Audio Design Ear+ HD User Manual

12B4A

12AX7

Ear+ Purist HD

Ear+ HD

High Definition Stereo Headphone Amplifier

12B4A

Users' Manual

Rev Oct. 17/13

Mapletree Audio Design

Lloyd Peppard

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

[phone]
www.mapletreeaudio.com
[e-mail]

© Copyright Lloyd Peppard 2003-13

2

Introduction _

The Mapletree Audio Design Ear+ HD Stereo Headphone Amplifier represents the
ultimate performance development of the Ear+ family. The use of premium passive
components, including Black Gate capacitors and Audio Note Tantalum film resistors,
yields noticeably enhanced bass definition, inner detail, and transparency. Features
include:

? ? The exclusive use of high quality new old stock (NOS) and current manufacture tubes

that can be obtained at modest cost from many suppliers.

? ? The use of premium passive components (Tantalum film plate load resistors, ultra

high speed rectifier diodes, and Alps volume control).

? ? Wide frequency response: 10 Hz – 20 kHz –1 dB.
? ? A para-feed cathode-follower headphone output circuit capable of driving a wide

range of headphones with impedances from 30 to 300 Ohms.

? ? DC heater power supply for low noise.
? ? Dual inputs for convenient patching into existing system.
? ? Passive preamp output jacks.
? ? High and low impedance headphone outputs.

Input/Output Connections______

The standard IEC line cord is attached to the receptacle on the rear panel of the Ear+ HD.
It is compatible with a 115-125 VAC line with a frequency of 50–60 Hz. A 1 A/250 V
fuse provides primary protection for the power supply. It can be accessed by removing
the bottom chassis cover. Turn off the power and unplug the unit at least 60 sec before
removing the cover. Replace the cover before again applying power. 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.

Two sets of Input RCA jacks are provided on the rear panel which allow connection to a
line-level stereo source (e.g. CD player) and to the line input of a preamp or integrated
amp. The input impedance without connection to a preamp is 50 k? which should be
compatible with all source output circuits. The input sensitivity is 0.4 V to produce a 10
mW headphone output power. The Passive Output jacks allow the use of the volume
control as a passive preamp with or without powering up the Ear+ HD.

3

From signal source

From signal source

To preamp line input

Examples of typical connections are shown below.

R

L

R

(e.g. CD player)

L

R

(e.g. CD player)

L

L

R

To power amp input

Note: The two inputs are not designed to accommodate the connection of two line
sources to the amplifier. This will load the outputs of the connected components and
result in low volume and distortion.