The ultra-low distortion, low noise and ultra-high slew rate achieved by some current feedback op-amps (including Tl's LME49713) are not entirely matched here by the CFA-1.2 because its levels of compensation -feedback - are very low. Crayon acknowledges this on its website: 'No stage with high-gain feedback exists for the back coupling of the signal (no all around feedback coupling). Of course, this causes distortion but primarily K2'. However, in practice, while THD is lower at low (sub-1W) signal levels it soon rises to typically 0.5% (falling back to ~0.3% at 55W/8ohm) with 2nd harmonic and 3rd, 5th, 7th, etc, odd harmonics dominating. Distortion also rises at high frequencies [see Graph 2, below] to ~1.7%/20kHz (re. 10W/8ohm) which is only 3x higher than through bass and midrange but still about 5-10x higher than the inherent distortion of a good HF dome tweeter [see p31, p37 and previous HFN loudspeaker lab reports].
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