Mapletree L2X Stereo Line Manuel utilisateur

Modular Series

L2X Stereo Line Preamplifier/Buffer

PSX Power Supply

User’s Manual

Revised Feb. 23/14

Mapletree Audio Design

Lloyd Peppard

R. R. 1, Seeley's Bay, Ontario, Canada, K0H 2N0

(613) 387-3830

www.mapletreeaudio.com

info@mapletreeaudio.com

Introduction _

The Mapletree Audio Design L2X Stereo Line Preamplifier/Buffer is a streamlined

version of the Line 2B SE line preamp without the dual heater voltage switch and balance

control. Nichicon polypropylene film capacitors and Alpha carbon volume control are

also employed. The L2X is matched to the compact PSX power supply that can be located

remotely from the preamp itself. The power supply features an all-solid-state full-wave

rectifier using high-speed diodes, and an unregulated dc heater supply. Other features

include:

??Compact chassis layout and separate power supply for low noise. Noise is less than

200 ?V.

??Exclusive use of NOS 12SN7GT octal tubes, known for low distortion and

musicality.

??Two switched inputs with user-specified gains of 0 or 10 dB. Unity gain (0 dB) is

available for buffer use, with the L2X inserted between the source and an integrated

or power amp where additional gain is not required.

Power Supply Connections______

The Mapletree L2X consists of a preamplifier chassis with provision for connection to the

separate PSX power supply. This allows separation between the two units and eliminates

induced hum originating from power supply circuitry and components. The Mapletree

PSX power supply provides 12 VDC at 0.6 A for the heater supply and +250 VDC at full

load (12 mA) for the B+ plate supply. 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. Do not use the PSX power supply for

any other preamp. The current ratings are for the L2X preamp only.

Once the interconnecting power cord is securely attached between the two chassis and the

line cord is plugged in, the switch on the front panel of the PSX is used to activate the

power supply. The pilot lamp 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 1 A, 250 V fast-acting fuse located inside the power

supply chassis. Under normal conditions, it should not be necessary to replace the fuse. If

power fails to come on, you can check the fuse and replace if necessary. Wait 60 sec with

the unit unplugged before removing the bottom cover. If the fuse blows a second time,

you should not try to operate the unit. Contact Mapletree Audio Design for information

regarding service.

Input/Output Connections______

The signal input/output jacks are located on the rear panel of the preamplifier chassis.

RCA jacks are provided for two stereo line inputs, and one stereo line output. The line

input source selector switch is located between the input jacks. Each input gain is custom

specified to be either 10 dB or 0 dB (unity gain) at full volume. The corresponding input

resistance is 100 k??or 470 k??respectively, which provides minimal loading for any line

source such as CD/DVD player, tape deck, tuner, or PC sound card. The line output

impedance is less than 500 ?, which is suitable for connection to a power amplifier

through cables up to 10 ft in length.

Preamp Controls____

The front panel volume control acts on both channels.

Tubes____

The vacuum tubes supplied are new-old stock (NOS) 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. Mapletree Audio Design will attempt to provide

replacement tubes to customers at cost plus shipping. Some listeners enjoy trying

different brands and variants of tubes. The highly regarded 12SX7GT is equivalent to the

12SN7GT.

Specifications______

Frequency response (100 k??50 pF load, 1 V output): 12 Hz–20 kHz –0.5 dB

Maximum input voltage: 5 V (rms)

Voltage Gain (100 k?load, 1 kHz): 10 dB or 0 dB (for use as a buffer)

Output impedance (1 kHz): 450?

Input impedance (1 kHz): 100 k??(10 dB gain) or 470 k??(0 dB gain)

Hum and noise at output (max volume): less than 200 ?V rms

Phase: Inverting

Power consumption: 20 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.

Mapletree Audio Design

L2X Stereo Line Preamplifier

L. output

47.5K 1%

10K 1%

1u/400V

511K 1%

V1a

12SN7GT

1u/400V

100K

Source

L. Line inputs

Rev. Feb. 18/14

Volume

chassis

0.1u/400V

1K 1%

511K

+250 V

R. output

47.5K 1%

10K 1%

1u/400V

511K 1%

V1b

12SN7GT

1u/400V

100K

Source

R. Line inputs

Volume

0.1u/400V

1K 1%

511K

+250 V

+54 V

+49 V

+250 V

475K 1%

12 VDC

Power In

(rear view)

5.1K 2W

100u/400V

12SN7s

475K 1%

1.9 V

Ground bus

chassis

Ground bus

100K 1%

Gain = 0 dB

Gain = 10 dB

Gain = 0 dB

Gain = 10 dB

47.5K

Input resistors shown for

gains of 0 dB (475K) and

10 dB (100K)

0.5A/250V

100u/400V

Chassis

Power

120AC 60 Hz

330K/1W

10000u/25V

1.5K

LED

115

VAC

Mapletree Audio Design Preamplifier Power Supply PSX

Rev. Feb 23/14

6.8K 5W

115

VAC

115

VAC

115

VAC

115 VAC

25 mA

115

VAC

210 VAC

1.2 A

Rear View

B+

GND

Power Out

MUR180

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