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    EL34 or KT88 for ST70 ?

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    RMG

    Posts : 16
    Join date : 2010-06-13

    EL34 or KT88 for ST70 ?

    Post by RMG on Tue Mar 01, 2011 10:31 pm

    Hello, I have a triode electronics ST70 with EL 34 output tubes. Does it pay to modify it for KT88's ? Would there be any worthwhile improvement in the sound or would it be wiser to build a ST120. Thanks.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: EL34 or KT88 for ST70 ?

    Post by Bob Latino on Wed Mar 02, 2011 6:14 am

    You can probably use KT88 tubes in your ST-70 amp but you won't get any more power at all out of the amp. Just using KT88 output tubes in an ST-70 based amp does not make the amp into a 60 WPC amp. The ST-120 has three different transformers and a larger power supply than the ST-70. The ST-120, although sharing the same driver board as the VTA ST-70, has a number of changes to the components on the driver board to better drive KT88, 6550 or KT120 output tubes.

    Bob

    RMG

    Posts : 16
    Join date : 2010-06-13

    Re: EL34 or KT88 for ST70 ?

    Post by RMG on Sat Mar 05, 2011 8:31 am

    Thanks for the reply. I am more curious as to whether the KT88 will change the tone of the amp in some desirable way. That being said, what are the differences in tubes? What actually determines the watt rating of the amp? Why an EL34 and not a KT88 or KT120? Thanks.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: EL34 or KT88 for ST70 ?

    Post by Bob Latino on Sat Mar 05, 2011 9:07 am

    A KT88 is designed to look at more voltage and also deal with higher current flow than an EL34. As such, KT88 tubes are considerably more expensive than EL34's. KT88's do change the "tone" of the amp slightly. Whether the tone difference is desirable or not largely depends on your musical tastes and your associated equipment. In general, EL34's tend to be "mid-rangy" tubes while KT88's seem to have more output at the very top and the very bottom of the audio frequency scale.

    Re: determination of watt rating of an amp > watts = volts X amps. An amp that can provide more current (amps) at higher voltages has more "power".

    Bob

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