Mapletree Ultra 4C, PS 2D User Manual

Mapletree Audio Design

Ultra 4C Preamplifier

Ultra 4C Stereo Phono/Line Preamplifier

PS 2D Power Supply

User’s Manual

Rev. Mar. 22, 2019

Mapletree Audio Design

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

[phone]
www.mapletreeaudio.com

[e-mail]

© Copyright Lloyd Peppard 2002-2019 -Specifications subject to change without notice-

Introduction _

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The Mapletree Audio Design Ultra 4C Stereo Phono/Line Preamplifier offers the
audiophile a number of desirable features:

 Exclusive use of NOS octal tubes, known for low distortion and musicality.

 Switchable for use with 12SN7GT or 6SN7GTB tubes.

 Precise RIAA equalization (±0.5 dB) using non-interacting passive and active filters.

 High input impedance and low output impedance.

 Parallel output jacks for bi-amp or headphone amplifier applications.

 Home Theater (HT) mode switch on front panel that bypasses the preamp circuitry

and connects the selected line input directly to the output jacks.

 Enhanced connectivity with 3 line inputs, phono input, and 2 line outputs.

 Phono gain of 48 dB suitable for all moving magnet (MM) and high-output moving

coil (MC) phono cartridges.

 Audio grade polypropylene and polystyrene film capacitors in signal path.

Power Supply Connections______

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Power

ON

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 low-noise ultra high-speed diodes to achieve low noise with the
high efficiency of the bridge rectifier topology.

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.

Once 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
replace the fuse. If power fails to come on, you can check the fuse and replace if

necessary. If the fuse blows a second time, you should not try to operate the unit. Contact

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Mapletree Audio Design for information regarding service.

Signal I/O Connections____ __

The signal input/output jacks are located on the rear panel of the preamplifier chassis.
RCA jacks are provided for phono input, three line inputs, and two line outputs. Left
channel jacks are at the top and right channel jacks are at the bottom. A binding post is
provided for phono ground. The phono input resistance is 47 k which matches standard
MM phono cartridge loading requirements. The input capacitance is approximately 50
pF. The line input impedance is 440 kwhich provides minimal loading of any line
source such as 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
through cables up to 10 ft in length. The ground wire from the turntable should be
connected to the ground binding post to minimize hum pickup.

In HT mode (see below), the selected line input is connected directly to the output jacks
and the preamp can be powered off.

The heater voltage switch located next to the power input jack allows you to
accommodate either 12SN7GT (supplied) or 6SN7GTB tubes in your Ultra 4C. Note that
the switch does not affect the heater voltage for the 12SC7 tubes. 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.

Front Panel Controls

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Ultra 4C Preamplifier

The front panel controls are (left to right) the 4-position Source selector switch (Line1­Line2-Line3-Phono), mode switch (Stereo or Home Theater), Volume control , and
Balance control. In HT mode, the selected line input is connected directly to the output
jacks on the rear panel. The preamp circuit is no longer connected to the output jacks so
the power supply can be turned off.

Tubes____

The preamp vacuum tube socket locations are shown in the following diagram. The
12SC7s are toward the rear of the chassis. The 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 heater voltage selector switch
permits the use of NOS 6SN7GTB tubes (see below). The highly regarded 12SX7GT is
equivalent to the 12SN7GT.

Note: With the heater voltage switch in the 6SN7 position, the two tube heaters are
connected in series. Many old stock 6SN7 tubes (e.g. 6SN7GT/GTA) may not have well
matched heater characteristics, which means that the two tubes may not share the 12
VDC evenly, which is not desirable. The 6SN7GTB was developed expressly for series
heater connections in early TVs so should work fine in the preamp. Some old and

currently manufactured 6SN7 tubes may work well in the series configuration but this

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should be verified by measuring the voltage across each tube heater (pins 7-8).

Care of your Ultra 4_____

The chassis finish is lacquer-based. 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.

Mapletree Audio Design Ultra 4C Specifications______

789

Phono Section (100 k load)

Max. RIAA error: 0.5 dB 30–20 kHz
Maximum Gain: 50 dB (1 kHz)
Noise: less than 1 mV for gain of 40 dB
Input resistance at 1 kHz: 47 k

Line Section (100 k load)

Frequency response (1 V output, 100K load): 20 Hz–20 kHz –0.5 dB (any volume

control setting)

Max. output voltage (100K load): 15 V rms
Gain: 14 dB
Channel balance: ±0.5 dB
Balance control: 3 dB channel shift at 9 and 3 o’clock with vol. control at 12 o’clock
Hum and noise: less than 150 V at 10 dB gain
Input impedance (1 kHz): 440 k
Output impedance (1 kHz): 450 

Power Supply (PS 2D)

Power input: 120 VAC, 50-60 Hz (can be wired for 240 VAC)
Power output: +12 VDC @ 1A, +180-250 VDC @ 14 mA (ground is common to both).
Fuse: 1 A, 250 V fast action 20 mm fuse
Power consumption: 30 W