RedRoo is a high-quality, single-ended, 5 Watt per-channel, Class-A valve stereo amplifier designed in Australia by Phil Wait. It can power loudspeakers or low-impedance headphones, and can also be configured as a 10 Watt mono-block amplifier.
The circuit is a no-compromise design using a two-stage 12AT7 Constant Current Draw Amplifier (CCDA) for the input amplifier driving single ended (SE) EL34 output stages. The CCDA draws a constant current from the power supply, and provides a low impedance drive to the output stage, (TubeCad CCDA article).
The circuit also uses DC heaters and a unique power supply design that produces no buzz or hum in the speakers, and extremely low background noise. The output transformers are unusually large for the power level, which ensures strong and accurate base reproduction while retaining delicate high frequency details. You can try different types of valves and each output stage can be configured as either a triode, pentode, or ultra-linear stage. There is also provision on the PC Board for an optional Bluetooth input module, if streaming from your smartphone or laptop is your thing.
The selection of professional-quality components and the use of a 2mm thick double-sided printed circuit board practically ensures trouble-free construction. With a little patience and skill you will have a superb sounding amplifier you can be proud of that will last you for a very long time, and at a fraction the cost of a similar commercially built amp.
The PC Board, chassis components, output transformers and the HV power supply module are all available from this website. Other components are available from Digikey.com, EVACTO.com.au and other suppliers. We estimate the total parts cost of this amplifier to be around A$800, or around US$600 (plus freight and local taxes). This is substantially lower than other comparable kitsets.
Please let us know what you think.