Valves (or ‘vacuum tubes’) are experiencing a real revival in the audio world, which can readily be seen from the large number of commercial amplifiers and DIY designs that have appeared in recent years.
Unfortunately, valve amplifiers are relatively costly compared withtransistor amplifiers, in part due to the need for a high voltage supply and output transformers. Output transformers in particular are a major investment.
This design attempts to remedy this situation by replacing the output valves and transformer.
5 February 2008.
In the parts list, the value of R11 is erroneously given as 18 ohm. The correct value is 18 kohm.
The correction has been incorporated in the parts list on the project web pagee.