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    Tube Rolling question


    Posts : 85
    Join date : 2011-04-10
    Location : pittsburgh

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    Post by pigface on Mon Apr 23, 2012 7:40 pm

    Since I’ve added the SP14 preamp to my system , With the ST120 , and having been
    listening to it alot recently , and since and the tubes and caps are breaking in , the highs
    have started getting “brighter”. Not bad but noticible and the bass though still tight and
    nice sounding it is getting a bit louder more pronounced . ( It still sounds better than the
    old Preamp ! ) Though I would like to tone them down a bit .
    What I would like to know , In which unit the ST120 or SP14 would have the most effect
    if I wanted to roll some tubes ?
    Six or so months ago I already rolled out the center tube in the ST120 . Originally I
    had the 4024 Mullards I got from Bob when I built the amp in all positions , but I
    changed the center to a Telefunken 12AT7 - ECC81 and I like how it sounded better than
    the NOS Mullard in the center spot . But just to make sure , last weekend I switched it
    back to the Mullard and I still like the Telefunken better . I could tell right away .
    I know I read that the center tube has more effect on the sound , but would changing out
    the two outer tubes make any difference ?
    Or should I try to roll the preamp tubes , I do have two other brands of tubes and a
    different rectifier for it ?
    I will be adding a PH15 to this system soon too .
    I was hopeing to keep it simple . And was thinking that the tubes in the amp would have an
    effect on both of the other two components.

    I’ve only been listening to the preamp on the first set of output capacitors , the
    Mundorfs S/O , so far . I haven’t listened to the Russian PIO caps on the second output
    yet .
    I’m going to do that before I go changing any tubes but I want to figure out what to do
    before hand if the PIO's sound similar if I need to .

    One other thing . Since this is my first tube preamp , I've noticed that after its warmed up for
    an hour or so the volume seems to creep up a bit on it then stabilize . Is this normal with tube
    preamps ? Part of the break in process ?

    Thanks .

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

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    Post by plexus on Mon Apr 23, 2012 11:21 pm

    my feeling is that tubes are going to potentially make more of a difference in lower signal areas. so in order phono stage, pre-amp, power amp driver gain stage, power tubes. but that doesnt mean a tube switch in the phono stage cant be more subtle than one with the power tubes. it also can depend on the tube and its specific characteristics. eg there might not be as big a difference between 6SN7s but more with 12AU7s and so you will get a wider range of tubes sounds rolling the latter more than the former.

    if i were you id be looking at the 6922s in the phono stage and 12__7s in the preamp. also dont forget the sonic effects of caps especially decoupling caps and also resistors. caps can make a dramatic change in sonic character too.

    Posts : 43
    Join date : 2010-02-26

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    Post by ruffian on Mon Apr 23, 2012 11:37 pm

    pigface wrote:Or should I try to roll the preamp tubes , I do have two other brands of tubes and a
    different rectifier for it ?

    You have them on hand so why not just do it. You can mix them up in each channel also, nothing says you need to run 4 of the same tube in there.

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