WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

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20 W Stereo Integrated Audio Amplifier
constraints relating to fine-groove disk record production and the legacy practices that existed at
the time the curve was adopted by the RIAA.
Table 7.1 provides tabular values for the characteristic curve, referenced to 1 kHz. The data
range from 20 Hz on the low end to 20 kHz on the high end.
In the following steps, the performance of the phonograph preamp circuits will be measured
against the RIAA curve.
1) Adjust the audio signal generator to produce 1 kHz at 0.002 V rms. Connect the generator to
the right channel Phonograph input. Connect the audio voltmeter to the right channel
speaker output.
2) Confirm that the Bass and Treble controls are set for their flat positions, and the Balance
control is centered.
3) Adjust the Volume control to produce an output of 1.25 V rms at the speaker terminals. Set
the audio voltmeter to read 0 dB.
4) Using Table 7.1 as a guide, adjust the audio generator frequency as needed and observe the
response on the voltmeter. Readings should agree with the values given in the table /
Table 7.1 Frequency Response as a Function of the RIAA Target Values
Frequency, Hz RIAA Curve Target
Level, dB Frequency, Hz RIAA Curve Target
Level, dB
20 +19.3 1,000 0
30 +18.6 1,500 –1.4
40 +17.8 2,000 –2.6
50 +17.0 3,000 –4.7
60 + 16.1 4,000 –6.6
70 + 15.3 5,000 –8.2
80 +14.5 6,000 –9.6
100 +13.1 7,000 –10.7
150 +10.2 8,000 –11.9
200 +8.3 9,000 –12.9
250 +6.7 10,000 –13.7
300 + 5.5 12,000 –15.3
400 +3.8 14,000 –16.6
500 + 2.6 15,000 –17.2
600 + 1.9 16,000 –17.7
700 + 1.2 18,000 –18.7
800 + 0.7 20,000 –19.6