This tube is as close as it gets the old Mullard GZ34 that we all know and love! In fact the plate construction looks to be almost identical to our large base Mullards with the straight edge plates. We've been using these in Bob's old SUNN amps now for years with great results. They seem to know just when to give-in to get that wonderful rectifier sag. We also use these in Mesa Dual and Triple Rectifier amps in place of the stock 5U4's to get a little less sag but to maintain that rectifier sound. A perfect tube to replace the chinese or sovtek 5AR4's that we have all grown to dislike so much... The JJ GZ34 will get your Deluxe sounding like a vintage amp.