Look .. I make the same mod on my 1974x clone and work pretty fine and is exactly the same way of Marshall 1974x with Phoenix … so I think to put on the first gain stage the 12AY7( maybe 12AX7 because now I have the master volume so I don’t care about gain ) sure the master volume must added ..
> Shades of the 5E3.
Yes. And several TEAC tape decks. But the features of the "backward potentiometer" are less valid for a Master Volume.
I do not know if it is a choice or a drafting error.
Yes. And several TEAC tape decks. But the features of the "backward potentiometer" are less valid for a Master Volume.
I do not know if it is a choice or a drafting error.
It’s doesn’t drafting error if you mean for the MV 1974x . Check it
Here is the assembly manual - go to cool modification down
https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/british18w_v20.pdf?1471355807
In the manual the written instructions on page 58 don't match with the diagram on page 59. The written instructions describe connecting the pot the way PRR advised.
I don’t see the instructions on page 58 just the diagram on page 59 ( master volume cont ) … I question is : can I do the same on Phoenix because I see it’s the same schematic after phase tube into power tube …
Here is page 58 from the manual you linked to in your post #47. See steps 12, 13 and 14. Step 12 says to connect terminal 2 of the pot to turret T38 on the turret board.
But on the diagram on page 59 terminal 2 of the pot is connected to turret T46 on the turret board.
I think that the diagram in the manual is wrong.
I advise you to connect the pot in your amplifier like in the attached schematic.
Addition: Maybe it's wise to add a 1M resistor from each wiper to ground. This prevents the control grids of the EL84's floating in case the pot goes dusty/bad.
But on the diagram on page 59 terminal 2 of the pot is connected to turret T46 on the turret board.
I think that the diagram in the manual is wrong.
I advise you to connect the pot in your amplifier like in the attached schematic.
Addition: Maybe it's wise to add a 1M resistor from each wiper to ground. This prevents the control grids of the EL84's floating in case the pot goes dusty/bad.
Attachments
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Yes you’re correct the page 58 is wrong but the diagram on the page 59 is correct . This is I make it and work fine . Without buzz or unwanted noises … 
you send me this diagram , that’s I’m thinking to make and this is the same with 1974x .. that is work ..
you send me this diagram , that’s I’m thinking to make and this is the same with 1974x .. that is work ..
I have one last question , just get out of my head .. the main transformer have 2 currents . The circuit voltage and the filaments voltage .. the circuit voltage are 2 x 220vac ( or something else ) and the tap on the centre … and the filament wires are 1x 6.3vac + 1x 0vac or 6.3 vac + 6.3 vac ????