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    4-ohm vs. 8-ohm transformer taps

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    eickmewg

    Posts : 38
    Join date : 2014-08-29

    4-ohm vs. 8-ohm transformer taps

    Post by eickmewg on Mon Sep 21, 2015 5:12 pm

    I have two tube amps, a kit-built VTA ST-120 and a Yaqin MC-30L.  I recently took the Yaqin out of storage to alternate it with the ST-120.  The Yaqin has separate 4-ohm and 8-ohm speaker connectors.  I've always used the 4-ohm connectors on the Yaqin and I wired the 4-ohm transformer tap to the positive speaker connectors on the ST-120.  However, in hooking up the Yaqin I inadvertently used the 8-ohm speaker connector.  I am using some Polk SRS SDA-2.3 speakers that have a nominal rating of 4 ohms.

    I was somewhat surprised that using the Yaqin 8-ohm connectors gave me what I perceived as better and tighter bass.  With that in mind, I decided to hook up the 8-ohm transformer leads in the VTA-120.  Again, with my speakers I think the bass is more pronounced and drum attacks sharper.  But, I also think at the same preamp setting I lose a little volume through the VTA-120.

    So, is this all in my head or is there some realistic basis for these observations?

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: 4-ohm vs. 8-ohm transformer taps

    Post by Bob Latino on Mon Sep 21, 2015 5:29 pm

    In regards to paragraph 1 > It is possible that although your Polk speakers are rated at 4 ohms, they are actually more compatible (because of their impedance curve at different frequencies) with 8 ohm taps on your Yaqin amp.

    You may lose a little volume through the VTA ST-120 when switching from the Yaqin to the ST-120 amp because the ST-120 has lower gain than the Yaqin. The Yaqin has (like many Chinese amps) fairly high gain in which the bulk of the volume comes on fairly quickly.

    Bob

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