Pre/Power Amplifiers

In our recent review of Emotiva's XPA-DR2 power amp I discussed the amplifier design 'trade-off' between the capacity to drive low impedance (4 or 2ohm) speaker loads while also satisfying the need to deliver very high power into more moderate (8ohm) loads. Driving low impedances is all about supplying sufficient current to maintain the voltage across the load, while driving higher impedances is more about supplying the volts in the first place. This is why most 500W+ amplifiers are bridged designs, doubling the amplifier's voltage envelope without complicating the PSU infrastructure.

Parasound's designer, John Curl, has aimed at 400W/8ohm for the JC5 which it achieves – just – with a tried-and-tested complementary output stage rather than two such stages bridged together. Otherwise, the JC5 can be 'bridged' with both left and right channels forming the positive/negative-going halves of a monoblock, rated at 1.2kW/8ohm. In practice, the JC5 uses the longstanding JC1 amp circuit, but with six rather than nine pairs of output devices per channel and a smaller power supply. Hence while both are rated at 400W/8ohm, the JC1 claims 800W/4ohm and 1.2kW/2ohm while the (lower current) JC5 has a specification of 2x600W/4ohm and no formal rating into 2 or 1ohm loads. PM