Originally Posted by purrin
Yikes. The Lyr sounds very interesting. It sounds similar a Melos, same tubes, MOSFET output stage, DC servo out, non-inverting, but the Lyr betters the Melos with more power, no-input caps, and probably much cleaner PCB layout. But Dynamically Adaptive Output Stage? Either the topology of the output is single-ended or not.
There are many amps that have those characteristics. The ECC88/6922/6DJ8 are all very common tubes in audio, and so is the very generic description.
No again to your topology statement. In 1991 Pass Labs developed a hybrid topology where a push-pull circuit is paralleled with a current source, which biases it into single-ended Class A. No doubt, a similar topology is used here. You parallel the P-MOS with the CCS, and voila single-ended.
@ Jason Stoddard, what is the crossover point, more precisely what is quantity of your bias current? What power levels do you support in class A (can be calculated from the bias current)?
BTW, Jason, very nicely spec'd amp. I never buy amps, I build my own, but yours sounds like something I would be interested in due to what I perceive to be an excellent cost point. Do you have other distortion measurements? I noticed the 0.1% THD @ 1V. What about higher levels, say 1% THD? At 40Vpp output, what distortion levels are you looking at? I'd presume that's in class AB when going into a 32-ohm load.
What is the B+ and the idle current of the tube? I would love to hear more of the topology of this circuit, ccs and common cathode perhaps? I understand if it's not feasible to do so.
I think you should make a bridged configuration for this one. ;) JMHO.