WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Руководство пользователя

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20 W Stereo Integrated Audio Amplifier
from the power amplifier. The Balance control provides a means to adjust for gain variations
between input source channels. A boost of about 2 dB and cut of infinity are available for each
channel at the extreme positions of the Balance control.
The tone-control amplifier uses a pair of NPN transistors connected through frequency-
sensitive (tone control) coupling networks in the feedback loop of the output stage.
The bass control in the coupling network can be adjusted to provide for up to approximately
12 dB of boost or attenuation (cut) at 20 Hz. The treble control has an adjustment range of
approximately 10 dB boost or cut at 20 kHz. With the bass and treble controls set at the mid-range
positions, the amplifier provides a flat response curve within approximately 1 dB from 7 Hz to a
remarkable 550 kHz
1
. The flat position for the bass and treble controls is at the approximate
center travel of each potentiometer. Owing to normal component tolerances, flat response may be
achieved slightly off-center for one or both potentiometers.
The clipping point of the tone control stage is approximately 3.0 V rms, which is achieved
with an input of 1 V rms at 1 kHz applied to the input terminals of the circuit (CONN103) with
the tone control potentiometers set for flat response. The nominal output operating level is 1 V
rms. At this level, THD is less than 0.3 percent; IMD is 0.01 percent or less. Noise is –75 dB or
better. Potentiometers R156 and R157 provide an adjustable output of the tone control circuit for
the right and left channels, respectively.
The Front Aux buffer amplifier (Q111/Q112) is essentially a duplicate of the tone-control
input stage (Q107/Q109). Because of the wide variety of personal entertainment devices currently
available, additional gain is provided beyond that typically achieved from the basic preamplifier
circuits. For an input of 0.3 V rms, the buffer amplifier delivers approximately 1 V rms to the
input selector switch, which is sufficient to drive the power amplifier section of the 20 W stereo
integrated amplifier to full output. At a typical operating level of 0.3 V rms input (1 V rms
output), frequency response is within 1 dB from 10 Hz to 50 kHz, THD is below 0.3 percent, IMD
is below 0.1 percent, and noise is –85 dB or better at the buffer amplifier output terminals
(CONN107).
1. This measurement was made on the bench in isolation. The overall performance of any audio system represents the concatena-
tion of the performance of the individual stages.