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    Funny buzz in a VTA ST70

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    Dave_in_Va

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    Funny buzz in a VTA ST70

    Post by Dave_in_Va on Mon Dec 19, 2016 11:49 am

    I get a low level "buzz" (not a hum) through the speakers when my ST 70 is on. The funny thing is that it disappears completely and is dead quiet when I turn on the SP 14. Since 99.9% of the time I turn on the preamp before the power amp I had never noticed this before.

    Since I don't sit around listening to the sound of the power amp, this is really no big deal and I'm just kind of curious as to what is happening.

    (The buzz is not loud but I can hear it from ten feet away.)
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    peterh

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    Re: Funny buzz in a VTA ST70

    Post by peterh on Mon Dec 19, 2016 11:52 am

    Dave_in_Va wrote:I get a low level "buzz" (not a hum) through the speakers when my ST 70 is on. The funny thing is that it disappears completely and is dead quiet when I turn on the SP 14. Since 99.9% of the time I turn on the preamp before the power amp I had never noticed this before.

    Since I don't sit around listening to the sound of the power amp, this is really no big deal and I'm just kind of curious as to what is happening.

    (The buzz is not loud but I can hear it from ten feet away.)
    My guess is :
    60 hz with overlayed thyristor noice is present in the area, and as the preamp is off
    it has a high impedance. When the preamp is turned on it will have a much lower
    impedance, this will dampen the disturbances.

    Test this with shortening the inputs, if shortening silences then it's true.
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Mon Dec 19, 2016 12:04 pm

    Peter, do you mean to short the extra inputs on the SP 14?
    The only things plugged into the SP 14 are the PH 14 phono preamp and the output from my DAC into "aux 1".
    How would I do this?
    Thanks.
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    Kentley

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    Re: Funny buzz in a VTA ST70

    Post by Kentley on Mon Dec 19, 2016 1:54 pm

    I believe that Peter means to short the two ST-70 inputs. Disconnect the SP-14 (that in itself may cause the buzz to disappear!). Then take two RCA plugs with an inch of wire still attached (from an old cheep interconnect) and on each one connect the hot and ground wires together. These will short your ST-70 inputs when subbed for your regular IC from the SP-14. Keep these stashed in your accessory drawer. They come in handy.
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    peterh

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    Re: Funny buzz in a VTA ST70

    Post by peterh on Mon Dec 19, 2016 2:41 pm

    Kentley wrote:I believe that Peter means to short the two ST-70 inputs. Disconnect the SP-14 (that in itself may cause the buzz to disappear!). Then take two RCA plugs with an inch of wire still attached (from an old cheep interconnect) and on each one connect the hot and ground wires together. These will short your ST-70 inputs when subbed for your regular IC from the SP-14. Keep these stashed in your accessory drawer. They come in handy.
    Nice that someone understands me :-) Thanks!
    And Happy X-mas !
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    Kentley

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    Re: Funny buzz in a VTA ST70

    Post by Kentley on Mon Dec 19, 2016 2:47 pm

    "Nice that someone understands me :-) Thanks!" {Peter H.}

    Not only is your English fine for a second-language writer, but it is better than many native speakers. Cool  Enjoy the holidays!
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    Peter W.

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    Re: Funny buzz in a VTA ST70

    Post by Peter W. on Mon Dec 19, 2016 4:09 pm

    Kentley wrote:"Nice that someone understands me :-) Thanks!" {Peter H.}

    Not only is your English fine for a second-language writer, but it is better than many native speakers. Cool  Enjoy the holidays!

    The average American speaks only one language. Badly.
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Mon Dec 19, 2016 4:35 pm

    "The average American speaks only one language. Badly."

    Ullbay Itshay!
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Thu Dec 22, 2016 12:12 pm

    Peterh was right as the "buzz" almost disappeared when I unplugged the inputs. Then I plugged in the shorted RCA's and it went dead quiet.
    I guess this is just something present in the house wiring (or possibly my bucker or power strip)?
    I appreciate the advice.
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    Peter W.

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    Re: Funny buzz in a VTA ST70

    Post by Peter W. on Thu Dec 22, 2016 2:30 pm

    OT:

    Some observations on extraneous hum, buzz and other artifacts. With apologies to Robert Heinlein.

    We are living in a world with a great deal more rF going on since the advent of the ST70, PAS2/3/3x and more. And the in all sorts of frequencies, generated locally and at a distance.
    Things are talking to other things all around us, locally and at a distance. WiFi, cell phones, garage door openers, rF remote controls and much more. Even thermostats to our computers, cell phones and Fit-Bits and more. Which are talking back.

    Look at a phono or auxiliary input on a pre-amp. What is it? But a series of components on a wire. And if that input is not 'shorted' it is the functional equivalent of a very short antenna, with various inductors, diodes and other bits in the system.

    It is no surprise to me whatsoever that this sort of stuff goes on, and much more so than in the past. I remember distinctly the day that I got a "BREAKER BREAKER..." message on my AR receiver through the phono input. One of the rivets had some corrosion on it - and that copper-oxide salt apparently rectified CB enough to cause the phenomenon. How did I make the connection? AR, in one of their several "white papers" mentioned that this had happened elsewhere - and when I checked, there that bit of copper corrosion was as-predicted.

    So, guys and gals, what with all the rF going on all around, inside and over us, SHORT THOSE INPUTS when not in use. All of them. I would not be willing to state that even a not-used input could not resolve enough rF to cause a problem nearby.

    Thoughts?
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Thu Dec 22, 2016 2:54 pm

    Peter W.,
    Do you mean I should short all of the currently unused inputs on my SP 14 preamp?
    Thanks.
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    Peter W.

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    Re: Funny buzz in a VTA ST70

    Post by Peter W. on Thu Dec 22, 2016 3:01 pm

    Dave_in_Va wrote:Peter W.,
    Do you mean I should short all of the currently unused inputs on my SP 14 preamp?
    Thanks.

    Yes, I do. I do that with both my tube and SS equipment. Does it make a difference? Not sure other than it is mighty quiet when not actually making music. Use those old patch-cord ends. Beats sending them to the landfill.
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Thu Dec 22, 2016 4:18 pm

    I ordered 20 shorting plugs. I could have made some more but I figured I'd drop $20 on neatness.
    When they get here I'll let you know if that buzz cleans up.
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    cci1492

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    Re: Funny buzz in a VTA ST70

    Post by cci1492 on Thu Dec 22, 2016 10:01 pm

    Peter W. I had to move my router to another room because my subwoofer every once in a while would make a very low but noticeable weird noise. Went nuts with that one. My M125s put out AM radio super low when the pre-amp is off. Once pre-amp goes on, dead silent....go figure.
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    Dave_in_Va

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    Re: Funny buzz in a VTA ST70

    Post by Dave_in_Va on Sat Dec 24, 2016 7:00 pm

    Late Christmas Eve many beers/NFL "buzz" update:

    My shorting plugs arrived in the mail and I immediately installed them in all open "inputs" on my SP 14 (and also my ancient Audio Control EQ in the loop).

    WOW!! Actually DEAD quiet.

    Well, actually just dead. No sound. I finally figured out I had shorted the extra set of outputs on the SP 14 which must be wired in to Output 1.

    Fixed that and the original buzz is still there but WAAAY reduced. Probably by 90%.

    So anyway, thanks Peter in Sweden and Kently in Ma.

    Happy Holidays.

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