Phono Preamplifiers

The E-Glo Petit is clearly a 'midi-sized' version of EAT's E-Glo S phono preamp [HFN Mar '17], so technical comparisons are very revealing. Both employ hybrid J-FET/triode gain and RIAA stages powered from an 18V wall-wart DC supply so there is a limit to both the equalised output level and available input headroom. Fortunately, both E-Glos offer the graceful clipping of an audiophile valve amp so distortion increases smoothly with output rather than clipping abruptly – from 0.025% at 1V to 1% THD at 5.5V and 3% at 6.5V (200Hz-5kHz). Distortion increases at the frequency extremes, however, though the Petit has an improved LF performance with THD rising from 0.042% at 20Hz/100mV to 0.4% at 500mV and just 3% at 1V output [see Graph 2, below]. The response [Graph 1, below] remains sensibly tailored at very low frequencies in the Petit (–0.75dB/20Hz and –3.0dB/20Hz with subsonic filter) but extends right out to 100kHz (–0.4dB), although the Petit's output impedance rises at LF from 95ohm/1kHz to 2.06kohm/20Hz.

The specified +40dB, +45dB, +50dB, +55dB and +65dB gain options are accurate to ±0.2dB (the final +70dB gain setting is closer to +68.2dB in practice), catering for pick-ups from 398µV (low o/p MC) to 5.62mV (high output MM). Input headroom is improved over the E-Glo S, in this case to 60mV, 55mV, 33mV, 16mV, 5.5mV and 3.9mV (for 1% THD), respectively. A 60mV input at the +40dB gain setting represents a headroom of +21.6dB (re. 5mV) which will just encompass the most dynamic of LP recordings. Noise is also reduced in the Petit over the S, with the first four gain settings offering an A-wtd S/N of 88.5dB and, treated as MC inputs, the +65dB/+70dB modes delivering a uniformly wider 69dB A-wtd S/N (re. 500µV in/1V out). PM