MEASUREMENTS
A much-touted benefit of an amplifier with a class-D output stage is that it can be smaller and much lighter than a conventional amplifier for a given power. I was surprised, therefore, when I unpacked LKV’s Veros PWR+ to find that it was both large and heavy. This is because the amplifier uses a linear power supply with three hefty transformers rather than a switchmode supply.1
I measured the Veros PWR+ using my Audio Precision SYS2722 system). As the LKV has a class-D output stage, it wasn’t necessary to precondition the amplifier by using it to drive a 1kHz tone at one-third power into 8 ohms. Nevertheless, before doing any testing I ran it for an hour at a moderate power level, following which the top panel was warm, at 93.9°F/34.4°C. Because class-D amplifiers emit relatively high levels of ultrasonic noise that would drive my analyzer’s input into slew-rate limiting, all measurements were taken with an Audio Precision auxiliary AUX-0025 passive low-pass filter, which eliminates noise above 200kHz. Without the filter, 218mV of ultrasonic noise was present at the loudspeaker terminals.
