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 Post subject: Location V1 at F50?
PostPosted: Wed Dec 21, 2011 4:18 am 
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Bottle Rocket

Joined: Tue Mar 22, 2011 3:19 am
Posts: 6
Location: Groningen, the Netherlands
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...


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 Post subject: Re: Location V1 at F50?
PostPosted: Wed Dec 21, 2011 5:07 am 
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Dual Recto

Joined: Mon Jul 16, 2007 1:01 am
Posts: 2828
Location: SoCal
jvanoort wrote:
... 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. :D


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 Post subject: Re: Location V1 at F50?
PostPosted: Wed Dec 21, 2011 5:16 am 
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Bottle Rocket

Joined: Tue Mar 22, 2011 3:19 am
Posts: 6
Location: Groningen, the Netherlands
Thanks! I was hoping for someone to provide some more clarity!


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 Post subject: Re: Location V1 at F50?
PostPosted: Mon Mar 19, 2012 9:09 am 
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Bottle Rocket

Joined: Thu Oct 13, 2011 9:48 am
Posts: 7
V1 preamp is just behind the front jack input.


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 Post subject: Re: Location V1 at F50?
PostPosted: Fri Dec 14, 2012 10:30 am 
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Bottle Rocket
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Joined: Fri Dec 14, 2012 6:01 am
Posts: 5
Location: Graz, Austria
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=pl ... Sl-l9aWDHw

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

_________________
F-50 Combo
V-Twin preamp
Boss DD-20
Morley Power-Wah, PWO Metal Cromo Box,'70s
Yamaha SG-1000 '70s w. Bare Knuckle Rebel Yells


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 Post subject: Re: Location V1 at F50?
PostPosted: Sat Dec 15, 2012 11:06 am 
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Single Recto
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Joined: Sat Jan 12, 2008 12:32 pm
Posts: 1279
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


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 Post subject: Re: Location V1 at F50?
PostPosted: Mon Dec 17, 2012 6:47 am 
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Bottle Rocket
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Joined: Fri Dec 14, 2012 6:01 am
Posts: 5
Location: Graz, Austria
Don wrote:
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

_________________
F-50 Combo
V-Twin preamp
Boss DD-20
Morley Power-Wah, PWO Metal Cromo Box,'70s
Yamaha SG-1000 '70s w. Bare Knuckle Rebel Yells


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 Post subject: Re: Location V1 at F50?
PostPosted: Tue Dec 18, 2012 4:21 pm 
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Single Recto
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Joined: Sat Jan 12, 2008 12:32 pm
Posts: 1279
serjrocker wrote:

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



V2.


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 Post subject: Re: Location V1 at F50?
PostPosted: Sat Jan 05, 2013 2:15 pm 
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Bottle Rocket
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Joined: Fri Dec 14, 2012 6:01 am
Posts: 5
Location: Graz, Austria
Don wrote:
serjrocker wrote:

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!!

_________________
F-50 Combo
V-Twin preamp
Boss DD-20
Morley Power-Wah, PWO Metal Cromo Box,'70s
Yamaha SG-1000 '70s w. Bare Knuckle Rebel Yells


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 Post subject: Re: Location V1 at F50?
PostPosted: Sun May 29, 2016 8:37 pm 
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Donating Member

Joined: Fri Apr 15, 2005 8:39 pm
Posts: 497
Location: Atlanta
Don wrote:
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?


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