[Harp-L] HOW TO PLACE THE PRE AMP TUBES IN FENDER BLUES JUNIOR

["Gianfrancesco Leone" <gianfrancesco_leone@xxxxxxxxx>]

I play harmonica with a Fender Blues Junior amp. 
I want to replace the three pre amp tubes. I have the following: 12 AT7 (Sylvania), 12 AY7 (General Electric), 12 AU7 (Sylvania).
But I don't exactly know in which order is better to place them.
May anyone help me with an advice?
Thank you in advance.

Gianfrancesco
Rome (Italy)