GM70 SET integrated amplifier

GM70 SET integrated amplifier
Lyrita Audio
L - 458, Sarita Vihar
New Delhi 110 076
Tel : 011-4140 1143
tube integrated amplifier
Lyrita Audio
This amplifier 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.
Within this period, Lyrita Audio will repair the amplifier
without charge, provided that failure was not due to
A separate guarantee card is not issued with this unit. The
guarantee period begins on the day you take delivery.
Model No. ________________
Input Tube
Russian 6N1P (1 nos)
Driver Tubes
Russian 6E5P (2 nos)
Output Tubes
Russian GM70 (2 nos)
Rectifier Tube
Russian 5C4S (1 nos)
Power Output
20 watts per channel into
8 ohms
Frequency Response
40 Hz to 20 kHz
Distortion (THD)
less than 1%
CD, Tape, Tuner
Source, Volume
Mains Power
230 V, 50 Hz, 250 W
Size W x D x H
360 x 520 x 200 mm
22 kg
The GM70 SET is a medium power tube, stereo integrated
amplifier, offering superb reproduction of sound.
Tube amplifiers need a load connected to their output.
Always connect the speakers before operating the
This GM70 SET amplifier accepts three line level source
inputs. The signal path is kept as simple and as short as
possible, to preserve the integrity of the music signal.
To power on:
The design is a single-ended triode tube amplifier, using the
GM70 DHT power tube. The entire signal in each channel
goes through a single output tube, making this class A
operation. All wiring is point-to-point. The tube input stage is
capacitor coupled to the driver stage, which in turn is coupled
through an interstage transformer to the tube output stage.
The output stage uses a custom designed audio output
transformer. No global feedback is used.
Flip the power switch UP to STANDBY.
LED glows ‘Red’.
Wait 1 minute, for the tubes to heat up.
Flip the power switch DOWN to OPERATE.
LED glows”Green”.
Switch centre position is OFF.
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.
Fixed bias is used for the output tubes. No user adjustment is
The power supply has an oversized transformer, to provide
good regulation for the supply voltages. Solid state
rectification is used for the output stage, and tube rectification
is used for the input and driver stages. Each stage of the high
voltage supply is independently filtered through chokes.
Individual filament transformers are used for low noise
operation. A DC filament supply is used for the output tubes.
The GM70 SET is housed in a naturally finished solid
sheesham cabinet. The design elegantly showcases the
beauty of the tubes.
! Warning : In operation, this amplifier has 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.
All input signal connections are made to RCA sockets on
the back panel of the amplifier. These are user specified,
for line level sources only.
The speaker output sockets accept banana jacks. The
norm here is Red for signal and Black for ground. Maintain
the colour code when connecting to the loudspeaker, so
that the speakers operate in phase.
The amplifier should be placed as close to the
loudspeakers as possible. This will allow the connections
to be made with short speaker cables. It is advisable to
keep the additional impedance seen by the amplifier as
low as possible. The best way to do this is to keep the
speaker cables short.
Good ventilation should also be provided around the
amplifier. The tubes generate a fair amount of heat, and
natural ventilation is necessary to dissipate this heat to the
surroundings. The amplifier chassis will get warm, but
should still be comfortable to touch.
Always place the amplifier on a firm, smooth surface.
The amplifier is protected against overload by fuses at
three points. The mains supply fuse is mounted on the
rear panel and is easily accessed from the outside.
Inside the amplifier are two fuses on the high voltage
supply. These are mounted on the inside panel above the
power supply capacitors. To reach the internal fuses,
remove the back top plate of the amplifier.
Mains supply fuse
2A, 250V (RQB 2000)
High Voltage supply fuse 500mA, 250V (RQB 500)
100mA, 250V (RQB 100)
On operation of the amplifier, if the fuses do blow, check
all possible causes before replacing the fuses. If any
doubt remains, contact Lyrita Audio for servicing.
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF