6S4S-6J4

The 6S4S–6J4 is an exclusive SE (Single Ended) Class A stereo tube amplifier created in Latvia, combining classic tube audio philosophy with the highest-quality materials and meticulous handcrafted workmanship. This amplifier is designed for audio enthusiasts who appreciate a natural, musical sound and an aesthetically refined construction.

The amplifier is assembled using the point-to-point (three-dimensional) wiring method, which helps avoid unnecessary interference, reduces parasitic capacitance, and ensures a maximum  clean and direct signal path. This approach is characteristic of high-end tube equipment and significantly improves sound quality.

• The chassis is made from solid oak wood and plywood, giving the unit natural warmth, mechanical stability, and a distinctive visual character. The wood texture harmonizes beautifully with brass elements, creating a striking contrast and turning the amplifier into an elegant and eye-catching interior object. The construction is massive and well thought out, providing both aesthetic appeal and effective vibration damping.

• Tubes:

  • Power Stage: two 6C4C tubes – directly heated triodes with a distinctly musical character, revealing music with both delicacy and power. The 6C4C is a directly heated triode (DHT) developed and manufactured in the Soviet era as an analogue of the Western 2A3, one of the most iconic audio triodes. These tubes were produced in the USSR from the mid-20th century (approximately the 1950s) until the 1980s, mainly in factories in Moscow and other Soviet republics.
    The tubes used in the 6S4S–6J4 amplifier are 1957 NOS specimens. Today, the 6C4C is highly regarded among audiophiles worldwide as one of the classic tubes for building high-quality audio amplifiers (Comparison of Power Triodes AD1, Ed, and 6S4S). It is known for its warm, rich, and natural sound, making it a favorite choice for Single-Ended Class A amplifiers.

  • Driver: two 6Ж4 tubes – Soviet-era vacuum tubes developed and produced in the USSR from the late 1950s through the 1970s. They were manufactured in several factories, including Saratov, Novosibirsk, and other radio-electronics centers. Designed originally for military-industrial applications, these tubes are characterized by good mechanical durability, stable operation, and long service life. The 6Ж4 is a high-frequency pentode originally intended for RF amplification, intermediate-frequency (IF) stages, and signal processing in radio equipment. In audio applications, it is often used in unconventional solutions—as a voltage amplifier or driver tube in power amplifiers. Thanks to its good sensitivity and high gain, the 6Ж4 can effectively drive output tubes with a relatively small input signal.

  • Rectifier: one BO188 – a rectifier tube used in the amplifier’s power supply to provide stable and clean DC voltage for the tubes. Such rectifiers help reduce power-supply noise and improve sound quality compared to semiconductor rectifiers. The BO188 minimizes electrical interference and power-supply ripple, delivering a more stable voltage, which is essential for refined tube amplifier performance.

• Output power: 2 x 3 W – suitable for high-efficiency loudspeaker systems (95 dB/W/m and above), where quality matters more than sheer volume.
• Dimensions: width 54 cm, height 20 cm, depth 30 cm
• Weight: 21 kg

The 6S4S–6J4 offers a warm, natural, spacious, and musically rich sound typical of SE Class A tube amplifiers. It creates a wide, three-dimensional soundstage in which each instrument occupies its own space with a natural timbre. Thanks to the 6C4C tube,  the midrange is full and lively, vocals sound organic and present. The high frequencies are smooth yet detailed, without harshness, while the bass is well structured and precise, emphasizing tone and texture rather than brute force. The sound is gentle yet powerful enough to highlight dynamic passages, while preserving calm and lyrical moments.

The 6Ж4 tubes are characterized by a clear, detailed midrange and high-frequency response. They provide good dynamics and a clean signal structure, allowing the 6C4C output tubes to fully reveal their musical potential. The sound of the 6Ж4 is neutral and precise, with a subtle “tube character” that adds liveliness and spatiality to the music. This combination of qualities makes the 6Ж4 an interesting solution for audio amplifier designs requiring stable and musical voltage amplification. The result is sound with excellent microdynamics, a wide soundstage, and natural flow, particularly well suited to acoustic music, jazz, vocals, and classical recordings.

The use of the BO188 rectifier in the power supply adds additional smoothness and calmness to the sound, reducing perceived “hardness” and creating more even dynamics.

This tube combination provides an excellent balance between detail, musical flow, and classic Class A sound.

The 6S4S–6J4 is a thoughtfully designed, classically styled, and highly musical tube amplifier in which technical solutions, tube selection, and design form a unified and harmonious whole. Overall, the 6S4S–6J4 is an amplifier for listeners seeking authentic tube sound, handcrafted quality, and a calm, deep musical experience.

• Technology: SE Class A stereo amplifier
• Assembly method: Point-to-point wiring
• Materials: Solid oak wood, plywood, brass
• Tubes: 2 x 6C4C; 2 x 6Ж4; 1 x BO188
• Output power: 2 x 3 W
• Dimensions (width x height x depth): 54 x 20 x 30 cm
• Weight: 21 kg