Pre/Power Amplifiers

On more than a few occasions I've mentioned that the 40dB+ gain built into modern integrated amplifiers (6-12dB for preamps, 25-35dB for power amps) is unnecessarily high for the 2V line output of most likely line sources. Primare's A35.8, however, has a far lower 19.8dB (x9.8) overall gain via its balanced XLR inputs, meaning that 289mV is required to raise 1W/8ohm or a full 3553mV (3.6V) input to realise the rated 150W/8ohm. The 89dB A-wtd S/N ratio (re. 0dBW) is very wide in this context, and especially so for a Class D architecture. To push the A35.8 to its limits you'll need in excess of 4V from your preamplifier – well within the compass of contemporary designs – because it'll deliver closer to 195W/8ohm and 373W/4ohm with 197W, 400W, 765W and 399W into 8, 4, 2 and 1ohm loads under dynamic conditions [see Graph 1, below]. The 'stiff' power output, very close to the theoretical doubling from 8 to 4 to 2ohm, is traded in these fine Hypex NC500 modules for almost zero headroom – so the A35.8's power output has the same limit whether it's measured under continuous or dynamic conditions.

The output impedance is a very consistent ~0.02ohm (20Hz-20kHz) and while the frequency response has a slight treble roll-off, amounting to –0.8dB/20kHz to –6.9dB/100kHz, the A35.8's bass extension is truly subsonic, reaching –0.2dB/1Hz. Harmonic distortion holds to as low as 0.00045-0.0055% (20Hz-20kHz, re. 10W), typically increasing at higher treble frequencies and with increasing output [see Graph 2]. CCIR intermodulation distortion is especially low at just 0.0002% (re. 19kHz/20kHz at 10W). There is a lot of amplifier here! PM