5+5 Stereo Tube Amplifier

Free Design Information - Build your own high quality tube/valve audio amplifier.
Non-commercial use only

Want to build your own valve/tube stereo amplifier that uses top quality components, sounds terrific, and doesn't cost an arm and a leg? If so, this RedRoo amplifier is for you.

No matter if you're a beginner or an experienced audiophile, this amplifier will impress you and your friends. Many of these amplifiers have been built over the past two years with excellent results. There is nothing like saying "I built it myself".

The information contained in this website is free to download and use by individuals for non-commercial purposes. Please read the section on valve safety the disclaimer below.

The Red Roo Amplifier

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. 

Why Tubes?

Many musicians and audiophiles still prefer the sound of an old-fashioned thermionic valve (aka Tube) amplifier. Valves have a typically "warm" and "open" sound produced by the synergy of many factors that solid-state devices just cannot simulate.
A RedRoo valve amplifier lets you experience your favourite recordings just as the original musicians and their sound engineers intended.

Is DIY for Me?

The difficulty level for this amplifier is 3. The number relates to the information in the table below. Levels 1 and 2 do not require previous experience. Levels 3 and 4 require some knowledge of electronic components and their usage, and moderate construction skills. Level 5 is for those who have experience handling very small electronic components and analysing complex circuitry. (We have recently reduced the experience level down from 4 to 3, as so many have been made without any apparent difficulty).

If you don't feel you do not have the necessary experience you should either seek help from someone who does, or you should build a few simple electronics kits first. Easy steps!
Please also read the section on valve safety.

Valve Safety

Valve amplifiers are safe unless they are physically damaged, misused, poorly located, or are being worked-on without taking appropriate safety precautions. 

Electrical Safety - Hazardous Voltages
Valve equipment contains hazardous voltages, (several hundred volts, or more), and it can hold that high-voltage charge for a very long time after the power is switched-off. If you are working on valve circuitry make sure it is switched-off and the high voltage power supply is fully discharged.

Burns or Fire Risk
Valves operate very hot and can cause a nasty burn. They can also ignite materials that come into contact with them, such as flapping curtains etc.

● Position valve equipment well away from combustible materials. Leave at least 200 mm clearance on all sides and the top for adequate ventilation.

● Never leave a valve amplifier switched on when unattended. Keep out of reach of small children

Read more about valve safety on the kit information page.


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