Audio Design Ear+ HD User Manual page 4

The headphone output jacks are a standard ¼" stereo phones jack with the left channel
connected to the tip contact. If your headphones are terminated in a 1/8" plug, an adaptor
is required (usually supplied with your headphones). Headphone impedances from 30 to
300 ? are suitable for use with either the high impedance (Hi Z) or low impedance (Lo
Z) output jacks. A sensitivity rating of at least 97dB/1mW is recommended. The low
impedance output provides a slightly reduced gain for low impedance phones such as the
Grado Prestige series which may be desirable depending on your preferred listening
levels..
Controls____
The switch on the left of the front panel turns on the ac power to the amplifier. The power
on condition is indicated by the illumination of the pilot light. It takes about 30 seconds
for the tubes to reach operating temperature ready for use. During operation, is it normal
for the chassis to become warm to the touch.
The front panel volume control acts on both channels simultaneously. Tracking between
channels is typically better than 0.5 dB over the control range.
Tubes____
A tube 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. You may have been supplied with
either a 5751, ECC83, or 12AX7 for V1 which are equivalent types (the 5751 exhibits
slightly lower gain). 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.
Warranty___
Factory assembled MAD components are warranted for 2 years to the original purchaser
for failure of all parts (excluding tubes). Tubes are warranted for 90 days exclusive of
shipping cost. Service, including parts and labor (but excluding shipping), is free within
the warranty period.
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