See attached pics and simplified schematic.
The vas and output stage are both single ended and sound quality is very nice.
The loop gain is reduced by providing feedback from the vas, so it's a low-ish feedback design. I experimented with different amounts of feedback with listening tests before settling on the values in the spice schematic.
Voltage rails are a high +/- 20V and output stage quiescent is 100mA.
Note: The distortion measurement was taken driving a 100 ohm load impedance. The first distortion chart shows the generator in loopback mode.
Note2. The square wave tests were performed at 10kHz and 100kHz. (3dB bandwidth is 1.7MHz)
Not shown is the temperature controller for the output stage current sink.
Output stage temperature is set, rather than current, which varies around the nominal 100mA.
The vas and output stage are both single ended and sound quality is very nice.
The loop gain is reduced by providing feedback from the vas, so it's a low-ish feedback design. I experimented with different amounts of feedback with listening tests before settling on the values in the spice schematic.
Voltage rails are a high +/- 20V and output stage quiescent is 100mA.
Note: The distortion measurement was taken driving a 100 ohm load impedance. The first distortion chart shows the generator in loopback mode.
Note2. The square wave tests were performed at 10kHz and 100kHz. (3dB bandwidth is 1.7MHz)
Not shown is the temperature controller for the output stage current sink.
Output stage temperature is set, rather than current, which varies around the nominal 100mA.
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