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    VTA ST120 Input Sensitivity

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    mazeeff

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    VTA ST120 Input Sensitivity

    Post by mazeeff on Wed May 16, 2018 3:41 am

    Can someone tell me the input sensitivity on the ST120 for full rated output? This would be for the newer "low gain" board. My DAC has the ability to switch between 1 volt and 2 volt outputs, and I get less distortion using the 1 volt output. Just curious how much headroom that I give up by using the lower voltage.
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    arledgsc

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    Re: VTA ST120 Input Sensitivity

    Post by arledgsc on Wed May 16, 2018 12:33 pm

    The ST120 assembly manual states sensitivity is 0.6v for 60 watts output. You should be OK with the low gain setting plus less noise perhaps.

    mazeeff

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    Re: VTA ST120 Input Sensitivity

    Post by mazeeff on Wed May 16, 2018 12:50 pm

    arledgsc wrote:The ST120 assembly manual states sensitivity is 0.6v for 60 watts output.  You should be OK with the low gain setting plus less noise perhaps.  

    Never thought to look at my manual. It states the sensitivity as 1.4 volts for 60 watt output. You must have a different board.
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    arledgsc

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    Re: VTA ST120 Input Sensitivity

    Post by arledgsc on Wed May 16, 2018 12:57 pm

    Interesting... I have the low gain board. Perhaps Bob should answer. But if it sounds great with lower gain then use it.

    From the manual I received with my low gain board.
    Sensitivity . . . . . . ………. 600 millivolts for 60 watt output

    jasn54

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    Re: VTA ST120 Input Sensitivity

    Post by jasn54 on Wed May 16, 2018 1:36 pm

    Uhhhh, my ST120 manual from 2015 specifies sensitivity as 1.1 volt in for 60 watt output.

    New2Tubez

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    Re: VTA ST120 Input Sensitivity

    Post by New2Tubez on Wed May 16, 2018 2:01 pm

    My ST-120 manual from 2/2018 reads: "Sensitivity.......... 1.4 volts for 60 watt output"
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    arledgsc

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    Re: VTA ST120 Input Sensitivity

    Post by arledgsc on Wed May 16, 2018 3:10 pm

    My low gain ST120 was ordered 2012 and Bob forwarded me a Word .doc of the manual while the unit was in shipment.

    Obviously specs received are most likely for the high gain version of the amp. Sorry about that!
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    arledgsc

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    Re: VTA ST120 Input Sensitivity

    Post by arledgsc on Wed May 16, 2018 4:01 pm

    At 1.0V input the amp's output power is about 32W with 60W@1.4V sensitivity. And about 49W with 60W@1.1V sensitivity. 8 ohms impedance

    Using a passive attenuator? Where is usually it set on the range control when listening? Cranking a passive attenuator all the way up would be a good thing. Are you running out of range?
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    Bob Latino
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    Re: VTA ST120 Input Sensitivity

    Post by Bob Latino on Wed May 16, 2018 4:10 pm

    The input sensitivity of the new lower gain CCS driver board is about 1.3 - 1.4 volts for full output on the VTA ST-120.

    The 600 millivolts for 60 watts out noted by arledgsc is for the older 12AT7 board used prior to April of 2012

    Bob
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    sKiZo

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    Re: VTA ST120 Input Sensitivity

    Post by sKiZo on Wed May 16, 2018 6:46 pm

    How about running 12AY7's on low input? That should put you in the ballpark for gain?

    mazeeff

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    Re: VTA ST120 Input Sensitivity

    Post by mazeeff on Thu May 17, 2018 7:10 am

    My ST120 is working well using the 1 volt output on my DAC, even though I'm running below the max of 1.4 volts. 40 watts or so, into a nice pair of Klipsch Cornwall's still makes things VERY loud!
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    Kentley

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    Re: VTA ST120 Input Sensitivity

    Post by Kentley on Sun May 20, 2018 8:22 pm

    This brings up a topic which fascinates me, and which I've mentioned from time to time, in my inevitably non-techspeak manner. That is the sublety of soundscape when the relative levels of source, preamp, and power amp are fiddled with. My ears tell me that the whole "shape" of your sound is quite dependent on these balances. Which is why I advocate especially the obtaining of the stepped attenuator in ST-XXX models.
    One can materially change the way the system sounds by altering the levels. Nice to have sources adjustable as well; though I hear less difference, there is still a synergy which can be optimized to my taste. Try it. You'll love it.
    In tandem with the usual tube rolling, speaker placement, and room treatment odysissies, of course.
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    tubenutr

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    Re: VTA ST120 Input Sensitivity

    Post by tubenutr on Mon May 21, 2018 3:35 am

    Kentley wrote:This brings up a topic which fascinates me, and which I've mentioned from time to time, in my inevitably non-techspeak manner. That is the sublety of soundscape when the relative levels of source, preamp, and power amp are fiddled with. My ears tell me that the whole "shape" of your sound is quite dependent on these balances. Which is why I advocate especially the obtaining of the stepped attenuator in ST-XXX models.
    One can materially change the way the system sounds by altering the levels. Nice to have sources adjustable as well; though I hear less difference, there is still a synergy which can be optimized to my taste. Try it. You'll love it.
    In tandem with the usual tube rolling, speaker placement, and room treatment odysissies, of course.

    poppycock
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    Peter W.

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    Re: VTA ST120 Input Sensitivity

    Post by Peter W. on Mon May 21, 2018 7:56 am

    poppycock[/quote]

    Well... .
    Sometimes.
    Certainly multiple attenuators will wreak havoc if not properly managed. Reasons for them:

    a) A wild mismatch between the amp and the source. I have a number of pre-amps capable of putting out 12 V or more. Were "step one" at say, 3 V, a passive attenuator on the amp would be necessary.
    b) Feeding a non-attenuated source directly into the amp - such as a tuner without a VC - which, actually, is not a multiple. But, this does happen to be a very good reason to have a power-amp mounted volume control.

    Reason against them:

    If one has a proper pre-amp - that is one with a working VC, putting one in the amp is an additional point of signal management (distortion).

    A few very good pre-amps allow for matching output levels such that they all are controlled equally by the main VC. This is a nice feature, but I have always been suspicious of that additional control in the system. I am OK with varying the main VC between sources. Some are not.

    Note that I have mentioned nothing about sound-stage - that is an entirely different discussion, with electronics - given a minimum level of quality - having little impact, and then only after speakers, speaker placement, recording quality, room dynamics and much more. But too much signal management will make mush of about anything.
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    sKiZo

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    Re: VTA ST120 Input Sensitivity

    Post by sKiZo on Mon May 21, 2018 4:49 pm

    Poppycock?
    (I assUme we're not talking male representatives of genus Papaveraceae?

    And I agree with Kentley.
    (That may be a first, and I'm sure that has him worried)  What a Face

    Being able to control the line level at every step can make a substantial difference in what comes out the speakers. Each component is fed exactly what it needs for best performance at it's particular sweet spot. I've got attenuation at the pre and amp, as well as the individual sources, and sometimes the slightest tweaks can really make the music bloom or collapse.

    One advantage to having dual attenuators on an amp is they act to balance the system too ... that can change as the signal passes through the system, even more so as the system gets more complex.



    PS ... don't worry about unused watts ... even though I don't max the controls, I use every bit for head room when cranking it.
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    tubenutr

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    Re: VTA ST120 Input Sensitivity

    Post by tubenutr on Mon May 21, 2018 9:55 pm

    sKiZo wrote:Poppycock?
    (I assUme we're not talking male representatives of genus Papaveraceae?

    And I agree with Kentley.
    (That may be a first, and I'm sure that has him worried)  What a Face

    Being able to control the line level at every step can make a substantial difference in what comes out the speakers. Each component is fed exactly what it needs for best performance at it's particular sweet spot. I've got attenuation at the pre and amp, as well as the individual sources, and sometimes the slightest tweaks can really make the music bloom or collapse.

    One advantage to having dual attenuators on an amp is they act to balance the system too ... that can change as the signal passes through the system, even more so as the system gets more complex.



    PS ... don't worry about unused watts ... even though I don't max the controls, I use every bit for head room when cranking it.


    What I should have said, is the more devices in the chain, the more distortions are getting between the music and the ear. IMHO
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    sKiZo

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    Re: VTA ST120 Input Sensitivity

    Post by sKiZo on Mon May 21, 2018 11:46 pm

    Exactly why I try to keep things simple here ...


    mazeeff

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    Re: VTA ST120 Input Sensitivity

    Post by mazeeff on Tue May 22, 2018 5:02 am

    sKiZo wrote:Exactly why I try to keep things simple here ...


    sKiZoiD. You have a sickness, and may need some professional help! There must be $20,000 worth of gear there. That Sansui QRX-9001 is worth its weight in gold, in Japan! What happened to the simpler days, when we just had a turntable and amp?
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    CletusB

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    Re: VTA ST120 Input Sensitivity

    Post by CletusB on Tue May 22, 2018 4:20 pm

    sKiZo wrote:Exactly why I try to keep things simple here ...



    Holy Crap!    ......SWEET! Laughing

    mazeeff

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    Re: VTA ST120 Input Sensitivity

    Post by mazeeff on Tue May 22, 2018 5:55 pm

    Skizo's setup looks like one big giant ground loop to me! He must need that "noise reduction" unit to reduce the hum!


    Last edited by mazeeff on Wed May 23, 2018 6:44 am; edited 1 time in total
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    sKiZo

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    Re: VTA ST120 Input Sensitivity

    Post by sKiZo on Tue May 22, 2018 7:46 pm

    And yet it's dead quiet in operation. Only noise I hear is a slight hum in the center channel tube amp, but that's a 50 year old Williamson design, and it's to be expected ...

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