WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Руководство пользователя

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7.1.5 Square Wave Performance
The square wave response of the amplifier can be measured if desired.Typical square wave
performance of the amplifier is documented in Figure 7.1 for input frequencies of 100 Hz, 1 kHz,
and 10 kHz at power output levels of approximately 5 W (average listening level) and 10 W (rated
output level). Measurements of the right channel and left channel should be essentially identical.
The following procedure is recommended:
• Set the volume controls at mid point.
• Apply a 100 Hz square wave signal to the input and adjust the generator to produce 5.1 V
rms output at the speaker terminals with an appropriate load. Adjust the audio generator to
produce 100 Hz, 1 kHz, and 10 kHz. Observe the results and compare with Figure 7.1.
• Adjust the generator to produce 7.2 V rms output at the speaker terminals with an
appropriate load. Adjust the audio generator to produce 100 Hz, 1 kHz, and 10 kHz.
The following observations can be made regarding typical square wave performance at
various power levels and frequencies:
• At 5 W power output – a ) A fair amount of low frequency tilt is observed at low
frequencies (100 Hz and below). b ) The response at 1 kHz looks quite good. c ) The
response at 10 kHz is respectable, with no signs of instability.
• At 10 W power output – d ) Considerable low frequency tilt is observed at low
frequencies (100 Hz and below). e ) The trace at 1 kHz looks good, with slight ringing on
the leading edge. f ) At 10 kHz the trace shows significant ripple, which is not entirely
unexpected at the operating limit.
Restating the obvious, operation of this amplifier (or any other amplifier) at its maximum
operating point has performance penalties. However, for listening at modest levels, the amplifier
performs quite well.
7.1.6 Bias Adjustment
The bias setting for the amplifier is critical to proper operation and long-term reliability. The
recommended bias setting of –30 V has been found to be a good operating point for this amplifier
and to provide for long tube life. If desired, however, the bias may be tweaked as follows: