Pass Labs
pass
X1000.5
X600.5
X350.5
X250.5
X150.5
X.5 amplifiers
he Pass Labs X series amplifiers
T
continue to reign as the biggest, most
powerful and popular amplifiers that we
have created. They were initially designed
as proof-of-concept of the SuperSymmetric
amplifier topology, achieving phenomenal
power and precision with only two gain
stages and very little feedback. Seven years
ago we began shipping the 1000 watt
model X1000, followed by the progressively
smaller X600, X350, X250, and X150.
Patented 10 years ago by Nelson Pass,
this new topology takes advantage of highly
matched components in a completely
symmetric circuit that intrinsically
nulls most distortion and noise across
the speaker, and then applies a small
amount of feedback to perfect this
symmetric behavior. The X series
amplifiers have received critical
acclaim throughout the world for their
sonic performance, sleek industrial
design, high reliability and rugged
construction.
Pass Labs is now very pleased to
introduce the next generation of
X series amplifiers: the Pass X.5
series. Select refinements from the
balanced single-ended Class A circuits
of the XA series amplifiers have been
incorporated into several new X.5
series models, significantly improving
their subjective performance while
keeping the high power and reliability.
Changes to these models include
improvements to power transformers,
paralleled high speed / soft recovery
rectifiers, improved AC EMI filters,
more paralleled power supply
capacitors, increased supply RC
filtering, refinements to the front-
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Mono block design
1000 watts
Gain: 30dB
+/- 145V Max
+/- 30A Max
19W x 11.5H x 28D
200LBS
Mono block design
600 watts
Gain: 30dB
+/- 105V Max
+/- 25A Max
19W x 11.5H x 22D
150LBS
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Stereo design
Stereo design
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350 watts
Gain: 30dB
+/- 80V Max
+/- 20A Max
19W x 11.5H x 22D
150LBS
250 watts
Gain: 30dB
+/- 55V Max
+/- 20A Max
19W x 9.5H x 22D
100LBS
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end input circuits, and the addition of
single-ended Class A bias circuits for
balanced single-ended Class A at low
power levels. All of these changes
bring the X.5 series closer to the
sonic signature of the XA series
amplifiers.
Four models of X series amplifiers
have been designated for X.5
refinement - the X150.5, X250.5
and X350.5 stereo power amplifiers,
and the X600.5 monoblock power
amplifier. These amplifiers feature
the distinctive front panel meters
indicating the level of current running
through the output stages that have
long been the visual signature of X
amplifiers.
These are inherently low distortion
circuits, but their performance is
improved through careful component
matching and operation in a balanced
output mode. The nearly identical
distortion and noise of both halves of a
matched balanced circuit disappears
across the speaker terminals, and
Supersymmetry takes this effect a
step further by using a small amount
of feedback to further perfect the
match. Any distortion and noise not
already identical to the two halves
is made more identical, and the
result is improved performance out
of proportion to the small amount
of feedback. Supersymmetry’s goal
is not to eliminate distortion within
each half of the balanced circuit as
such, rather it seeks to null it through
improving the match between the two
halves.
Stereo design
The result is very simple and elegant,
and as is often the case in such
circuits, it sounds far superior to
complex many-stage amplifiers using
lots of feedback.
Previously these kinds of simple
circuits have been popular for their
sound quality in low power amplifiers,
but have not been practical in high
power amplifiers for performance
reasons. Supersymmetry breaks
this barrier, delivering the sweetness,
staging, and detail of very simple
circuitry to kilowatt power levels.
The X.5 series amplifiers have the
tremendous dynamic range to do
justice to the 24 bit recordings of
the 21st Century and the elegance to
retrieve the micro dynamics offered
by the most sensitive loudspeakers.
This simplicity and power moves
easily from total silence to explosive
transients with ease and without
information loss. This performance
is consistent across the audio
spectrum, and the amplifiers are
unconditionally stable into any speaker
load.
150 watts
Gain: 30dB
+/- 50V Max
+/- 20A Max
19W x 7H x 20D
70LBS
If you need high power for difficult
loads and want to retain the qualities
of the finest low power Class A
amplifiers, the X.5 Series is a logical
choice. Only the XA amplifiers exceed
this quality, of course with much lower
efficiency and output power.
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Pass Laboratories, PO 219, Foresthill, CA 95631 - Voice: 530.367.3690 - Fax: 530.367.2193 - www.passlabs.com
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