Pass Labs INT-150 User Manual

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TM

Aug 27, 2009

INT-150 Owners Manual

INT-150 Owner’s Manual

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WARNING

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.

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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.

INT-150 Owners Manual

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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Introduction

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-It­Yourself ” 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

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