AAAVT distribuirà le elettroniche valvolari JJ-Electronic (JJ Tesla)
La AAAVT, l’azienda che distribuisce sul territorio nazionale i marchi YARLAND e FOUNTEK,è lieta di annunciare che dal prossimo mese di febbraio distribuirà – in via esclusiva sul territorio italiano – le elettroniche valvolari prodotte dalla JJ-Electronic (JJ TESLA).
La JJ Electronic nasce, nel 1993, dalla privatizzazione del glorioso marchio Tesla; l’azienda si trova nel cuore dell’Europa, nella Repubblica di Slovacchia.La JJ Electronic è attualmente l’azienda leader europea, con oltre 20 anni di esperienza, nella progettazione e realizzazione di valvole termoioniche (utilizzando gli stessi macchinari Tesla, modificati con le ultime novità tecnologiche), di condensatori elettrolitici ad alto isolamento e di amplificatori audio valvolari di altissima qualità.
Gli amplificatori adottano circuitazioni innovative e componentistica prodotta direttamente in fabbrica.
Si tratta quindi di apparecchi progettati e realizzati completamente in Europa.
Quanto sopra a conferma dell’impegno profuso della AAAVT teso ad offrire il miglior livello di servizio di vendita proponendo amplificatori valvolari di ottima qualità.
JJ322 HIGH-END STEREO SINGLE- ENDED PURE CLASS A. POWER AMPLIFIER 2X20W 4@8 OHM , JJ323 DUAL MONOBLOC PARALLEL TRIODE 300B – (2A3).
Pair of monoblocks (with optional selection of three inputs), in one chassis, with triodes 300B (JJ322) or 2A3 (JJ323) in the power stage.
The “retro” design of the JJ322, JJ239 and JJ243 comes from the era when triodes 300B and 2A3 were introduced. Maple wood in cherry, black or natural stain, combined with a stainless steel top plate plated with pure gold or white brass, creates a distinguished look for this piece of equipment.
The only common elements for both JJ322 channels are the ALPS Blue volume control, the power outlet with power switch and a star ground point. The JJ322 belongs to the JJ Electronic High-End product line. The circuit design follows exclusively the goal of the highest sound quality. The electronic components are selected using extensive listening tests and the output transformers and electrolytic capacitors are developed in-house to assure maximum sound quality. Our efforts were rewarded at the 2000 CES Show in Las Vegas when the JJ322 received the Design & Engineering Showcase Award – as the first European audio product in the history of the show. At this biggest electronics show in the world, only one award is given in the audio category each year.
JJ243 INTEGRATED STEREO TUBE PREAMPLIFIER WITH PHONO STAGE FOR MM&MC HIGH OUTPUT CARTRIDGES UP [AND] 0,6mV.
JJ239 HIGH-END, SINGLE ENDED CLASS A1, ALL TRIODE MONOBLOCK, 10 W INTO 4 AND 8 OHM. JJ239 USES ONE ECC99 AND ONE 2A3-40 JJ ELECTRONIC TUBE
J239 uses one ECC99 and one 2A3-40 JJ Electronic tube. The JJ Electronic triode 2A3-40, introduced at the 2003 Las Vegas CES show, has, in contrast to the triode 300B, a heater voltage of only 2.5V. This, when combined with a heater center tap, results in a smaller potential difference with respect to the bias voltage and larger active cathode surface. The result is a better sound quality. For the audiophiles who prefer the 300B as a power tube, we offer alike monoblocks under the name JJ309. The output power of 10W may seem low, but the JJ239 monoblocks are intended for speakers of the highest quality, with high sensitivity: for example WLM, Lowther, Fostex, Cabasse, Loth-X, and so on. When multiple-way speakers are used, we recommend bi-amping, using 4 x JJ239. These 4 x 10W can make many audiophiles’ ultimate sound dreams come true.
The JJ239 operates in a clean Class A in all stages. Signal path capacitors, as well as anode supply smoothing capacitors are high quality, very fast (100V/uS) custom made polypropylene types. Both tubes use DC voltage for heater supply. Anode voltage filtration is achieved through a pi-network using JJ Electronics electrolytic capacitors with a total capacitance of 1050uF. The result then is a good separation from hum (<300uV/8Ohms). JJ239 features an anode voltage soft start circuit with a time constant of 25 seconds. The power transformer contains an electrostatic shield between the primary] and heater windings. Bias for power triode is set via a potentiometer on the back panel. Turn the potentiometer until the LED light barely comes on. This represents the setting of the 2A3-40 anode current of 80mA. This is the optimum current for Ub=420 V and output transformer impedance of 3700 Ohms. Output transformer is a double C-core output transformer.
JJ828, HIGH CLASS A1, PUSH-PULL PRALLELL ULTRALINEAR KT88, WITH CATHODE FEEDBACK, INEGRATTED STEREO AMPLIFIER REMOTE CONTROLLED, 2X70W, 4@8 OHM.
JJ828 is an integrated power tube stereo amplifier with an independent power supply for each channel.
The beam tetrode KT88 with an anode dissipation of 35 W has been selected as an output tube for this amp.
The choice of output circuitry is the result of compromise between output power, distortion and damping factor. Two KT88 used as a pentode in class B can deliver 120W, or, on the other hand, when used as a triode in class A, 22 W. We have decided on ultra linear circuitry using four KT88 with cathodes feedback.
The output power of 70 W per channel may seem to be low but it is justified in accomplishing the final outcome. When the KT88 current is 70mA and Ub= 420V (Pa ~30W), a distortion of approximately 1% is achieved at full power without any feedback. For comparison, distortion at Ia=40mA is about 5%. Introduction of feedback of 10DB (3X) sets the output impedance to a satisfactory low level.
The bias current is set individually for each output tube and it is indicated by LED diodes. At the moment the diode light goes off, the cathode current is 70mA. This accurate setting is important when tubes are replaced, because of their high tube conductance slope (up to 18mA/V). Improper bias, for example by 4V, can increase Ia current by up to 70mA and this could destroy the tubes in a few minutes. The output transformer is based on a C-core with air gap 2×0.005 mm, with two OT coils and 20 windings.
The driver consists of three stages. The first stage amplifies the input voltage and the overall feedback is applied to its cathode. We decided on a split load phase inverter. It features low distortion, the amplitude magnitudes are determined only by accuracy of the cathode and anode resistors (0.1%), and it’s unaffected by replacement tube quality. Even when the tube replacement differs by more than 50% from the original, it will not significantly affect this “concertina” phase splitter. By contrast, this is not at all the case with the differential phase splitter, which will suffer greatly from any tube mismatch.
Next follows a driver with the ECC99 tube, which amplifies the signal from the phase inverter and drives the KT88 power tubes. It has sufficient amplitude swing, low internal resistance (~4kOhms) and therefore can drive the KT88 as triodes.
The input section (5 inputs), controlled via a remote control unit, uses Meder relays for input selection and a blue motor potentiometer from ALPS for volume control. Signal from the selected input can be routed at the output “Tape”. Input selection, volume control, turning amplifier standby on, can also be done via controls on the front panel. The front panel is made of wood with brown, black or natural finish.
JJ543 INTEGRATED PUSH PULL TUBE STEREO AMPLIFIER 2X35W WITH REMOTE CONTROL.
The JJ543 is an integrated power tube amplifier. Used in conjunction with high quality input signal sources (CD, PHONO) and high quality stereo speakers, this amplifier is intended for medium sized listening rooms.
The operation of the amplifier is controlled by a microprocessor. The user communicates with the amplifier via a remote control unit and all functions are shown on the amplifier display. All electronic parts used in the JJ543 come from reputable manufacturers. Capacitors in the signal path are special custom made polypropylene types for audio applications.
The JJ543 has four linear inputs. Inputs 1, 2 and 3 have sensitivity 0.775 V; input 4 has sensitivity 2 V at full power. Input 4 is intended for sources with a higher level of signal as is the case of phone preamplifiers. In addition to the speaker outputs L and R, the JJ543 also has three low power level outputs.
The first stereo output is level controlled by the main attenuator. The second output is not level controlled.
The third output is L+ R sum to be used for sub-woofer applications. The level control for this output is accomplished by means of special internal circuitry (a resistor matrix controlled by the microprocessor).
Therefore this is not the case of volume control in the feedback loop or a volume control using D/A converter. The level is shown on the display.
The signal path is comprised of four active stages. Only the last two stages are within the balanced negative feedback loop.
The first stage amplifies the signal 10 times. The second stage is a split load phase inverter.
In order to guarantee excellent phase balancing, this phase inverter was designed using a high accuracy anode and cathode resistors (0.1%).
The first and second stages are not part of the global feedback loop. The third stage is the power tubes driver. Its cathodes are fed from a balanced feedback loop from the bifilar OPT secondary winding.
The feedback loop is also symmetrically connected to the cathodes of the power tubes. The driver is not connected differentially, which eliminates the cancellation of even harmonics. The total feedback is only 10 dB.
The power tubes operate in high class AB (45mA bias per tube). The idle current is adjusted by a negative bias voltage source (fixed bias). Both the cathode currents and the output pair balance can be adjusted by trim pots (P1 and P2).
The output transformer is of a highly sophisticated design. The transformer is wound on a double C-core made of laminations 0.15 mm thick, with an air-gap of 4×0.05 mm. The transformer has 8 primary and 4 secondary bifilar windings, the UL tap is at 25%, which, together with the cathode feedback, results in a feedback ratio of 30%. Due to symmetrical feedback, the secondary windings have a grounded centre tap. Therefore the JJ543 cannot be used in a bridged connection.
JJ283 IS AN ALL TUBE STEREO PREAMPLIFIER, INTENDED TO AMPLIFY AUDIO SIGNALS FROM TURNTABLES WITH A MOVING MAGNET (MM) TYPE CARTRIDGE.
IT CAN BE USED ALSO FOR MC TYPE CARTRIDGES WITH AN OUTPUT VOLTAGE OF MORE THAN 1 mV.
JJ283 All-Tube Stereo Phono Preamplifier, for MM & high output MC cartridge,50dB, 4xECC83S.
This preamplifier is a set consisting of two pieces: a power supply and a preamplifier. The power supply is connected to the power mains with a power cord and to the amplifier with a feeding connector.
The JJ283 has one pair of input connectors and one pair of output connectors. These connectors are high quality gold plated RCA connectors (CINCH) with internal insulation made of Teflon. We recommend using high quality signal cables, less than one meter long for both input and output connections.
The ground connector for the turntable chassis is located next to the RCA connectors.
Selectors for input capacitance or resistance (blue switches) are located in the front section of the JJ283. They are accessible by removing the top panel. These switches have four positions. All positions in OFF give input capacitance 150pF and input resistance 47kOhms. Both positions 1 and 2 ON provide 100pF, which together with base capacitance results in 350 pF / 47 kOhms. Positions 3 and 4 are for MC type cartridges with output voltage more than 0.8 mV. Position 3 ON connects an input capacitance of 150 pF and position 4 ON connects 1000 Ohms resistance. In some circumstances, setting 3+4 ON, or, for some MC cartridges, 1+2+3+4 ON, can be appropriate. After the selectors are set, the ground connector of the top panel must be reconnected and the panel reassembled with all provided screws.
The sound quality of the JJ283, based on listening tests, far exceeds the level which may be indicated by its price.
The JJ283 is one of the few phone preamplifiers on the market which are able to drive most of the power amps directly without a line preamplifier. This is because in the case of classic MM cartridges, the JJ283 provides 1V output voltage.
Informazioni: AAAVT – Web: www.aaavt.it