The gain of the circuit is 15.15 dB. The input impedance is 101 Kohm, and the output
impedance is 0.1 ohms, for a damping factor of 80.
The noise of a properly laid out circuit is about 30 uV with a quiet supply, and raw supply
with two 29,000 uF capacitor and 70 mV ripple will give about 100 uV noise (measured in
the band from 20 to 20,000 Hertz).
Figure 7 shows the harmonic distortion + noise plotted against output power, taken at 1 KHz
into 8 ohms. This is the lowest distortion yet achieved by either a Zen or First Watt
amplifier, descending to .001% below 1 watt.
Figure 8, spectrum distribution of the distortion at 1 watt, and you can see the dominant 3
rd
harmonic, as well as 2
nd
, 4
th
and 5
th
. The vertical scale is in decibels relative to 1 watt. In
this picture, you can also see the noise floor of the system and amplifier at -135 dB or so
below 1 watt.
Figure 9 shows the harmonic distortion + noise plotted against output power 4 ohms load,
reaching 0.2% at 40 watts.
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