XA30.5 Owner’s Manual
May 17, 2007
XA30.5 Owner’s Manual
Nelson Pass has been designing audio electronics since about 1971,
new company, Threshold in 1975. Threshold pioneered the design
Pass sold Threshold and created Pass Laboratories in 1991, where he
Along the way he found the time to design successful lines of
Yourself ” hobbyist community.
performance his design signature. The hardware tends to run heavy
based on the “SuperSymmetric” topology (U.S. Patent #5,376,899)
which elicits high power and performance from simple circuits with
minimal feedback.
The first X amplifier, the X1000 was intended as the premier
into 8 ohms at low distortion. By itself of course, this is no miracle,
but you have to consider that products with comparable performance
have complicated circuits with as many as nine consecutive gain
The difference was the unique balanced circuit topology in which
path.
The SuperSymmetric circuit consists of two identical matched
Most of the distortion and noise appears in phase across the
loudspeaker, and is not seen.
XA30.5 Owner’s Manual
We start with simple FET circuits already having low distortion and
noise, and arrange them in two symmetrical halves. The two halves
portion of distortion and noise without feedback. A small amount
polarities of the balanced output.
with feedback, and this is the operating principle of X amplifiers.
by the Class A “XA” amplifiers. Subsequent improvements to the
phenomenal success has led to the Class A “XA.5” series.
As always the goal has been the best musical and objective
performance possible with minimal parts in the signal path and
minimal feedback. This process is not completely understood, and
many of the improvements are the result of trial and error and
Measurement of performance is important to us, and we feel that
well-designed product sounds good and measures good. Apparently
it is possible to make an amplifier which measures well but which
X.5 and XA.5 amplifiers utilize the same basic circuit topology
AB, with an idling dissipation similar to the rated output. The XA
Within any given chassis size, the X and XA amplifiers are designed
leads to two channel amplifiers with half the output power per
half the output of Class AB amplifiers.
The X amplifiers deliver more output power per dollar, and the XA
unconditionally stable into low impedance and reactive loads.
XA30.5 Owner’s Manual
All the usual performance metrics - power, distortion, noise, input
impedance, damping factor and bandwidth have all been improved
in this latest generation. The power supplies are larger, with fast
rectifiers gating to larger capacitor banks. The increases in AC line
noise worldwide have been addressed with heavier EMI filtering
improved biasing regulation, the circuits give much more consistent
performance under varying AC line voltages and over a variety of
All this is very nice, but only if it improves your listening experience.
We listen very carefully and critically to our amplifiers with a wide
variety of associated equipment and we take our time with it.
Musical performance is most important, and is the basis of our
manufacturing decisions have to balance subjective performance
That is why we make more than one amplifier, but all are built with
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Tel (530) 367 3690
Pass Labs,
PO Box 219
XA30.5 Owner’s Manual
X amplifiers run at about the same power as their output rating, and
XA amplifier run more than twice that. The heat sinks on the side
You can put this amplifier anywhere you want, but it must have good
ventilation. Do not place it in enclosed cabinets or small closets
without means for air to circulate freely. Stacking these power
reason. You should have a minimum of about 6 inches clearance to
When not actually intending to play music the amplifier should be
left in standby mode, where it draws only a few watts of bias on
recommend that for minimum noise this switch should be toggled in
We have provided a standard IEC power cord that fits into the
With the exception of the largest of the X and XA series, there is no
This amplifier is equipped for operation with an earth ground
provided by the users AC outlet. Never defeat this ground
but provides isolation from system ground loops.
last cable installed on your power-amplifier. You may, if you wish,
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.
XA30.5 Owner’s Manual
The amplifier’s voltage and current rating are indicated on the
rear panel. It will be either 230 volts, 115 volts or 100 volts. The
larger amplifiers have a circuit breaker of the appropriate capacity.
The smaller power amplifiers use a slow-blow 3AG type fuse. The
input, be certain that the XLR connector has a gold shorting plug
between pins 1 and 3, which connects the “minus” input to ground,
plug, just contact the factory – we give them away all the time.
The question comes up all the time – are balanced inputs (XLR)
better than single-ended (RCA)? The answer is that balanced lines
generally give lower noise and slightly less distortion. They are
recommended unless your favorite source component has only RCA
Also on the rear panel are the output connections for the
loudspeakers. On stereo amplifiers there is one pair per channel, and
is positive polarity, and the black one is negative.
Please note that, being a balanced output, both of these terminals
manufacturers of the products involved – both they and we will be
happy to advise you.
reason, we provide a dedicated 5 way binding post just for that on
XA30.5 Owner’s Manual
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 dim for a moment as the power supply charges the
will protect the amplifier, but it does not provide personal shock
protection in the manner of a ground-fault interrupter. One more
reason why it is important not to defeat the Earth connection of
your power cord.
blue, indicating that AC power is available and the capacitor banks
Now turn off the rear power switch and unplug the AC power cord
posts on the amplifiers, observing correct polarity. The output
binding posts will accept either bare wire or spades. (Regulatory
not to each other and never to the amplifier case.
ground, particularly if you are using a powered subwoofer with this
The amplifier may be driven single-end or balanced, your choice.
balanced input will always occur through the XLR connector.
Again, if you drive the amplifier single-ended then leave the supplied
pin 3 is inverted (negative) input. Pin numbers are marked on the
XA30.5 Owner’s Manual
XLR. If you re-install the jumper incorrectly or leave it lying about,
Now that the source component is connected, turn the volume all
Push the front panel button to activate the amplifier. The lights will
You are ready to play music
With any luck, you can now enter that blissful state, and we won’t
work, but it will get fixed, and often it’s something really simple.
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
beyond the first few hours of operation. You will very likely notice
This generation of amplifiers warms up faster and is more bias-stable
hour for critical listening. At the factory we adjust the bias and offset
values initially and then after warm-up and then again after 48 hours,
without undue discomfort for 5 seconds or so.
The amplifier has a thermal cutout that will disconnect AC power if
XA30.5 Owner’s Manual
would indicate a serious problem.
We have a general recommendation about interconnects, and
recommendations.
The amplifier is not sensitive to source interconnects. It is also not
usually a very good idea. For long runs balanced cables are highly
recommended for their inherent rejection of noise.
We prefer speaker cables that are short and stout. Oxygen-free
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
withstand the levels of torque that may be easily applied by wrench.
good technician.
After that, the longevity will depend upon the number of operating
XA30.5 Owner’s Manual
in the field in excess of 20 years with no particular mortality, and we
More to the point, you should not worry about it. This is a
Pass Laboratories
PO Box 219
www.passlabs.com
sales@passlabs.com
protected by law.
service@passlabas.com
XA30.5 Owner’s Manual
XA30.5 SPECIFICATIONS
Power Output
Distortion @ 1 KHz
Maximum Output Voltage
Maximum Output Current
Damping factor
Dynamic range
Balanced CMRR
DC offset
Power Consumption
Temperature
XA30.5 Owner’s Manual
Warranty Information
All Pass Laboratories products purchased new from an authorized
Pass Laboratories dealer in North America are covered by a
This warranty includes parts and labor charges incurred at the repair
The customer assumes responsibility for shipping and insurance to
Non-North American customers should consult with their original
Pass Labs dealer or distributor for warranty repair instruction prior
North American product must be returned to the country of origin
imported.
purchased outside the United States may vary depending upon the
Any modifications to Pass Laboratories products that have not
received written factory approval nullify all claims and void the
warranty. Should a modified product be returned to the factory for
repair the owner will be required to pay all necessary charges for the
repair in addition to those charges required to return the product to
its original configuration.
recent accepted standards.
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
international markets either to authorized Pass Labs dealers or to
XA30.5 Owner’s Manual
Water and moisture:
water ( as per example, near a bathtub, washbasin, kitchen sink,
laundry tub, wet basement or swimming pool ). Care should be
liquid is never spilled onto or into the device enclosure through
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
Adequate precautions should be taken so that the
grounding provisions built into an electrical product are never
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 supply cords should be routed so
placed on or against them, paying particular attention to cords where
Never under any circumstance
Never under any circumstance
insert a cut or damaged power cord into a mains power socket.
insert a cut or damaged power cord into a mains power socket.
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
product and may cause the electronics to self-protect and shut down.
To reduce the risk of fire, electrical shock or other
injuries, the user should not attempt to service the device beyond
read the following:
read the following:
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