Artemis Labs SP-1 Owners manual

Artemis Labs SP-1

Single-Ended Stereo Power Amplifier

Operating Manual

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.

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.

Page 2

This symbol is intended to alert the user to the presence of
important operating and maintenance (servicing) instruction in
the literature accompanying the appliance.

INTRODUCTION & SPECIFICATIONS

The Artemis Labs SP-1 Stereo Power Amplifier is a no-compromise purist design. It is designed to get the
most from the “super 300Bs” such as the KR 300BXLS and Full Music 300B+, delivering from 13 to 18 watts
(depending on the tube type) of clean single-ended power. Careful power supply filtering and regulation of
critical voltages ensure stable, quiet operation. All aspects of the design were done by John Atwood of One
Electron™.

Given that the SP-1 amplifier puts out about 15 watts per channel, it must be used with relatively efficient
loudspeakers. The minimum efficiency required depends on many factors including room size, room absorb
tion, preffered listening levels, etc., but in general, an efficiency of 90dB or higher per watt at 1 meter is
needed. Work with your dealer for the best speaker combination for your listening set-up.

The SP-1 is conservatively designed and is built to last for many years. The only maintenance needed is the
occasional bias adjustment and replacement of tubes. Please read this entire user’s manual so that you can
understand all the features and get the most from the SP-1. The Warranty is on a separate card. Read it and
send it in to get full warranty coverage.

SPECIFICATIONS:

Input Impedance: 100K ohms.

-

Power Gain

Frequency Response & Distortion

1 watt output:
Frequency Response: 14Hz – 38KHz ± 1dB
THD+N at 1KHz, < 0.5%
10 Watts output:
Frequency Response: 15Hz – 35KHz ± 1dB
THD+N at 1KHz, < 1.5%

Output for 5%THD (1KHz): 13 to 18W, depending on output tube

Damping Factor: (1KHz, 5W): 4.8

Output Noise: (grounded input, 8 ohm output into 8 ohm load, rms detector):

22Hz - 30KHz: < -88dB below 10W output
“A-weighted”: < -105dB below 10W output

Crosstalk

1KHz: < -81dB
20KHz: < -57dB

Mains Voltage: Wired at factory for one of the following voltages: 100, 110, 120, 220, 230, 240V, 50 to 60Hz.

Power Consumption when powered-off (rms): 2.3 Watts nominal

: 0.7VRMS in for 10W out (1KHz)

: (measured with KR 300BXLS tubes)

:

Power Consumption when powered-on (rms)

Size: Power Supply Chassis: 9 ½" (241 mm) Height, 12 ¼" (311 mm) Width, 13

Amplifier Chassis: 9 ½" (241 mm) Height, 12 ¼" (311 mm) Width, 16

Mass: Power Supply Chassis: 51 lbs. (23.2Kg)
Amplifier Chassis: 55 lbs. (25Kg)

Note: These specifications are subject to change at any time.

: 340 Watts nominal

3

⁄4 " (425 mm) Depth

3

⁄8 " (340 mm) Depth

Page 3

INSTALLATION & OPERATION

To install the SP-1

1. Locate the SP-1 amplifier and SP-1PS power supply where they can receive adequate fresh
air for cooling. Do not block the cooling holes on the bottom, i.e. do not set on carpet. They
may be operated without the perforated covers, unless they can be accessed by small children or
animals, in which case the covers must be used. The tubes will run coolest without the covers.

Leave enough slack in the interconnecting cable so that there is no strain on the connector. The
power supply puts out a small magnetic hum field - make sure that is located far away from
components sensitive to hum, such as phono cartridges or preamps.

2. Connect the amplifier to the signal source by RCA interconnect cables to the left and right
inputs. The SP-1 has no volume control, so the signal source must have some means of controlling
the volume. Do not change cables while the SP-1 is power-on.

3. Connect the speakers to the SP-1 by speaker cables to the output banana jacks. Choose the
impedance so that it is equal to or lower than the rated impedance of the speaker. On highly­sensitive speakers 8-ohm, it may be helpful to connect them to the 4-ohm outputs.

The amplifier must not be run with the outputs unconnected. If only one channel is used or
while being tested, dummy load resistors should be connected to the unused outputs. These
can be 8 to 20 ohms, rated at least 10 watts.

4. Connect the SP-1PS to an AC power source. It consumes 340 watts when running, so any
power conditioning, if used, must accommodate this power level. If problems with hum occur,
it is recommended that the signal source and SP-1 be connected to the same AC outlet.

Amplifier, follow these steps:

The SP-1PS consumes about 2 watts of power, even when turned-off. If the amplifier will
not be used for a long time, or if lightning or other power surges are expected, it should be
unplugged. The SP-1PS contains built-in surge suppression which can be damaged by excessive
surges. If the power fuse is blown by lightning or another kind of power surge, contact AYDN
for authorization to return the SP-1PS, even if it still works.

The Power Switch on the front of the amplifier chassis applies power when flipped up. The
Power Indicator will glow red while the tubes warm up, then after approximately 60 seconds,
will glow green. The SP-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.

Voltage Rating Fuse Rating

Page 4

IEC Power Connector

Power Fuse

Cable to SP-1

REAR PANELS

Refer to the photo on the previous page:

Make sure that the Voltage Rating of your SP-1PS 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.

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 location.

The Power Cable supplies power to the amplifier chassis. To connect the power cable to the
amplifier chassis, gently rotate the female cable connector body against the male chassis con
nector until you feel it engage. Then rotate the screw shell clockwise until a slight click is felt.
Do not force the connector! Only gentle force is needed to engage it.

Never disconnect the Power Cable when the amplifier is powered-on!

-

Right Speaker Connections

Cable from SP-1PS

connects here

The amplifier is driven by RCA cables connecting to the Right and Left Input Connectors.

The speaker cables connect to the Right and Left Speaker Connectors. Either banana jacks,
wires, or spade lugs can be used. If bare wire is used, be careful that no stray strands get
loose that could cause a short-circuit. The “Common” or “Ground” lead connects to the
black jacks. The “Hot” lead goes to either the 4 ohm or 8 ohm red jacks, depending on the
speaker used.

High-Voltage fusesRight Input

Left Speaker Connections

Left Input

The High Voltage Fuses are used to protect the amplifier from damage if an output tube or
other component short-circuits. If there is no sound and it is impossible to bias the ampli
fier tube, check the fuse for the affected channel. The Fuse is a 1" x 1¼" “3AG” standard
type (not slow-blow) rated at either 3/8 Amp (0.375A) or 1/2 Amp (0.5A).

-

Page 5

TUBES

There are six tube types used in the SP-1 ampli
fier. Their use and replacement strategy are
described here.

6N1P (Russian

as the first audio amplifier and part of the voltage
regulator. This is similar to the 6DJ8/ECC88, but
has better sonic properties. This tube was widely
used in Russian industrial and military equipment
and is currently available from most tube distrib­utors. Some types are marked 6Н1П-EB - this is a
enhanced reliability version.

EL34/6CA7 - This tube is triode-connected and
is used as the driver tube. This is one of the most
common output tubes, and many versions are
available. Another equivalent, but rare, type is the
KT-77. All will work in the SP-1, and you can try
different versions for the best sound. Remember
to re-bias after changing tubes.

Occasionally an EL34 will be found that is too
microphonic, i.e. is very sensitive to mechani
cal vibrations. All tubes are microphonic to a
degree, but if sound is heard from the speakers if
the chassis is lightly tapped, then a different EL34
should be used.

Since the EL34 is run very lightly in the SP-1, it
should last a long time, and fail by eventual cath
ode wear-out. This will be evidenced by an inabil­ity to correctly bias the tube. There is no need to
match the two EL34s, since each one is used for
each channel and is individually biased by the Bias
Panel.

300B+/300BXLS - This is the power output tube,
and is crucial to the sound quality and power
output of the amplifier. This tube is a “super”
300B and must have a plate dissipation rating of
at least 60 watts. Both the KR 300BXLS and Full
Music 300B+ have been tested in this amplifier.
New versions of super 300Bs may become avail
able, so check with your dealer or AYDN on the
applicability of newer types.

Do not use regular 300Bs, since the Bias Panel will

6Н1П) - This twin triode is used

-

-

-

-

set their bias to 120mA - which results in a plate dis
sipation of 60 watts - far higher than the 40 watt rating
of conventional 300Bs. Artemis Labs is not responsible
for damage caused by the use of unqualified output
tubes!

Depending on the tolerances of the tube sockets
and pins, it may be possible to incorrectly insert the
300BXLS/300B+, causing possible damage to the
amplifier. Make sure the two large pins are inserted
facing the outside edge of the chassis, as shown in the
diagram on the next page.

The normal failure mode for these tubes is wear-out
of the cathode coating, resulting in low current or
the inability to bias up the tube. However, if the tube
goes gassy, it is possible for the tube to arc over. This
will likely blow the high-voltage fuse on the amplifier
chassis. When replacing the tubes, there is no need to
match the two tubes, since each one is used for each
channel and is individually biased by the Bias Panel.

5U4G/274B - Two of these are rectifiers in the high­voltage power supply. Although any rectifier with the
same pin-connections and power ratings as the 5U4G
or the Western Electric type 274B could be used, other
types may produce an incorrect high voltage. Only
exact equivalents of the 5U4G (such as the 5U4GB,
5AS4, Russian

These rectifier tubes are exposed to high voltages and
currents, and although protected by delayed high-volt
age and transient snubbers, may fail by arcing. This
will typically blow the line fuse on the power supply
chassis. There is no need to match the two rectifier
tubes, but it is recommended that they be replaced as a
pair.

6AL5/5726/6H2P (Russian

diodes are used to generate the negative bias supply.
Although no longer manufactured, these tubes were
extensively used in televisions, FM radios, industrial
and military equipment, and are readily available as
“N.O.S.” (New Old Stock) for reasonable prices. The
5726 is a ruggedized version of the 6AL5, and the
6H2P (6Х2П) is a Russian equivalent. All equivalent
types will work well.

5Ц3C, etc.) or 274B are recommended.

6Х2П) - These dual

-

-

Page 6

TUBES

IMPORTANT! Large Pins Face Outside!

The 6AL5 type tubes should last a long time, but
when worn-out, will fail to produce enough bias
voltage. This will not initially affect the bias cir­cuits, since they are regulated, but if the unregu­lated bias falls too much, a protective circuit will
prevent the high-voltage from turning on.

0G3/5651 - This is an 85 volt gas reference tube,
which regulates the bias for the driver stage and

TUBE LOCATIONS

The two drawings below show the location and orientation of the tubes. Note that the 4-pin
super-300B tubes are indexed by the position of the two larger pins. These large pins must be
inserted as shown below - facing the outside edge of the chassis.

voltage regulator. This type is very reliable, and
should last longer than any of the other tubes in
the amplifier. If the tube no longer glows or the
driver and output tubes can no longer be biased, the
0G3/5651 may be bad. If replacement is needed, it is
available as N.O.S. from tube dealers.

Page 7

EQUA-BIAS™ ADJUSTMENT

Bias Adjustment holes

The Bias Switch has five positions, one for each of the driver and output tubes and a center­off position. Normally the Bias Switch is kept off. To adjust the bias for a particular tube,
switch the Bias Switch to the tube to be adjusted and insert a small flat-blade screwdriver
into the matching Bias Adjustment Hole. Make sure the screwdriver is perpendicular to the
panel. You may have to rotate the screwdriver carefully to find the slot. Adjust for identical
brightness on the two yellow LEDs just below the “OFF” position

Note that the Bias Adjustment Holes are in the same relative positions as the tubes they con
trol on the chassis.

The bias should be adjusted immediately after new tubes are installed. If used tubes are
exchanged in their sockets, the bias should also be re-adjusted.

If selected while operating, it is normal for the LEDs to flicker as music is played, especially
on the output tubes V5 and V6.

The bias can slowly drift during the first 15 minutes of operation, so the final bias adjust
ment should be done after the amplifier has been operating at least this long. Once set this
way, the bias is quite stable, and should not have to be checked for at least another 100 hours
of operation, unless trouble is suspected.

-

-

Page 8

If the bias LEDs cannot be balanced for a particular tube, then it is likely that the tube is bad
or inserted incorrectly. Check the orientation of the tube. Also check the High-Voltage fuses
on the rear of the amplifier chassis. If the LEDs still cannot be balanced after a known good
tube is inserted, then contact your dealer or AYDN for service.

SIMPLIFIED SCHEMATIC

Artemis Labs

ASE-1

25mA

+500V

+520V

-216V

12VAC

-100V

-25V

+220V

-85V

-85V

-216V

+500V

120m

A

100K

to bia s

indica tor

EL34/6CA7½ 6N1P

300BXL

S/

300B+

COM

Left

Input

Righ

t

Input

COM

to bia s

indica tor

Outpu t Bias Ci rcuit

(V

oltag e Compens ated)

Drive r Bias Ci rcuit

Relay

Left Channel

2 x EL34

2 x 6N1P

Right Channel

( Same as Above )

Negative Bias Supply

5651/

0G3

2 x 6AL5/5726

Plate Supply

(Choke-Input

)

2 x 5U4G/274B

12V 1A Supply

(Choke-Input)

60-second

time delay

5V 3A Supply

(Choke-Input,

Regulated)

5V 3A Supply

(Choke-Input,

Regulated)

House-Keeping

Supply

(always on)

V1A

½ 6N1P

V1B

V3

V5

V2 V4 V6

Bias Indicator

V3

V5

V4

V6

Power

Lin e

vol tages

ava ilabl e:

100 V

,

110V

,

120 V

,

220 V,

230 V,240 V

50/ 60Hz

SP-1 St ereo Po wer Amp lifi er

Simplified Schematic

rev 1.0 12/31/05

Amplifier Chassis

Po

wer Supply Chassis

Artemis Labs

Page 9

TECHNICAL FEATURES

High-power directly-heated triode output with no

feedback

Directly-heated triodes have the lowest distortion
of all power tubes. The high-power versions used
in the SP-1 are premium quality for low distortion
and long life. There is no feedback around the
output stage, giving absolute stability with any load.

Custom output transformer

The single-ended output transformer, key to the
performance of a no-feedback amplifier like the
SP-1, is a custom design with a large core for good
low-frequency performance without saturation,
and carefully interleaved windings for good high­frequency response. The high-frequency response
of the 4-ohm output is virtually identical to the
8-ohm output, something rarely found in most
output transformers. High-quality Microsil
laminations are used for low distortion.

Modest feedback stabilizes driver gain without

hurting sonic quality

About 2dB of feedback is used across the two driver
stages. This helps stabilize the gain while improv
ing the drive to the output stage. This low amount
of feedback does not alter the distortion character­istics the way a high amount of feedback does.

Two-stage driver gives low distortion with low

impedance.

The two-stage driver allows each driver tube to be
optimized for its role: a low-noise 6N1P for the
first stage and a high-current triode-connected
EL34 for the second stage. The EL34 may seem like
overkill for a driver, but it is quite linear and its low
impedance is a perfect match for driving the highly
capacitive load of the output tube grid.

Choke-loaded driver tube

A key factor to the low distortion and wide dynam­ics of the SP-1 the use of a choke plate load for
the EL34 driver stage. An inductor (choke) is an
energy-storage device that allows the plate of the
tube to swing to twice the plate supply voltage.
This effectively doubles the headroom of the driver

- the same as doubling the B+ voltage, without the

-

power loss of a resistor load. It also presents the
driver tube with essentially an infinite load imped
ance, giving the maximum gain and best linearity.

Driver stages shunt regulated

The high-voltage supply for each channel’s driver
stages are regulated by a low-gain hybrid shunt
regulator. This regulation ensures a rock-solid
power supply, free from low-frequency surges and
instability inherent in conventional R-C or L-C
filters.

Shunt regulators have the nice characteristic of
keeping the current draw from the power supply
constant - thus not polluting the power “upstream”
of the regulator. This reduces cross-talk and keeps
interactions between the driver and output stages
to a minimum. The hybrid design, using one half
of a 6N1P and a high-voltage bipolar transistor give
good linearity and high reliability. The low gain of
the regulator ensures good sonics, without the “tran
sistor sound” of high-gain regulators.

Fixed bias on both output and driver tubes

Fixed bias is used on both the EL34 driver stage and
the output stage. This means that the tube bias is
absolutely constant with changes in the signal. Tran­sient and overload performance are therefore excel­lent. There are no electrolytic capacitors required,
which would be necessary with conventional cath
ode bias.

Bias compensation used in output stage

A compensation network is used to bias the output
tube. This keeps the bias current constant over
wide changes in mains voltage, reducing the need
to re-bias the output tubes. Bias compensation is
not needed on the driver, since its supply voltage is
regulated by the shunt regulator.

Equa-Bias

Fixed bias requires the user to periodically check and
possibly re-bias tubes, due to tube aging and when
tubes are changed. This requirement is made very
simple by the Equa-Bias method. The tube to be
biased is selected by a rotary switch, and the bias is
adjusted by a small screwdriver in the hole selected

™

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-

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Page 10

TECHNICAL FEATURES

by the switch. When the two yellow LEDs are equal
in intensity, the bias is correct. This method is accu
rate to well within 2% of optimum bias.

Separate power supply filtering for each channel

While using a common power transformer and rec­tifier, the SP-1 splits the filtering for each channel.
This reduces cross-talk between channels.

DC heater supplies for input and output tubes

A well-filtered DC heater supply keeps hum low in
the 6N1P input and regulator tube. Separate regu­lated DC filament supplies are used for the output
tubes. DC eliminates hum from the output tube
filaments. Regulation allows output tubes with
varying current draws (1.5A for the 300B-XLS to

3.0A for the 300B+) to have an accurate filament
voltage of 5.0V.

Delayed high-voltage relay

The high voltage plate supply is applied to the
tubes after a delay of about 60 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.

High-quality, high temperature capacitors

-

All electrolytic capacitors are high-quality 105°C­rated Panasonic® types for best reliability. All
capacitors in the signal path are either polypropyl­ene or silvered-mica types.

Choke-input filtering on all major power supplies

Choke input filters are used on the high-voltage
supply and all three of the DC filament supplies.
Compared to conventional capacitor-input filters,
choke-input filters have a better “power-factor”
which reduces heating of the power transformer
and is more friendly to the power mains.

Electrostatically-shielded power transformer and

tube/solid-state rectification

Power supply noise is kept to a minimum by the use
of a custom power transformer with electrostatic
shielding between the primary and secondaries.
Both the high-voltage and bias supplies use a com­bination tube/solid-state bridge rectifier. The tube
section gives a slow turn-on while the solid-sate half
of the bridge reduces the peak voltage on the tubes,
ensuring long-life. High-speed rectifiers are used
where feasible. Tuned snubbing circuits are used to
reduce rectifier switching noise.

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 bias monitoring circuits.
All critical circuits in the audio path use point-to­point wiring on military-style terminal boards using
silver-plated turrets. This technique minimizes the
sonic effects of PC boards and allows easy compo­nent replacement.

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 SP-1 transformer connec­tions. These are set at the factory or can be re-wired
by a qualified technician.

Page 11

Page 12

Artemis Labs products
are distributed by:

AYDN Vacuum Tube Audio
679 Easy Street, Unit E
Simi Valley, California 93065 USA

www.aydn.com
Tel: [phone]
email: [e-mail]

rev 1.0 4/06