Measurements
Contents
Measuring a Class D power amplifier like the Primare A35.8 can be a bit complex. This has to do with the switching frequency that partly exits te terminals. This affects the power measurement. The Prism stops measuring at a certain point because the distortion becomes too high. Now that’s totally fine with Class A and AB, but with Class D it can happen too early. And it does in this case. So we need to put a filter between the amplifier and the analog input of the Prism for accurate measurements on output power. With the filter in place ánd the gain adjusted properly we can do some power-measurements.
As expected, the Primare passes the test. We see 172 watt in 8 Ohm, around 300 – 340 watt in 4 Ohm, 450 in bridge, 8 Ohm and almost 900 watt in bridge, 4 Ohm. Serious power!
Distortion is – as expected – low across the band. Noise is also very low and shows few spikes after the 1 KHz input. No 50 Hz hum either; just a bump at -120 dB. That, we can simply ignore.
Frequency response is pretty straight with 0.5 dB roll at 25 kHz. 50 kHz is -2dB. In short: fine. The residue measurement shows a class D amplifier. No real sine wave anymore, but more of a choppy pattern in which something of a sine can be recognized. Typical for class D and class AB with crossover distortion.
The THD measurement shows maximum 0,0125% distortion at 1 watt into 8 Ohms. That rises to 0.05% at 10 watts into 8 Ohms. In short: negligible in our opinion. Both measurements peak around 5400 Hz.
