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    2 or 4 12AX7`s ?

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    pscottlowe

    Posts : 37
    Join date : 2011-09-04

    2 or 4 12AX7`s ?

    Post by pscottlowe on Wed Nov 16, 2011 4:05 pm

    does my pas 3 use all four 12AX7 tubes when not using the phono stage ? and if it uses only two could I use two cheap new tubes and two NOS tubes ? and get twice the life from four NOS than if I used all four ?I dont know if I even understand enough to even ask this ? thanx Scott

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: 2 or 4 12AX7`s ?

    Post by tubes4hifi on Wed Nov 16, 2011 4:22 pm

    yes, all the tubes are powered all the time, so if you don't use the phono at all, put some cheap tubes in there.
    On a PAS3, all of the tubes MUST be in their sockets, or the voltages will be too high due to poor power supply design.

    pscottlowe

    Posts : 37
    Join date : 2011-09-04

    Re: 2 or 4 12AX7`s ?

    Post by pscottlowe on Fri Nov 25, 2011 4:21 pm

    which sockets are the phono stage?

    Bob Latino
    Admin

    Posts : 2413
    Join date : 2008-11-26
    Location : Massachusetts

    Re: 2 or 4 12AX7`s ?

    Post by Bob Latino on Fri Nov 25, 2011 4:50 pm

    The board just to the right of the selector switch that runs from the front to the back of the PAS preamp is the phono board. The board behind the tone controls is the line stage board.

    Bob

    pscottlowe

    Posts : 37
    Join date : 2011-09-04

    Re: 2 or 4 12AX7`s ?

    Post by pscottlowe on Sun Nov 27, 2011 9:29 pm

    when i opened up the pre amp i found that there are three in a row and one at right angles to these .now if i called the three in a row : 1,2&3 and the one at the bottom [of the "L"if you will ]#4 then which ones are not the phono : 1&2 OR 3&4 ? thanx very much i dont want to run all 4 of my NOS mullards .i paid almost $45.00 each and they all tested within 2% !thanx once again,Scott

    tubes4hifi
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    Join date : 2008-11-30

    Re: 2 or 4 12AX7`s ?

    Post by tubes4hifi on Sun Nov 27, 2011 10:13 pm

    post a photo, it seems what you have is not a stock PAS3, it must have some modified circuits
    picture below is a stock PAS3 - phono board on the left

    pscottlowe

    Posts : 37
    Join date : 2011-09-04

    Re: 2 or 4 12AX7`s ?

    Post by pscottlowe on Mon Dec 05, 2011 11:48 am

    Thank you Bob I just opened my pas 3 and it is just like the photo you posted. So I replaced the two you said and I left two new ones in the phono stage and all i can say is stunning .This completely transformed my system. I am not kidding . why did solid state ever replace this sound.this is such an huge change.I have never really heard my system at even close to its true potential .It is a mystery to me why production of this kind of quality ever stopped It is as if i replaced my whole system.Now [ironic I know }I am thinking of setting up my turntable ! [Thorens TD 146 ] .I use a pas 3 with an ST-70 And a pair of La scalla .It has taken 5 years to put this together and after all this time I am finally hearing it ! thanx again , I am half way to saving the $ for an ST-120 .Can hardly wait Scott

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