Mapletree Ultra 4B SE Manuel utilisateur

Modular Series

Ultra 4B SE Special Edition

Stereo Phono/Line Preamplifier

User’s Manual

Rev. Feb. 22/13

Mapletree Audio Design

Lloyd Peppard

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

(613) 387-3830

www.mapletreeaudio.com

info@mapletreeaudio.com

-Specifications are subject to change without notice-

Volume

Balance

Phono Line1 Line2

Mapletree Audio Design

Ultra 4B SE Stereo Preamplifier

Introduction _

The Mapletree Audio Design Ultra 4B SE Stereo Phono/Line Preamplifier offers the

audiophile a number of desirable features:

? ? Compact chassis layout for use with separate power supply for low noise.

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

? ? Switchable for use with 12SN7GT or 6SN7GT 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.

? ? 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______

The Mapletree Audio Design PS 2 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 a slow start cathode type rectifier tube (6X5GT) in conjunction

with low-noise ultra high-speed diodes to achieve all the advantages of tube rectification

(low noise, soft startup) with the high efficiency of a 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 1 A/250 V fast-acting fuse, which can be accessed by

removing the bottom chassis cover 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 with a spare if necessary. If the fuse blows a

second time, you should not try to operate the unit. Contact 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, two 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 470 k???which provides minimal loading of 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. The ground wire from the turntable should be

connected to the ground binding post to minimize hum pickup.

The heater voltage switch located next to the power input jack allows you to

accommodate either 12SN7GT (supplied) or 6SN7GT tubes in your Ultra 4A. 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.

Out

12SN7

6SN7

Line

Gnd Phono

Front Panel Controls

The front panel controls are (left to right) the 3-position Source selector switch (Phono-

Line1-Line2), the Balance control, and the Volume control, which

adjusts the gain of both channels simultaneously. If you find that you hear pops from your

speakers when switching between sources, turn down the volume control before

switching.

Tubes____

Volume

Balance

Phono Line1 Line2

Mapletree Audio Design

Ultra 4B SE Stereo Preamplifier

12SC7 (L)

12SN7GT (L)

12SN7GT (R)

12SC7 (R)

Vacuum tube socket locations are shown in the diagram on p. 6. 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 6SN7GT (or the 5692 special red version) tubes of NOS or current

manufacture. The highly regarded 12SX7GT is equivalent to the 12SN7GT.

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.

MAD Ultra 4B SE Phono/Line Preamplifier

R3a

332K 1%

R2a

3.3M 1%

V1a

12SC7

L. Phono input

L. outputs

chassis

Gnd.

R1a

47.5K

C2a

0.1/400

R5a

432K 1%

R4a

3.3M 1%

R7a

221K 1%

C4a

0.1/400

C3a

820 pF 2%

R6a

432K 1%

R8a

100K 1%

R11a

47.5K 1%

R15a

1K 1%

C9a

1/200

R17a

1M 1%

V2a

12SN7GT

C5a

0.001 5%

C7a

1/200 P1a

100K

SW1a

Source

L. Line inputs

100K

Volume

Balance

J1a

J2a

J3a

J5a

+55 V

R9a

221K

C8a

0.1/400

R16a

10K 1%

R14a

511K

Rev. Jan. 21/13

R3b

332K 1%

R2b

3.3M 1%

V1b

12SC7

R. Phono input

R. outputs

R1b

47.5K

C1b

0.012 2%

C2a

0.1/400

R5b

432K 1%

R4b

3.3M 1%

R7b

221K 1%

C4b

0.1/400

C3b

820 pF 5%

R6b

432K 1%

R8b

100K 1%

R11b

47.5K 1%

R15b

1K 1%

C9b

1/200

R17b

1M 1%

V2b

12SN7GT

C5b

0.001 5%

C7b

1/200

P1b

100K

SW1b

Source

R. Line inputs

Volume

J1b

J2b

J3b

J5b

-0.67 V -0.86 V

+63 V

+76 V

+144 V

+172 V

+71 V

+200 V

R9b

221K

C8b

0.1/400

R16b

10K 1%

R14b

511K

+51.8 V

+52 V

J4a

J4b

C1a

0.012 2%

R20a

475K 1%

R21a

475K 1%

R20b

475K 1%

R21b

475K 1%

R18

22K 2W 5%

+C12

100/400

12 VDC

Power In

R19

5.1K 2W 5%

C11

100/400

+200 V

+172 V

+144 V

12SC7s

12 V 6 V

SW2

Heater Voltage 12SN7s

D1a

red LED

D1b

red LED

Ground Bus

Parts List______

Reference No. Description

C1a,b 0.012uF/160V 2% polystyrene capacitor

C2a,b, C4a,b, C8a,b 0.1uF/400 V polypropylene film capacitor

C3a,b 820pF/630V 2.5% polystyrene capacitor

C5a,b 0.001uF/100 V 5% polypropylene capacitor

C7a,b, C9a,b 1uF/200 V polypropylene film capacitor

C11a,b, C12a,b 100uF/400V electrolytic capacitor

D1a,b 10 mA red LED

J1a,b–J5a,b RCA gold plated phono jack

J6 4-pin chassis jack (power in)

J7 Ground binding post

P1a,b 100K dual audio taper potentiometer

P2a,b 100K linear potentiometer

R1a,b, R11a,b 47.5K 0.5W 1% metal film resistor

R2a,b, R4a,b 3.3M 1W 10% carbon film resistor

R3a,b 332K 0.6W 1% metal film resistor

R7a,b, R9a,b 221K 0.6W 1% metal film resistor

R5a,b, R6a,b 432K 0.6W 1% metal film resistor

R8a,b 100K 0.5W 1% metal film resistor

R14a,b 511K 0.6W 1% metal film resistor

R15a,b 1K 0.6W 1% metal film resistor

R16a,b 10K 0.6W 1% metal film resistor

R17a,b 1M 0.5W 1% metal film resistor

R18 22K 2W 5% metal oxide resistor

R19 5.1K 2W 5% metal oxide resistor

R20a,b, R21a,b 475K 0.6W 1% metal film resistor

SW1 3 position, 4-pole rotary switch (2 poles used)

SW2 DPDT heater voltage selector switch

V1a,b 12SC7 tube

V2a,b 12SN7GT tube

Circuit Operation______

Referring to the schematic diagram, both channels are identical. The following

description refers to either channel unless otherwise noted. The phono input signal is

applied to input jack J1, loaded by resistor R1, then capacitor coupled to the grid of the

first section of the 12SC7 which is configured as a common-cathode voltage amplifier.

Capacitor C1 sets the low frequency breakpoint in the RIAA equalization curve at 50 Hz.

The negative grid bias is obtained through the grid resistor R2. The output from this stage

is capacitor coupled through C2 to the second stage which uses the second section of the

12SC7 also configured as a common-cathode voltage amplifier. The feedback network

consisting of R5, R6, and C3 implements the turnover frequency of the RIAA curve at

500 Hz. Bias is again obtained through the leakage grid current flowing through the 3.3

M?resistor R4.

The signal is then capacitor coupled through C4 to the phono terminal of the source

selector switch (SW1). The passive network comprised of R8 and C5 implements the

roll-off frequency of the RIAA curve at 2130 Hz. The selector switch is used to steer

either the amplified phono signal or one of two line input signals (jacks J2 and J3) to the

third stage, which utilizes the first section of the 12SN7GT in a common-cathode voltage

amplifier configuration giving a gain of around 22 dB. This stage is biased by a light-

emitting diode (LED) which provides the required dc bias voltage while presenting a low

resistance to signals. This eliminates the necessity of an electrolytic cathode resistor

bypass capacitor. The output of this stage is capacitor coupled through C7 to the volume

control potentiometer P1 and to the balance control potentiometer P2. The wiper of the

level control is capacitor coupled through C8 to the grid of the output stage, which

employs the second section of the 12SN7GT configured as a cathode-follower. This stage

has a voltage gain of less than unity but provides a low output impedance suitable for

driving cable capacitance without loss of high frequencies. Grid bias is obtained by

resistors R14 and R15 while R16 establishes the plate voltage and current to provide

maximum output voltage swing. The output voltage is taken from the cathode of the

output stage, capacitor coupled to the output jacks J4 and J5 through capacitor C9.

MAD Ultra 4B Specifications______

Phono Section (100 k?load)

Max. RIAA error: 0.5 dB 30–20 kHz

Maximum Gain: 50 dB

Noise: less than 3mV for gain of 48 dB; 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: 18 dB

Channel balance: ±0.5 dB

Hum and noise: less than 150 ?V at full gain, input shorted

Input impedance (1 kHz): 475 k?

Output impedance (1 kHz): 450 ? ?

Power requirements: +12 VDC @ 1A, +180-250 VDC @ 14 mA (ground is common to

both supplies)

Power Supply Parts List ______

Reference No. Description

BR1 6A/200V diode bridge

C1a,b Dual 50uF-50uF/500V electrolytic capacitor

C2 10000uF/16V electrolytic capacitor

D1 1N4007 diode

D2 10 mA LED

D3, D4 MUR180 high speed diode (800 V)

FU1 ½ A/250 V fast action fuse

J1 4-pin chassis jack

J2 IEC ac line receptacle

IC1, IC2 7812 voltage regulator

R1 6.8K 5W 5% wire-wound resistor

R2 220K 1W 5% metal film resistor

R3 1.8K 1W 5% carbon film resistor

SW1 SPST power switch (250 V rated)

TR1 230 VAC/25 mA power transformer

TR2 14 VAC/1.4 A filament transformer

TR3 6.3 VAC/0.9 A filament transformer

V1 6X5GT rectifier tube

FU1

0.5A/250V

C1b

50/500

C1a

50/500

Chassis

SW1

Power

120AC 60 Hz

220K/1W

TR1

10000/25

LM7812

1N4007

BR1

1.8K

LED

IC1

115

VAC

Mapletree Audio Design Preamplifier Power Supply PS 2

Rev. Feb. 17/13

6.8K 5W

115

VAC

4 8

6X5GT

D3, D4

MUR180

TR3

115

VAC

115

VAC

TR2

115

VAC

115

VAC

115 VAC

25 mA

115

VAC

6 VAC

0.9 A 6X5

214 VAC

1.4 A

7812

123

IC1

Mounting tab

connected to pin 2

insulated from chassis

3 1

LM7812

IC2

Rear View

B+

GND

Power Out

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