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    5V3 test vs. 5AR4

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    audiobill

    Posts : 270
    Join date : 2014-03-13
    Location : Philadelphia

    5V3 test vs. 5AR4

    Post by audiobill on Fri Oct 02, 2015 8:04 am

    I just wanted to share my test of a 5V3 in an ST70 with KT88s, vs a 5AR4:

    Line voltage: 120

    Voltage across pins 4/6 of rectifier: 716vac

    B+ at pin 8 of 5AR4: 416.0 vdc
    B+ at pin 8 of 5Y3:   411.3 vdc

    In summary, about a 5vdc drop in B+ using the 5V3.

    I'll measure on an ST120 soon.

    Bill

    GP49

    Posts : 733
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: 5V3 test vs. 5AR4

    Post by GP49 on Fri Oct 02, 2015 9:35 pm

    That's the quiescent B+ but how about under current draw? We don't hear amplifiers when they are quiescent (zero outout).

    audiobill

    Posts : 270
    Join date : 2014-03-13
    Location : Philadelphia

    Re: 5V3 test vs. 5AR4

    Post by audiobill on Sat Oct 03, 2015 6:40 am

    A good thought - but that's not how I tested this.

    GP49

    Posts : 733
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: 5V3 test vs. 5AR4

    Post by GP49 on Sat Oct 03, 2015 3:23 pm

    I know, but that is how an amplifier operates when playing music. Current is drawn and different rectifiers, with different internal impedances, will sag different amounts of voltage. The output voltage to the smoothing capacitors thus varies according to current draw, which varies according to the music played. So different rectifiers will sound different, and a no-load test will not give a clue as to the behavior of a particular tube.

    audiobill

    Posts : 270
    Join date : 2014-03-13
    Location : Philadelphia

    Re: 5V3 test vs. 5AR4

    Post by audiobill on Sat Oct 03, 2015 3:26 pm

    Again, good thoughts. Please feel free to share your further tests with the group.

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