This PCB serves as the core of our acclaimed Melpomene VAT913 stereo vacuum tube power amplifier.

Fully Assembled Stereo Tube Amplifier PCB – VAT289-513. Designed for building a stereo tube audio amplifier based on 6H9C(6N9S) and 6H5C(6N5S)/6H13C(6N13S) vacuum tubes. Tubes are not included.
The 6H8C (6N8S) can also be used as the input tube. This can reduce harmonic distortion, but it requires an input signal level of 6 Vrms.

This PCB is used in our Melpomene VAT913 power amplifiers.

This amplifier board requires TWO power supplies to operate:

• 6.3V for tube heaters, PSP75-6.3 is recommended;
• 420/-100V for tube power supply and grid bias, PSV68-420/-100 is recommended.

Professional Stereo Tube Amplifier Platform

The VAT289-513 is a fully assembled High-End stereo vacuum tube amplifier PCB developed by GRA & AFCH for audiophiles, experienced DIY enthusiasts and manufacturers seeking a proven amplifier platform without the complexity of designing a tube circuit from the ground up.

Unlike typical DIY amplifier boards, the VAT289-513 is not an experimental design. It is the very same amplifier platform used in our commercial Melpomene VAT913 stereo power amplifier, where it has been extensively tested and refined to ensure consistent performance, long-term reliability and outstanding musical reproduction.

Every aspect of the circuit has been developed with a clear engineering objective: to preserve the natural character of vacuum tube amplification while maintaining excellent technical performance and wide frequency bandwidth.

 

Proven SRPP Output Stage

At the heart of the VAT289-513 lies a carefully optimized SRPP (Series Regulated Push-Pull) output stage.

Unlike conventional single-ended tube amplifiers, the SRPP topology operates as a push-pull circuit while eliminating direct current through the output transformer. Since no DC component magnetizes the transformer core, the amplifier can fully benefit from the unique advantages of high-quality toroidal output transformers.

This design approach provides several important benefits:

• Extended low-frequency response due to higher primary inductance
• Excellent magnetic coupling between primary and secondary windings
• Wide high-frequency bandwidth with low phase shift
• Lower output impedance resulting from reduced primary winding turns
• Improved damping factor for better loudspeaker control
• Higher power-to-weight ratio compared to conventional EI-core transformers

 

Optimized for High-Performance Toroidal Output Transformers

The amplifier board was specifically developed for use with toroidal output transformers employing sectioned layer-by-layer winding.

This transformer construction combines two characteristics that are often difficult to achieve simultaneously:

• high magnetic coupling;
• low parasitic capacitance between primary and secondary windings.

The result is excellent bandwidth, accurate transient reproduction and a highly linear frequency response across the audible spectrum and beyond.

With the recommended GV-50 output transformer, the amplifier achieves a measured frequency response of 6 Hz to 28 kHz (-3 dB).

Engineered for Musical Transparency

Rather than relying on complex circuitry, the VAT289-513 follows a carefully optimized signal path that preserves the natural harmonic structure of vacuum tube amplification. The design philosophy focuses on minimizing unnecessary complexity while maintaining excellent measured performance, allowing the amplifier to reproduce music with clarity, openness and natural tonal balance. Its combination of wide bandwidth, low distortion and carefully optimized operating conditions makes the VAT289-513 suitable for demanding high-fidelity audio systems.

 

Factory Assembled and Tested

Each VAT289-513 PCB is delivered fully assembled, eliminating the challenges associated with soldering high-voltage tube circuits. Every board is manufactured using high-quality printed circuit boards and carefully selected electronic components before undergoing functional testing. This allows builders to focus on transformer selection, enclosure design and system integration rather than PCB assembly.

Tube Compatibility

Input Stage

• 6H9C (6N9S)
• 6H8C (6N8S)

* The optional 6H8C input tube can provide lower harmonic distortion but requires an input signal level of approximately 6 Vrms.

Output Stage

• 6H5C (6N5S)
• 6H13C (6N13S)

Vacuum tubes are not included.

Power Supply Requirements

The amplifier requires two external power supplies:

Heater Supply

• 6.3 V AC/DC – Recommended: PSP75-6.3

High Voltage and Bias Supply

• +420 V / -100 V – Recommended: PSV68-420/-100

Applications

The VAT289-513 provides an excellent foundation for a wide variety of custom audio projects, including:

• High-End stereo power amplifiers
• Home Hi-Fi systems
• DIY audio projects
• Boutique audio equipment
• Educational and experimental vacuum tube designs

Whether integrated into a custom enclosure or used as the core of a premium audio amplifier, the VAT289-513 offers a professional platform based on a proven commercial design.

Designed and Manufactured by GRA & AFCH

The VAT289-513 represents years of practical development and refinement. Rather than being created solely for demonstration or experimentation, this amplifier board serves as the core amplification stage of our Melpomene VAT913 stereo tube amplifier, combining proven engineering with the timeless musical character of vacuum tube technology.

Listing includes:

• Amplifier Board VAT289-513

Vacuum tubes are NOT included.

 

 

Specifications:

• Output Power: 2 × 5 Watts
• Output Impedance: 8 Ohm (with GV-50 output transformer)
• Frequency Range (-3 dB): 6 Hz – 28.000 Hz
• Distortion (THD): 0.5% at 1 Watt output

Vacuum Tube Amplifier Board VAT289-513