Descrição
Estado de conservação: 9/10
Thank you for selecting the MV55 to power your audio system. The MV55 draws on two decades of research at conrad-johnson into the reproduction of recorded music. The result is a power amplifier with a remarkable ability to recreate the the dynamics, textures, tonalities, and ambience of live musical performances. With the MV55, we believe that you will experience the excitement of discovery in hearing more from your favorite recordings than ever before. At conrad-johnson, we expect our products to be a source of satisfaction and of pride to their owners for many years to come. Accordingly, circuit designs, parts and materials for all conrad-johnson products are selected with a view to maintaining optimal performance over the years. Our reputation for producing among the industry’s most reliable components is a natural consequence of this engineering approach. Although operation of the MV55 is quite straightforward, please take a few minutes to read this manual for useful information on it’s installation and operation. In closing, we’d like to welcome you to the family of conrad-johnson owners. We want you to enjoy your conrad-johnson product to the fullest. To this end, our staff stands ready to answer any questions you may have about the function and application of your MV55, and to provide any needed service both during, and after the warranty period. Our goal is to heighten your enjoyment of recorded music.
C IRCUIT DESIGN The MV55 circuit is notable for its elegant simplicity. A triode input amplifier comprised of paralleled sections of a 12AX7A is direct coupled to a cathode coupled differential phase inverter using high current triodes to provide balanced, low impedance drive to the push-pull output stage. The output stage features ultralinear operation of a pair of EL34s, which permits high power levels while greatly reducing the source impedance of the stage. As a result, the amplifier is capable of supplying the large current demands of high amplitude musical transients driven into reactive speaker loads. A substantial main power supply of massive polypropylene capacitors enables the MV55 to easily meet these extraordinary current demands. Voltage regulators for the voltage amplifiers and phase inverters provide nearly absolute isolation of these sensitive stages from the output stages. Optionally, the MV55 may be reconnected internally for triode operation of the output stage, for exceptionally musical performance, but at considerably reduced output power. The conversion is simple, but does require soldering. Consult your dealer as to which configuration will perform best in your system.
T UBE REPLACEMENTS The MV55 uses eight vacuum tubes of three different types: two 12AX7A (V1 and V2), two 6SN7 (V3 and V4) and four EL34s (V5 through V8). The brands of tubes we supply have been chosen by first selecting those brands which are known to be most reliable, then by extensive auditioning of these acceptable brands with the final choices being made solely on the basis of sonic performance. We know of no vacuum tubes available which will improve the sonic performance of your MV55. We highly recommend that you purchase replacement tube sets from conrad-johnson design. We anticipate tube life to accomodate two to three years of operation without degradation in normal use – if the amplifier is switched off when not in use. If it is left on at all times, tube life can be exhausted in a matter of a few months. The MV55 has been designed to make tube replacement as simple as possible. Because the output tubes are individually biased, replacement tubes need not be matched pairs. No a-c balance adjustment is necessary. It is necessary to re-bias the amplifier when the output tubes are replaced. The MV55 has built in bias indicators so that no instruments are required to make this adjustment. ADJUSTING OUTPUT TUBE BIAS Biasing the amplifier is a simple procedure that can easily be done by the owner. Only a plastic screwdriver is required. A red plastic screwdriver has been included with your amplifier for this purpose. After replacing the tubes, the amplifier should be connected to a load (your loudspeakers will work fine) and there should be no signal applied to the amp. It should be connected to you preamplifier with the volume control turned fully down. Turn the amplifier on. After about one minute, turn each of the four screwdriver adjustable controls counterclockwise until the associated indicator LED just goes off. Clockwise rotation may be necessary first to turn the LED on; do not turn the adjusting screw any further in the clockwise direction once the LED has come on. After the amplifier has warmed up thirty minutes, the procedure just described should be repeated. NOTE: It is normal for these LEDs to flash or flicker when the amplifier is in use.
SPECIFICATIONS: Power (ultralinear operation): 45 watts per channel RMS both channels driven into 8 ohms from 30Hz to 15KHz at no more than 1% total harmonic distortion or intermodulation distortion. Power (triode operation): 22 watts per channel RMS both channels driven into 8 ohms from 30Hz to 15KHz at no more than 1.5% total harmonic distortion or intermodulation distortion. Sensitivity: 550 mv to full power. Small Siganal Distortion: Less than .1% at midband Phase: Phase correct (non-inverting) Frequency response: 20Hz to 20KHz +0, -.5dB Hum and noise: 95dB below full power output. Input impedance: 100K ohms. Dimensions: 12.75D x 17.5W x 7H inches. Weight: 39 lbs.
