WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

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20 W Stereo Integrated Audio Amplifier
Target performance of the 20 W stereo amplifier is given in Table 7.2 (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.
The performance targets listed in Table 7.2 are just that—targets. Any given amplifier may
perform better than the target or worse than the target. It is not uncommon for one channel to
perform slightly better than the other with regard to THD and/or IMD. The most likely
explanation is differences in tube performance, although other items may factor in as well. In any
event, the amplifier should be able to come close to the numbers listed in most cases without the
need to tweak the bias operating point beyond the default value of –30 V.
Table 7.2 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, 6 Hz to
55 kHz
THD 0.5% Note 1
IMD (at 2.3 V rms output) 0.5% 4:1 mix ratio
Noise unweighted, (shorted
input terminals)
–65 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, 9 Hz to
50 kHz
THD 0.7% Note 1
IMD (at 5.1 V rms output) 1.4% 4:1 mix ratio
Noise, unweighted, (shorted
input terminals)
–70 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 0.8% Note 1
IMD (at 7.2 V rms output) 2.0% 4:1 mix ratio
Noise, unweighted, (shorted
input terminals)
–75 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.