Hypex NC252MP class D amplifier review

This test review was performed to comply with FTC: 16 CFR Part 432 (July 5, 2024) - Power Output Claims for Amplifiers Utilized in Home Entertainment Products

Hypex NC252MP is a class D amplifier module with SMPS and with rated power 2 x 250W/4ohm/1kHz/THD+N<1%. My OEM implementation is in a 3U 19" case with large and efficient heatsinks to achieve best thermal management.

1. Test conditions

The amplifier was tested with both channels running, each loaded with a 4ohm resistor load. I have one 4ohm/400W and one 4ohm/200W resistor loads, both mounted on heatsinks.

2. Pre-conditioning

First of all, the amplifier was pre-conditioned for one hour at 1/8 of the rated power in both channels, i.e. at 2 x 31.25W/4ohm. At the end of the pre-conditioning period, the amplifier remained cold, with detectable rise of case temperature. There was almost no change in distortion during the test. It started with THD = 0.00083% and finished with THD = 0.00084%.

3. Power frequency response and distortion

Frequency response was measured at 250W output power into 4ohm, from 10Hz to 40kHz with measuring BW45kHz.

Power frequency response covers whole audioband at 250W/4ohm with THD < 1% almost everywhere except for 50Hz - 100Hz. The amplifier did shut down at 27kHz.

4. Distortion

4.1. THD vs. level at 1kHz/4ohm stepped sine method 0.8s burst 0.5s interval with measuring BW90kHz

The amplifier distortion is below 1% at 250W/4ohm

4.2. THD vs. frequency at 250W/4ohm with measurement bandwidth 45kHz

4.3. 5 minute sine test

The amplifier has not passed the 5 minute test at 2 x 250W/4ohm/1kHz. It was fine first 4 minutes, but then it shut down. Started with THD = 0.11% and reached THD = 0.5% before the shut down. The heatsink fins were slightly warmer at the end of the test period, but some hot air could be detected from the vent slots of the cover plate. After the shut down, the amplifier has recovered in a few minutes.

Pavel Macura 12/2/2024