restorer-john
Grand Contributor
I hope I am not beating a dead horse but I noticed that NAD also gives the FTC rating on some of their Class D amps. For example, from the manual of the M22 (nCore):
Continuous output power into 8 ohms and 4 ohms (Stereo mode) 300 W (20 Hz-20 kHz at 0.1% THD, both channels driven)
Continuous output power into 8 ohms (Bridge mode) 900 W (20 Hz – 20 kHz at 0.1% THD)
THD+N (20 Hz – 20 kHz, CCIF IMD, SMPTE IMD, DIM 100) <0.005 % (250 mW to 290W, 8 ohms and 4 ohms) Note: Measured with Audio Precision AUX-0025 or Prism dS-LPF passive low pass filter
So maybe the hypex amps can deliver a lot of power at 20KHz?
The NAD M-22 uses two OEM NC-400 modules which are de-rated from Hypex's numbers to be FTC compliant specifications. It also uses a considerably more advanced SMPS than the standalone Hypex PSUs.
When Stereophile tested the NAD M-22, they only tested it at 100W (consider it is rated at 250W/ch) and this is the result (THD vs Freq).
Graph courtesy Stereophile, John Atkinson.
https://www.stereophile.com/content/nad-masters-series-m22-power-amplifier
We are seeing skyrocketing THD at high frequencies, and at only 40% of its rated power. That is with the AUX-0025 filter up front of the AP, so he is directly looking at harmonics (and other non-linearities) hopefully above 20Khz but below 200kHz.
The IMD plots at 200W/4R show plenty of in band products and again, this is well below its rated power.
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