Very Nice!I like the idea of using a smaller Bias supply and a CCS on the input. One could even use a grid choke in place of input resistor, if they wanted to go over the top.
And the price: $1.90 for a 6BQ7 @ AES, @2.90 @ Uncle Neds. Matched pair of JJ's $30. @ Uncle Neds.
Center tapped grid choke could be PSA-2N(nickel) from Elecrtra-Print.
Joe