Pass Labs Music Mixer INT 150 User Manual

passTM  
INT-150 Owner’s Manual  
Aug 27, 2009  
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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  
tel: (530) 367 3690  
fax: (530) 367 2193  
“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).  
Introduction  
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-  
Yourselfaudio 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  
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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 “XAamplifiers. 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.  
Setup  
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”.  
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INT-150 Owners Manual  
 
1)  
2)  
3)  
4)  
5)  
6)  
7)  
8)  
Vacuum Florescent display ; shows operational status.  
Mute, indicator (Blue LED)  
Stand-by Power on, indicator (Blue LED)  
Stand-by Power on, momentary push button (on / off)  
Mute, momentary push-button (on / off)  
Input selection buttons (inputs 1-4)  
IR remote, receiver window  
Volume control  
A)  
B)  
C)  
D)  
E)  
F)  
Pre-amplifier inputs (1&2 XLR/RCA , 3&4 RCA)  
Pre-amplifier outputs (XLR OR RCA)  
Right Channel speaker connector  
Signal ground connector  
IEC 520 AC power inlet module  
Main Power switch (not a safety disconnect)  
Fuse holder  
G)  
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 “offmode  
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.  
You are ready to play music  
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.  
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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!  
Speaker Interface  
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.  
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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.  
Product Life  
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.  
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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.  
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.  
Pass Laboratories, PO Box 219, Foresthill, CA 95631 USA, 530.367.3690  
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INT-150 Owners Manual  
 

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