Circuit Operation; Specifications; Warranty - Mapletree Line 2B SE User Manual

Circuit Operation______

Both channels are identical as shown in the schematic diagram. Operation will be
described for the left channel. The selector switch (SW1) selects from one of the three
line inputs (jacks J1–J3). Series resistors (R1) determine the gain of each line input. The
maximum gain, with zero resistance, is approximately 22 dB. The selected signal is
applied to the grid of the first section of the 12SN7GT which is configured as a common-
cathode voltage amplifier with current feedback. The output from this stage is capacitor
coupled through C2 to the top of the volume control potentiometer P1. The signal at the
wiper of the level control is capacitor coupled through C3 to the grid of the output stage
comprising the second section of the 12SN7GT configured as a cathode-follower stage.
The grid bias voltage is established by R7 and the plate voltage by the sum of R7 and R8.
The operating conditions are chosen to provide the maximum possible output voltage
swing (around 13 V rms). The output voltage is taken from the cathode of this stage,
capacitor coupled to the output jacks J4 and J5 through capacitor C4. The gain of this
stage is less than unity but the output impedance is sufficiently low (less than 500? ) to
enable driving capacitive interconnect cables without high frequency loss.

Specifications______

Frequency response (100 k? ?50 pF load, 1 V output): 10 Hz–20 kHz –0.2 dB
Maximum input voltage: 5 V (rms)
Voltage Gain (100 k? load, 1 kHz): 10 dB (standard configuration)
Output impedance (1 kHz): 450?
Input impedance (1 kHz): 100 k? ?for 10 dB gain configuration
Hum and noise at output (max volume): less than 200 ? V rms
Phase: Inverting
Power consumption: 30 W

Warranty___

Assembled MAD components are warranted for 2 years to the original purchaser for
failure of parts (excluding tubes) and workmanship. Tubes are warranted for 90 days
exclusive of shipping cost. Service, including parts and labor (but excluding shipping), is
free within the warrantee period.
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