Phono Preamplifiers

Although we never tested the original E-Glo, we did look at the stripped-down E-Glo S [HFN Mar ’17] and E-Glo Petite [HFN Feb ’19] which, despite being simpler FET/tube hybrids, still show parallels in performance with the all-tube E-Glo 2. The RIAA network is similar and the response remains flat and extended from –0.3dB/20Hz to +0.1dB/20kHz, out to –2.6dB/100kHz and with the option of a second-order subsonic pole yielding a –2.5dB/20Hz to –12dB/10Hz roll-off [see Graph 1, below]. Otherwise, the E-Glo 2’s separate, high voltage PSU endows it with a healthy 4.8V output (re. 1% THD) and, with THD increasing linearly with output, 7.9V is possible at 3% THD and 9.5V at a ‘non hi-fi’ 5% distortion. This increasing THD trend is a function of the (low-feedback) pairs of ECC83 and ECC88 triodes wrapped around the RIAA eq and driving the output where EAT specifies a <150ohm impedance. This is true from 250Hz-20kHz – at bass freqs. the source impedance surges to 2.5kohm [red, Graph 1].

This partially explains the ‘sweetspot’ in the presence/lower treble [see Graph 2] where THD drops from 0.2-0.3% at 100Hz and 20kHz to 0.092%/5kHz, values that, while high, are still not as high as the distortion we measure from typical MM/MCs. Three gain options are offered – a +45dB setting for MMs that’s closer to +45.9dB (for a 5.05mV sensitivity) in practice, and a high +70.4dB (1.5mV, MC2) and +75.7dB (780μV, MC1) for the MC modes. The former is pure tube gain, the latter XLR/RCA MC inputs also boosted via a Lundahl step-up transformer. Noise is low for an all-tube circuit, supporting deeply impressive A-wtd S/N ratios of 80dB (MM) and 77-78dB (MC1/2). Finally, for a discussion about input headroom, [see boxout]. PM