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    Tube Rolling with the ST120

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    Reid

    Posts : 9
    Join date : 2009-02-05

    Tube Rolling with the ST120

    Post by Reid on Tue Apr 13, 2010 6:53 am

    Bob,
    What tubes can be rolled with the ST120 amp? Power and pre-amp tubes?

    Many thanks.

    Bob Latino
    Admin

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

    Re: Tube Rolling with the ST120

    Post by Bob Latino on Tue Apr 13, 2010 11:34 am

    Reid wrote:Bob,
    What tubes can be rolled with the ST120 amp? Power and pre-amp tubes?

    Many thanks.

    Hi Reid,

    For the ST-120 amp ...

    1. For output tube you can use KT88, 6550 or KT90 output tubes. My favorite tube in there now is the Genalex Gold Lion KT88. It's an expensive tube ($50 each) but I haven't found anything yet that sounds better ..

    2. For the 12AT7 driver tubes I like the Mullard CV4024 (12AT7 equivalent tube). They are easy to source as NOS tubes and only $20-$30 a tube. I have some extra Mullard CV4024's in the "For Sale thread" on this Forum. If you can find a good Telefunken or RCA black plate 12AT7 they are great tubes also.

    3. Rectifier tube - new stock - the best is the Ruby GZ34
    old stock - Mullard GZ34 (expensive!)
    solid state - Weber Copper Cap model WZ68

    Bob

    Jhoman

    Posts : 25
    Join date : 2010-01-03
    Age : 56
    Location : Meridian, MS

    Re: Tube Rolling with the ST120

    Post by Jhoman on Tue May 25, 2010 8:16 am

    Bob Latino wrote:
    Reid wrote:Bob,
    What tubes can be rolled with the ST120 amp? Power and pre-amp tubes?

    Many thanks.

    Hi Reid,

    For the ST-120 amp ...

    1. For output tube you can use KT88, 6550 or KT90 output tubes. My favorite tube in there now is the Genalex Gold Lion KT88. It's an expensive tube ($50 each) but I haven't found anything yet that sounds better ..

    2. For the 12AT7 driver tubes I like the Mullard CV4024 (12AT7 equivalent tube). They are easy to source as NOS tubes and only $20-$30 a tube. I have some extra Mullard CV4024's in the "For Sale thread" on this Forum. If you can find a good Telefunken or RCA black plate 12AT7 they are great tubes also.

    3. Rectifier tube - new stock - the best is the Ruby GZ34
    old stock - Mullard GZ34 (expensive!)
    solid state - Weber Copper Cap model WZ68

    Bob

    Bob, I'm running the Mullard CV4024s in the two outside sockets & I just recently put a vintage Telefunken 12AT7 in the center position. Sounds sweet. The Telefunken sounds a little more defined than the CV4024 that I had in the center position.

    What is your take on this? I'm still running my Ruby KT88s and my RCA 5U4 GA rectifier. So far so good. I love the amp paired with my Cornwall's.

    Bob Latino
    Admin

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

    Re: Tube Rolling with the ST120

    Post by Bob Latino on Tue May 25, 2010 8:53 am

    Hi,

    The Telefunken 12AT7 seems to have just the tiniest bit more output at the frequency extremes. If this works with your other components and you like the sound of your system this way then by all means use one. The Mullard CV4024 (IMHO) is a nice midrange tube and is really good for vocals and acoustic instruments. I listen to a lot of acoustic jazz and still like the Mullard in the center position. The Mullard is also cheaper and easier to find NOS.

    I guess it all boils down the old addage that tube gear users should > "use what tube sounds best to YOU with the system that YOU have and the type of music that YOU listen to ..." The VTA boarded ST-70 and ST-120 respond very well to tube changes and that's a good thing because it makes it easier to tailor the sound of the amp to your liking. I had someone Email me who said his ST-120 sounded a little "bright" to him. Now I know from listening to at least 75 different ST-120's that they don't sound bright at all BUT with his other components (CD player, preamp and speakers) he needed something to tone down the high's just a bit. I had him put a Mullard CV4024 in the center position and use a matched quad of Svetlana 6550C tubes in place of the KT88's he had. He Emails me back in a week or so and Volia! - the amp sounds perfect to HIM now.

    As an aside - I once bought a USED set of very expensive speaker cables locally from someone at about 1/4 the price of what they sold for new. I put the system together and the whole system sounded a little "bright" with slight sibilance on many female vocals. This went on for months until on a chance I brought some other cables from my workshop downstairs and put them in place of the expensive cables ... Again - another Viola! moment. Changing out the speaker cables straightened out the system ... No more sibilance ... Now the original speakers cables may have not have worked in my system but could have worked wonders in someone else's system. I wound up selling the expensive speaker cables on Audiogon for more than what I paid for them ...

    Bob

    GP49

    Posts : 735
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Tube Rolling with the ST120

    Post by GP49 on Tue May 25, 2010 12:38 pm

    Bob Latino wrote:
    As an aside - I once bought a USED set of very expensive speaker cables locally from someone at about 1/4 the price of what they sold for new. I put the system together and the whole system sounded a little "bright" with slight sibilance on many female vocals. This went on for months until on a chance I brought some other cables from my workshop downstairs and put them in place of the expensive cables ... Again - another Viola! moment. Changing out the speaker cables straightened out the system ... No more sibilance ... Now the original speakers cables may have not have worked in my system but could have worked wonders in someone else's system. I wound up selling the expensive speaker cables on Audiogon for more than what I paid for them ...
    Bob

    And then again, they may have been a set of speaker cables with high capacitance, enough to cause the power amplifier to operate on the verge of instability due to capacitive loading. It's surprising to some, how often this can happen. It's surprising to ME, how some cable manufacturers don't even TEST their product for this kind of thing. Or if they DO test, they regard the PROBLEM...because that is really what it is...as an ASSET.

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