Sun Audio SV-2A3TSX
2A3 PSE mono amplifier kit from Japan

The SV-2A3TSX is a new design from Sun Audio.
This is a mono Parallel-Single-Ended (PSE) amplifier using 2 pcs 2A3 output tubes for a combined output of 6Watt

SV-2A3TSX shown here with the optional aluminum tone faceplate

Sun Audio SV-2A3TSX
mono PSE 2A3 amplifier.

This kit has everything you want. The output tubes are driven through an interstage transformer, just like in the flagship of the Sun Audio line (SV-300BSM). Using an interstage does have several advantages. The driver tube can make a much larger voltage swing, has lower distortion, higher gain and the grid of the output tube is connected through a much lower (dc)-resistance to ground. However the"concept" depends heavily on the quality of the interstage transformer. A good interstage is much more difficult to design as an output transformer. The supplied interstage is specially designed and made by Tamura.

The use of parallel 2A3 not only increases output power (or when you look at it in a different way, reduce distortion for a given output level) but also increases the damping factor. The damping factor tell you something about the control an amplifier has on the connected loudspeaker. The higher the damping factor, the better the control. Normally "feedback" is used to increase the damping factor, but sound wise this is not the way we want to do it.

The interstage makes also for a much easier wiring schematic. Parts count is even lower then in a CR design (anode resistor + coupling capacitor). This amplifier does not use a PCB, but is still easily assembled.

A simple schematic is used. Input tube is a parallel connected 6SN7 tube. The output of this stage is DC connected to the grid of the triode strapped 6V6GT tube. The 6V6GT is connected to the primary side of the interstage transformer. The output tube girds are connected to the secondary side of this interstage.
The 2A3 tubes are "self-biased" with an individual cathode resistor.

The SV-2A3TSX uses the same new chassis as the SV-2A3/300BE

Sun Audio has developed a new chassis for their SV kits.
The new chassis looks almost exactly the same as the old version (so happy that they did not change that), but the humm balance potentiometers have been relocated. These are now located directly in front of the output tubes and can be set without the need to put the amplifier upside down.

All (brands of) output tubes are made a little different. When changing output tubes it is sometimesnecessary to adjust the "humm balancing potentiometer" to achieve the lowest output humm.

Re-designing the chassis also offered the possibility to use new high quality input sockets and new loudspeaker terminals

To increase reliability and sound, expensive Yamamoto tubes sockets are supplied for the output tubes.


• Mono amplifier
• 1x 6SN7 input tube
• 1x 6V6GT driver tube
• 1x 5U4G rectifier
• 2x 2A3 output tube: 6W output power
• Input impedance : 100KOhm
• Output terminal : 8 Ohm
• Frequency response : 20Hz ~ 25KHz / -3dB
• Output noise : 2,5mV or less
• Dimensions : W360xH190xd270
• Weight : 16Kg.

Input tubes, output tubes and rectifier are included.

Price :

Sun Audio SV-2A3TSX
230Vac Power transformer

€ 3429.75
€ 4150.00
Pair (2 pcs mono bloc)