Mapletree Line 2CRM User manual

Modular Series
Line 2CRM Stereo Line Preamplifier
PS 2D Power Supply
User’s Manual
Rev. Dec 6, 2019
Mapletree Audio Design
R. R. 1, Seeley's Bay, ntario, Canada, K0H 2N0
[phone]
www.mapletreeaudio.com
[email protected]
© Copyright Lloyd Peppard 2002-2019 -Specifications are subject to change without notice-
Line 2CRM Preamplifier

Introduction _
The Mapletree Audio Design Line 2CRM Stereo Line Preamplifier offers the audiophile a
number of desirable features:
Remote volume control with handset.
Bypass switch on front panel for home theatre (HT) operation.
Exclusive use of N S octal tubes, known for low distortion and musicality.
Switchable for use with 12SN7GT or 6SN7GTB tubes.
High input impedance and low output impedance.
Parallel output jacks for bi-amp/headphone amp/HT applications.
Audio grade polypropylene film capacitors in signal path.
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Power Supply Connections______
The Mapletree Audio Design PS 2D power supply provides +12 VDC (regulated) heater
supply voltage and +200 VDC B+ plate supply voltage at a current of 15 mA (see
specifications). It utilizes ultra high-speed diode bridge rectification to achieve low noise
and high efficiency.
The separate power supply eliminates induced hum originating from power supply
circuitry and components. The power connections to the preamplifier chassis are made
through a special 3-conductor power cord that plugs into jacks located on the rear panels
of the power supply and preamplifier chassis.
CAUTION: Do not operate the power supply when it is not connected to the
preamp. Damage of components may result.
nce the interconnecting power cord is securely attached between the two chassis and the
line cord is plugged in, the power supply can be turned on. The pilot lamp on the power
supply chassis indicates that the unit is on. It takes about 30 seconds for the tubes to reach
operating temperature ready for use. During operation, is it normal for the power supply
chassis to become warm to the touch.
The power supply is protected by a 20mm, 1 A/250 V fast-acting fuse, which can be
accessed by removing the fuse drawer from the ac inlet receptacle after the unit has been
unplugged for at least 60 sec. Under normal conditions, it should not be necessary to
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replace the fuse. If the fuse blows, you should not try to operate the unit. Contact
Mapletree Audio Design for information
Signal I/O Connections____ __
The signal input/output jacks are located on the rear panel of the preamplifier chassis.
RCA jacks are provided for three line inputs and two line outputs. The outputs can be
used for bi-amp operation, connection to a headphone amp, or to the front channel inputs
to a home theatre (HT) system. Left channel jacks are at the top and right channel jacks
are at the bottom. The line input impedance is 100kwith standard 10 dB gainwhich
provides minimal loading of any line source such as DAC, CD/DVD player, tape deck,
tuner, or PC sound card. The output impedance is less than 500  which is suitable for
connection to a power amplifier(s) through cables up to 10 ft in length.
The heater voltage switch located next to the power input jack accommodates either
12SN7GT (supplied) or 6SN7GTB tubes in your Line 2C. While it will do no damage to
switch to 6SN7 position with 12SN7 tubes installed, operation in the 12SN7 position
with 6SN7 tubes may damage the tubes.
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Front Panel Controls
The front panel controls are (left to right) the 3-position Source selector switch (Line1-
Line2-Line3), Mode switch (Stereo or HT), Volume control, and Balance control. In HT
mode, the selected input source is connected to the output jacks and the active preamp
output is disabled; the power may be turned off.
Remote olume Control
The volume control IR sensor is located between the volume and
balance control as shown above. The remote handset has buttons for
volume up and down. The power button is disabled. When first
turning on the power supply, the volume control will reset to zero and
then advance to the 9 o’clock position. It is designed to avoid
unexpected high volume levels when powering up.
Tubes_____
The tubes supplied are new-old stock (N S) and have been pre-tested. A burn-in period
of several hours may be needed to achieve the best sonic performance. Tube life should
be thousands of hours. Aging tubes may result in a reduced gain in one or both channels
or an increase in noise levels. Infrequently, a heater may burn out which is indicated by
total loss of sound. Replacement tubes can be obtained from several suppliers in the U.S.
and Canada. Some listeners enjoy trying different brands and variants of tubes. The
heater voltage selector switch permits the use of 6SN7GTB (or the 5692 special red
version) tubes of N S or current manufacture. The highly regarded 12SX7GT is
equivalent to the 12SN7GT.
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Line 2CRM Preamplifier

Care of Your Line 2_____
The chassis finish is lacquer-based and, while hard (and continues to harden over time), is subject
to chipping on impact with another object. Both the chassis and labels/logos are moisture resistant
but you should avoid cleaning with water, alcohol, or other strong chemical. A soft 1” paintbrush
is recommended to dust the chassis periodically.
Heat is the most troublesome enemy of electronic components, especially capacitors. Heat can be
properly dissipated by ensuring free air circulation around the preamp and power supply chassis.
It is not recommended that you leave the power on when not in use.
Warranty___
Assembled 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 warranty period.
Line 2CRM Specifications______
Fre uency response (1 V output, 100K load): 20 Hz–20 kHz –0.3 dB (any volume
control setting)
Max. output voltage (100K load): 15 V rms
Gain: 10 dB (standard—can be ordered with input gains of 0 dB to 20 dB)
Channel balance: ±0.2 dB
Balance control: 3 dB channel shift at 9 and 3 o’clock position with vol. control at 12
o’clock
Hum and noise: less than 1 mV at full gain, no input
Input impedance (1 kHz): 100 k(with standard 10 dB gain)
Output impedance (1 kHz): 450 
Power Supply ( PS 2D )
Power output: +12 VDC @ 1A, +180-250 VDC @ 14 mA (ground is common to both).
Fuse: 1 A, 250 V fast action
Power consumption: 30 W, 120 VAC, 50-60 Hz
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