I suspect that there's about 20 hours on the stock rectifier. It would have to change drastically to get the mid range I desire. Of course, all this is system dependent along with personal taste. If you like stock recti, the Bendix 5852 is an interesting tube. I'm tempted to play with it more. You have to flip the switch because its also a 6V rectifier. To me it seemed like a little more refined 6Z5. Maybe one of these days I'll give the stock one some more hours.