Primare 928 System Lab Report

Lab Report

Both the 928 preamp and 928 monoblock power amps perform precisely as promised in Primare's literature from 1986. The preamp offers a +20dB overall gain (or +14dB in the '–6dB' position), its balanced output delivering a maximum 22V from a vanishing low 1ohm source impedance. Distortion [black trace, Graph 2] is low at between 0.0004–0.0016% (20Hz-20kHz, over the top 3V of its output). Noise is also low and the S/N acceptably wide at 94dB (re. 0dBV) while the response is flat within ±0.02dB from 100Hz-100kHz. There's some tailoring at very low frequencies with a very gentle 'shelf' starting at 100Hz and reaching –0.25dB/50Hz and –1.0dB/20Hz. The 'Low Cut' option operates below 20Hz with –6dB/12Hz and –18dB/7Hz.


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 30.9A


THD vs. extended freq for 928 pre (1V out, black trace) vs. 928 monoblock (10W/8ohm, red)

The partnering 928 power amp is a fully balanced design where Primare claims to have 'eliminated negative feedback'. The flat 0.13-0.14ohm output impedance is not worrisomely high, as might be the case with no feedback, and the response very extended from 3Hz-70kHz (–1dB), but the lack of conventional compensation is revealed in the long warm-up time where THD slowly reduces from 0.7% (1kHz/0dBW) down to 0.08% over 30mins and to 0.035% over 60mins. Once stabilised, distortion is a consistent 0.04-0.06% over the full 20Hz-20kHz audio range [red trace, Graph 2] over the first 20W of its output. From 20W to the rated 100W/8ohm, THD climbs gently to 0.25% [black trace, Graph 1]. In practice its power delivery is prodigious and the PSU astonishingly 'stiff' as evidenced by the 140W/8ohm and 270W/4ohm output. Its supreme speaker load tolerance is also illustrated by its dynamic output capability of 140W, 280W, 530W and 955W into 8, 4, 2 and 1ohm loads [Graph 1]. PM

Continuous power (<1% THD, 8/4ohm) 140W / 270W
Dynamic power (<1% THD, 8/4/2/1ohm) 140W / 280W / 530W / 955W
Output imp. (20Hz–20kHz, pre/power) 1.04ohm / 0.133–0.144ohm
Freq. resp. (20Hz–100kHz, pre/power) –1.0 to +0.0dB / +0.0 to –1.7dB
Input sensitivity (for 0dBV/0dBW) 100mV (pre) / 214mV (power)
A-wtd S/N ratio (re. 0dBV/0dBW) 93.9dB (pre) / 83.6dB (power)
Distortion (20Hz-20kHz, 1V/10W) 0.0004–0.0016%/0.042–0.068%
Power consump. (pre/idle/rated o/p) 32W / 41W/228W
Dimensions (WHD, Pre/Power) 200x200x320/200x200x320mm