MastersounD Compact 300B

MastersounD Compact 300B – a pure triode single-ended integrated amplifier in Class A

The 300B valve in its purest circuit form

Built around two 300B output valves, two ECC802 and two 6SN7, the MastersounD Compact 300B delivers 2× 15 W of pure Class A power with zero negative feedback. Since every signal passes through a single-ended triode circuit with no corrective loops, the musical signal arrives at the speaker terminals wholly intact. Consequently, voices and instruments reproduce with a directness and fluency that solid-state designs rarely match. Every unit is hand-built in Italy by MastersounD, with hand-soldered connections and carefully selected components throughout.

Bespoke output transformers and auto-bias

At the heart of every MastersounD amplifier are the company's own custom-wound output transformers, designed specifically for the 300B to achieve optimal energy transfer and minimal distortion. Furthermore, automatic bias adjustment keeps the output valves at their optimal operating point at all times — no manual tweaking required. As a result, the Compact 300B is as easy to live with as it is musically rewarding. A volume remote control is included as standard.

Flexible connectivity and zero feedback

Inputs cover one balanced XLR line input plus a direct XLR input, and three single-ended RCA line inputs plus a direct RCA input. Since input impedance is 50 kΩ, the amplifier works with virtually any source component. Bandwidth extends from 8 Hz to 40 kHz at 0 dB, thereby ensuring the finest recorded detail is faithfully reproduced. Above all, the absence of negative feedback means the circuit never corrects or colours the signal — what goes in comes out.

Italian craftsmanship and lasting quality

MastersounD has been building amplifiers by hand in Italy for over thirty years. Each Compact 300B is finished in natural Italian walnut veneer with high-quality metalwork, and at 46×41.5×27.5 cm it fits comfortably into most listening rooms. Those seeking more power can step up to the MastersounD EVO 300B, which uses four 300B valves in a parallel single-ended circuit for 2× 21 W.

Specifications

• Type: pure triode single-ended Class A integrated amplifier
• Output power: 2× 15 W Class A
• Valves: 2× 300B, 2× ECC802, 2× 6SN7
• Inputs XLR: 1× line + 1× direct
• Inputs RCA: 3× line + 1× direct
• Input impedance: 50 kΩ
• Bandwidth: 8 Hz–40 kHz, 0 dB
• Output transformer: bespoke MastersounD
• Bias: automatic
• Load impedance: 4–8 ohm
• Negative feedback: 0 dB
• Remote control: included
• Dimensions: 460×415×275 mm
• Weight: 33 kg
• Origin: hand-built in Italy

Frequently asked questions about the MastersounD Compact 300B

What makes the 300B valve so special?

The 300B is a triode output valve that has been prized since the 1930s for its direct, fluid and emotionally involving sound. Since a single-ended circuit uses one amplifying element per channel with no negative feedback, the musical signal passes through with nothing added and nothing corrected.

Which loudspeakers suit the Compact 300B?

With 2× 15 W Class A on tap, the Compact 300B works best with high-sensitivity loudspeakers — ideally 90 dB or above. Consequently, it pairs particularly well with sensitive monitors such as the Graham Audio LS5/9 or similar BBC-derived designs.

How does the Compact 300B differ from the EVO 300B?

The EVO 300B uses four 300B valves in a parallel single-ended configuration, delivering 2× 21 W and offering a wider input selection. Both share the same pure 300B design philosophy — the Compact 300B is the more accessible entry point into that sound.