Интегральные усилители — Feliks Audio ARIOSO 300B

The Arioso 300B is a single-ended Class A valve integrated amplifier from Feliks Audio, the Polish company from Lubliniec that is otherwise known for valve headphone amplifiers, and it is the brand's only amplifier made purely for loudspeakers. It appeared around 2021. The maker price is EUR 8,199. Feliks also makes the EOS, a valve amplifier for both headphones and loudspeakers.

Key specs that matter

Output is 2 x 8 W from a pair of 300B triodes, with taps for 4 and 8 ohm loads. The drivers are two 6N8S valves, a CV181 or 6SN7 type, and a 5C3S valve rectifies the supply. Frequency response is 15 Hz to 32 kHz ±3 dB. Input sensitivity is 1 V RMS and input impedance 100 kOhm, and there are three RCA inputs. THD is 0.3% at 1 W and 2.5% at 8 W, measured at 1 kHz. Power consumption is 140 VA, which reflects the constant current drawn by single-ended Class A valves regardless of volume. Feliks gives the dimensions as 41 x 38 x 21 cm and the weight as 25 kg. A remote control handles power, input, volume and mute. The three line inputs accept CD players, DACs, streamers and an external phono stage.

Engineering and use context

With a single-ended Class A output, one 300B per channel amplifies the whole waveform without switching between devices, and the output transformer couples it to the loudspeaker. This topology limits output but avoids the crossover region of push-pull designs, and the rising distortion figures reflect its behaviour near full power. The filaments of the output valves are heated from a stabilised DC supply, separate from the main stabiliser, which keeps hum from the heaters out of the signal. The amplifier is wired point to point. Level is set with a motor-driven ALPS pot, so it can be adjusted from the remote while staying analogue. The transformers are made by Leszek Ogonowski in Poland, and Jantzen coupling capacitors and Caddock resistors are used in the signal path. Valve rectification with the 5C3S brings the high-voltage supply up gradually.

Pairing

With its low output, the Arioso 300B belongs with high-sensitivity speakers, and it has been used with speakers of 96 and 102 dB sensitivity. The two output taps match the nominal impedance of the connected speakers.

Alternatives

The Feliks Audio EOS is the valve amplifier from the same maker that drives both headphones and loudspeakers.