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Original Message
RE: PSE 2a3 operating points?
Posted by Neff on May 26, 2012 at 09:15:51:
Parallel 2A3 with higher than specified load impedance should sound great. I noticed when I use higher than manufactures recommended impedance for maximum power out at usually 5% distortion, the tube sounds better. I find the magic starts around 50% higher impedance on a few amps I built using different taps. At 100% increase you could push the plate voltage to 275-290 volts and set bias for 45ma. The JJ 2A3-40 would be very comfortable at that voltage & stock 2A3 or 6B4G should be fine. Longest stock 2A3s life are likely at 250 volts & 35ma. But, we are not talking a seriously rare tube here.
I built a SE 2A3 with 260 volts plate @ 50ma using 3.5K primary impedance. Audio is crystal clear, bass strong enough & midrange delightful. I do not need another amp. Speakers are 98dB efficient.