Pass Labs X150.5 User Manual
pass
TM
May 17, 2006
X150.5 Owners Manual
X150.5 Owner’s Manual
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Introduction
The Pass Laboratories ™ X150.5 stereo amplifier embodies the design
technology and refinements of the “X” series amplifiers including extensions of the patented Supersymmetry™ circuit. Additionally selected
refinements of the XA series amplifiers have been incorporated into the
X150.5 to significantly improve this products sonic performance in comparison to it’s immediate predecessor, the Pass Laboratories™ X150.
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 performance is improved when operated balanced. Distortion and noise identical to both halves of a balanced circuit will disappear at the output, and
in a well-matched symmetric circuit, most of the distortion and noise is
identical.
Supersymmetry™ enhances this effect by providing a connection between the two halves of the balanced circuit that further perfects this
match. Any distortion and noise not already identical to the two halves is
made more identical by a factor of about 10, and the result is improved
noise cancellation at the output of the amplifier.
Unlike feedback techniques where the goal is to correct for the distortion
by feeding a gain stage an inversely distorted signal, Supersymmetry™
seeks merely to create perfect matching.
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 amplifier. 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, it goes away at the speaker terminals. This gives good
measured performance, which because a simple circuit produces it, also
sounds excellent.
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.
X150.5 Owners Manual
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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 performance 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.
X150.5 Owners Manual
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Setup
You can position this amplifier most anywhere you wish, but it requires 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 typically idles at
slightly more than 250 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
2 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 replaceable type 3AG slow blow fuse.
For units rated at either 220 or 240 volts the fuse will be a 2-1/2 amp
type 3AG, 250V slow blow and for units rated at either 100 or 120
volts the fuse will be a 5 amp type 3AG, slow blow. Do not substitute
other types, voltage, amperage or time constant fuses for the specified
replacement.
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™ X150.5 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 removes high frequency noise coming into and going out of the amplifier 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.
X150.5 Owners Manual
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