Pass XP-15 User manual

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XP-15 Owner’s Manual
passTM
XP-15 Owner’s Manual
March 27, 2009

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XP-15 Owner’s Manual
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.
WARNING

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XP-15 Owner’s Manual
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.
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
[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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XP-15 Owner’s Manual
Pass Laboratories has long been respected for building some of the
finest phono-stages in the audio industry. Since 1999 the venerable
Pass Laboratories X-ono has been respected by both consumer and
professional user as one of the premiere reference phonostage pre-
amplifers.
As associated equipment in the audio chain has improved we at
Pass Labs found ourselves longing for an improved phono-stage
with even lower noise, greater resolution and sonic ease than we
had enjoyed with the Pass Labs X-ono. The culmination of that
investigation resulted in the XP-15, Wayne Colburn’s latest phono-
stage and successor to the X-ono.
Thank you for purchasing the XP-15, we trust that you will find it
easy to set up and a joy to use.
The XP-15 has a very accurate RIAA equalization curve. This curve
is accurate to better than 1/10 dB over 10 octaves. The accuracy
of this curve does not vary with an adjustment change of gain or
cartridge loading.
The XP-15 features gain adjustable from between 46dB and 76dB; a
range sufficient to allow successful operation of not only high output
moving magnet cartridges, but also the lowest output moving coil
cartridges without the use of an auxiliary step-up transformer.
By the early 1980’s audiophiles recognized that in general lower
output moving coil cartridges were capable of retrieving more fine
detail from record grooves than higher output cartridges, in many
instances this was simply a case of having lower moving mass to
excite in the electrical generator of the cartridge. Moving coils with
less than a half dozen turns of the finest wire possible attached
to the lightest and stiffest cantilevers were capable of accurately
tracking musical passages that a few years before would have seemed
impossible.
The cartridge makers had clearly taken a page from the automotive
and motorcycle racing engineers who were doing everything in their
power to lower “un-sprung mass” in an effort to get tires to stay in
intimate contact with rough terrain at high speeds. In both regards
the ability to accurately track the impossible is the ultimate goal….
less moving mass attached to the suspension is a big part of the
answer.
Unfortunately the active electronics that could extract signal at those
low levels typically added noise. Step-up transformers generally
Introduction

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XP-15 Owner’s Manual
addressed the noise issues, but frequently lost the very fine detail
somewhere in the transformers iron core.
The XP-15 gives vinyl playback the gain structure we need and
low noise figures we want. The ability to play extremely low output
cartridges without a head transformer allows for a clarity with these
cartridges that we’ve personally never experienced.
This extremely low noise / high gain structure of the XP-15 is
capable of cleanly and quietly delivering in excess of 0.5V line level
signal output with a phono cartridge input of 80 micro-volts. As far
as we know these are the best performance figures in the industry for
a phono-stage. Performance metrics aside this is beyond question
the most user friendly and sonically enjoyable phono-stage that Pass
Laboratories has ever offered.
Cartridge loading can be adjusted from a couple ohms to 47k-Ohms,
with a parallel capacitance from 100 pF to 750 pF.
The XP-15 is a single chassis design with internal power supply
which attaches to house power through a standard fused and
grounded IEC inlet. A tag affixed to the chassis will indicate voltage
and current requirements for the XP-15. Before operation, please
verify that the indicated line voltage is consistent with the line voltage
where you intend to install this piece of equipment. Line voltage
is determined at the time of construction and not user changeable.
Line voltage will be 100 Vac, 120 Vac, 220 Vac or 240 Vac.
In addition the rear panel also has a standard IEC 320 inlet socket,
which accepts standard detachable power cords for connection to
house power and a panel-mount fuse holder for safety. Unit’s built at
100 / 120 Vac will be fused for  amp; units intended for 220 / 240
Vac will be fused at  amp. In all instances the fuse will be a 3AG
single use (type 313) slow blow fuse (1/4” x 1-1/4”). Substitution
of another time constant other than slow blow will not harm the
amplifier but we would not expect longevity from the fuse element.
It is strongly suggested that you not substitute any other type fuse or
fuse rating.
We include a power cord with this product that meets all recognized
compliance standards for safety. Should you wish to add an
aftermarket power cord you are welcome to do so. The product
accepts any cordest with an IEC 60320 C13 connector or equivalent.
We strongly suggest that you only use cordsets that meet the legal
directives of your specific country.
Setup

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XP-15 Owner’s Manual
The single chassis XP-15 comes with two sets of input connections,
two sets of output connections, and a single 5-way binding post for
turntable grounding. These are located on the rear panel of the pre-
amplifier.
On the rear panel you will see two sets of 8 pole DIP switches for
each channel, these switches allow you select cartridge type (moving
magnet or moving coil), select gain, and adjust cartridge loading.
Next to the IEC inlet you will see graphic representation of how the
two pairs of switches interact. From the factory the XP-15 ships
with a default setting of moving coil at 100 ohms with a gain of 76
dB.
In order to set the XP-15 for your particular cartridge you will need
to have some salient information on the cartridge. If you do not
have that cartridge information please contact your dealer or the Pass
Laboratories factory. We will attempt to help you with that data, but
by no means do we have factory data on every cartridge ever built.
Please be aware that the XP-15 is a dual mono design, whatever
setting you select for one channel the other channel will need to be
set identically.
You will first need to select Moving Magnet (MM) or Moving Coil
(MC) as appropriate for your specific cartridge. In all instances the
switch-tab for any selection will need to up for “on” and down for
“off ”. If you have a moving iron cartridge, you will most likely
need to select Moving Magnet if the output is greater that 2mV. A
moving iron cartridge with an output of less than 1mV will typically
Adjustment

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XP-15 Owner’s Manual
do best with Moving Coil selected. Only one type of input may
be selected as “ON”, the alternate input type must be “OFF”. If
Moving Magnet is selected as “ON”, all eight (8) resistive loading
switches should typically be selected “OFF”.
Once you have selected an input type you will need to attach the
RCA connectors from your turntable to the appropriate input on
the XP-15 (Moving Magnet or Moving Coil). You will also need
to attach the ground connection from your turntable to the single
white five way binding post on the XP-15. The XP-15 will function
without this connection made up but the background noise level will
likely be excessive.
If you have selected Moving Magnet you will also need to select
capacitance. It will be impossible to give suggestions for correct
capacitance with any given cartridge, due to the huge variation in
capacitance on the cables. The optimal value is selected by listening.
There are three capacitive loading switches with values of 330pF,
220pF and 100pF; these are in addition to a fixed value of 100pF.
You may select any switch or number of switches, the values are
additive. The range of values available is 100pF – 750pF. The
correct value is that which gives the best overall tonal balance.
Typically if the cartridge sounds too bright more capacitive loading
will be required. The typical Moving Magnet cartridge has a fairly
predictable output, the XP-15 gain in moving magnet is fixed at
46dB.
Resistive loading for moving magnet is fixed at 47k-ohm. If you
require something other than 47k-ohm, please contact the factory. It
is suggested that all moving coil loading switches be set to off.
Correct settings for moving magnet gain are shown below.
MM MC G1 G2 G3
46dB ON OFF OFF OFF OFF
Moving Iron cartridges typically load at 47k-ohm and are not at all
sensitive to capacitive loading. It is suggested that you treat them as
moving coil cartridges if their output permits.
Moving Magnet
Moving Iron

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XP-15 Owner’s Manual
Moving coil cartridges are the typical cartridges of choice for
the serious vinylphile and generally the lower output moving coil
cartridges are preferred. We have successfully operated the XP-15
with cartridges that output a voltage of 50uv, this pre-amp may be
used with even lower output cartridges (without an auxiliary step-up
transformer), but we don’t know of any.
To operate the Pass Labs XP-15 as a Moving Coil pre-amp, you may
need to deselect Moving Magnet (from the factory, the XP-15 ships
Moving Coil enabled) and select Moving Coil “On”. In addition
you will need to attach the turntables phono cartridge to the XP-15’s
Moving Coil input.
Your next task is going to be to set gain. This will be a very
straightforward task. The available gain settings are 56 dB, 66 dB, &
76 dB. Gain is selected by a combination of MM, MC and switches
G1, G2 and G3
MM MC G1 G2 G3
56dB OFF OFF ON OFF ON
66dB OFF OFF OFF ON ON
76dB OFF ON OFF OFF OFF
The gain controls attenuate the overall gain of the Moving Coil
stage in such a way that as the gain is reduced the noise levels seen at
the output of the XP-15 are reduced by a like amount. In this way
there is no penalty to selecting one gain setting over another. The
exemplary signal vs. THD + noise figures of the XP-15 are never
compromised by changing gain settings.
Chose a gain setting that allows your pre-amp volume control to
operate within a range similar to what you experience with other
source components. If phono is your only source component, then
pick a gain setting that allows your pre-amp a fairly advanced gain
setting at whatever you consider a comfortable listening level.
The predominate loading effect on Moving Coil cartridges will be
resistive loading, however like Moving Magnet adding capacitance
will selectively reduce perceived output at higher frequencies.
Resistively the XP-15 has a fixed moving coil input value of 47k-
ohms and user selectable values of 10, 25, 50, 100, 250, 500, 825 and
1k-ohm. Selecting “On” for any of these values places that value in
parallel with the 47k-ohm or any other value selected. From a purely
mathematical perspective this gives a possible 2^8 resistive loading
selections according to Ohm’s law for parallel resistors. We’re very
Moving Coil

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XP-15 Owner’s Manual
grateful to Georg Simon Ohm for sharing his discovery with us,
but leave the math of all the 256 perturbations to those so inclined.
From a practical standpoint the 9 values indicated are likely sufficient
to cover the needs of all but the most obscure cartridge.
After you have selected a resistive cartridge loading that gives the
best overall spectral balance and the most dynamic presentation you
may choose to add or subtract capacitive loading to slightly trim the
high-end response.
Please understand the loading of a moving coil cartridge is a very
inexact science at best, specific recommendations should be taken
(and offered) very lightly. I encourage you to think separately from
the cartridge manufacturer and choose your resistive loading values
accordingly. The cartridge maker may have for example anticipated
a transformer being used as the initial stage of gain, the XP-15
with its active elements is a very different proposition. As an added
complexity part of the cartridge loading is provided by the lead-in
wiring, the resistance, and reactance of that wire must be accounted
for in choosing loading values in the XP-15. As long as you derive
your final setting empirically you may ignore these effects, your
moving coil cartridge will not.
An improperly loaded cartridge will suffer every unwanted sonic
anomaly, ranging from lack of definition and bass to a very strident
and screechy high end. Making the mistake of not loading channels
identically adds additional confusion. Please verity that loading for
one channel is duplicated in the other accurately.
Cartridge loading is a compromise between what works best for
the cartridge and what sounds best for the listener. Specifically we
are looking for a compromise loading which sounds best across the
whole audio spectrum.
I suggest you start with the following:
Always, ALWAYS mute or turn the volume of you pre-amp to a
minimal setting (better yet, turn your power-amp off) before making
any adjustments to the XP-15. Changes made to the XP-15 loading
have the possibility of sending pulses to your pre-amplifier that could
damage speakers if the volume of the pre-amplifier is set sufficiently
high.
Once the volume setting is reduced and the power amp turned off
set the loading to 100 ohms (switch position 4 “on” and positions

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XP-15 Owner’s Manual
1-3, 5-8 “off ”. Give the XP-15 a couple minutes to settle in
electronically and turn the power-amps back on. Listen to the system
critically for some time (10 minutes to an hour) using various musical
selections that you are familiar with.
Now turn the volume down and the power amps off again, set the
loading switches to the next lowest resistive value (50 ohms). Once
again give the XP-15 a couple minutes to settle in, turn the power
amps back on and listen to the same musical selections as before. If
your test selections sound better with the new loading you can be
assured that the loading change was in the correct (lower resistance
in this example) direction.
If the change in loading resulted in a more pleasant presentation of
your chosen musical selections, once again turn down the volume on
the preamp and the power supply off. Select the next lowest resistive
loading (25 ohms) and listen to the same selections again. At some
point you will find a value where the sound deteriorates, move back
to the last value that sounded excellent. Once this has done you have
reached the optimal resistive loading.
If going below 100 ohm resulted in degraded sound, then obviously
the correct change would have been to have gone upward next
highest level above 100 and repeat the listening. I am sure you get
the idea, its not complicated but it can be time consuming.
The eight values available should cover any cartridge needs nicely.
However should you wish to get very creative resistors can be
selected in parallel for almost limitless experimentation. Some
examples of additional loading values follow on page 12. Should
you wish any combination of switches may be selected “ON”. The
resultant values will follow Ohm’s law for resistors in parallel. Once
again this shouldn’t be necessary, but it is available should you wish
to calculate the myriad of permutations possible.
Again I would like to stress that you are listening for a musical
balance in the selections that you play. Some loading selections will
offer better bass but poor high-end resolution, some will have better
high-end and definition but with a flat sound stage. You are seeking
an optimal balance of correct spectral balance in conjunction with
correct spatial information. Finding the best compromise will take
time.
Do not make the mistake of setting the pre-amp so that it enhances
one recording only, listen to a variety of material and adjust
accordingly.

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XP-15 Owner’s Manual
Capacitive loading will not affect moving coil cartridges to the same
extent that capacitive loading affects moving coil cartridges but
there may be some small benefit to adjusting this parameter once the
resistive loading is optimal.
Once you have found the optimal setting, take the time to record
those setting so that should the need ever arrive, you can replicate
your personal settings with little effort. Of course when you change
either cartridge or wires between the cartridge and pre-amp you may
need to revisit your selected settings.
For a very long time there has been faith in the technical community
that eventually some objective analysis would reconcile critical
listeners subjective experience with a repeatable laboratory
measurement protocol. Perhaps this will occur, but in the meantime
audiophiles largely reject bench specifications as an indicator of
audio quality. This is appropriate; the appreciation of audio is a
completely subjective human experience. We should not more let
the numbers define audio quality than we would let chemical analysis
be the ultimate arbiter of fine wines. Measurements are certainly
critical, they can and do provide a measure of insight, but are no
substitute for human judgment of that which is pleasant.
As in art, classic audio components are the results of individual
and collective efforts that reflect a coherent underlying goal and
philosophy. If successful, they make both a subjective and objective
statement of quality, which is meant to illicit appreciation in the final
product. It is essential that that the circuitry of an audio component
reflects a philosophy which addresses the subjective nature of its
performance first and foremost.
Lacking the ability to completely characterize performance in an
objective manner, we should take a step back from the resulting
waveform and take into account the process by which it has been
achieved. The history of what has been done to the music is
important and must be considered a part of the result. Everything
that has been done to the signal is embedded in that signal, however
subtly.
Experience correlating what sounds good to knowledge of
component design yields some general guidelines as to what will
sound good and what will not sound good in real life.
1) Simplicity and a minimum number of components is a key
element, and is well reflected in the quality of better tube
designs. The fewer pieces in series with the signal path, the better.
Design Comments

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XP-15 Owner’s Manual
This is often true even if adding just one more gain stage will
improve the measured performance.
2) The characteristic of gain devices and their specific use is
important. Individual variations in performance between like
devices is important, as are differences in topological usage.
All signal bearing devices contribute to the degradation, but
there are some different characteristics that are worth
attention. Low order nonlinearities are largely additive in
quality, bringing false warmth and coloration, while abrupt high
order nonlinearities add harshness.
3) Maximum intrinsic linearity is desired. This is the
performance of the gain stages before feedback is applied.
Experience suggests that feedback is a subtractive process; it
removes information from the signal. In many older designs,
poor intrinsic linearity has been corrected out by large
application of feedback, resulting in loss of warmth, space
and detail.
We give these precepts a great deal of thought in the design and
voicing of product. You only need to address the cartridge loading
till it sounds good to you.
Some Suggested Resistive Loading Values
in 1 2 3 4 5 6 7 8
ohms 10 25 50 100 250 500 825 1K
10 ON OFF OFF OFF OFF OFF OFF OFF
17 OFF ON ON OFF OFF OFF OFF OFF
25 OFF ON OFF OFF OFF OFF OFF OFF
33 OFF OFF ON ON OFF OFF OFF OFF
50 OFF OFF ON OFF OFF OFF OFF OFF
83 OFF OFF OFF ON OFF ON OFF OFF
91 OFF OFF OFF ON OFF OFF OFF ON
100 OFF OFF OFF ON OFF OFF OFF OFF
166 OFF OFF OFF OFF ON ON OFF OFF
200 OFF OFF OFF OFF ON OFF OFF ON
250 OFF OFF OFF OFF ON OFF OFF OFF
311 OFF OFF OFF OFF OFF ON ON OFF
333 OFF OFF OFF OFF OFF ON OFF ON
452 OFF OFF OFF OFF OFF OFF ON ON
500 OFF OFF OFF OFF OFF ON OFF OFF
825 OFF OFF OFF OFF OFF OFF ON OFF
1000 OFF OFF OFF OFF OFF OFF OFF ON
47000 OFF OFF OFF OFF OFF OFF OFF OFF

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XP-15 Owner’s Manual

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XP-15 Owner’s Manual

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XP-15 Owner’s Manual

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XP-15 Owner’s Manual
Gain 40 dB @ 1 KHz (MM) max, single ended
46 dB @ 1 KHz (MM)max, balanced
71 dB @ 1 KHz (MC) max, single ended
76 dB @ 1 KHz (MC)max, balanced
RIAA response plus/minus .1 dB 20-20 KHz
Distortion < .01 % THD @ 1mV MC input
< .002 % THD @ 10mV MM input
Maximum Output 20 volts rms.
Output Impedance 300/300 ohms
Input Impedance 47 K or 1K / 0-650 pF (MM)
5 ohm - 47K ohm moving coil
Unweighted Noise -90 dB ref. 10 mV
input moving magnet
-81 dB ref. 1 mV input moving coil
Power consumption 15 watts
Dimensions, 17”W x 12”D x 4”H
Shipping Weight 25 pounds in packing carton
Pass Laboratories
PO Box 219
24449 Foresthill Rd
Foresthill, CA 95631 USA
www.passlabs.com
[e-mail]
tel: [phone]
fax: [phone]
XP-15 Specifications

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XP-15 Owner’s Manual
Please note: Conditions of warranty service and customer rights for
product purchased outside the United States may vary depending upon
the distributor and local laws. Please check with your local distributor for
specific rights and details.
All Pass Laboratories products purchased new from an authorized Pass
Laboratories dealer in North America are covered by a transferable, limited
3-year warranty. This warranty includes all parts and labor charges incurred
at the factory or factory specified repair facility, exclusive of any subsequent
or consequential damages. Damage due to physical abuse is specifically
excluded under this warranty.
For this warranty to apply the customer is responsible for returning the
product unmodified to the factory within the specified warranty period.
The customer assumes all responsibility for shipping and insurance to
and from the factory or a factory specified repair facility. The conditions
and stipulations of this Pass Laboratories warranty only applies to units
originally sold new through an authorized dealer. Warranty on factory
repair is 60 days and covers only the scope of the original repair.
Non-North America customers should consult with their original Pass Labs
dealer or distributor for warranty repair instruction prior to contacting the
factory or shipping product to the factory for repair. Non-North American
product must be returned to the country of origin for warranty service.
Foreign distributors are only required to offer warranty service on Pass
Laboratories product that they have imported, verifiable by serial number.
Any modifications to Pass Laboratories products that have not received
written factory approval nullify all claims and void all provisions of the
warranty and liability by the maker or authorized distributor. Should a
modified product be returned to the factory for repair the owner will be
required 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 suspect as
counterfeit or stolen 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 international markets either to authorized Pass Labs dealers or
to third parties located in the United States or Canada.
For more information please contact: Pass Laboratories Inc.
© 2009 Pass Laboratories Inc..
Warranty Information