"Arny Krueger" wrote in message
...

Slew rate and bandwidth. Those Philbrick and HP tube
op-amps
really did not have the bandwidth for anything
approaching
audio. --scott

When I was an undergraduate back in the 60s, I did some time
*programming* analog computers. My recollection is the
Philbrick parts posted at
http://www.national.com/rap/vacuumtubes.html were
bottom-of-the barrel parts.

The sort of vacuum tube op amps I'm thinking of were more on
the order of this one:

http://ed-thelen.org/dc_amp.gif

There's really no excuse for vacuum tube amplifiers to be
terribly slow, after all Tektronics made some pretty fast
'scopes out of bottles....

Right, but the Philbrock jobs were optimized for DC and low-frequency
operation, not audio. As you say, they were for analog computing, and that
usually didn't involve much in the way of high frequencies.

Peace,
Paul0