WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Manual, Page: 164 / 194

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7.2 Reference Measurements
It is recommended that the performance of each channel be recorded for future reference. Table
7.3 is provided for that purpose.
Charts are provided with each amplifier of the measured performance of the unit over a wide
range of operating points. Figures 7.2 through 7.5 show typical performance of a representative
amplifier. The charts were produced with both channels driven.
Note that THD measurements (Figures 7.3 and 7.5) are taken from 30 Hz to 20 kHz, with a
measurement bandwidth of 22 Hz to 80 kHz. The lowest measured frequency (30 Hz) is the low
frequency operating point specified by the output transformer manufacturer (Hammond).
Figure 7.5 graphically demonstrates the high level of reserve power available from the
amplifier. The power bandwidth curves are produced by driving the input signal to each channel
at an increasing level until a specified distortion point is reached; in this case 1.5%, over a
frequency range of 30 Hz to 20 kHz. Note that for most mid-band frequencies, the amplifier can
deliver in excess of 15 W per channel.
Table 7.3 Measured Performance of the 20 W Stereo Amplifier
Conditions Parameter Right Channel Left Channel
Measurements taken at 1 W
power output (2.8 V rms) Input voltage 0.30 V rms 0.30 V rms
Frequency response
THD
IMD (at 2.3 V rms output)
Noise unweighted, shorted
input terminals
Measurements taken at 5 W
power output (6.3 V rms) Input voltage 0.80 V rms 0.8 V rms
Frequency response
THD
IMD (at 5.1 V rms output)
Noise, unweighted, shorted
input terminals
Measurements taken at 10 W
power output (8.9 V rms) Input voltage 1.0 V rms 1.0 V rms
Frequency response
THD
IMD (at 7.2 V rms output)
Noise, unweighted, shorted
input terminals