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DIY 12AU7 Tube Preamplifier

DIY 12AU7 Tube Preamplifier

Alan has put together a very simple tube preamplifier around 12AU7 vacuum tubes. The preamp was built using parts that Alan had on hand. To keep costs down, the preamp can be built using 12V transformers put back to back in order to get the required high voltage.
The power supply is also very simple. All you need is couple of 12 volt transformers (which you can put back to back to isolate 120V), a bridge rectifier, resistors and some caps. For the filament supply I used a simple 7812 regulator circuit to reduce noise. Because the preamp is very low power, he was able to use a 5 pin key board plug, not the PS2 type but the old bulky type. This plug works quite well and is fairly sturdy


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