|Dave Stork||Re: U.L. Fenders (calling Ken Gilbert)|
If you really wanted to, you could use a big choke in place of the grid resistor. That would offer a high impedance to signal while keeping the grid near DC ground, minimizing unintentional "grid leak bias" pushing the tube into a nonlinear operating class. Transformer coupling will do the same thing as the choke. Neither approach is as cost-effective as using a smaller grid resistor and a lower-impedance driving stage, or using a series grid resistor (grid stopper) to reduce loading on the driving stage when the grid is driven into conduction. In my own overdrive preamp designs, I use fairly big stoppers (>100k) in series with the grids, which also helps a lot in preventing high frequency oscillation.