I tried the 6DJ8, set up as follows: - 1k tail resistor - grid bias set for about 30V (i.e. about 15mA per triode) - B+ 150V or lower This works pretty well also, with useful suppression when the inputs are quite large (5v peak) (remember that my application is primarily for a TX mixer). Increasing B+ didn't increase the output noticeably. 73, ian K3IMW