Pass Laboratories INT-150 User manual

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INT-150 Owners Manual
passTM
INT-150 Owner’s Manual
Nov 19, 2007

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INT-150 Owners Manual
Please keep these instructions and heed all warnings.
Use product only for intended function.
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 owners manual.
Please verify that the AC mains voltage specified in the product manual
match those requirements indicated on the unit and the AC voltage
provided to your location by the power company. Unplug this apparatus
during lightening storms or when unused for long periods of time. To
completely disconnect this apparatus from mains power, disconnect the
power cord from the AC receptacle. The equipment power switch does not
provide adequate protection to be considered a service disconnect.
Grounding: Adequate precautions should be taken so that the grounding
provisions built into an electrical product are never defeated.
Power Cords: Pass Labs 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 a polarized cord that is fully safety rated by the necessary local
authority. Under no circumstances defeat the safety purpose of any
polarized plugs. If the supplied power cord does not fit your power outlet;
consult a qualified electrician, never modify the plug.
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 cause injury,
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. Never block any ventilation
openings. Allow at least 6 inches of clearance around these products for
proper ventilation.
WARNING

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INT-150 Owners Manual
Crush and Tip Hazard: When moving or placing these products use
caution to avoid injury from tip-over or fall. Make sure that any stand,
cart, table, bracket or tripod used to support this product is weight rated
sufficient to the task.
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 Units With Externally Accessible Fuse Receptacle: Unplug the
device from all sources of power before changing or inspecting any
fuse. Replace fuse with one of same physical size, type and rating as that
specified by the manufacture for that product.
Pass Laboratories
PO Box 219
24449 Foresthill Rd
Foresthill, CA 95631 USA
www.passlabs.com
[e-mail]
tel: [phone]
fax: [phone]
“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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INT-150 Owners Manual
Nelson Pass has been designing audio electronics professionally since
about 1971, first with ESS (remember Heil Air Motion transformers?), and
then forming a new company, Threshold in 1975. Threshold pioneered
the design of high power Class A power amplifiers and later, high power
amplifiers using only local feedback (the Stasis series).
Pass sold Threshold and created Pass Laboratories in 1991, where he
concentrated first on elevating single-ended Class A power amplifiers to
new power levels and performance, the Aleph series.
Along the way he found the time to design highly successful lines of
amplifiers for such companies as Adcom and Nakamichi, and has
contributed approximately 60 designs (so far) to the public “Do-It-
Yourself ” audio hobbyist community.
Over the years, Nelson Pass has made power, simplicity, and performance
his design signatures. The hardware tends to run heavy and hot, but elicits
high performance and reliability from simple circuits with little or no
negative feedback.
In 1998 Pass Labs released the X series of audio power amplifiers, based
on the trademarked “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 example of
the power of this principle, delivering 1000 watts rms 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 stages and lots and lots of negative
feedback. The X1000 had only two stages and used only minimal local
feedback.
The difference was the unique balanced circuit topology in which circuit
errors are replicated at both output terminals so as to cancel and disappear
across the loudspeaker terminals. The high quality of the sound reflects
both the low distortion and simplicity of the gain path.
The SuperSymmetric circuit consists of two identical matched circuits
arranged like the wings of a butterfly, showing symmetry from left to right,
and operating balanced to the loudspeaker. The amplified signal appears
with opposing phase and equal potential across the loudspeaker. Most of
the distortion and noise appears in phase across the loudspeaker, and is not
seen.
We start with simple FET circuits already having low distortion and
noise, and arrange them in two symmetrical halves. The two halves of
the amplifier channel are closely matched, eliminating a large portion of
distortion and noise without feedback. A small amount of feedback is also
applied, not so much for the purpose of reducing distortion but to make
Introduction

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INT-150 Owners Manual
the distortion as identical as possible on both polarities of the balanced
output.
It is easier to make distortions in the two halves more identical than to
remove them with feedback, and this is the operating principle of X
amplifiers.
Since the X1000, Pass Labs products have continuously evolved toward
higher performance. The Class AB “X” series was joined by the Class
A “XA” amplifiers. Subsequent improvements to the Class AB “X”
amplifiers resulted in the “X.5” products, and their 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 quantified, and many of the improvements are
the result of trial and error and extensive listening.
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 does not
please the ears, and so we let our ears be the final judge.
The X amplifiers deliver more output power per dollar, and the XA
amplifiers have a better subjective performance. All of the amplifiers drive
known loudspeaker loads without misbehaving, and all are unconditionally
stable into low impedance and reactive loads.
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 and dramatically quieter power
transformers. In addition, through improved biasing regulation, the circuits
give much more consistent performance under varying AC line voltages
and over a variety of ambient temperatures.
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 success over the years.
It’s true that we also value the other things. The design and manufacturing
decisions have to balance subjective performance against reliability, cost,
specs, and ego (in approximately that order). That is why we make more
than one amplifier, but all are built with the same commitment to quality.
The Pass Laboratories INT-150 Integrated Amplifier was designed
specifically to bridge the gap between so called high-end audiophile product
and the need for a simple “no nonsense”, convenient, user-friendly, high

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INT-150 Owners Manual
satisfaction audio product. From a measured and subjective viewpoint this
is an outstanding product, we trust you will sit back and listen with a big
grin on your face.
If you have purchased this amplifier, we thank you for your confidence,
and hope that you enjoy it for many years. If you need product service,
have any questions or comments, or if we can help you with your audio
system, please don’t hesitate to contact us.
X topology amplifiers run at about the same power as their output rating,
and a large part of that energy gets dissipated across the heat sinks. Expect
the heat sinks on the side of the amplifier run hot to the touch – about
25 to 30 degrees C. above ambient, so you can expect 50 to 55 degrees C.
temperatures on the heat sinks. It is very important to the long life of the
amplifier that they get good ventilation.
You can put this amplifier anywhere you wish, but it must have good
ventilation to properly cool. Do not place this product 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. You should have a minimum of about 6 inches clearance to
the top and sides for adequate air circulation. Never block any ventilation
openings in the chassis. Never expose this product or it’s remote control
to excessive heat sources, such as domestic heaters or open fires. Keep all
electrical devices away from liquids, and liquids away from electrical devices.
When not actually intending to play music the amplifier should be left
in standby mode from the front panel switch, where it draws only a few
watts of bias on the output stage. If you wish to reduce the power draw
to 0, you can shut the amplifier off via the rear panel switch, however we
recommend that for minimum noise at the loudspeaker this switch should
be toggled in stand-by mode, only. If you are not going to use this product
for an extended period of time or if you are expecting an atmospheric
electrical disturbance (lightening storm) un-plug it. We have provided a
standard IEC polarized power cord that fits into the standard 15 amp IEC
receptacle at the rear of the amplifier chassis.
Given the character of these amplifiers current draw, we generally do not
recommend active line conditioners, although they are unlikely to damage
the amplifier. Save your line conditioner for the low level components, like
your cd player.
This amplifier is equipped for operation with an earth ground provided by
the users AC outlet. Never defeat this ground connection or the polarized
plug of the power cord. The signal ground of this amplifier is connected
to earth through a power thermistor, which provides a safety ground but
provides isolation from system ground loops. Should your audio system
have a device that requires an additional signal ground you will find that
ground on the rear of the INT-150 at the white binding post which is
marked “Signal Gnd”.
Setup

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INT-150 Owners Manual
1) Vacuum Florescent display ; shows operational status.
2) Mute, indicator (Blue LED)
3) Stand-by Power on, indicator (Blue LED)
4) Stand-by Power on, momentary push button (on / off)
5) Mute, momentary push-button (on / off)
6) Input selection buttons (inputs 1-4)
7) IR remote, receiver window
8) Volume control
A) Pre-amplifier inputs (1&2 XLR/RCA , 3&4 RCA)
B) Pre-amplifier outputs (XLR OR RCA)
C) Right Channel speaker connector
D) Signal ground connector
E) IEC 520 AC power inlet module
F) Main Power switch (not a safety disconnect)
G) Fuse holder
H) Left Channel Speaker connector

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INT-150 Owners Manual
For maximum safety 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 polarized 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. Always 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 indicated as either 100 volts, 120 volts, 220 volts, 230 volts or
240 volts. The smaller Pass Laboratories power amplifiers, preamps
and integrated amplifiers use a slow-blow 3AG (equivalent to 313 in EC
markets) type fuse. The required value of the fuse will be indicated on
the amplifier. The frequency rating of the AC line source is 50 to 60
Hz. Please verify that the amplifiers indicated voltage requirements are
consistent with the supplied voltage and current at your location.
On the rear panel you will find both RCA and XLR type input connections
for single-ended or balanced inputs. If you use the RCA input, be certain
that the XLR connector has a gold shorting plug between pins 1 and 3,
which connects the “minus” input to ground, otherwise the amplifier will
not operate properly. If you lose this shorting 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 outputs.
Also on the rear panel are the output connections for the loudspeakers. On
stereo amplifiers there is one pair per channel, and on mono amplifiers we
provide two pairs wired in parallel to facilitate “bi-wiring” a loudspeaker.
As you are probably familiar, the red one is positive polarity, and the black
one is negative.
Please note that, being a balanced output device, both of these terminals
are electrically live – neither is grounded and neither should not be treated
as ground. This is particularly important if you are using the output of
the amp to also drive a subwoofer amplifier or other active component. If
there is any question, please contact the manufacturers of the products
involved – both they and we will be happy to advise you.
If you happen to need a clean signal ground connection for any reason,
we provide a dedicated 5 way binding post just for that on the rear of the
amplifier.

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INT-150 Owners Manual
So the amplifier is sitting there unconnected.
Make sure that the rear panel power switch is off (down). Plug the AC
cord into the back of the amplifier, and then into the wall. Then turn the
power switch on (up). The lights in your house may dim for a moment as
the power supply charges the capacitors.
Please note that this switch is not a “safety device” or “emergency
disconnect” for this product. This switch does not provide personal
shock protection in the manner of a ground-fault interrupter, nor is it
intended to. One more reason why it is important not to defeat the Earth
connection of your power cord. Safety or Emergency disconnect involves
removing a power cord, we feel that this is the most positive and safest
solution.
On the front panel, the “power” LED indicator should be glowing blue,
indicating that AC power is available and the capacitor banks are charged.
If the “LED” is not glowing blue, then cycle the front panel power button
to “on” and turn the volume control just to verify operation.
Now turn off the front and rear power switches and unplug the AC power
cord from the wall while you connect the speakers and inputs. Amplifier
output terminals and speaker terminals will be electrically live when the
amplifier is on.
Check to make certain that the loudspeaker cables aren’t shorted at the
loudspeaker end, and then connect speaker cables to the output binding
posts on the amplifiers, observing correct polarity. 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.
Remember the warning about treating the output connections as ground,
particularly if you are using a powered subwoofer with this amplifier. If
you need a ground, use the one provided specifically on the rear panel of
the amplifier.
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.
Again, if you drive the amplifier single-ended then 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, and you will be able to tell.

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INT-150 Owners Manual
Choose either XLR or RCA inputs. If you run both at once on a single
input from different components, the sound is not likely to be optimal, but
it shouldn’t cause damage anywhere.
Now that the source components and loudspeakers are connected into
the amplifier; plug the power cord back into the wall, and turn on the rear
power switch.
Push the front panel power button to activate the amplifier and turn the
volume control down (counter clock-wise). The front panel display should
now be illuminated.
The controls on the front of the Pass Labs integrated amplifier should be
intuitive. You should however understand that the volume control is always
active and over rides the mute control. Meaning that if at some point you
activate the mute control you can un-mute the amplifier by either pushing
the mute control a second time or by either advancing or retarding the
volume control knob.
The hand remote has some additional convenience features that the front
panel does not. Balance from the remote raises or lowers the speaker
volume levels relative to each other. Display provides a choice of normal
luminance, reduced luminance or display off. In the display “off ” mode
the display will be normally dark, yet will provide reduced luminance
for several seconds any time a control function on either the remote or
integrated amplifier front panel are activated.
Please note: The hand remote is common to several Pass Labs products,
not all of the functions on this remote are applicable to your integrated
amplifier. Input 5, tape loop, pass through and external amp on are not
applicable to the INT-150, integrated amplifier.
The hand remote has two (2) AAA batteries that can be replaced after the
back cover from the remote has been removed. These batteries will need
to be changed occasionally.
If you are not comfortable removing the rear cover of the remote and
changing batteries, have your dealer change them for you. Batteries may
explode if exposed to excessive heat, never leave your remote or any
battery powered device in direct sunlight or exposed to excessive heat
sources.
With any luck, you can now enter that blissful state of musical nirvana, and
we won’t expect you back for a while.
It’s always possible that something may go wrong. If so, don’t get excited.
We know It’s really aggravating when a product doesn’t work, but it will get
fixed, and often it’s something really simple.
You are ready to play music

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INT-150 Owners Manual
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 amplifier beyond the first few hours
of operation. You will very likely notice the difference in sonic character
between cold and normal operating temperature over the first hour, so we
recommend letting these amplifiers warm up before any serious listening.
This generation of amplifiers warms up faster and is more bias-stable
during warm up than previous versions, but we still recommend an 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, if necessary.
The “sweet spot” is a sink temperature between 50 and 55 degrees C., but
this is not critical, and will vary with your room temperature. You should
be able to put your hands on the heat sinks without undue discomfort for 5
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. This is a very rare occurrence, and would indicate a
serious problem.
We have a general recommendation about interconnects, and speaker
cables: They should cost less than the amplifier, and contain 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 as to
your purchase of cables. Under all circumstances you should unplug power
cords before changing signal cables…. you’ve been warned!
The amplifier is not sensitive to source interconnects. It is also not
sensitive to radio frequency pickup, which allows some flexibility in
choosing source interconnects without shields, though shields are 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 copper and
silver are the suggested materials. If you find any really exceptional cable
made of gold, please gift us a couple hundred meters.
Fortunately this amplifier is not sensitive to the capacitive/inductive
character of some of the specialty speaker cables, so feel free to
experiment.
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 Interface

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INT-150 Owners Manual
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 tightening
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.
So how long should 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 particular 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
catastrophic failure. If it breaks, we will simply get it fixed, so sleep well.
INT-150 Specifications Volume control: 63dB range, 1dB steps
Gain: 32 dB
Freq. Response: -3 dB at 1.5 Hz and 60 kHz
Power Output: 150 watts @ 8 ohms
300 watts @ 4 ohms
Distortion @ 1 KHz: 1% at rated output
0.003% @ 5 watts into 8ohms
Maximum Output Voltage: +/- 35 volts
Maximum Output Current: +/- 20 amps
Input Impedance: 36 kohm balanced,
18 kohm unbalanced
Damping factor: 150 ref @ 8 ohms nominal
Slew rate: +/- 50 V/uS
Output Noise: <300 uV unweighted 20-20 kHz
Dynamic range: 140 dB
Balanced CMRR: < -50 dB @ 1 KHz
DC offset: < 50 mv
Power Consumption: 225 watts idle, 600 watts maximum
Dimensions: 19W x 7H x 19D
Weight: 60 lbs. approx .
Product Life

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INT-150 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
Pass Laboratories, PO Box 219, Foresthill, CA 95631 USA, 530.367.3690