MEASUREMENTS

I tested the T+A Caruso R with my Audio Precision SYS2722 system,1 repeating some of the measurements with the magazine’s APx500. I controlled the Caruso R with the front-panel touchscreen and with the Caruso Navigator app on my iPad mini. Because the Caruso R uses a class-D output stage, I inserted an Audio Precision AUX-0025 passive lowpass filter between the test load and the analyzers. This filter reduces (but does not completely eliminate) RF noise that could drive their input circuitry into slew-rate limiting. I used it for all the loudspeaker output tests other than frequency response. Without the auxiliary filter and with the amplifier loaded with 8 ohms, there was 720mV of ultrasonic noise present at the speaker outputs.

I looked first at the Caruso R’s behavior as a conventional integrated amplifier via its single-ended analog inputs. The amplifier inverted absolute polarity at both the loudspeaker and headphone outputs but preserved polarity at the preamplifier output. The analog input impedance