Усилители мощности стерео — PrimaLuna EVO 100-4

The EVO 100-4 is the entry model among the all-valve EVO power amplifiers from PrimaLuna, a Dutch marque belonging to Durob. A mono/stereo switch, shared by all four EVO power amps, lets one unit drive two speakers or one in bridged mono. The US list price is USD 3,095.

Key specs that matter

In ultra-linear operation the amplifier delivers 40 W per channel with EL34 tubes and 42 W with KT88 in stereo, or 82 and 84 W in mono. Frequency response is 12 Hz to 85 kHz within 1 dB and 10 Hz to 95 kHz within 3 dB. THD with the auto bias circuit is below 0.2% at 1 W in stereo and below 0.17% in mono, with under 2% at rated power in both cases. Signal to noise ratio is 92 dB in stereo and 93 dB in mono. Input impedance is 100 kOhm and 880 mV drives it to rated power. Maximum gain is 25 dB with EL34 and 28 dB with KT88, and consumption is 270 or 280 W. The chassis is 405 x 280 x 190 mm and weighs 17 kg.

Engineering and use context

Fitted valves are four EL34 output tubes with two 12AX7 and two 12AU7. Adaptive AutoBias sits outside the signal path and adjusts bias in real time, and it also drives a bad tube indicator that puts the amplifier into protection and lights a red LED next to the failed valve. PrimaLuna lists 6L6G, 6L6GC, 7581A, EL34, EL37, 6550, KT66, KT77, KT88, KT90 and KT120 as usable output types, though this model is not KT150 compatible. Plates and screens run at about 417 V, which the maker cites as a way to extend tube life. Wiring runs point to point in thick-gauge wire, transformers are custom potted toroidal and in-house output units, and a PTP circuit opens the power transformer primary if it overheats. SoftStart limits thermal shock at switch-on, and a relay-based protection stage guards the output transformers and high-voltage supply if a tube fails. Ceramic tube sockets and solid-shaft gold-plated speaker terminals are fitted, with a damping coefficient of 4 KD at 1 kHz.

Pairing

Inputs are one stereo pair of RCA sockets plus one mono RCA socket. The speaker terminals offer 4, 8 and 16 ohm taps in stereo and 2, 4 and 8 ohm taps in mono, so a wide spread of speaker loads can be matched. There is no remote control on this model, and balanced XLR inputs, Takman resistors, Swiss OCC signal wiring, the AC Offset Killer and triode switching are reserved for the EVO 300 and EVO 400 power amps.

Alternatives

PrimaLuna also makes the EVO 200-4, a stereo valve power amplifier with the same mono/stereo switching in a larger chassis.