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    Power Output of VTA ST-70

    StevieRay
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    StevieRay


    Posts : 67
    Join date : 2009-01-09
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    • Post n°1

    Power Output of VTA ST-70 Empty Power Output of VTA ST-70

    Post by StevieRay Tue Jun 19, 2018 2:58 pm

    I've seen a post from Bob in 2014 saying that the power output of a VTA ST-120 is nominally ~60 wpc, but rises to ~72 wpc with KT-88 tubes and ~77 wpc with KT-120 tubes.

    What about the VTA ST-70?  Nominally rated for ~35 wpc (with EL34's I suppose?), what is the output with other tubes (KT-66/77, 6550, KT-88, etc.)?

    I'm about to pull the trigger on either the ST-70 or ST-120.  I use Quad ESL-57's and Magneplanar MMG's -- quite a swing as far as power requirements go.  I'm leaning more towards the ST-120 because of the MMG's (and the Quads for that matter, as in Triode mode I bet the ST-120 would make them sing) -- but the price of the ST-70 is a LOT more appealing.  Besides, I have an old (modified heavily) Hafler DH-200 to pull out for MMG duty...

    Right now I'm using the power amp section of a NAD 3020B, which at ~25 wpc is plenty for the Quad's in my room.....
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°2

    Power Output of VTA ST-70 Empty Re: Power Output of VTA ST-70

    Post by Bob Latino Thu Jun 21, 2018 5:58 pm

    StevieRay wrote:I've seen a post from Bob in 2014 saying that the power output of a VTA ST-120 is nominally ~60 wpc, but rises to ~72 wpc with KT-88 tubes and ~77 wpc with KT-120 tubes.

    What about the VTA ST-70?  Nominally rated for ~35 wpc (with EL34's I suppose?), what is the output with other tubes (KT-66/77, 6550, KT-88, etc.)?

    I'm about to pull the trigger on either the ST-70 or ST-120.  I use Quad ESL-57's and Magneplanar MMG's -- quite a swing as far as power requirements go.  I'm leaning more towards the ST-120 because of the MMG's (and the Quads for that matter, as in Triode mode I bet the ST-120 would make them sing) -- but the price of the ST-70 is a LOT more appealing.  Besides, I have an old (modified heavily) Hafler DH-200 to pull out for MMG duty...

    Right now I'm using the power amp section of a NAD 3020B, which at ~25 wpc is plenty for the Quad's in my room.....

    The VTA ST-70 was tested a few years ago by customer Russ Knize. Russ checked out power output, frequency response, distortion and the output was also run through a scope to check out the square wave characteristics. (see link below) The VTA version of the ST-70 will reach 45 watts at midband in pentode ultralinear mode and about 21 watts in triode mode. I have had a pair of MMG's here at one time and IMHO, you should use the ST-120 as the amp to drive them. The MMG's are only 86 dB efficient which is fairly low. You need more power to get some real volume out of the MMG's.

    VTA ST-70 performance test by Russell Knize (click on each chart once and then once again for a larger version of each chart)

    Bob
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