Reporting question for Vacuum Tube - EL844, JJ Electronics

Vacuum Tube - EL844, JJ Electronics

I’m about ready to order this for my vox ac4. Would I have to have the bias adjusted or just plug it in and play?

With any retube, you may need to make adjustments to your amp depending on the type of bias it has. Your amp will either be fixed adjustable bias (has bias pot on the back of the amp) , Fixed non-adjustable bias (bias is fixed by a resistor in your amp), or cathode bias (self biasing no bias required). The manual for your amp should be able to tell you what type of bias you have. Rebiasing an amp is something that should be done by an experienced tech.