MEASUREMENTS

When I unpacked the PrimaLuna EVO 400 preamplifier, it looked very familiar. It appears identical to PrimaLuna’s ProLogue Premium line preamplifier that Herb Reichert reviewed in our June 2017 issue.¹ But on closer inspection, while the earlier preamp had single-ended inputs and outputs, the EVO 400 adds two pairs of balanced input jacks and a pair of balanced output jacks. And while the EVO 400 still uses two 5AR4 rectifier tubes, there are now six 12AU7 twin triodes compared with the ProLogue Premium’s four 12AU7s.

I measured the PrimaLuna EVO). The gain from the unbalanced inputs to the unbalanced output with the volume control set to its maximum was slightly lower than the specified 10dB, at 9.1dB. From the balanced inputs to the balanced output, it was 7dB. The preamplifier preserved absolute polarity (, was noninverting) from all the inputs and outputs. Specified as offering a very high input impedance of 220k ohms, the unbalanced inputs measured 175k ohms at 20Hz and 1kHz, dropping to a still very high 105k ohms at 20kHz. The balanced inputs had a much lower input impedance, at 4k ohms at 1kHz and 3.5k ohms at 20Hz and 20kHz. While this will not be a problem with sources having a direct-coupled, solid-state output stage, it will result in lightweight low frequencies with tubed sources that have a capacitor-coupled output.