STATUS - SOLD
Click here for more pictures
Description :
Jadis enjoys a worldwide reputation in audiophile circles for exceptional musicality and a natural sound. The company only design with valves, and have no qualms about using as many as are required for the output stage. The Jadis JA80 amplifier is made to a high standard and is clearly craftsman built; the components used all reflect a long development process aimed at maximizing the sound quality. It is also strongly made, using a welded chassis of stainless steel. Each channel is rated at a minimum of 60 watts class A at 8 ohms in the Jadis JA80, the power supply is rated to ensure that result, and with normal mains in each channel drawing a continuous 242 watts. It can claim full power delivery down to 15Hz, and in normal use there is no danger of reaching the output transformer operating limits. Tracing through the circuit, the input signal is direct-coupled via a 470k film potentiometer which allows the user to preset the gain to a maximum sensitivity of 600mV, suitable for direct connection of a number of sources, including CD.
The first stage consists of a differential amplifier using the two triode sections of an ECC82. The second grid is grounded, while overall feedback from the speaker terminals goes in the normal manner to the cathode connection of the input section. The bi-phase outputs of the Jadis JA80 from the first anodes are direct-coupled to the grids of the next stage, employing the lower-current ECC83. It is common to place this valve in the first stage and followed with the ECC82, where a larger voltage swing is useful to drive the output stage. A small feedback loop runs from the output cathode connections to a resistive divider, placed between grid and anode of the drive stage, improving its otherwise sluggish high frequency delivery. The ECC83 tube driver stage is coupled to the output valve grids by capacitors claimed to be the only ones lying in the signal-path: 0.47uF 1600V top-quality polypropylene types. Some additional capacitors are present in the Jadis JA80; for example, the electrolytic bypasses present in the cathode circuit of the differential driver stage.
The output stage of the Jadis JA80 comprises four KT88s per channel operating in pure class A, push-pull transformer-coupled in a feedback connected variation of the ultra-linear configuration. The output stage is self-biased, this simple technique being based on the use of pre-aged and precision-matched tubes. With class A operation the supply current variations are very small, and no regulators are needed for HT feeds to the earlier stages, simple R-C decoupling serving well here. A small printed-circuit is used, mainly as a terminal board for the power supplies, the solid-stage LED bias indicator circuits, and the output transformer terminals. The transformer secondaries may be arranged in three modes, either as supplied for 4 to 12 ohms, or alternatively for 2 to 6 ohms and 8 to 24 ohms, these options accommodating typical loudspeaker load variations. The active circuitry of the Jadis JA80 is hard-wired in single-strand conductors, and the shortest possible signal paths are employed, this technique helping to maintain clarity.
Jadis JA80's performance from the upper bass to the mid treble can be described as eminently musical. It has a real beauty of tonal rendering coupled with fine inner dynamics, achieved without any exaggeration of drive or presentation. The midrange was liquid, exceptionally relaxed, yet reproduced with first-rate transient and harmonic definition. Sounds such as open plucked strings and small drums were especially telling. Coupled with a high resolution of detail and an excellent separation of individual sounds and instruments, the Jadis JA80 presented a feeling of assured imperturbability. The bass was articulate, tonally pure and well differentiated, lacking only a modicum of slam and extension at the lowest frequencies. In the treble, the JA80 also set a strong pace. Treble sounds were faithful to the original; bells and triangles were beautifully airy and shimmered with the right degree of brilliance. A minor failing concerned the trace of excess sibilance heard on the more forward of vocal recordings, accompanied by a mild breathiness or glaze audible in the extreme treble range. Stereo focus and stage width were excellent, and proved particularly adept at the portrayal of orchestral perspectives. Musicians were nicely ranked into the depth dimension of the soundstage. Ultimately, the Jadis JA80 was satisfying because its whole performance was so well proportioned and because its exceptional accuracy over the broad midrange counted for so much in the listening experience.
Specifications :
Nominal Power.................................60 watts per channel
.................................Pure class A at 1kHz for 0.6% total harmonic distortion
Input Sensitivity...............................Nominal: 0.775V
Bandwidth.......................................20 to 20000 at 0dB
At Low Frequencies..........................Full power at 15Hz
Bias...............................................Automatic bias, no adjustment
Load Impedance..............................Adjustable: 1, 4, 8, 16 ohms. Internal strapping
Input Impedance..............................100k ohms
Power Supply..................................AC input voltage corresponding to the country of destination
Power Consumption.........................242 watts for each mono amplifier
Tubes Per Channel...........................1 x ECC82/12AU7
...........................1 x ECC83/12AX7/7025
...........................4 x EL34/6CA7A or 6550A or KT88
Dimensions(w x d x h)......................26 x 62.5 x 23 cm
Weight............................................35kg per side
Miscellaneous :
Matching.........................................Jadis JPS2S Preamplifier
Made In...........................................France
Condition.........................................7/10
Product Information :
http://www.jadis-electronics.com/popup-ampui.php?id=71&lang=eng (Manufacturer's Website)
http://www.freeinfosociety.com/electronics/schematics/audio/jadisja80.pdf (Schematic)
http://www.audioparts.ch/upload/img/big2/6b1b33b0d2786d383da8386e20db1d16.JPG?artID=1654&PHPSESSID=dca95692de03d71ff00a5c47add83361 (Specifications)
Reviews :
http://www.audioreview.com/cat/amplification/amplifiers/jadis/ja-80/prd_128589_1583crx.aspx
http://www.audio.grobel.com.pl/files/rec/jadis/518ja80_hifi-news&record-review_vol.33_no.6_june_1988_gb.pdf |
