Following the assumptions on possible influence of ultrasonic noise and carrier frequency residuals to tweeter output I have prepared an experiment where the tweeter is driven by 2.82V sine tone of 6kHz from 2 different amplifiers. One of the is AIYIMA A07, see my review
the other one is a bridged amplifier based on my re-designed Sinclair Z-30 circuit
Both amplifiers work deeply below clipping, as the output voltage was set to 2.82V.
In addition, 19+20kHz CCIF distortion test was made as well.
This is the measurement setup
Focusrite 2i2 Gen3 soundcard was used, set to 96kHz/24bit sampling.
The results
1. Distortion of sine 6kHz
Class AB amplifier
Class D amplifier
2. Distortion of 19+20kHz twin tone
Class AB amplifier
Class D amplifier
Conclusion
It is above any doubts that the spectrum at acoustical side measured from the class AB amplifier under test is more clean. The spectrum from the class D amplifier under test is messy and contains strange non-harmonic components.
AIYIMA A07 TPA3255 Amplifier Measurements and Review - LM4562 (and OPA2134) option
AIYIMA A07 TPA3255 Amplifier Measurements LM4562 option I received my A07 yesterday, on January 6, 2021, shipped from Italy. Purchased at Amazon.de and as stated on their website, it arrived without a power supply. I am testing the A07 with 2 different power supplies. One of them is a linear...
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the other one is a bridged amplifier based on my re-designed Sinclair Z-30 circuit
Both amplifiers work deeply below clipping, as the output voltage was set to 2.82V.
In addition, 19+20kHz CCIF distortion test was made as well.
This is the measurement setup
Focusrite 2i2 Gen3 soundcard was used, set to 96kHz/24bit sampling.
The results
1. Distortion of sine 6kHz
Class AB amplifier
Class D amplifier
2. Distortion of 19+20kHz twin tone
Class AB amplifier
Class D amplifier
Conclusion
It is above any doubts that the spectrum at acoustical side measured from the class AB amplifier under test is more clean. The spectrum from the class D amplifier under test is messy and contains strange non-harmonic components.