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    VTA ST-120 phase?

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    Rich

    Posts : 31
    Join date : 2013-01-17

    VTA ST-120 phase?

    Post by Rich on Fri Nov 07, 2014 9:13 pm

    The preamp I'm using now with my st120 inverts phase at the output.
    At the owners manual, it say to invert speakers polarity.
    I doubt this is not applicable to St120 because of the preamp low gain card.
    Am I right?

    Best regards.

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: VTA ST-120 phase?

    Post by sKiZo on Sat Nov 08, 2014 12:28 am

    Easiest way to check ... switch the +/- leads and see which setup gives you the best bass.

    Does sound a tad strange though ... what pre, and could you post up the exact text from the manual telling you to do this?


    Rich

    Posts : 31
    Join date : 2013-01-17

    Re: VTA ST-120 phase?

    Post by Rich on Sat Nov 08, 2014 12:56 am

    Hello,
    The pre is a Cary SLP98.
    The manual text: " Amplifier – Speaker Connection • The SLP 98 (line and phono) preamplifier is phase inverting. • This will require you to connect the positive speaker terminal to the negative binding post on your amplifier. The negative speaker terminal will connect to the positive binding post on your amplifier. "

    Already did this way.
    Awfull sound...!!!

    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: VTA ST-120 phase?

    Post by PeterCapo on Sat Nov 08, 2014 9:43 am

    Yes, the SLP-98 has inverted phase at its output, and the solution is to simply reverse the connections either at the speakers or the power amp outputs (not both).  I believe there are some other preamps on the market that do this, as well.  In and of itself, it should not be the source of "awful sound" - I'd look elsewhere for the cause, if something sounds that bad.

    Rich, can you clarify your meaning when you wrote in your original post: "I doubt this is not applicable to St120 because of the preamp low gain card."

    Thanks.
    Peter

    Rich

    Posts : 31
    Join date : 2013-01-17

    Re: VTA ST-120 phase?

    Post by Rich on Sat Nov 08, 2014 10:16 am

    Hello Peter,
    I read that two of the three drivers tubes are phase inverters.

    Best regards

    Bob Latino
    Admin

    Posts : 2413
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA ST-120 phase?

    Post by Bob Latino on Sat Nov 08, 2014 10:25 am

    The VTA ST-120 does NOT invert phase. Neither does the VTA ST-70 or the VTA M-125 monoblocks. If your preamp does invert phase then the audio signal (out of phase) will be sent to your VTA amp. The out of phase signal will then be sent to your speaker outputs. As has been said above, all you have to do is reverse the two positive and negative wires on your speaker and your system will be in phase.

    I had a customer (John Inlow of Inlow Sound in Portland, OR) who made a custom speaker installation using two M-125's to drive two bass horns in a multiamp setup with crossovers. When he first ran the system, it didn't sound right. It turns out that the midrange amp had reverse phase and the M-125's do not. Reversing the speaker wires to the M-125's straightened out the issue. Go to John's web site below and click on "125 watt KT88 tube amplifier" on the left side of the page. It explains in more detail about John's issue with his multi amp setup.

    Inlow Sound

    Bob

    Rich

    Posts : 31
    Join date : 2013-01-17

    Re: VTA ST-120 phase?

    Post by Rich on Sat Nov 08, 2014 11:01 am

    Thank you Bob!

    Best regards.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: VTA ST-120 phase?

    Post by tubes4hifi on Mon Nov 10, 2014 1:21 pm

    quite a few preamps invert phase so not surprising that the Cary is one of them

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: VTA ST-120 phase?

    Post by zx on Tue Nov 11, 2014 10:36 am

    Conrad-johnson ,Cary an othes invert phase at the outputs of there preamps Because......Thay would have too add one more stage....one more tube for the output to go though just to put the output back in phase....
    So you got to run wire to the speaker anyway an the speaker dose not mind if your Reversing the input..in this case.....have fun with tubes............ in 2014 .....gofig




    Thanks for the site Bob.....................

    Rich

    Posts : 31
    Join date : 2013-01-17

    Re: VTA ST-120 phase?

    Post by Rich on Tue Nov 11, 2014 10:57 am

    Thanks for your input.
    I've already reversed my speakers connections.
    It sounds amazing.


    Best regards.

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