Just found a interesting article on how to convert 01a tubes to solid state. Only drawback is "plate voltage" is 18 volts compared to 90 volts originally supplied. So all tubes in a set would have to be done, and feed it 18 volts instead of the normal 90.
My question: is there a small solid state component that will take 90 volts and drop it to 18? Or a component that could be tied in under the tube socket to drop the voltage?
http://www.greenhillsgf.com/Project_SS-Tubes.htm

There is no shortage of devices to do the job. If it were me, I'd use a power zener diode of about 47 Volts in series with an 18 Volt regulator chip, the 7818. How much current do you need?

There is no shortage of devices to do the job. If it were me, I'd use a power zener diode of about 47 Volts in series with an 18 Volt regulator chip, the 7818. How much current do you need?

1-10mA

why not just use an 18V power supply in the first place? With two 9 volt transistor radio batteries in series you could run it long enough to get bored.

Don't forget any linear regulator bringing 90 volts down to 18 will waste 80% of
the power consumed as heat. A honest-to-goodness ss substitute for tubes will
use fairely high voltage FETs or other devices to emulate tube performance
correctly. Regards.