The SB-230 has a bright future, thanks to the brainchild of VA1DER, whose modification I worked up in parallel with his. Our SB-230 amps now run on GI-7BT tubes with modified anodes. We cut off the threaded rod intended for a finned cooling assembly and, instead, we press the flat anode surface against the BeO cooling block, just as the 8873 was configured. The circuitry supporting the tube is still essentially the same. At a minimum, all that needs to be done is eliminate the tube socket and bring up wires for the filament, cathode and grid (or just leave the tube socket there to serve as a terminal strip and bring up the lines). The cathode bias must be increased to 24 volts, but that is just a matter of installing a different zener diode. Also, an anode clamp has to be fabricated -- that's very doable for hams that are mechanically adept in the workshop. Oh yes, the GI-7BT tube has a 12 volt filament instead of 6 volts. I simply installed a small transformer, but there are alternate ways of dealing with this. Kurt, VA1DER is working up a detailed description of the tube mod and will post it soon (although he's been a bit busy lately). But I wanted to get you owners of SB-230 amps aware that your "quiet amps" have a bright and quiet future after the 8873 tubes bite the dust!