best replacement tube for 7199 in old Ampegs?

[cpollack]

The 7199 can be reliable, but some amps (like Dyna St-70s and EL-34 Sunns) can be rough on them. They are a little sensitive to the heater / cathode voltage differential. Since the triode section is commonly used as a split load inverter, it can see some high cathode voltages. Biasing the heater supply up 40-50 volts on these amps isn't a bad idea and will keep the 7199 happy for years. HiFi guys do this often. I did this in my Sunn Sentura and it's had the same 7199 for 15 years.

[crbowman]

With plenty of good sounding 6GH8A, 6BL8/6U8 tubes available there's no reason to use 7199's unless you really want to pay more...

H.H. Scott amps briefly used 7199's in their amp but quickly switched to the 6GH8A, 6BL8/6U8 family of tubes and used them in mosts of their tube amps from that point on....

my .02

TT

Only prob here is that for any Ampeg made after 1967, you're going to have to do some PCB surgery to make it work. Usually no biggie, but not my idea of a party either. Most old PCB Ampegs have preamp tube sockets on the board so they've taken a lot of heat and abuse over the years and can be kinda brittle so proceed with caution.