Pass Laboratories XP-25 Owner's Manual

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TM

Feb. 4, 2010

XP-25 Owner’s Manual

XP-25 Owner’s Manual

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INTRODUCTION:

Pass Laboratories, specifically Nelson Pass and his co-designer
Wayne Colburn have a long history of imagining and successfully
bringing to the discriminating consumer some of the finest phono
stage pre-amplifiers ever offered. Each new incarnation of the
Pass Laboratories phono preamps has pushed their personal limits
as to what level of acoustic bliss is realistically achievable from
“Streaming Analog”©.

Since 1997 the guiding credo for these phono pre-amps remains the
vision that music must flow effortlessly from LP surface to listeners
ear. With each evolution of product that effortless flow should
issue forth with greater detail and clarity while never forgetting or
sacrificing the soul of the music and the artistic intent. The Pass
Laboratories XP-25 does not disappoint.

The XP-25 was brought to market both by copious measurements
and extensive listening through a multitude of tone arm and
cartridge combinations. Listening was given precedent over the
numbers but never at the expense of measured performance. The
result is a dynamic, lush and smooth sound with dramatic detail and
spectacular layering. Those listeners familiar with Pass Laboratories
previous phono pre-amps will be struck by the clear delineation
of bass notes in the XP-25 and the greater sense of music in a real
physical space.

Like some great musicians we get requests! You spoke and we
listened… so that you can listen better. Now the XP-25 a product
designed at the intersections of excellence, adaptability and
convenience.

The twin chassis XP-25 eclipses the already exceptional performance
of the well-reviewed and well-received XP-15: delivering enhanced
RIAA performance at a fraction of the previous distortion. With
the XP-25 you are going to discover a whole new dimension of
dynamics, inner detail and spectral richness on your favorite LP’s.

The XP-25 brings all control and cartridge loading functions to
the front panel and presents them in a clear easy to understand
layout. The XP-25 boasts two separate and selectable inputs, ample
adjustable gain along with generous resistive and capacitive loading
choices.

Those listeners and archivists with the desire or need to sample
music from two tone-arms or turntables will be able to do so
instantly with a single XP-25, thus simplifying their complement
of analog equipment and removing one more variable from their
listening chain.

XP-25 Owner’s Manual

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The addition of a user selectable high pass (low cut) filter makes
possible the playing of recordings with excessive subsonic
information.

The addition of a user selectable mute control makes possible the
cuing of records and needle drop in absolute silence.

The XP-25 is an uncommonly fine match with very low output
moving coil cartridges which would normally require a transformer
first stage.

By the early 1980’s it was generally acknowledged that lower output
moving coil cartridges were capable of retrieving significantly more
fine detail from record grooves than higher output moving magnet
cartridges. In many instances this was simply a case of having lower
moving mass to accelerate in the electrical generator mechanism of
the phono-cartridge. Moving coils with 3 or 4 turns of the finest
wire attached to the lightest and stiffest cantilevers were capable of
accurately tracking complex musical passages that a few years prior
would have seemed impossible tasks to engineer and listener alike.

The really astute cartridge makers had clearly taken a page from the
automotive and motorcycle racing cognoscenti, whose engineers who
were doing everything in their power to lower “un-sprung mass”
in an effort to get tires to say in intimate contact with the roughest
terrain at the highest possible speeds. In both worlds the ability to
accurately track the impossible landscape is the ultimate goal…..
minimal moving mass associated with a compliant suspension is a big
part of the answer.

Unfortunately the active electronics that were capable of extracting
signal at those low levels, frequently then buried much of that signal
in their own noise floor. Step-up transformers generally addressed
the noise issues, but frequently lost the very fine detail somewhere
in the transformers iron core. For the time, the promise of the best
moving coil cartridges went un-realized

The XP-25’s high gain and exceptionally low noise figure allow for
ample output and detail from cartridges providing as little as 40 uV
(micro-volts) of signal at the phono input.

The adjustable gain options of the XP-25 make this unit immune
from overload with any high output cartridge of which we are
familiar.

XP-25 Owner’s Manual

The XP-25 is as much a pleasure to use as it is to listen through,
thank you for trusting your ears and your vinyl collection with us.

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Before you sit back and listen, take time to read and understand
cartridge loading. When you find the desired setting, please record
that setting so that you can come back to it in the future. For your
convenience we left space at the end of this manual for just these
sorts of details.

TECHNICAL DETAILS:

As previously indicated the XP-25 is a twin chassis design. One
chassis holds the fully filtered and regulated power supplies and
the second chassis houses the analog gain circuits, input switching,
loading and all those details and features normally associated with a
reference RIAA phono stage.

The two chassis are interconnected with a shielded and filtered Din­25 cable. This Din-25 cable only carries power, never analog signal.

As far as this product is concerned you may use either Din-25 power
connector on the power supply chassis to link-up with the XP-25
control module. Both power connectors are identical and provide
identical performance from the phono-stage. The second Din-25
connector is capable of powering either another XP-25 phono-stage
or a Pass Laboratories XP-20 pre-amplifier without degradation of
measured or perceived performance.

Consumers frequently ask us if they may substitute a Din-25 cable
of their choice for the one Pass Laboratories supplies. The answer is
yes, provided that cable carries all the necessary legal approvals. For
those of you so inclined, please pick a shielded and filtered cable so
as to not degrade the full measure of performance your new XP25 is
capable of producing.

Never attach or detach the Din_25 cable with the power supply,
powered up from the wall. Always unplug your XP-25 from line
voltage prior to attaching or removing the Din 25 cable.

The rear of the power supply chassis has a standard IEC 320 power
inlet module a fuse holder and twin Din-25 power connectors. As
with the Din-25 cable, the user is free to substitute a suitable IEC
power cord of their choice. This product accepts any cordset with
an IEC 60320 C13 connector or equivalent. Be aware however that
the XP-25 power supply is not particularly sensitive to differences in
properly terminated power cords.

If you substitute an aftermarket power cord you need to be aware
of the following. The ground pin on the power cord provides this

XP-25 Owner’s Manual

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product’s safety ground, for your safety and the integrity of this
product the safety ground must never be defeated. Additionally this
product has filter components in the AC line that are designed to
shunt unwanted noise from the power-line to ground. Defeating
the safety ground will ultimately defeat some of the performance
advantages built into this product.

To insure maximum performance and maximum safety use only
power cords that are grounded and carry all the necessary approvals
and directives from the local regulating authorities.

Lets talk about AC power requirements. Your new XP-25 is built
voltage specific to your market. Line voltage is determined at the
time of construction and is not changeable. The products voltage
and current requirements will be indicated on a tag affixed to the rear
panel of the XP-25’s power supply chassis. This tag will indicate a
nominal 100 volts, 120 volts, 220 volts, or 240 volts with allowances
for normal variations of the nominal indicated build voltage.

The AC Line Voltage in all instances will be 50 - 60 Hz. Please verify
that that voltage indicated on the product is consistent with the
nominal voltage supplied at your location.

All XP25 products are protected by a voltage specific type 3AG
fuse (1/4” x 1-1/4”). For 100 Volts ac and 120 Volts ac the fuse
will be 1 amp, for 220 Volts ac and 240 Volts ac the fuse will be 
amp. In all instances the fuse will have a slow blow time constant.
Substitution of another time constant other than “slow blow” at
the same amperage will not harm this product, but we would not
expect longevity from the fuse element. It is not suggested that
you substitute any other fuse type or fuse rating, deviation from the
indicated physical size of fuse (1/4” x 1-1/4”) may cause significant
physical damage to the fuse holder and put the product and your
safety at risk.

ADJUSTMENT:

In order to set the XP-25 in a way which optimizes the performance
of your phono-cartridge it will be helpful though not absolutely
necessary that you have some information and set up suggestions
on that specific cartridge. If you do not have data on the cartridge
and do not wish to re-invent the wheel, contact the dealer or the Pass
Laboratories factory. We will attempt to help you with that data, but
by no means do we have data for every cartridge arm combination
ever built.

XP-25 Owner’s Manual

At the bare minimum you should know and have set the suggested

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