Pass Laboratories X600.5 User manual

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X600.5 Owners Manual
passTM
X600.5 Owner’s Manual
May 17, 2006

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X600.5 Owners Manual
The Pass Laboratories ™ X600.5 stereo amplifier embodies the de-
sign technology and refinements of the “X” series amplifiers includ-
ing extensions of the patented Supersymmetry™ circuit. Additionally
selected refinements of the XA series amplifiers have been incorpo-
rated into the X600.5 to significantly improve this products sonic
performance in comparison to it’s immediate predecessor, the Pass
Laboratories™ X600.
The Supersymmetry™ circuit topology was granted a U.S. patent in
1994, and was the result of 19 years of effort by legendary analog
designer and company founder Nelson Pass. The amplifier uses
highly matched components in a classically simple single ended Class
A circuit. The amplifier contains only two simple stages: the first is a
balanced Class A gain stage. Its output drives a bank of high power
devices operated as followers.
These are inherently low distortion types of circuits, but their perfor-
mance is significantly improved when operated as balanced devices.
Distortion and noise identical to both halves of a balanced circuit can
be made to disappear at the output, and in a well-matched symmetric
circuit, most of the distortion and noise is identical.
Pass Laboratories Supersymmetry™ enhances this effect by provid-
ing a connection between the two halves of the balanced circuit that
further perfects the match of common mode artifacts. Any distor-
tion and noise not already identical to the two halves is made more
identical by a factor of about 10. The result of this perfected match
is improved noise cancellation at the output of the amplifier. From a
listeners standpoint this results in a more accurate presentation of the
soundstage and better resolution of low level detail.
Unlike feedback techniques where the goal is to correct for the distor-
tion by feeding a gain stage an inversely distorted signal, Supersymme-
try™ seeks merely to create perfect matching between the two halves
of an otherwise well matched circuit.
Matched balanced power circuitry typically sees a distortion and noise
reduction of about 90% (20 dB) through a balanced connection
without any additional effort. The Supersymmetry™ circuit delivers
another 90% reduction, so that the X series has about 1/100 of the
distortion of a conventionally simple and otherwise identical ampli-
fier. Distortion and noise can still be seen at the output of one half of
the circuit, but since it is virtually identical on the other half, these un-
desirable artifacts largely go away at the speaker terminals. This gives
good measured performance, and because a simple circuit produces it,
also sounds quiet excellent.
Introduction

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X600.5 Owners Manual
Previously these kinds of simple Class A circuits have been popular
for their sound quality in low power amplifiers, but have not found
application at high power levels due to excessive distortion and low
efficiency. Supersymmetry™ overcomes this barrier, delivering the
sweetness, staging, and detail of very simple circuitry up to kilowatt
power levels and beyond.
The X.5 Series amplifiers have the tremendous dynamic range (>140
dB) to do justice to the high-resolution digital recordings of the 21st
Century and the elegance to retrieve the micro dynamics offered by
the most sensitive loudspeakers. The simple but powerful circuitry
moves easily from total silence to explosive transient and back to
silence without a trace and without information loss. Very unlike
conventional high power amplifiers, they provide this level of power
with a subtlety befitting some of the better tube amplifiers. This per-
formance is consistence across the audio spectrum and the amplifiers
are unconditionally stable into all speaker loads.
So relax and enjoy your amplifier. Call us if you ever have a problem
or question. You are welcome to ask questions or offer comments.
Thank you for buying our product.

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X600.5 Owners Manual
You can position this amplifier most anywhere you wish, but it re-
quires adequate 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 about 550
watts, most of which dissipates as heat across the heatsinks. As a point
of reference, these heatsinks should never become too hot to touch
for several seconds.
Let’s talk about AC power requirements. This amplifier draws about
5 amps (continuous rms) at 120 volts out of the wall during normal
operation, and this power draw reflects mostly the idle current that
we run through the output stage. If you are driving a low impedance
load, you will draw more power than this, but this will not be typical.
The amplifier’s voltage and current rating are indicated on the rear
panel. It will be 240 volts, 220 volts, 120 volts or 100 volts, all with
an appropriate rear mounted resetable circuit breaker. The frequency
rating of the AC line source in all instances will be 50 to 60 Hz. Please
verify that the amplifiers indicated voltage requirements are consistent
with the line voltage supplied at your location.
The Pass Laboratories™ X600.5 is provided with a conventional IEC
detachable AC line cord, which is rated at 15 amps. The safety ground
is attached to the chassis in the conventional approved manner. The
AC power input to the amplifier runs through a RF filter, which re-
moves high frequency noise coming into and going out of the ampli-
fier power supply.
Under no circumstances should you defeat the ground connection of
the power cord. For your safety, the chassis of the amplifier should be
earth grounded. Signal ground is isolated from chassis, safety ground,
to reduce the incidence of ground loop noise. The presence of a
safety ground will not degrade the audio signal chain.
You may substitute an aftermarket detachable IEC 320 style power
cord of your choosing; provided it is rated for at least 15 amps and it
meets all legal requirements and has been approved by the local testing
authority for such things.
Looking at the rear panel you will see the IEC 320 AC power cord
receptacle, a thermal magnetic breaker switch, two pairs of output
connectors, a pair of binding post connectors for remote turn-on, one
RCA input connector and one XLR balanced input connector.
Setup

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X600.5 Owners Manual
Make sure that the breaker switch is off (down). Plug the AC cord
into the back of the amplifier, and then into the wall. Then turn the
breaker switch on (up). The lights in your house will blink when the
power supply charges the capacitors; this is normal. This magnetic
breaker switch is not to be used as a safety disconnect during servicing
and is not a substitute for unplugging the power cord.
On the front panel, the “Standby” LED indicator should be glowing
blue, indicating that the power is on. 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 into 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, as yet. You can go ahead
and connect the source and speakers. Some speaker cables are very
difficult to work with due to physical size and construction, make sure
the speaker connections do not short together. It is recommended
that you connect the speaker ends of these cables first.
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 Laborato-
ries™, this is an incorrect and unsafe assumption. On all Pass Labo-
ratories™ 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 fac-
tory for specific instructions.... you have been warned.
The amplifier can be driven single-end or balanced, if driving the am-
plifier single-ended, leave the supplied jumper in place (between pins
1 & 3 on the XLR). Your amplifier will operate without the jumper
in place, but performance will be significantly diminished. 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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X600.5 Owners Manual
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, 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 hap-
pens accidentally all the time, and the amplifier is designed to survive,
mostly.
Of course it’s always possible that something could go wrong. If so,
don’t get excited, just relax. It’s really aggravating when something like
this 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 often interested in how long it takes for these amplifiers to
break in. Perhaps a more salient question is how long does it take them
to reach their sonic best after turn on. It takes about an hour for them
to fully warm up, and this is where we adjust 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 and
the heat sinks will rise approximately 25 degrees C. above that, for an
average on heat sink temperature of 48 degrees C. Sonically they are at
their best when the heatsinks are approximately 50 degrees C.
In your setup the temperature may vary a bit due to line voltage varia-
tions and ventilation, but this is not a big deal. You should be able to
put your hands on the heat sinks without discomfort for 10 seconds or
so. It is normal for the heasink temperature to vary side-to-side and
front to back.
The amplifier has a thermal cutout that will disconnect AC power if the
temperature exceeds 75 degrees Centigrade. This should never occur
in real life.
More things to know
You can remotely operate the stand-by mode by applying 12 volts DC
to the single pair of binding post connectors on the rear of the ampli-
fier. The positive of the 12 volts DC goes to the red connector. This
connection has an actual operating range of about 9 volts to 15 volts at
a current draw of approximately 5.0mA. This switching will override
the front panel button, so if you want the front panel button to operate,
leave the rear connection open.
You are ready to play music

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X600.5 Owners Manual
The Pass Laboratories™ X600.5 is optimized for loads nominally rated
at 4 ohms and above. You can run the amplifiers into a lower nominal
impedance without difficulty, and we are not aware of a speaker on the
market that presents unusual difficulty with these amplifiers.
The X.5 series 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, but will make the
amplifier run a little hotter. The X.5 circuit was designed to be quite
happy driving electrostatic and other difficult speakers.
When driving transformer-coupled loads directly, as in some elec-
trostatic and ribbon designs, some attention must be paid to the DC
character of the situation. If the transformer primary is being driven
raw with no protection from DC and your source has DC voltage, or
in cases where the small offset of the power amplifier is still too much,
you may create distortion in the transformer and get less than optimal
performance from it. Generally this is not the case with transformer-
coupled loudspeakers, but it does occasionally surface. In these cases,
take special care that the source does not contain a differential DC
component, and confirm the differential DC offset of the pre-ampli-
fier is sufficiently low. This differential voltage is easily adjusted by a
qualified technician armed with the appropriate service documents.
We have a general recommendation about interconnects, which is that
they should cost less than the amplifier, and be flexible enough to work
with. We have tried a lot of products and most of them work well, but
as a practical matter we cannot make blanket recommendations.
The amplifier is not sensitive to source interconnects or ground loops.
It is also not sensitive to radio frequency pickup, which allows some
flexibility in choosing source interconnects without shields, though
shields are always in good taste.
We prefer speaker cables that are thick and short. Silver and copper
are the preferred metals. If you find any cable made of gold, please
gift us a couple hundred meters.
Fortunately the amplifier is not sensitive to the capacitive/inductive
character of some of the specialty speaker cables, so feel free to ex-
periment.
We have found that about 90 per cent of bad sounding cables are in
reality bad sounding connections, and we recommend that special at-
tention be paid to cleanliness of contact surfaces and proper fit.
Speaker Interface
Interconnects and Speaker
Cables

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X600.5 Owners Manual
Speaker cables should be firmly tightened down at the speaker output
terminals, but do not use a wrench. These connectors will not with-
stand unrealistic foot-lbs of torque. Hand tightening without exces-
sive force is plenty.
Hardware Facts
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
20 years before needing replacement. Fortunately these components
die gracefully; typically with years of warning and are easily replaced.
After that, the longevity will depend on the number of operating ther-
mal cycles, but we can attest to having had amplifiers operating in the
field in excess of 20 years with no particular mortality except capaci-
tors. We don’t have good information beyond that. More to the point,
we would suggest that you not worry about it. This is a conservatively
built industrial design, not a tweaky tube circuit run on the brink of
failure. If it breaks, we will simply get it fixed, so sleep well.

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X600.5 Owners Manual
For more information please contact:
Pass Laboratories Inc.
P.O. Box 219,
24449 Foresthill Rd.,
Foresthill, CA 95631
Tel: [phone]
Fax: [phone]
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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X600.5 Owners Manual
Please check with the factory-authorized distributor in the country you are
purchasing this product for specific 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.
Warranty Information

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X600.5 Owners Manual
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.
For your protection please
read the following: