Artemis Labs DP-2 User Manual
Contents
1. 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 elec CAUTION ATTENTION tric shock do not remove the covers No user serviceable parts inside RISK OF ELECTRIC SHOCK RISQUE DE CHOC ELECTRIQUE M ppi DO NOT OPEN NE PAS OUVRIR 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 elec tric shock to persons This symbol is intended to alert the user to the presence of important operating and maintenance servicing instruction in the literature accompanying the appliance Page 2 INTRODUCTION amp SPECIFICATIONS The Artemis Labs DP 2 Power Amplifier is a purist design comprising a pair of mono block amplifiers It uses the classic 2A3 directly heated triodes in push pull class A with transformer phase splitting Careful power supply filtering and regulation of critical voltages ensure stable quiet operation Given that the DP 2 amplifier puts out about 10 watts per channel it must be used with relatively effi cient loudspeakers The minimum efficiency required depends on many factors including room size room absorption preferred listening levels etc but in general an efficiency of 92dB or higher per watt at 1 meter2. a MOSFET source follower This reduces any low frequency coupling from the output stage to the input stages and also isolates the drivers from power supply hum and line voltage variations The relatively low gain of the source follower compared to an op amp based regulator gives decent regulation without the solid state sound typical of high gain regulators The high voltage power supply uses a filamentary rec tifier the 5U4GB with a conventional pi filter circuit The power transformer has primary taps to allow use with virtually any AC power source in the world The voltage taps are soldered internally and should only be changed by a qualified technician or by AYDN www aydn com Tel 1 818 216 7882 email info aydn com rev 1 0
3. can manufacturers in 1954 and was an updated version of the 5U4G 1939 which was an octal version of the 5Z3 designed in 1934 by RCA It was very widely used in televisions audio amps and industrial equipment in America These rectifier tubes are exposed to high voltages and currents and may fail by arcing This will typically blow the fuse Otherwise failure is indicated by cathode wear out which will reduce the high voltage and hence cause higher distortion Do not use plug in solid state rectifiers since their fast turn on and lower voltage drop will unduly stress the amplifier 274B 5U4G Artemis Labs Dp 2 Dush Dull Amplifier 6550 KT88 12AU7 ECC82 The tube locations are marked on the black plates on the top of the chassis Note that on both the left and right amplifiers the two large pins of the 2A3s face right when viewing the front of the chassis as shown above Page 6 SIMPLIFIED SCHEMATIC 12AU7 ECC82 Input EE 100K os 050 Artemis Labs DP 2 Power Amplifier Simplified Schematic rev 1 0 12 31 06 O 8A O 4Q O COM Low Drop 2 5V Regulator voltages available 100V 110V 120V 220V 230V 240V 50 60Hz to 12AU7 KT88 heaters ov Z CIRCUIT DESCRIP TION The Artemis Labs DP 2 is a modern version of the classic push pull directly heated triode amplifier Amplifiers similar to the DP 2 were made right from the start of the availabili
4. Artemis Labs OD 2 Push Pull Stereo Power Amplifier om Artemis Labs DP 2 Power Power Operating Manual Important Safety Instructions Read these instructions Keep these instructions Heed all warnings Follow all instructions Do not use this apparatus near water PT ET Clean only with a dry cloth 7 Do not block any ventilation openings Install in accordance with the manufacturer s instruc tions 8 Do not install near any heat sources such as radiators heat registers stoves or other appa ratus 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
5. atched pairs to insure the best low frequency response and lowest distortion Do not use other triodes such as the 300B or PX 4 since their filament voltage is different than the 2A3 Depending on the tolerances of the tube sockets and pins it may be possible to incorrectly insert the 2A3s 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 below The 2A3 was designed by RCA and announced in 1932 The very early RCA 2A3s had a single plate but all later American built 2A3s have the double plate construc tion essentially two triodes in parallel Modern 2A3s are made with either single or double plates 274B 5U4G Artemis Labs DD 2 Dush Dull Amplifier 12AU7 ECC82 6550 KT88 The normal failure mode for these tubes is wear out of the cathode coating resulting in low current and higher distortion However if the tube goes gassy it is possible for the tube to arc over which in the worst case will cause the fuse to blow 5U4GB This is the high voltage power supply rectifier Although any rectifier with the same pin connections and power ratings as the 5U4GB or the Western Electric type 274B could be used other types may produce an incorrect high voltage Only exact equivalents of the 5U4GB such as the 5U4G 5AS4 Russian 503C etc or the 274B are recommended The 5U4GB was brought out by all the major Ameri
6. is needed Work with your dealer for the best speaker combination for your listening set up The DP 2 is conservatively designed and is built to last for many years The only maintenance needed is the occasional replacement of tubes Please read this entire user s manual so that you can understand all the features and get the most from the DP 2 The Warranty is on a separate card Read it and send it in to get full warranty coverage SPECIFICATIONS Input Impedance 100K ohms Rated Output Loads 4 and 8 ohms Sensitivity 8 ohm load 1KHz 0 9Vrms in for 8W out Frequency Response amp Distortion 1 watt output Frequency Response 20Hz 40KHz 1dB THD N at IKHz lt 0 5 8 watts output Frequency Response 20Hz 40KHz 1dB THD N at IKHz lt 2 10 Watts output Frequency Response 20Hz 40KHz 1dB THD N at IKHz lt 4 Damping Factor 2 8 not including voice coil resistance Output Noise grounded input 8 ohm load rms detector 22Hz 30KHz lt 85dB below 10W output A weighted lt 95dB below 10W output Mains Voltage Wired at factory for one of the following voltages 100 110 120 220 230 240V 50 to 60Hz Power Consumption rms 135 Watts nominal 150 Watts maximum Size each amplifier 1234 311 mm Height 8 12 216 mm Width 17 32 445 mm Depth Weight each amplifier 40 lbs 18 Kg 45 lbs 20 5 Kg shipping weight Note These specifications are subject to change at any ti
7. me Page 3 Page 4 REAR PANEL OAMAADKDKLADALKLALKLAAAAAAAAAAAAAAAAAAAAAAAJAJA AA AM M OA ki ii i A A A Ji WAARDRKARBKLARBKARDKADRDBKALKDBKABKAKAAAAAAAAAAAAAAAAAAAAAJAJAA A OA ki ii i A A AA WW V A A A i A i ib A A A A A A A A A A GS ww a N T ww A A A hk A V A A IEA A wo n A L gt ks T Y V a 4 A i A ANN MA 4 EAA A y ay A A j j 2 2 025 20 99 01 9 9 29 00 9 ND s ZN www a a a CTS a a A d han AA AA AA JAA j Input Speaker Connections Voltage Rating IEC Power Connector Fuse Rating Fuse The rear panel of a single channel of the DP 2 amplifier is shown above Note that the com ponent placement for the two amplifiers are mirror images of each other The amplifier is driven by RCA cables connecting to the Input Connectors The speaker cables connect to the 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 jack marked 0 The Hot lead goes to either the 4 ohm or 8 ohm red jacks depending on the speaker used Make sure that the Voltage Rating of your DP 2 matches the power mains voltage at your location The voltage is changed by internal rewiring which can be done by Artemis Labs or by a qualified technician The Fuse is a 1 x 134 3AG Slow blow type Its val
8. ny power conditioning if used must accommodate this power level If problems with hum occur it is recom mended that the signal source and DP 2 be connected to the same AC outlet If the power fuse is blown by lightning or another kind of power surge contact AYDN for authoriza tion to return the DP 2 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 green After about a 45 second warm up the DP 2s are ready for use TUBES There are four tube types used in the DP 2 ampli fier Their use history and replacement strategy are described here For best performance the tubes should be periodi cally tested between several months to several years depending on the amount of use on a quality tube tester such as a Hickok TV 7 U or similar tester If a bad tube is suspected and a tube tester is not avail able try substituting a known good spare tube to see if the problem goes away 12AU7 ECC82 One half of this twin triode is used as the first audio amplifier This is a very common type both for new production and New Old Stock N O S so there are many opportunities to try different brands The 12AU7 was designed by RCA and announced in 1946 It consists of two 6C4 triodes in a single enve lope and is similar although with lower power to the 6SN7GT dual triode It was very widely used in audio television industrial and military a
9. pplications The ECC82 is a European designation for the 12AU7 There are many variations of the 12AU7 which can be used in the DP 2 For example the 5814 and 6189 are ruggedized types that are compatible Since only one half of the tube is used and the left and right chassis are wired to different sections the two tubes can be swapped to use the fresh sections essen tially doubling the tube life A worn out tube will pro duce a dull or distorted sound KT88 This triode connected tube is used as the driver tube This is similar to the 6550 which can be used here also The KT88 was designed by M O Valve in England in the mid 1950s It is very similar to the 6550 designed in America by Tung Sol in 1954 Modern KT88s are made in China supposedly on the original M O V tooling Page 5 TUBES Occasionally a KT88 will be found that is too micro phonic 1 e is very sensitive to mechanical 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 KT88 should be used Since the KT88 is run very lightly in the DP 2 it should last a long time and fail by eventual cathode wear out There is no need to match the two KT88s since each one is used for each channel and is individually biased 2A3 This type is used as the power output tube and is crucial to the sound quality and power output of the amplifier The 2A3s on each chassis should be m
10. roved by the use of several dB of feedback from the KT88 plate to the 12AU7 cathode This is low enough to avoid the hard cold sound caused by large amounts of feedback The inductive nature of the interstage transformer has the benefits of making the KT88 run into effectively and infinite load which gives the lowest distortion and allowing to plate voltage to swing up to twice the plate supply voltage which further reduces distortion and increases the headroom The output stage uses two 2A3 triodes in push pull Cathode bias is used which is essentially self correct ing eliminating the need for a bias control The two tubes should be matched however for lowest distor tion The low grid circuit resistance provided by the interstage transformer helps keep the 2A3 s bias stable even if the tubes are slightly gassy or have grid current It also helps reduce blocking if the grids are momentarily over driven Artemis Labs products are distributed by Page 8 AYDN Vacuum Tube Audio 679 Easy Street Unit E Simi Valley California 93065 USA The 2A3 s filaments are driven by a solid state low voltage drop regulator that supplies a clean stable 2 5 volts The problems of filament hum are eliminated by the use of this DC power supply A choke input filter is used for the filament supply to reduce current spikes and improve the power factor of the power supply The plate voltage for the two driver stages is regulated by
11. ty of the 2A3 in 1932 As the use of pentodes spread in the 1930s the directly heated triode amplifier became uncommon but it was revived after World War II with the rise of stand alone high fidelity amplifiers In the United States the most notable examples were the Brook Amplifiers made from 1947 to the mid 1950s The cheapness and high power of push pull beam power tube amplifiers again pushed directly heated triode amplifiers to obscurity in the mid 1950s The revived interest in tube audio in the 1970s and 80s brought back the use of triodes first in Japan and later elsewhere The resulting demand for the obsolete N O S triodes pushed their prices sky high but there are now several manufacturers of quality filamentary triodes with the 2A3 being one of the most com monly manufactured The Artemis Labs DP 2 is a straightforward design with a two stage driver transformer coupled to a push pull output stage The only modern features are a 2 5VDC regulated filament supply for the 2A3s and a MOSFET source follower voltage regulator for the driver stage The driver circuit uses the medium mu 12AU7 triode capacitively coupled to a triode connected KT 88 Page 7 CIRCUIT DESCRIPTION The use of such a large driver tube here may seem unconventional but its low plate resistance and low distortion work well in driving the interstage trans former to its full bandwidth The freguency response of the driver stage is further imp
12. ue 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 the cord 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 INSTALLATION 8 OPERATION To install the DP 2 Amplifiers follow these steps 1 Locate the DP 2 amplifiers where they can receive adeguate fresh air for cooling Do not block the cooling holes on the bottom 1 e do not set directly on carpet 2 Connect the amplifier to the signal source by RCA interconnect cables to the left and right inputs The DP 2 has no volume control so the signal source must have some means of controlling the signal level Do not change cables while the DP 2 is power on 3 Connect the speakers to the DP 2 by speaker cables to the output banana jacks Choose the imped ance so that it is equal to or lower than the rated impedance of the speaker On highly sensitive 8 ohm speakers 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 DP 2 to an AC power source It consumes 135 watts when running so a
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