Where to insert preamp bias-vary tremolo?

[Phil_S]

Because the gain factor of a 6SL7 is less than a 12AX7, it is going to be difficult to match the intensity of the 12AX7. If the 6SL7 is showing itself to be used, you may do better with one that tests close to new. Otherwise, you just need to bias for more gain. The LED is doing that. Good luck.

[funkgang49]

Using a new production Tungsol. Got a socket adapter on the way to plop-in a 12AX7. If that doesn't do it for me I'll try that circuit sluckey used on his Jet.