Primare A35.8 Multichannel Power Amp Lab Report

Lab Report

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


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 20.0A


Distortion versus frequency versus power output (1W/8ohm, black; 10W, pink; 100W, red)

Power output (<1% THD, 8/4ohm) 195W / 373W
Dynamic power (<1% THD, 8/4/2/1ohm) 197W / 400W / 765W / 399W
Output imp. (20Hz–20kHz/100kHz) 0.019–0.021ohm / 0.19ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.0dB to –0.8dB/–6.9dB
Input sensitivity (for 0dBW/150W) 289mV / 3553mV
A-wtd S/N ratio (re. 0dBW/150W) 88.8dB / 110.6dB
Distortion (20Hz-20kHz, 10W/8ohm) 0.00045–0.0055%
Power consumption (Idle/Rated o/p) 62W / 220W (1W standby)
Dimensions (WHD) / Weight 430x145x400mm / 15kg
Price £4500

Primare AB
Supplied by: Karma-AV Ltd, York
01423 358846