Fender Pro Junior..... tube configuration

Pete Knapton · Post by **Pete Knapton** » 28 Oct 2004 2:44 am

Hi,
Looking at the back of the amp, the two preamp tubes are on the right side, right?
And the two output (EL84)tubes are on the left.
I understand that the two preamp tubes are for 1. preamp gain stage, and 2. output tube inverting.
Which tube is for the preamp gain stage? Is it the far right tube, or second to right?
Many thanks,
Pete

Sam Marshall · Post by **Sam Marshall** » 28 Oct 2004 6:44 am

The far right tube (V1) is the preamp tube. The next tube (V2) is the phase inverter that "differentially" drives the 2 EL84 (V3 & V4) power amp tubes.

Regards,
Sam

Pete Knapton · Post by **Pete Knapton** » 28 Oct 2004 10:29 am

Sam, thank you...got it.

Oh, yeah, I understand how altering the gain stage tube can affect the tone characterist of the amp.
What about altering the phase inverter tube?
The std. tube for this is 12AX7.
What effect will having a 12AT7 or 12AU7 in the phase inversion have on the amps performance and/or characterist?

Many thanks,
Pete