage
of the character of specially matched balanced amplifiers that are cross-
coupled to provide cancellation of distortion and noise. The result
provides high performance with very simple linear circuits, better than
previous similar efforts by an order of magnitude. It was named Super-
symmetry™ as an homage to particle physics, but it is popularly known
as the X circuit.
Balanced amplifiers improve performance by differentially rejecting dis-
tortion and noise. To the extent that distortion and noise are identical,
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they vanish at the output, typically by a factor of 10 or so for matched
single-ended Class A circuits.
Supersymmetry™ extends this concept by using feedback only to make
the distortion and noise more identical on each half of a balanced cir-
cuit, not to eliminate it as such. This gives as much as a 100:1 reduc-
tion in unwanted distortion and noise without requiring the equivalent
amount of negative feedback. It is simply much easier to tweak the two
halves of the circuit into identical symmetry than to eliminate all the
distortion in each half of the circuit.
The result has been a successful series of high power amplifiers offering
low distortion, and stunning dynamic range and control, with only two
gain stages and very minimal feedback.
Supersymmetry™ is ideally used to obtain high quality performance
from very simple gain circuits, and particularly favors single-ended Class
A topologies due to their smooth second harmonic characteristic, which
cancels easily.
Aleph Single-Ended ClassA
Single-ended Class A has long been known as the “King of the Class
A’s”, the simplest, most pure and least efficient form of audio amplifi-
cation. Before the Aleph™ amplifiers, it was reserved for preamplifier
circuits, high quality amplifier front-ends, and other very low power
output stages.
US Patent # 5,710,522 describes the single-ended Class A power ampli-
fier biased by a constant DC current source which negatively “ghosts”
the speaker load with simple but effective current modulation. If you
have followed developments in audio for the last 10 years, you know this
design as the Pass Laboratories Aleph™. The Aleph™ is an incredibly
successful ground breaking amplifier design, hailed in Stereophile maga-
zine as “The Amplifier of the Decade” and winner of virtually every
international design award for audio that we know of.
The key virtue of the Aleph™ design lies in its simplicity and effective-
ness. With only two stages and no adjustments it delivers measured
performance rivaling the most complex designs, but retains the sonic
elegance and nuance of a truly minimalist gain path – only two gain
devices in series from input to output.
The Supersymmetery
Aleph™
The two design concepts are not mutually exclusive, and we approached
the development of the XA series with an eye to creating a warm/sweet
X amplifier, or conversely, a powerfully dynamic Aleph™. The success-
ful result is a circuit which is described as balanced single-ended Class
A, consisting of two balanced Aleph™ amplifiers sharing a single dif-
ferential input pair of transistors.
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The amplifier has only the two stages, an input stage of a balanced pair of
input devices, and the output stage, a balanced pair of single-ended Class
A power Mosfets. Like the Aleph™, you can trace a path from input to
output through only two gain devices. Like the X amps, feedback is used
only to set the gain and correct for dissimilarities between the two matched
output stages.
There are no adjustments. There are no frequency compensation capaci-
tors. The amplifiers are unconditionally stable and reliable into any load.
They are not fragile, temperamental or prone to failure.
The XA amplifiers operate at approximately 33% efficiency, which is to
say they idle at three times their rated output. The XA200 is rated at 200
watts output into 8 ohms and draws something over 600 watts of AC
power. This design is an exercise in highly conservative engineering, which
provides exceptional reliability and product longevity. The output devices
are exposed to no more than a fraction of the voltage and wattage they are
designed to endure.
These rugged power devices are matched to about .3% and mounted on
Mica insulators. Their massive heat sinks run at about 25 degrees C. above
ambient temperature, so that actual chip temperatures are about 70 degrees
below their rating. The output devices are designed to last a very long time
under these conditions, with a probable life of about 50,000 hours.
The power supply of the XA 200 uses elaborate RF filtering and noise sup-
pression designed to block AC noise and line DC. The substantial toroidal
power transformer is followed by high speed rectifiers, and significant uF
of computer grade capacitors in a passive filter arrangement. In addition
to a main power switch the amplifier has a standby mode, which shuts
down the bias to the circuit while keeping the supply active, significantly
extending the life of the filter capacitors.
The sound of the XA amplifiers is a quantum leap over the parents. They
retain the sweet warmth and lushness of the Aleph™ series without the
fluffy coloration’s. The dynamic contrast is even better than the X series;
transients leaping from black to crescendo and back again with no tele-
graphing or hangover.
The bass has as much control over the speaker as the original X amps, but
is a bit more neutral and carries subtler nuance. The midrange is a little
deeper and the soundstage wider than the Alephs™.
Are the XA’s better than Alephs™ and X’s in every respect?
Yes, except for the higher power/current ratings of the X amps.
Are they the best audio amplifiers that money can buy? Absolutely!
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