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Old 4th November 2021 | Show parent
Gear Head
Yes, 7000V/us slew rate is Very Fast. Will make a good UHF oscillator.
The question is, for audio, what is needed?

The 12AX7's don't have the current drive capability provided by other tubes of that series like the 12AU7. These tube were developed for 5 tube radios. Not quality electronics. They work great where the users are not that picky. Applications like guitar amps. I don't use them. There are better tubes.

The TI TL072 op-amp has a bandwidth roll off built in. We used them for phone company 54kHz chopper modulators back in the 1980s when some engineer decided to actually design to published specs. That caused a lot of problems with parts we were making for MCI, SP and others until we figured it out. Then we went to another company brand. That fixed everything.

This is a good link for Slew Rate with graphics. They mention tubes too.

Jim Moss

Originally Posted by Jim Williams ➡️
The common 12AX7A has a 12v/us slew rate, similar to a TI TLO72 opamp. Driver tubes like 12BH7 are slower. 12AY7's are faster due to less stray capacitance.

Some rf tubes are very fast but not suitable for audio usage. Transistor designs here go up to 7000V/us slew rate, that is very fast.

Transistors are faster than tubes.