Location V1 at F50?

[jvanoort]

I have a question regarding the exact location of the preamp tube that controls the first gain stage (V1).
My F50 manual says V1 is the 12ax7 tube nearest the guitar input jack, which makes perfect sense.

However I have heard, from supposedly knowledgable people, that in the case of the F50 the first tube that the signal passes through is in fact not the one nearest the input jack, but the second one.

Is that true? I ask this, because I bought a F50 retube kit with a special V1 tube, which is supposed to be extra quiet so it will 'pollute' the first gain stage as little as possible with noise and hum.
But then I first have to know the exact location in which to pop it of course...

 

[MrMarkIII]

... However I have heard, from supposedly knowledgable people, that in the case of the F50 the first tube that the signal passes through is in fact not the one nearest the input jack, but the second one...

They must be thinking of the Express.
The manual, available at Mesa's website, shows that V1 is, indeed, the first input stage.

 

[jvanoort]

Thanks! I was hoping for someone to provide some more clarity!

 

[Graon]

V1 preamp is just behind the front jack input.

 

[serjrocker]

Hi jvanoort!

I just retubed my F-50 Combo and was confused myself which was the V1 location, since in the combo the tubes are "upside-down". I took the caps off and tapped the pre-amp slightly with a pencil listned to the output with the volume set to a moderate level. The tube that rings the loudest is the V1 Tube because it is at the beginning of the amplification chain. i.e.: I recconed that the V1 is the position closest to the input jack as you assumed previously. I used the low-microphonics and noise tube SPAX-7 for V1 as well, sounds great and very clean.

See MESA's maintainance video: http://www.youtube.com/watch?feature=player_embedded&v=wSl-l9aWDHw

Btw.: I put a SPAX in V3 which is the FX-send/return tube and now the FX loop sounds amazingly clear. :mrgreen:

 

[Don]

The tube's numbering is it's physical location on the amp's chassis, not it's location in the circuit.

According to the schematic V2 is the first tube that the guitar signal passes through. V1 is after the tone controls.

The clean channel's path is-
Input > V2B > tone controls > gain control > V1B > V3A

The dirty channel's is-
Input > V2A > gain control > V2B > tone controls > V1A > V3A

 

[serjrocker]

The tube's numbering is it's physical location on the amp's chassis, not it's location in the circuit.

According to the schematic V2 is the first tube that the guitar signal passes through. V1 is after the tone controls.

The clean channel's path is-
Input > V2B > tone controls > gain control > V1B > V3A

The dirty channel's is-
Input > V2A > gain control > V2B > tone controls > V1A > V3A

So does this mean I want the SPAX-7 in V2 or in V1 postion for less noise in total? :roll:

Btw.: I have the F-50 model with 4 Pre-amp tubes

 

[Don]

So does this mean I want the SPAX-7 in V2 or in V1 postion for less noise in total? :roll:

V2.

 

[serjrocker]

So does this mean I want the SPAX-7 in V2 or in V1 postion for less noise in total? :roll:

V2.

Hey!

I just swaped the V2 12AX-7 with the V1 SPAX-7, sounds better to my ears thanks for the post!!

 

[Nomad]

The tube's numbering is it's physical location on the amp's chassis, not it's location in the circuit.

According to the schematic V2 is the first tube that the guitar signal passes through. V1 is after the tone controls.

The clean channel's path is-
Input > V2B > tone controls > gain control > V1B > V3A

The dirty channel's is-
Input > V2A > gain control > V2B > tone controls > V1A > V3A

I know this is an old thread but thought I would ask about clarifying this. The manual states the signal goes like this:


V1 A= Input Stage both Channels
V1 B= Clean Channel
V2 A= 2nd Input Stage bothChannels
V2 B=Channels 2 & 3 Boost Stage
V3 A=Channels FX Send
V3 B= FX Return
V4 A=Phase Splitter
V4 B=Output

Don,

Are you stating the manual is incorrect?