Pass Laboratories Xs Preamp User manual

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XsPreamp Owner’s Manual
PASSTM
X s Preamp Owner’s Manual
Sept. 2013

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XsPreamp Owner’s Manual
Introduction There are people who do not know that Wayne Colburn has
designed the Pass Labs preamplier products for the last 20 years.
Wayne’s modesty has tended to keep him out of the spotlight, and
he does not like to write, and so it falls on me to trumpet his latest
achievement. It follows in a smooth progression of successful pre-
ampliers and phono stages, each recognized as offering a genuine
improvement in sound quality.
When we began development of the Xs power amplier ve years
ago, we knew that we would also need a companion piece. Of
course, back then we thought we could have this done in a year or
so...
Wayne was given carte blanche on the design and an unlimited
budget, and as progress on the amplier was very slow, he had lots
of time to acquire and play with many exotic parts and materials.
And spend money.
Naturally the comparison will be made with its predecessor, the
XP-30 line stage preamp, which achieved incremental performance
improvements over the XP-20 and XP-10. The most obvious
difference is that the Xs comes in only two chassis, where the XP-30
had at least three chassis, one for supply and control, and one chassis
per channel for as many channels as you might reasonably want. The
Xs is designed solely for two channel operation, and it ts in two
(larger) boxes.
The XP-30 had a few unique features, among them independently
adjustable dual output sets for use in bi-amping and the high voltage
output swing capable of driving unity gain power ampliers such as
the First Watt F4.
The Xs preamp expands on these features and adds some nice new
touches, such as remote control of the absolute phase switching.
The volume controls are improved in performance with 0.5 dB steps,
expanded dynamic range and lower noise. The harmonic content of
the 0.001% distortion gure of the volume control has been tweaked
to favor 2nd harmonic over 3rd. The buffer stage for the volume
control has been eliminated, giving an even simpler gain path.
Improved circuit boards layout puts the cherry on top.
The gain stages still use matched complementary Toshiba Jfet inputs,
Bipolar cascodes, and Mosfet outputs. Pass Labs has some of
the few remaining stocks of these largely unavailable parts. Some
changes have been made – the Class A bias has been doubled,

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XsPreamp Owner’s Manual
For your protection please
read the following:
accompanied by much larger heat sinks, and the circuit will now drive
any reasonable load (I have successfully used it to drive my 16 ohm
Lowthers).
The circuits are now completely DC coupled throughout (no
capacitors), and the frequency response is at to 100 Khz.
The XP-30 could swing enough voltage to drive a balanced follower
output stage to 80 watts rms. The Xs increases that gure to over
150 watts.
Some of the materials have gotten more exotic – the gain stages are
mounted on ceramic circuit boards with gold plating. The channel
motherboards are made of Panasonic Megtron with immersion gold,
which performs about as well as Teon or Polyamide but without
the adhesion properties. The power supplies use 4 ounce plated-
through high temp FR406.
While the two channels share a chassis, they are isolated on separate
board systems with distance between them, so the crosstalk gures
between channels are as good as the XP-30 separate chassis. Each
channel and the digital control circuits have their own isolated
supplies, each mounted on it’s own board in a separate chassis.
The three separate power supplies use the lowest noise transformers
available from Plitron and they incorporate EMI lters on the AC
line input, secondary output, fast/soft recovery rectiers, large
storage capacitance and extensive regulation. The active regulation is
both series and shunt types, and is followed by passive ltering using
polypropylene capacitors.
All this in machined aluminum cases. If like me your eyesight is not
what it once was, you will also appreciate the larger display on the
control panel.
It does not automatically follow that more money and more exotic
parts and such will result in a better sounding product. Indeed,
some of things Wayne tried did not work as hoped, although they
measured well enough. Fortunately there was lots of time available,
and the back-and-forth process between Wayne and the four other
listeners assured the nest product we could possibly make.
At this point, I can only say that if you are on a restricted budget you
might be wise to avoid borrowing one of these.
Nelson Pass 2013

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XsPreamp Owner’s Manual
WARNING, IMPORTANT SAFETY INSTRUCTIONS
Read these instructions, Keep these instructions
Heed all warnings, Follow all instructions and precautions
Water and moisture: Electrical devices should never 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. Electrical devices should never be
left exposed to the weather, dampness, splashing or dripping. Clean this
device only with a dry cloth.
Power Sources: An electrical device must be connected to a mains power
source in strict accordance with the supplied product owners manual and
local standards. Please verify that the AC mains voltage specied in the
product manual match those requirements indicated on the unit and the AC
voltage provided to your location by the power company.
Grounding: Adequate precautions should be taken so that the grounding
provisions built into an electrical product are never defeated. This product
is supplied with a polarized and grounding type IEC 320 power cord. An
IEC 320 grounding power cord has two blades, which conduct power and
a third grounding prong. The grounding prong is essential for personal
safety and proper operation of this product. If the grounding prong does
not t your outlet, please consult an electrician and have the obsolete
receptacle updated before operating this device.
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 one that is fully safety rated by the necessary local authority.
The mains cord is intended to function as the safety disconnect for this
product and must remain readily accessible for this purpose at all times.
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, or where they intersect trafc paths. Never walk on a
power cord. 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. Unplug mains cable before attaching or removing
signal or speaker cables Failure to heed this warning may damage or destroy
equipment and result in personal injury.
Ventilation: Electronic devices frequently run hot, but you should be able
to place your hands on them without discomfort. You must allow for this

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XsPreamp Owner’s Manual
heat in installation, by providing for free air circulation around the product.
The Xs Preamp is not expected to generate much heat; A 10 degree C
rise above ambient would be typical of the control chassis and the power
supply is expected to have a negligible temperature rise above ambient.
A minimum of 5 cm (2 inches) should be allowed for both side-to-side
and vertical clearance.
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. Under no circumstances may the
ventilation openings be blocked with items such as newspapers, cloths or
drapes. No naked sources of ame, such as candles may be placed on or
near this product.
Servicing: To reduce the risk of re, 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 qualied service personnel.
Servicing by a qualied technician is mandatory when the apparatus has
been damaged in any way; such as when a power cord is damage, when the
device has been exposed to moisture or liquids, been dropped or does not
operate normally in any way.
For Units With Externally Accessible Fuse Receptacle: Unplug the device
from all sources of power before changing or inspecting any fuse. Replace
fuse only with one of same physical size, type and rating as that specied
by the manufacture for that product.
There is no power switch on the Xs Preamp, the unit is presumed to
operate continuously.
Safety disconnect for this product is the detachable power cord by design.
There are no internally mounted user serviceable fuses or other
components within this product. Any service issues must be refereed to a
qualied electronics service technician
Installation: It is presumed that the two Xs Preamp chassis will be stand
mounted. If installed on a cart or stand, the cart or stand must be rated by
the manufacturer to support beyond the product weight. Extreme caution
must be exercised if moving the product while installed in stand or cart to
avoid tipping and possible physical injury.
Ambient Temperatures: Normal temperature rise of this device in
extended operation is 10 degrees C. Do not operate this device in an
environment greater than 45 degrees Celsius.

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XsPreamp Owner’s Manual
You can place this pre-amplier anywhere you wish but it is
suggested that you choose it’s placement in such a way that input
cables can be short, neatly dressed and away from AC power lines.
You may stack the Xs Preamp power supply and control chassis,
however performance of this product will be enhanced if some
distance separates power supply chassis and control chassis.
Alternately the two chassis may be arraigned in a side-by-side
conguration, separated by no less than 15 cm roughly 6 inches for
lowest noise and best performance.
As previously indicated each Xs Preamp consists of two independent
chassis connected to each other by twin umbilical cable terminated
at both ends with a powerCON connector. The connector should
never be attached or removed from either chassis with the power
supply chassis attached to mains power.
Once the Xs Preamp chassis are placed in their physical location you
may start making input and output connections, you may wish to
reference the following section Physical Description and Operation.
The signal connection may be either single ended (RCA) or balanced
(XLR), choose one or the other.
If running single ended please verify that a jumper is installed
between pins 1 and 3 of the XLR. Proper placement is shown on
silkscreen on the back of the Xs-preamp control chassis.
Pin 1 XLR - Signal Ground
Pin 2 XLR - Plus signal
Pin 3 XLR - Minus signal (Inverted)
Physical Setup
Electrical setup

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XsPreamp Owner’s Manual
If you have lost the jumpers, please contact either your dealer or
the factory for replacements. A single ended input without the XLR
jumper will result in diminished performance.
You may now connect the power supply to it’s control chassis
stages. Other than being line voltage specic the power supplies are
universal to the Xs Preamps. Both right and left channel powerCON
connections must be properly made up before AC power is applied.
powerCON cable end connectors insert into their respective
chassis connectors and then lock with a 1/8 turn clockwise.
Insert the cable connector into the chassis receptacle; turn to
lock until they click and latch. Verify that they latch and lock
before proceeding.
Last cable to be attached is the mains cable. Please make connection
with the power supply IEC 320 socket rst, house mains last.
Failure to follow this sequence can damage speakers and in some
instances result in increased likelihood of electrical shock. As with
all electrical devices the power cord (when used) is always the rst to
be removed and the last to be connected, no exceptions.
At this point you should be ready to play music.
The powersupply chassis connects to the electrical mains by a
standard IEC 320 detachable power cord and to the control chassis
by two 1.5 m powerCON umbilicals. On the rear of the power
supply chassis is a single IEC 320 power inlet for connection to the
mains, below a single 3AG fuse holder rated for AC mains duty. To
the left and right side two locking powerCON connectors, which will
accept the supplied, interconnecting powerCON umbilicals.
Safety disconnect is provided only by the detachable AC power
cord. Under normal operation access to the AC power cord must
be maintained in the event of electrical failure. The AC power
cord should be removed from the mains and then the power supply
when the unit is left unused or during atmospheric electrical events
(lightening storms). Under normal circumstances and for best sonic
performance the unit is left powered up continuously.
The control chassis is a true dual mono design: Right and left
channels receive power independently via independent dedicated
powerCON umbilical cables. In all instances of power and signal
Physical Description
and Operation

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XsPreamp Owner’s Manual
the upper bank represents left channel, the lower bank represents the
right channel.
Viewing the control chassis from the front.
Extreme right hand side is the rotary volume control opto encoder.
The knob of the opto encoder lets you manually raise or lower the
volume in 0.5 dB steps from –89.5dB to + 9.5dB (100 discrete steps).
Left of center on the front panel is the vacuum orescent which
shows all operational characteristics of the preamp.
Underneath the vacuum orescent display, four small push buttons
and window for the IR receiver (remote control function)
Buttons are labeled “Mute, Mode, Input < and >”
MUTE: Pressing the mute button once, quiets the output of the Xs-
Preamp. Pressing the button a second time restores normal output.
MODE: Pressing the mode button, brings up the status of the slave
(auxillary) output. The relative level of the Slave (Aux) output can
then be set by the INPUT < and > buttons on the Xs-Pre front
panel. This function is only available on the front panel. A second
pressing of the mode button reverts the display back to normal
status and returns the INPUT< and > to their normal function of
manual input selection.
INPUT < and >: A single press on either of these buttons
increments the input selection for rear panel inputs (XLR or RCA)
selecting inputs 1-5 in the “normal” mode. In the “AUX” mode

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XsPreamp Owner’s Manual
as previously indicated these buttons allow for the relative offset
(displayed in 0.5dB steps) of the slave (auxiliary) outputs in relation
to the master (main) outputs.
The buttons on the hand remote duplicate most but not all of the
functions on the Xs Preamp front panel. Level setting for the slave
(auxiliary) output is not available from the hand remote.
From the hand remote you can direct access the following functions:
Phase: ips the absolute phase of the output. A “-” will appear on
the preamp display to indicate the phase.
Mute: Mutes the output.
inputs 1-5: duplicating the manual Input < and Input > buttons on
the front panel.
Tape button, selects and deselects the tape input (virtual input #7).
Tape output is always live.
Balance < and Balance > buttons set the relative levels between right
and left channel.
Volume ^ increases the output level in 0.5 dB steps to a maximum of
+9.5dB
Volume v decreases the output level in 0.5 dB steps to a minimum of
–89.5 dB.
Pass Thru is a multi step software operation that selects the “pass-
thru” input (virtual input #6) and slowly ramps the gain up to 0 dB.
At any time during the “ramp-up” period, a second button push
will cancel the “Pass-Thru” command and operation. Pass thru is
intended to be used with a multi-channel processor. This feature
allows the multi-channel processor total control over the analog
signal chain.
Ext amp on (External Amp On) This button toggles a voltage
between +12 Volts DC and 0 Volts DC. This switched DC signal is
available at both right and left channels of the Xs-pre control chassis
and is intended to control the turn on circuits of the associated
power ampliers. The power ampliers if so enabled can be
connected to the red and white binding posts on the rear panel of
the Xs-Preamp control which are marked “ext amp on”.
Display: The display button controls the luminosity of the vacuum
volume
displayext amp on
pass thru
balance
tape
3
mute
54
21
phase
PASS
Xs Preamp

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XsPreamp Owner’s Manual
uorescent display on the front panel of the Xs-Preamp control
chassis. The default setting is “bright”. One push on the button and
the display re-sets to “dim”. A second push on the button and the
display extinguishes. A third push and the blank display reverts to
the default setting of “bright”.
With the display extinguished any command function, such as a
volume change will illuminate the display in the “dim” mode for
approximately 5 seconds and then return to a blank, extinguished
state.
Viewing the gain channels from the rear… right to left.
There are 6 inputs of XLR and RCA, these inputs are labeled 1-5
and pass-thru. At any input you may choose either RCA or XLR.
To properly input RCA one of the supplied gold jumpers must be
placed between pins 1 & 3 of the associated XLR. You may use a
mix of RCA and XLR, not however on the same channel.
RCA inputs will function without the jumper but gain will be low by
6dB and noise will be up by a like amount.
The Pass Thru input deserves special mention. Pass Thru is identical
to all other inputs with one exception. Pass Thru is associated
with a software sequence that sets the gain of that input to 0 dB
specic for use with a surround sound processor. However there is
no requirement that the Pass Thu be used at the 0 dB default. The
user is free to set Pass Thru manually to any level they wish after the
initial ramp up.
Immediately to the left of the normal inputs is a side loop named
conventionally as Tape In and Tape out. The selected input always
appears at the Tape out without benet of the volume control. One
could use this loop for a conventional analog recording system or
just as easily an analog signal processor. We do not anticipate a
large number of users will have need of this feature, it is however

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XsPreamp Owner’s Manual
available. More frequently users will simply wish to use Tape In as
the 7th input.
That pretty much covers the gamut of available inputs, next we
have the three outputs which also are available both single ended
and balanced. Two are considered “Master” (main) and one “Slave”
(auxiliary). Any or all outputs may be utilized at the same time in so
much as each one has it’s own output buffer and is fully independent
of all other outputs .
The Master (main) outputs track the volume control directly in 0.5
dB steps (-89.5 dB though +9.5 dB) as indicated on the main display
as true gain gures.
The Slave (auxiliary) outputs may be set equal to or less than the
levels of the Master (main) outputs. Once set from the front panel
of the control chassis the Slave (auxiliary) outputs will accurately
track the Master (main) from either the front panel volume control
or the hand remote.
Immediately to the left of the outputs a pair of ve way binding
posts which supply a 12 volt DC signal to control “on/off ”
functions on a number of power amps.
Next to that pair of binding posts and at the extreme left hand side
of the rear panel as single locking powerCON connector.

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XsPreamp Owner’s Manual
Lets talk about AC power requirements. The XsPreamp draws 80
watts of current continuously.
The voltage and current rating are indicated on the rear panel of the
power supply chassis. The power supply will be rated for either 100
Vac, 120 Vac or 240 Vac. Voltages are xed at the time of build and
are not changeable in the eld.
The frequency rating of the AC line source will be 50Hz to 60Hz
nominal in all cases. Please verify that the power supply voltage
and current rating are consistent with the local mains power before
connecting this product to the electrical mains.
The Pass Laboratories Xs Preamp power supply is provided with a
conventional IEC power cord rated at 15 amps. The safety ground
is provided by this power cord and attached at the chassis in the
conventional approved manner.
The AC power input to the power supply runs through an RF lter,
which reduces high frequency noise coming into and going out of
the amplier power supply. This lter and the safety ground both
depend upon a quality earth ground from the ground pin on the
power cord.
Under no circumstance should you defeat the ground connection
of the power cord. Safety ground is isolated from signal ground to
reduce the incidence of ground loop noise. The presence of 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 meets all legal requirements and has been approved by the
appropriate local testing authority.
Power requirements

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XsPreamp Owner’s Manual
“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.
PASS®
Pass Laboratories Inc.
13395 New Airport Rd., Suite G, Auburn, CA 95602
voice: 530.878-5350 - fax: [phone] - web: passlabs.com

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XsPreamp Owner’s Manual
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 specied repair facility, exclusive of any subsequent
or consequential damages. Damage due to physical abuse is specically
excluded under this warranty.
For this warranty to apply the customer is responsible for returning the
product unmodied to the factory within the specied warranty period.
The customer assumes all responsibility for shipping and insurance to
and from the factory or a factory specied 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,
veriable by serial number.
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
specic rights and details.
Any modications 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
modied 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 conguration.
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
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For more information please contact: Pass Laboratories Inc.
Pass Labs Warranty