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Ear+ Purist HD
Ear+ HD
High Definition Stereo Headphone Amplifier
12B4A
12B4A
12AX7
Users' Manual
Rev Oct. 17/13
Mapletree Audio Design
Lloyd Peppard
R. R. 1, Seeley's Bay, Ontario, Canada, K0H 2N0
(613) 387-3830
www.mapletreeaudio.com
info@mapletreeaudio.com
© Copyright Lloyd Peppard 2003-13
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Summary of Contents for Audio Design Ear+ HD
- Page 1 Ear+ Purist HD Ear+ HD High Definition Stereo Headphone Amplifier 12B4A 12B4A 12AX7 Users' Manual Rev Oct. 17/13 Mapletree Audio Design Lloyd Peppard R. R. 1, Seeley's Bay, Ontario, Canada, K0H 2N0 (613) 387-3830 www.mapletreeaudio.com info@mapletreeaudio.com © Copyright Lloyd Peppard 2003-13...
- Page 2 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.
- Page 3 Examples of typical connections are shown below. To preamp line input From signal source (e.g. CD player) To power amp input From signal source (e.g. CD player) Note: The two inputs are not designed to accommodate the connection of two line sources to the amplifier.
- Page 4 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.
- Page 5 Line In Passive Out AC Receptacle 12B4A (R) 12B4A (L) 12AX7/5751 pilot power volume...
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Page 6: Parts List
Parts List Reference Description Qty. 6 A rectifier bridge C2a,b 47uF/25V electrolytic capacitor (Nichicon Muse) C3a,b 33uF/160V electrolytic capacitor (Nichicon) C5, C6, C7 100uF/400V electrolytic capacitor 10000uF/16V electrolytic capacitor D1-D4 MUR180 ultra high speed rectifier diodes 10 mA LED (pilot light) with holder 1 A/250 V 1-1/4"... - Page 7 Mapletree Audio Design Ear+ HD Headphone Amplifier © Copyright Lloyd Peppard 2003-2013 Rev. March 25/13 ½ 12AX7/ECC83/ ¼" Phones 5751 +95 V 12B4A +193 V Volume Low Z L. In 33/160 TR3a ¼" Phones 100K 600:8 Tant Chassis +110 V High Z +0.8 V...
- Page 8 MAD Ear+ HD Specifications ______ Headphone Output (100 ? load) Frequency response at 1 V rms (10 mW) output: 1000 10000 100000 Frequency (Hz) Maximum undistorted output at 1 kHz: 1.5 V rms (70 mW across 32 Ohms) Gain 10 dB...
- Page 9 Circuit Operation______ Refer to the schematic diagram for the following description of the operation of the Ear+ HD. The left channel (top of the schematic) will be described. The right channel is identical. The line inputs (J1) are directly coupled to the volume control potentiometer P1 which controls both channels.
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