Integrated Amplifiers

A key difference between T+A's PA 1100 E, and original PA 1000 E [HFN Mar '17], versus the costlier R-series PA 2000 R [HFN Feb '16] and PA 2500 R, is the E-series' use of Class D technology to offer high outputs and limited waste heat, all at an attractive price. While T+A's discrete MOSFET switching output stage is its own design, the PWM (Pulse Width Modulation) core of the Class D amplifier is based on an Infineon Technologies' IRAUDAMP Class D 'reference design' [HFN Sep '15].

Unlike the competing Hypex UcD/Ncore Class D modules, the IT/T+A approach still indicates some of the drawbacks of 'traditional' Class D amplifiers. In particular, the amplifier's inductive output filters push up the output impedance at ultrasonic frequencies [inset Graph: grey trace]. This has an impact on both distortion and frequency response within the 20kHz audio range, the latter varying with loudspeaker load impedance [inset Graph: unloaded/8/4/2/1ohm = black (dashed)/black (solid)/red/blue/green traces]. Into 8ohm it rises +1dB/20kHz but falls to –0.4dB/20kHz into 4ohm (and –7dB/1ohm). So if the impedance trend of your speakers rises through the treble then the PA 1100 E will likely sound brighter, and vice-versa. PM