This amplifier was built at the last year. I got a lot of  PL509 valves. This valves use in TV, as line driver. I try to use as triode. Mr. Bruce Rozenblit give me help to proper connecting.  Then I measure the valve as triode, the result was very nice. Low mu, low plate resistance. I build the first version, wich based on the famous Williamson amplifier. It sound nice, but my friend tell me some idea.

    The planning ready, and under building. The schematic:
    First stage has regulated power supply, it help to minimize drift and improve PSRR. The current regulator result big AC resistance at the tail of the first stage, it gives good AC balance. The second stage tail connected to -120V to make better balance.
    There are only one coupling capacitor at the signal path, it gives better sonic performance, better low frequency response. The overall feedback 16dB only. It's enough to stabilize the circuit, and gives flat response.
    The output stage work in class AB, quiescent current 100mA each valve. It's results 11W class A output power. This eliminates the crossover distortion. Plate resistance 2240 ohm plate to plate. 2.5k output transformer gives good performance and 40W output power. I use home designed transformer.
    The power supply schematic:
    I found, the simple power supply give better sound. Hard regulated supply can make hard AC pulses to the HT voltage. Simple RC filtering gives less noise, and more dinamics.
    Large energy storage at the output stage gives very good bass, two 2200uF capacitor results 200J energy storage. All electrolytic capacitor bypassed with polypropilene film capacitors.
    I don't use printed board. Hard wire makes less distortion, and better sonic performance.