Following the discussion in the NCx500 review thread, I was curious how my PMA-NC252MP amplifier based on NC252MP module would perform in a bridged configuration. Original Hypex datasheet allows for this configuration, as we can see in the following part from the datasheet:
It declares 400W/1kHz/4ohm at THD 1% peak power. So I have configured my PMA-NC252MP exactly according to the datasheet scheme and started measurements. I would add that my amplifier has huge heatsink and there should be no problem with thermal management.
Let's have a look into my "audio kitchen", this is my measuring place:
This isolation transformer for the PC breaks possible loop through mains supply:
and finally this is my PMA-NC252MP amplifier configured to BTL load:
My amplifier: https://pmacura.cz/pma_nc252mp.htm
First, I have to say that the amp was doing quite well in the BTL setup. It was able to get 400W/4ohm at much lower distortion than 1% - you will see later. At about 430W/4ohm, the current protection was shutting down the amp, but immediately after lowering the output power it started to work again.
Measurements
I have measured THD and THD+N vs. power and vs. frequency, into 4ohm load, at 1kHz and 6kHz, with 45kHz measuring bandwidth. I use LC filter before the ADC input and this filter has -3dB cut off at 30kHz, and the slope is -40dB/decade.
Filter response
First, THD and THD+N vs. power at 1kHz/4ohm and 45kHz measuring BW
A comparison of THD vs. power at 1kHz and 6kHz, 4ohm load, 45kHz BW
Comparison of THD+N vs. power at 1kHz and 6kHz, 4ohm load, 45kHz BW
THD vs. frequency at 210W/4ohm, 45kHz BW
Conclusion
I find the results very good. NC252MP was doing well in my test, also for the reason that it is very well cooled by large heatsinks. 4 ohm BTL operation works, with purely resistive load, however one has to be carefull. Maybe someone of Hypex might comment, @Hypexsales ?
It declares 400W/1kHz/4ohm at THD 1% peak power. So I have configured my PMA-NC252MP exactly according to the datasheet scheme and started measurements. I would add that my amplifier has huge heatsink and there should be no problem with thermal management.
Let's have a look into my "audio kitchen", this is my measuring place:
This isolation transformer for the PC breaks possible loop through mains supply:
and finally this is my PMA-NC252MP amplifier configured to BTL load:
My amplifier: https://pmacura.cz/pma_nc252mp.htm
First, I have to say that the amp was doing quite well in the BTL setup. It was able to get 400W/4ohm at much lower distortion than 1% - you will see later. At about 430W/4ohm, the current protection was shutting down the amp, but immediately after lowering the output power it started to work again.
Measurements
I have measured THD and THD+N vs. power and vs. frequency, into 4ohm load, at 1kHz and 6kHz, with 45kHz measuring bandwidth. I use LC filter before the ADC input and this filter has -3dB cut off at 30kHz, and the slope is -40dB/decade.
Filter response
First, THD and THD+N vs. power at 1kHz/4ohm and 45kHz measuring BW
A comparison of THD vs. power at 1kHz and 6kHz, 4ohm load, 45kHz BW
Comparison of THD+N vs. power at 1kHz and 6kHz, 4ohm load, 45kHz BW
THD vs. frequency at 210W/4ohm, 45kHz BW
Conclusion
I find the results very good. NC252MP was doing well in my test, also for the reason that it is very well cooled by large heatsinks. 4 ohm BTL operation works, with purely resistive load, however one has to be carefull. Maybe someone of Hypex might comment, @Hypexsales ?