Phono Preamplifiers

More than a few 'tube' phono stages will still employ, for example, a low-noise J-FET MC input/gain stage, so all-tube phono stages that offer a decent gain range, low noise and healthy input overload margins are rare. PrimaLuna's EVO 100 Tube Phono belongs in that latter category, even exceeding the brand's own specification in several key areas. Gain is indicated at 40dB (MM) and 60dB/56dB/52dB for the High/Medium/Low MC settings, and while the former +40dB/MM spec. is correct, the MC options are, in practice, closer to +63.9dB, +59.8dB and +55.5dB, respectively. So the EVO 100 has sufficient gain to accommodate low-ish output MCs (ideally no lower than 300µV types) matched with a huge headroom of 250mV (MM) and 16mV (MC, High), 26mV (MC, Medium) and 43mV (MC, Low) to buffer it against the very highest output pick-ups in the most demanding of playback roles.

Noise is below the vinyl threshold and so the A-wtd S/N ratios of 79.1dB (MM) and 63.2-64.7dB (MC Low to MC High) are adequate if not up with the best solid-state designs. The RIAA-corrected response is also subtly 'shaped' [see Graph 1] to offer a +1dB boost around 20Hz while also offering a steep attenuation of warp frequencies. Distortion decreases with increasing input/output level until 2V output above which THD increases again from 0.015% to 0.02%/4V, 0.04%/10V and 1% at the maximum (and massive) 25.1V output. It's probably no coincidence that PrimaLuna specifies its best distortion at 2V output but, unusually, the lowest THD is at a high 10kHz frequency (0.001%) as illustrated by the THD vs. frequency traces [see Graph 2]. Again, these figures are not vanishingly low but are still lower than the levels of distortion typically encountered with even the finest MM/MC pick-ups tested in HFN. PM