Pass Laboratories X1 Manuel utilisateur
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X1 Owner’s Manual
passTM
X1 Owner’s Manual
Aug 10, 2006
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X1 Owner’s Manual
The X1 is an ultra high quality minimalist audio preamplifier that
features a remote control and external power supply. It combines
a completely new circuit topology with traditional construction
representing thirty five years of amplifier design.
This preamplifier flows from a commitment to create the best
sounding product: a simple circuit with the most natural sonic
characteristics. Derived from US Patent # 5,376,899, the X1
integrates power MOSFET and JFET devices in a simple Class A
topology in order to deliver the finest sound possible.
The patent-pending Super-Symmetric gain circuitry is unique in
providing superior flexibility and performance with both balanced
and unbalanced inputs and outputs, converting one to the other as
desired without extra circuitry and without performance degradation.
The X1 minimizes the number of components in the signal path,
and yet retains exemplary objective performance specifications. It
pushes the edge of the art in exploring how much subjective quality
is obtainable with a new but very elementary gain stage.
The X1 employs a new type of volume control that offers an order
of magnitude better performance than seen before in an electronic
control. It provides over 60 dB of range, large voltage swing and
very good measured performance. Most importantly it is subjectively
outstanding; better than any potentiometer we know of. We are
justifiably proud of this new device, which is registered as having a
patent pending.
Very few people are involved in the production of this product. I
supervise all phases of the construction, and I test each preamplifier
myself. If you have questions, comments, or problems, please feel
free to contact me directly.
Thank you for purchasing this preamplifier. It is my sincere hope
that you will enjoy its sound as much as I do.
Wayne Colburn,
Vice President, Design
Introduction
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X1 Owner’s Manual
The preamplifier main chassis / control unit has four sets of input
connections, both single-ended and balanced output connections, a
tape loop and a full function remote control that mirrors the front
panel functions.
The main chassis also has a DB-25 connector that connects to the
remote power supply and a single pair of 5-way binding posts that
are used for remote amplifier turn-on. The preamplifier’s voltage
and current rating are indicated on the bottom of the power supply.
It will be either 240 volts, 220 volt, 120 volts, or 100 volts. A 0.5
amp 3AG slow blow fuse is provided with 100-120 volt units, and a
0.25 amp slow blow fuse is provided with 220-240 volt units. The
frequency rating of the power supply in all cases is 50 to 60 Hz. The
preamplifier typically draws 30 watts during operation. Please verify
that the pre-amplifier’s indicated voltage requirements are consistent
with the voltage available at your location, prior to operation.
The main preamplifier chassis is connected to the power supply
with a custom shielded cable that carries both the analog and digital
power. Please note this power cable must be installed before
the preamp is powered up. The power cable plugs, into and then
screws into, the rear panel of the main chassis and the power supply.
The connectors are a tight fit but should never need to be forced.
The X1 will function with either DB-25 on the power-supply chassis.
The additional DB-25 is for future performance enhancements.
We have provided a standard AC power cord that fits into the
IEC line receptacle at the right rear of the power supply chassis. The
preamplifier is equipped for operation with an earth ground which
is provided by the user’s AC outlet. Never defeat this ground, its
use will not adversely affect the performance of this product. The
chassis and circuit ground of the preamplifier are connected to earth
through a power thermistor, which gives a ground connection for
safety but helps avoid troublesome ground loops.
The X1 has a total of four inputs and a separate tape loop. Two
of the four inputs (Input numbers 1 & 2) can be used single-ended
or balanced. The other two inputs (inputs 3 & 4) are single-ended
only. The tape loop has both single-ended and balanced inputs
and outputs. Balanced inputs and outputs are via XLR connectors.
Single-ended inputs and outputs are via RCA connectors. On the
XLR connectors, pin 1 is grounded, pin 2 is the positive signal, and
pin 3 is the negative signal. Left channel RCA connectors are marked
with white spacers. Right channel RCA connectors are marked with
a red spacers. Balanced XLR inputs and outputs are marked with
“L” for left and “R” for right channel.
Setup
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X1 Owner’s Manual
If your signal source is unbalanced, input will always occur through
the RCA input connector. Inputs 1 and 2 give you a choice or either
single ended or balanced inputs. When single-ended inputs are used
on input 1 and input 2, a shorting plug, which is provided, should
be inserted between XLR pins 1 and 3 of the associated connector.
This plug shorts the negative input to ground thus optimizing the
input connection. You can run the X-1 without this shorting plug,
but performance will not be ideal. (NOTE: inputs 3 & 4 are single
ended only and do not have XLR’s associated with them.) You are
free to use any combination of balanced and unbalanced connections
with the X1. The unbalanced input impedance of the preamplifier is
33 kOhms. In balanced mode, the input impedance is higher, with a
differential impedance of at least 66 kOhms.
Next to the inputs on the rear panel, the preamplifier offers tape
inputs through both XLR and RCA connectors. This output is a
direct connection to inputs 1, 2, 3, and 4 when they are selected from
the front panel. Input 5 (TAPE IN) is deliberately not available
through the tape output connection. Input 5 is designated for use
with a tape recorder if you have one, and we have arranged that it
will not place its output on the tape out, which will prevent you from
accidentally creating a feedback connection with your tape machine.
The main outputs are located at the left-hand side (viewed from the
rear) of the rear panel, two male XLR connectors, and two RCA
connectors, “R” (right) and “L” (left). The RCA connectors ground
is in parallel with pin 1 of the XLR outputs and the RCA hot is fed
from an independent summing junction that maximizes the X circuit
benefits. The RCA, single-ended, outputs are buffered from the
balanced outputs. You may use both the single ended and balanced
outputs at the same time. On the XLR, pin 1 is ground, pin 2 is
positive, and pin 3 is negative.
The X1 takes maximal advantage of four identical gain paths (two
identical paths per channel) very much unlike the typical two gain
path (one signal path per channel) pre-amplifier you may be familiar
with. Almost without exception traditional audio pre-amplifiers,
unlike their science and industry counterparts, have maintained single
signal path per channel (two identical paths in a stereo pair).
In order to manage balanced signals these two gain path pre-
amplifiers must utilize phase combining networks to process
incoming signals and subsequently drive outputs via phase splitting
circuits to re-establish a quasi-balanced signal. This manipulation of
signal typically adds additional gain stages and degrades the inherent
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X1 Owner’s Manual
noise and distortion superiority of balanced signal, coloring what you
eventually hear.
Pass labs through its unique patented “Supersymmetry” topology
maintains the advantages of a true balanced signal throughout
the electronics chain. The salient point of this approach affords
significantly less signal manipulation, higher input impedance, as
much as a 100:1 (20dB) reduction in distortion while providing
greater gain, and twice the dynamic headroom of identical circuits
running single ended.
The X1 maintains the integrity of its received signal by treating
all sources internally as balanced signals and converts seamlessly
between balanced and unbalanced inputs and outputs without any
additional components in the signal path. This was a conscious
effort by Pass Labs to enhance the consumer’s ability to integrate
source components and power amps with otherwise incompatible
requirements through a virtually transparent control center.
The rear mounted pair of five-way binding posts are intended to
control the on/off function of our own X series power amplifiers
from the X1’s front panel, or via the four button remote. When
the preamp mode “Amp” is selected it allows the user to switch a
nominal 12 volts DC at maximum draw of 50 milliamps to these
binding posts. In some instances this voltage may have the ability
to control products from other manufacturers, but we by no means
have a comprehensive listing of their compatible features. If you
have questions about compatibility, your service technician and dealer
are an excellent source of information.
In application the X1’s front panel controls and alphanumeric
display are quite straightforward and intuitive. We encourage you to
become familiar with their operation prior to establishing any input
connections with this unit. Experience indicates that engaging in
a few minutes of exploration and playtime will add much to your
ultimate enjoyment of this exceptional Pass Labs product.
The Mode switch moves between 10 different functions. They are
Volume, Input, Mute, Tape, Balance, Display, Mono, Unity, Amplifier
(power amplifier turn on / turn off), and Gain adjust. Actuating
the Mode “<” switch moves the display to the function one step
to the virtual left and “>” button moves to virtual right, one step.
The Select switch then alters the function of the displayed mode.
The knob on the right is always the Volume control, and it is always
active. The Select “^” button turns on a function or increases its
value it is also balance right. The select “v” turns a function off or
Description of Operation
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X1 Owner’s Manual
decreases its value; and is also balance left. If any control is used the
display reverts to the last saved output level, therefore we suggest you
reduce the volume before switching inputs.
The remote control uses the same four-button protocol, though it is
physically arranged slightly different than the X1’s front panel. The
far left button “<” is mode left and the far right button “>” is mode
right. The top button “^” is select up, and the bottom button “v” is
select down. The display shows the active function, just as it would
when using the front panel controls. The display has two brightness
levels and off, selected by the up “^” and down “v” buttons when
the mode “display” is visible.
The electronic volume control allows greater than 60 dB range and
is driven by a microcontroller that reads an optical encoder that
serves as a front panel volume control. In this manner tracking of
the volume of the two balanced channels is possible with accuracy
unavailable on any ordinary volume control, assuring precise level
steps and high common mode rejection in balanced circuits.
Wayne has included some unique features on the X1 that give it
unprecedented versatility.
At the extreme virtual right of the mode selection is the function
labeled “gain”. This control allows you, the user to adjust the gain
of the X1 to extract the best possible performance out of a variety
of source components of different manufacturers. The “Low Gain”
setting allows for 4 dB of gain from the X1 and the “Hi Gain”
allows for 14 dB of gain. The 10 dB difference between these two
settings require that you pay attention to volume as you switch back
and forth between High and Low Gain. With a number of products
one setting may convey a greater sense of musicality than the other.
Let your ears be the final arbiter. With our own X series amplifiers
which are quite high gain (30 dB), we find the +4 dB setting to be
most satisfying.
The unity function too bears special attention. This control is
associated only with input number 4 and has two positions selected
with the up/down arrows. The up arrow toggles to a straight-
through function with neither attenuation nor gain. This function is
useful in that it allows the preamplifier to function as a unity buffer
for use with components that best function with their own volume
controls, such as surround processors. When the right-front and
left-front outputs of the processor are routed through input 4 of
the X1 (with the gain of the X1 set for Unity gain), the volume will
be under full control of the processor and the X1’s action will be
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X1 Owner’s Manual
totally transparent. When the user chooses “Unity” this sets the X1’s
gain to the low (+4dB) setting, regardless of how it was previously
configured. When at Unity both left and right level controls on
the X1 will have a displayed value of 24, and any previous balance
settings will be lost. Both of these default conditions are intentional,
and intended to make the most advantageous use of your source
electronics. You may also set any of the four inputs to unity (0dB
gain) by selecting low gain and setting the volume to indicate 24 on
the front panel display.
Before selecting this option, it is imperative that the input device on
input number 4 has its gain set to minimum. Failure to follow this
precaution could result in a volume level intolerable to both ears
and speakers. To further protect your hearing and valuable audio
equipment, Wayne has designed this product so that the volume
setting of the preamplifier will always revert to zero as you change
inputs. We trust that the remote control, with its four buttons that
duplicate those of the preamp front panel will enable you to quickly
select inputs and establish levels of output.
1) Circuit simplicity and a minimum number of components is a key
element. The fewer parts in series with the signal path, the better.
Adding more parts and gain stages may improve measured specs, but
will seldom improve the perceived sonic quality.
2) The characteristic of gain devices and their specific use is
important. Individual variations in performance between like devices
are important, as are differences in topological usage. All signal
bearing devices contribute to the degradation, but there are some
different characteristics that are worthy of attention. For example,
smooth low order nonlinearities are additive in quality, bringing false
warmth and coloration, while abrupt high order nonlinearities add
harshness and false brightness.
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
factored out by large application of feedback, resulting in loss of
warmth, space, and detail. The trick is to get good performance
without this excessive reliance on feedback.
The art of high end audio design lies in the approach to combining
these elements to get high reliability and simplicity, high quality
measured performance, and high quality subjective performance. It
Product Philosophy
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X1 Owner’s Manual
takes imagination and hard work to get as much of these as possible
at once without trading them off adversely against each other.
We recommend the use of the balanced output mode where possible.
It will retain the character of the input mode, but offers less
distortion, less noise, more gain, and more voltage swing, without
compromising the sound.
With balanced operation, the common mode rejection of the preamp
reflects the intrinsic common mode rejection of the topology, the
matching of the gain devices, and the matching of the attenuator
channels. In this case we have been able to keep the total mismatch
to about .1%, for a common mode rejection of approximately -60
dB.
The input system of the preamplifier will exhibit full common mode
noise rejection with passive balanced sources, where the negative
input is connected to ground at the source through the appropriate
source impedance. This allows adaptation of unbalanced sources to
balanced operation with passive cable connections in a manner that
achieves the noise rejection of active balanced sources.
The use of a micro-controller allows all of the preamplifier functions
to be repeatable and accurately controlled. The micro-processor
only controls the functions of the preamplifier. At no time does
any of the input or output signal come into contact with the digital
control signals. The digital circuits are powered by a power supply
that is completely separate from the analog supply. Should it ever
be necessary to update the software that controls the functioning
of the preamp only the socketed micro processor need be changed.
There is a single custom made shielded cable that connects the power
supply to the main preamplifier module. The power supply cable
does not carry any audio signals or digital clock lines and is filtered
against noise.
The power supply for the X1 is contained in a separate chassis and
consists of a toroidal power transformer delivering an unregulated
+/- 45 volts which is actively regulated before feeding passive
filtering which powers the constant current sources that bias the
gain stages. Each channel has its own regulation. The power supply
noise reaching the circuit is on the order of a microvolt, and the
little of that which gets through the circuit is rejected at the output
in a balanced system. The relays and control systems are regulated
independently from a separate toroidal transformer. All digital
circuitry is isolated in the power supply control unit. The power
Other Design Comments
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X1 Owner’s Manual
supply cable does not carry any audio signals or digital clock lines
and is filtered against noise.
Muting relays, which delay connection during turn-on and shut off
the output when insufficient power supply is available to maintain
regulation, guard the output of the X1. The preamplifier is designed
to run constantly, and will exhibit optimum measured performance
within about 10 hours of turn-on. The omission of a power switch is
intentional.
The X1 consists of two full-size aluminum chassis. Both chassis are
machined from solid aluminum stock by computer controlled milling
machines. There are no stamped or sheetmetal products in this
product. One of the full-size chassis houses the control functions,
active elements and display. The second chassis houses the power-
supply.
For more information please contact:
Pass Laboratories Inc.
P.O. Box 219,
24449 Foresthill Rd.,
Foresthill, CA 95631
Tel: 530.367.3690
Fax: 530.369.2193
www.passlabs.com
© 2006 Pass Laboratories Inc.
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X1 Owner’s Manual
Gain selectable 4 dB or
14 dB balanced output
selectable 4 dB or
14 dB single-ended output
Freq. Response -3 dB @ 2 Hz,
-3 dB at @ 100 kHz
Distortion < .1 % THD typically .003%
@ 2 volts @ 1KHZ
Maximum Output 10 volts rms bal out,
7 volts rms unbal out
Output Impedance 200 ohms unbalanced,
750 ohms balanced
Input Impedance 33 kOhm unbalanced,
66 kOhm balanced
CMRR typical -55 dB, 1KHz
Crosstalk typical -85 dB, 1KHz
Output Noise floor < -125 dBV, 20Hz-20 KHz
External amp turn on 12 volts DC 50 mA
Power Consumption 35 watts
Dimensions chassis 17”W x 11.5 “D x 3.5”H each
Shipping Weight 46 pounds in packing carton.
X1 Specifications
“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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