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    PAS4 Preamp

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    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

    Re: PAS4 Preamp

    Post by Bob Latino on Tue Mar 22, 2016 10:16 am

    The PAS-4 was very well made. One large PC board with sealed solder traces ... These units still sell for big bucks if you can find one ... See photo below ..

    Bob



    pmarcin

    Posts : 131
    Join date : 2009-01-20
    Age : 69

    Re: PAS4 Preamp

    Post by pmarcin on Thu Mar 24, 2016 5:03 am

    I wasn't that impressed with the linestage. I had built your SP9 and found that unit at least as satisfying.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: PAS4 Preamp

    Post by tubes4hifi on Wed Apr 20, 2016 8:08 pm

    OK guys, come and get them!!   PCBs and parts came in today, here's a photo of the board.
    PCBs shipping out tomorrow.  I've got one left for myself, and one more left for someone lucky who grabs it up quick!
    I should have the board stuffed with parts by Saturday (got to finish another customer preamp tomorrow) and likely
    powered up and tested by middle of next week, so check back here for more photos!



    The left half of the board is the phono stage and line stage, identical to the original, although I'm adding the provision to substitute
    6FQ7 or 12AU7 tubes in the line stage with minor resistor changes. The right half of the board includes two filament regulators,
    one for the phono section, one for the line stage, and SIX individual high voltage regulators, one for each tube (same scheme as the orginal,
    but using newer, better parts). The HV rectification is done using schottky diodes, each with an RC filter across it.
    And finally, in the bottom right, is the original auto mute circuit, using a timer IC and a relay to disconnect the outputs during warmup.
    Right down the middle are 6 large film capacitors for HV bypass (one for each tube), also same as original.


    Last edited by tubes4hifi on Thu Jun 02, 2016 9:03 pm; edited 1 time in total

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: PAS4 Preamp

    Post by tubes4hifi on Sat Apr 23, 2016 3:10 pm

    OK, so here's the board stuffed with all parts, now just need to power it up and test, check back in a few days . . .


    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: PAS4 Preamp

    Post by tubes4hifi on Sat May 21, 2016 5:37 pm

    check out the new Dynaco PAS-4 clone (yes, it's finally a reality!)

    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

    Re: PAS4 Preamp

    Post by Bob Latino on Wed Oct 12, 2016 10:49 am

    Someone requested a PAS-4 schematic .... See below ..

    NOTE - If the whole image does not show up on your screen then right click on the photo and then "Save image as" and you will save the full sized photo on your computer.



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    Re: PAS4 Preamp

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