DHT Line Lyrita Audio L - 458, Sarita Vihar New Delhi 110 076 Tel : 011-4140 1143 email:firstname.lastname@example.org www.lyrita-audio.in preamplifier Manual Lyrita Audio Specifications Tubes, line stage Russian 4P1L (2 nos) Tube, rectifier Russian 5C4S (5Z4G) (1 nos) This preamplifier is guaranteed against any defect in material and workmanship for a period of two years from the date of purchase. Tubes are guaranteed for thirty days. Frequency Response 10 Hz to 100 kHz Distortion (THD) less than 1% Within this period, Lyrita Audio will repair the amplifier without charge, provided that failure was not due to misuse. Gain 12 dB (voltage gain of 4) Output impedance 1250 ohms Inputs CD, Tuner, Tape Outputs Main Out / Line Out Mains Power 230 V, 50 Hz, 150 W (max) Size W x D x H 360 x 400 x 130 mm Weight 10 kg Guarantee A separate guarantee card is not issued with this unit. The guarantee period begins on the day you take delivery. Serial No. _________________ Description Operation To power on: Flip the Power Switch down. LED glows “Green”. Power to the circuit ramps up gently. In about a half minute, the preamp will be operational. When making or breaking any connections, always turn off the power to the amplifier first, so that no hum or transients are transferred to the speakers. When sitting down to a listening session, it is a good idea to let the system warm up for a half-hour. This stabilizes the circuitry, and makes it sound better. The DHT Line preamplifier is a purist design, and provides basic control functions in an audio system. This design uses directly heated tubes/triodes (DHT) as single gain stages, with their characteristic rich textured sound. The signal path is kept as simple and as short as possible. This preserves the integrity of the music signal; as any additional circuitry only adds complexity and distortions of its own. This, of course, eschews the use of unnecessary switching and filter circuits, as well as tone controls. The overall design is simple and direct. Line level inputs have only one amplification stage through the Russian 4P1L DHT tube (configured as triode). This provides a low level of gain. All wiring is point-to-point. All gain stages operate in Class A mode. No global feedback is used. Installation Good ventilation should be provided around the preamplifier. The tubes generate a fair amount of heat, and natural ventilation is necessary to dissipate this heat to the surroundings. The preamplifier chassis will get warm, but should still be comfortable to touch. Always place the preamplifier on a firm, smooth surface. The 4P1L tubes are microphonic—emit some bell ringing sounds when new, even though they are mounted on a plate on rubber grommets to prevent vibrations. However, after some use, the ringing settles down. The power supply uses a large, shielded power transformer. Tube rectification is used. The high voltage supply is independently filtered through chokes and RC filters. The tube heaters use a choke filtered DC supply. The DHT Line preamplifier is housed in a naturally finished solid sheesham cabinet. Connections Fuses Power ! Warning : In operation, this preamplifier has very high voltages. Always switch off, and unplug the amplifier from the mains supply before working on it. Wait for 5 minutes for the high voltages to die down, before opening the amplifier! Mains supply connection is through a detachable power cable with an IEC-type connector. The mains power switch is mounted on the front panel of the amplifier. Signal All signal connections are made to RCA sockets on the back panel of the preamplifier. These are clearly marked. CD / Tuner / Tape These are all line level inputs, and can be used with the sources indicated. Main Out This set of output connectors sends the output signal to the power amplifiers. Line Out This set of output connectors can be used to send the signal to a subwoofer, or other controller. The preamplifier is protected against overload by a fuse at one point only. This is the mains supply fuse, mounted on the rear panel and is easily accessed from the outside. Mains supply fuse 2 A, 250 V (RQB 2000) On operation of the preamplifier, if the fuse does blow, check all possible causes before replacing the fuse. If any doubt remains, contact Lyrita Audio for servicing.
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