Page 1
Artemis Labs PL-1
Phono Preamp for Low-Output Cartidges
Operating Manual
Page 2
Important Safety Instructions
CA UT IO N
RIS K OF ELEC TRIC SHO CK
DO N O T O PEN
AT TE NT IO N
RISQU E DE CHOC ELECT RIQUE
NE P A S O UVRI R
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a dry cloth.
7. Do not block any ventilation openings. Install in accordance with the manufacturer’s instructions.
8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers).
9. Do not defeat the safety purpose of the grounding-type plug. A grounding-type plug has two
blades and a third grounding prong. The third prong is provided for your safety. If the provided
plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet.
10. Protect the power cord from being walked on or pinched particularly at plugs, convenience
receptacles, and the point where they exit from the apparatus.
11. Only use attachments/accessories specified by the manufacturer.
12. Unplug this apparatus during lightning storms or when unused for long periods of time.
13. Refer all servicing to qualified service personnel. Servicing is required when the apparatus
has been damaged in any way, such as if the power-supply cord or plug is damaged, liquid has
been spilled inside the appliance or it has been exposed to moisture, the appliance does not
operate normally, or has been dropped.
14. WARNING: To reduce the risk of fire or electric shock, do not expose this apparatus to rain
or moisture.
Explanation of Safety Symbols:
CAUTION: To reduce the risk of electric shock, do not remove the covers.
No user-serviceable parts inside.
Refer Servicing to qualified service
personnel.
This symbol is intended to alert the user to the presence of
uninsulated “dangerous voltage” within the product’s enclosure
that may be of sufficient magnitude to constitute a risk of electric shock to persons.
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This symbol is intended to alert the user to the presence of
important operating and maintenance (servicing) instruction in
the literature accompanying the appliance.
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INTRODUCTION & SPECIFICATIONS
The Artemis Labs PL-1 Phono Pre-amplifier is specifically designed for low-output moving-coil
phono cartridges. It combines the clean, accurate sound of a purist phono preamplifier with the con
venience and reliability of a solid, well-built product. Special care is taken with all parts in the audio
path. All aspects of the design were done by John Atwood of One Electron™.
The PL-1 is conservatively designed and is built to last for many years. The only maintenance needed
is the occasional replacement of tubes, and even this has been reduced by the use of Cool-Swap™
technology. Please read this entire user’s manual so that you can understand all the features and get
the most from the PL-1. The Warranty is on a separate card. Read it and send it in to get full war
ranty coverage.
SPECIFICATIONS:
Mid-Band Gain (47K load, 1KHz): 52dB +/– 2dB
-
-
Frequency Response & Distortion (measured with inverse RIAA curve applied to generator)
Worst-case Loading (12K ohms, 1000pF):
Frequency Response: 25Hz – 30KHz +/– 0.5dB
THD+N at 1KHz, 2Vrms output: < 0.2%
Average Loading (47K ohms, 250pF):
Frequency Response: < 10Hz – 42KHz +/– 0.5dB
THD+N at 1KHz, 2Vrms output: < 0.2%
Maximum output voltage (47K load, 1KHz, 0.5% THD): 40Vrms
Output Noise (grounded input, 47K load, rms detector):
22Hz - 30KHz: < –59dB below 2Vrms output
“A-weighted”: < –69dB below 2Vrms output
Crosstalk
1KHz: < –TBDdB
20KHz: < –TBDdB
Effective Output Impedance: approx. 1300 ohms (1KHz)
Input Impedance: 47.5K ohms, lower with optional shunt resistors.
Mains Voltage: Wired at factory for one of the following voltages: 100, 110, 120, 220, 230, 240V, 50 to 60Hz.
Power Consumption (rms) : 40 Watts nominal, 49 Watts maximum.
Size: 6 ½" (165 mm) Height, 8 ½" (216 mm) Width, 14
:
5
⁄8 " (371 mm) Depth
:
Mass: 24 lbs. (11Kg)
Note: These specifications are subject to change at any time.
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FRONT & REAR PANEL
FRONT PANEL
The Power Switch applies power when flipped up. The Power Indicator will glow red while the tubes warm up,
then after approximately 40 seconds, will glow green. About 4 second after that a faint click will be heard, indicating the muting relay turning off. The PL-1 is now ready for use. If the power is removed, even briefly, then
restored, the warm-up time delay process will start over again.
REAR PANEL
Voltage Rating
Ground
Terminal
Right Input
Left Input
Input Cover
Make sure that the Voltage Rating of your PL-1 matches the power mains voltage at your location. The voltage
can be changed by internal rewiring, which can be done by Artemis Labs or by a qualified technician. The Fuse
is a 1" x 1¼" “3AG” Slow-blow type. Its value is given on the Voltage Rating sticker.
Fuse
IEC Power
Connector
Right Outputs
Left Outputs
Outputs 1 and 2
A power cord is supplied with each unit. If the mains plug does not match your socket, contact your dealer to
exchange it for the correct type. The power cord plugs into the IEC Power Connector. If the power cord is
frayed or damaged, replace it with a new one. Use only power cords that meet the safety standards of your loca
tion.
The Ground Terminal is used to connect the chassis of the PL-1 to the turntable and other equipment in your
system to help minimize hum and noise. Experiment with different connections for the best results.
The phono cartridge connects to the preamp through the Right and Left Inputs.
There are two pairs of outputs: Outputs 1 and 2. These are essentially in parallel, separated by low-value resis
tors. This allows the preamp outputs to drive another device in addition to the line amp or power amp.
The Input Cover is attached by three thumb screws. A Philips screwdriver may be needed to loosen the screws if
they are tight. Under the cover are the two bias batteries and the ZIF socket that holds the input load resistors. It
is recommended that the phono inputs be disconnected when the input cover is removed.
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REAR PANEL
The Bias Batteries supply a fixed grid bias to the 6N1P input tube. No current is drawn from them, so the batteries will last as long as their “shelf-life”, typically five years or more. Replace the batteries if they measure 1.4
volts or less. Symptoms of weak batteries are distortion and the 6N1P running hotter than normal. Replace
only with type “N” or “AM-5” 1.5 volt alkaline batteries. Make sure that the batteries are installed with the + end
(with the bump) upwards.
ZIF Socket
Ground
Terminal
Right Input
Bias Batteries
Left Input
Input Loading Resistors
(100 × required value)
All moving-coil cartridges require a load resistance, and sometimes a load capacitance. The PL-1 allows the optimum load to be selected by inserting the load resistors or capacitors into the ZIF Socket. The 3M TexTool® ZIF
(Zero Insertion Force) Socket, originally designed for the semiconductor industry, provides a convenient way to
attach additional shunt resistors or capacitors. When the lever is flipped out, the socket apertures open up. The
components are then inserted. Flipping the lever back towards the chassis firmly clamps the component leads.
The gold-plated socket blades provide a high-quality reliable electrical connection.
As shown on the simplified schematic on page 7, the top three positions of the ZIF socket are available for the
right channel and the bottom three positions are for the left channel. The middle position is not used.
The loading resistors are on the secondary of the step-up transformer. In order for the phono cartridge to see
the load it expects, the loading resistors have to be scaled in proportion to the square of the transformer ratio.
Since the step-up transformer is 1:10, the loading resistors must be 100 times the value required by the car
tridge. Similarly, any loading capacitors must by scaled by 1/100 or 0.01 times the required value.
For example, the Dynavector 17D2 cartridge has a recommended load of >100 ohms. The loading resistors in
the ZIF socket would thus be > 10K ohms (100 ohms × 100).
The main effect of changing the loading resistance is to alter the upper frequency response and the overall tonal
quality. Experiment with different loading values to achieve the best sound for your cartridge.
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TUBES
6 Volts6 Volts
No
Co
nnec tion
No
Connecti on
A B
B
A
6 Volts6 Volts
No
Co
nnec tion
No
Connecti on
Cool-
Swap
TM
Left Right
The PL-1 uses Cool-Swap™ technology to let the
tubes run cooler and provide a built-in spare.
Many dual triodes, including the 5687 and 12AX7,
have split heaters, allowing them to run from either
6.3V or 12.6V. This heater set-up allows only one
of the two triodes to be heated. In the Cool-swap
configuration, one tube is used for each channel, each
with one half heated. The right channel uses triode
#1 and the left channel uses triode #2. Since the main
failure mode in modern tubes is cathode wear-out,
the unused triode in each tube is essentially a spare.
By swapping the two tubes, the unused spare is
brought into use. Thus Cool-Swap effectively dou
bles tube life, and since only half the tube is heated,
the tube runs cooler, an important factor in the
normally hot-running 5687. A side benefit is reduced
cross-talk between channels, since each channel has
its own tube.
One effect of the Cool-Swap technology is that only
one half of each tube will be “lit-up”. This is normal
in the PL-1.
-
How often you have to swap tubes, or replace them
with new tubes if already swapped, depends on how
you use the PL-1. The tubes supplied with the PL-1
should last several thousand hours of active use.
Signs that the tubes are weak include: less gain than
usual, a “flabby” sound, excess noise, and a weak
reading on a tube tester.
Since the PL-1 uses a soft heater turn-on and delayed
application of high voltage, tube lifetime is not
degraded by power cycling. Thus, it is recommended
that the PL-1 not be left on all the time, but only be
turned-on when needed, with perhaps a one-half
hour warm-up time, if desired.
Tube Types: The tube manufacturer and tube type
will have an effect on the sound of audio equipment.
The PL-1 was designed for the following tubes: the
Russian 6N1P, any high-quality 12AX7/ECC83, and
the American 5687 tube, originally developed by
Tung-Sol (the same manufacturer that developed the
5881 and 6550).
The 6N1P is a Russian type widely used by their mili
tary. “N.O.S.” (New Old Stock) of this type is readily
available. Since this the first amplifying stage, noise is
critical, and selection of the 6N1P for low noise will
give about 2 to 3 dB less noise than the average tube.
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Note: the 6N1P does not use Cool-Swap technology, so both
section are always used.
Any reputable 12AX7 or ECC83 type can be used. Current
production is widely available, and various N.O.S. types are still
available, although rather expensive.
The 5687 tube is no longer manufactured, but large N.O.S.
quantities are still available. The 5687 was used in industrial
and military equipment and as a result, nearly all tubes available
are built to higher quality and reliability standards than tubes
for consumer equipment. The 5687WA and 5687WB are later
versions with tighter control of their characteristics.
Although not identical in characteristics to the 5687, the fol
lowing tubes can also be used in the PL-1 in place of the 5687:
6900, 7044, 7119, and E182CC. If you try these, listen carefully
to the sound, and only use the types that sound the best. The
PL-1 was optimized for the 5687, however.
Warning: Do not use any other types of dual triodes than
those recommended here. The pin connections of all other
dual triodes are different and damage to both the tube and the
PL-1 will occur if used. Artemis Labs is not responsible for
damage caused by using incorrect tubes!
The tube shields can be removed by gently rotating counterclockwise until they pop up and are replaced by pushing down
and gently turning clockwise. The tube shields are needed to
reduce hum pick-up.
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TECHNICAL FEATURES
2
1
3
V4
1/2 5687
V4
V5
Power
Rig ht
Out puts
1
2
5
4
8
5
4
8
+160V +250V
+250V
+6V
+163V r eference
Muting relay
control
Lundahl
500H
choke
V2V1
V3
5
5
4
4
8
5
4
8
Power Supply
(unreg ulated )
40 sec ond
Delay
4 seco nd
Delay
Lin e volt ages
ava ilable :
100 V
,
110V
,
120 V,
220 V
,
230 V
,
240 V
50 or 60H z
Fea tures:
- E lectro stati cally
-
shi elded trans forme
r
- H igh-sp eed r ectifi ers
- High-t emper ature
(10 5°C) e lectr olytic s
Lef t
Out puts
1
2
+160V
GainRIAA E qualiz ationGainStep-U p Muting & Out put Low-Ga in Reg ulatio n Power Supply & Tim e Dela ys
PL- 1 P ho no Pre amp
Simpl ified Schem atic
Artemis Labs
Rig ht
Inp ut
1.5V
N or AM -5
Sowter
1:10
Tr
ansform er
Sowter
1:10
Tr
ansform er
2
3
1
V2
1/2 12AX7
V1
6N1 P
2
3
1
7
9
6
V5
1/2 5687
Lundahl
500H
choke
Lef t
Inp ut
1.5V
N or AM -5
7
8
6
V3
1/2 12AX7
7
8
6
TexTool®
"ZI F" Soc ket
for R or
C
loa ding
High-quality Step-up Transformer
After many listening and lab tests, the Sowter
moving-coil step-up was selected. Cartridge loading
is done on the secondary of the transformer to insure
flattest frequency response.
Low-noise first preamp stage with battery bias
With typical signals at the microvolt level, the first
amplifier stage is extremely critical. Parts are chosen
carefully for low noise and minimum low-level
nonlinearities. To get around the problems of cath
ode biasing and the typical electrolytic capacitor,
fixed bias using a single “N” alkaline cell is employed.
Being in the grid path, virtually no current is drawn,
letting the battery last for many years. Unlike circuits
where the battery is in the cathode, any imperfections
or nonlinearities in the battery are not manifested by
the tube’s current flow.
The plate supply for the first stage is filtered by an
R-C filter using a 15µF polypropylene capacitor. This
insures minimum noise without the sonic degrada
tion of electrolytic capacitors.
Extended high-frequency response
Many phono preamps’ response drops quickly above
20KHz. The PL-1 maintains its RIAA equalization to
above 40KHz, important for high-resolution playback
systems and for use with 96KHz digital systems.
Passive RIAA equalization using hand-selected capac
itors
By using passive equalization the problems of feed
-
back equalization are eliminated: slew-rate distortion,
deviation of equalization curves at high frequencies,
and instability problems. To permit flat equalization
to within +/–0.2dB, the capacitors in the equalization
network are pairs that are hand-selected on a precision
impedance bridge to better than +/–0.5% accuracy.
-
Two-stage output stage with modest feedback
About 5dB of feedback is used across the two stage
-
output amplifier. This stabilizes the gain and makes
the frequency response less sensitive to loading. The
inherent distortion of the 12AX7 and 5687 with
choke loading is already very low, so the high-order
harmonics that can be generated by excessive feedback are minimal.
Strong triode output driver with choke loading
The output stage in the PL-1 uses the 5687 triode.
This tube has excellent linearity. Its low plate resistance allows it to drive heavy loads without the use
of a cathode follower stage.
The use of an inductor (choke) load instead of a
conventional plate resistor offers several significant
advantages to the PL-1 design. A good-quality audio
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choke is essentially a perfect current source, allow
ing the triode to operate into an infinite-resistance
load, giving the lowest distortion. Unlike semiconductor constant-current devices, an inductor is an
energy-storage device. This allows the plate voltage
to swing 100% above the B+ plate supply voltage,
doubling the “head-room” and allowing a lower B+
supply voltage to be used, reducing power consumption. This large headroom permits output of over 40
volts rms before clipping.
The audio chokes used in the PL-1 are made by
Lundahl, a Swedish firm that uses a proprietary core
material that has low distortion. Two windings are
used on a single “C-core”, which reduces pick-up of
hum and noise.
DC heater supply
A well-filtered DC heater supply helps keep hum
low and allows the use of tubes that would otherwise have too much hum in AC-heated systems.
Delayed high-voltage with delayed muting relay
The high voltage plate supply is applied to the
tubes after a delay of about 40 seconds. This gives
the tubes ample chance to warm-up without the
chance of “cathode stripping” (degradation of the
cathode by bombardment by positive ions before it
is hot enough to build-up a protective space charge
around the cathode.) This helps extend tube life. A
muting relay shorts the audio outputs until about
4 seconds after the high voltage is applied. This
allows start-up transients to die away.
Can drive 12K ohm (aggregate) or higher loads
Despite the lack of a cathode-follower output stage,
the PL-1 can drive loads as low as 12K while still
meeting specifications. This is important when
driving certain sound cards or pro audio equipment
which can have input impedances as low as 12 or
15K ohms.
Each channel individually voltage regulated
Each channel has its own MOSFET source-follower
low-gain regulator. This insures there is no coupling
between the two channels through the power supply.
The source follower regulator gives good regulation
without the “transistor sound” typical of high gain
regulators using op-amps. Protection resistors and
diodes help prevent burn-out of the MOSFETs.
True voltage regulation minimizes noises and
changed operating conditions due to power line
shifts. Since the impedance of the power supply,
as seen by the amplifier, is low and flat, the bass
response is even and solid.
High-quality, high temperature capacitors
All electrolytic capacitors are high-quality 105°Crated Panasonic® types for best reliability. All film
capacitors in the signal path are either polypropylene or silvered-mica types.
No troublesome integrated circuits
All time delay and regulation circuits use timeproven, simple discrete semiconductor devices.
Critical audio circuits point-to-point wired with
military-style terminal boards
Conventional fiber-glass PC boards are used for
the power supply and for the rear panel jacks and
switching. All critical circuits in the audio path use
point-to-point wiring on military-style terminal
boards using silver-plated turrets. This technique
minimizes the sonic effects of PC boards and allows
easy component replacement.
High-speed rectifiers and electrostatically-shielded
power transformer
Power supply noise is kept to a minimum by the use
of a custom power transformer with electrostatic
shielding between the primary and secondaries.
High speed rectifiers are used for both the plate and
heater supplies.
Available mains voltages (wired at factory): 100V,
110V, 120V, 220V, 230V, 240V, 50 or 60Hz
Virtually all the power systems of the world can be
accommodated by the PL-1 transformer connections. These are set at the factory or can be re-wired
by a qualified technician.
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Artemis Labs products
are distributed by:
AYDN Vacuum Tube Audio
679 Easy Street, Unit E
Simi Valley, California 93065 USA
www.aydn.com
Tel: +1 818 216-7882
email: info@aydn.com
rev 1.0 11/04
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