WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Manual

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7.1 Power Amplifier Performance Measurement
Measurements should be made on one channel at a time; the input terminals of the channel not
being measured are shorted. For the measurements, an 8 Ω 10 W (or greater) noninductive
resistor must be connected to the output terminals of each channel. Connect the generator output
to the Line input RCA jacks on the back panel. Set the Volume control to full clockwise.
Target performance of the 20 W stereo amplifier is given in Table 7.1 (bias voltage = –30 V
dc and the B+ voltage = +345 V dc). Note that the input voltages shown in the table will result in
approximately the desired power output.
Table 7.1 Target Performance of the 20 W Stereo Integrated Amplifier
Conditions Parameter Target Value Notes
Measurements taken at 1 W
power output (2.8 V rms) Input voltage 0.30 V rms Volume control fully
clockwise
Frequency response ±1 dB, 10 Hz to
65 kHz
THD 0.8% Note 1
IMD (at 2.3 V rms output) 0.4% 4:1 mix ratio
Noise unweighted, (shorted
input terminals) –75 dB Volume control fully
clockwise
Measurements taken at 5 W
power output (6.3 V rms) Input voltage 0.80 V rms Volume control fully
clockwise
Frequency response ±1 dB, 12 Hz to
50 kHz
THD 0.8% Note 1
IMD (at 5.1 V rms output) 1.0% 4:1 mix ratio
Noise, unweighted, (shorted
input terminals) –80 dB Volume control fully
clockwise
Measurements taken at 10 W
power output (8.9 V rms) Input voltage 1.0 V rms Volume control fully
clockwise
Frequency response ±1 dB, 15 Hz to
45 kHz
THD 1.0% Note 1
IMD (at 7.2 V rms output) 1.5% 4:1 mix ratio
Noise, unweighted, (shorted
input terminals) –85 dB Volume control fully
clockwise
Notes:
1 Measurements taken at 30 Hz, 100 Hz, 1 kHz, 10 kHz, and 20 kHz. The highest reading is the one
recorded.