PrimaLuna EVO 400 series Pre/Power Amplifier Lab Report

Lab Report

PrimaLuna devotes considerable webspace detailing the quality of its PSU and output transformers, its 'AutoBias' regime, passive component selection, dual-mono layout and other engineering niceties – but the upshot is a preamp and, particularly, a power amp of exceptional quality. Noise, as claimed, is very low indeed with A-wtd S/N figures of 98dB for the preamp and a full 94dB for the power amp (re. 0dBV and 0dBW, respectively). The latter is 10dB better than that achieved by many solid-state amplifiers! Distortion increases with output in both amplifiers, from 0.03% at 100mV to 0.38%/1V and 0.8%/2V with the preamp and 0.19% at 1W to 0.8%/10W and 0.9% at the rated 70W/8ohm for the EVO 400 power amp (UL mode). I discuss the differences between triode and ultralinear/pentode modes in my boxout but in both cases THD increases at low frequency through transformer core saturation, reaching ~2% at 10W/8ohm and ~1.3%/20Hz at 0dBV from the preamp [see Graph 2, below].

This is perfectly typical, as is the increasing source impedance of the preamp at LF from its moderate 270ohm midband figure to 1.1kohm at 20Hz. The power amp has a high but consistent ~5.5ohm output impedance that will influence the overall system response according to the impedance trend of the attached speaker. Into a 'flat' 8ohm load it offers an extended bass (–0.3dB/ 20Hz) allied to a treble that rises slightly above 20kHz/+0.5dB to 'peak' at 40kHz/+1.55dB. This will be 'magnified' in practice because the EVO 400 pre also has a +3.1dB lift at 42kHz. Power is plentiful too, those double pairs of EL34s achieving 2x73W/ 8ohm and 2x85W/4ohm with 112W, 110W, 105W and 82W into 8, 4, 2 and 1ohm under dynamic conditions [see Graph 1]. PM


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 9.0A


THD vs. frequency for EVO 400 pre (1V out, black trace) vs. EVO 400 power (10W/8ohm, red)

Continuous power (<2% THD, 8/4ohm) 73W / 85W (2.45V, preamp)
Dynamic power (<5% THD, 8/4/2/1ohm) 112W / 110W / 105W / 82W
Output imp. (20Hz–20kHz, pre/power) 264-1.1kohm / 5.6–5.0ohm
Freq. resp. (20Hz–20kHz, pre/power) –0.0 to +0.0dB / –0.3 to +0.5dB
Input sensitivity (for 0dBV/0dBW) 429mV (pre) / 147mV (power)
A-wtd S/N ratio (re. 0dBV/0dBW) 97.5dB (pre) / 94.0dB (power)
Distortion (20Hz-20kHz, 1V/10W) 0.36–1.25%/0.70–2.0% (UL)
Power consump. (pre/idle/rated o/p) 57W / 273W/475W
Dimensions (WHD, Pre/Power/weight) 386x206x404mm/24kg/31kg
Price £4150 (each)

The Netherlands
Supplied by: Absolute Sounds Ltd
0208 971 3909