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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    VTA MKIII noise floor.

    Bryans12v
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    Bryans12v


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    Join date : 2016-10-04
    • Post n°1

    VTA MKIII noise floor. Empty VTA MKIII noise floor.

    Post by Bryans12v Sun Dec 09, 2018 3:12 pm

    Built a pair of new VTA MKiiis a few years back. Didn't use them much but when I did I was pairing them with original large advents.

    Hooked them up today to my altec votts and the background noise is unbearable. Is there something I can do to quiet these things down?
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    Blitzen
    Blitzen
    Blitzen


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    Join date : 2009-07-10
    • Post n°2

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Blitzen Sun Dec 09, 2018 8:59 pm

    I don't believe VTA ever did a MK III. Are you sure that's what you have?
    In any case, there should be little to no noise depending on the efficiency of your speakers. With high-efficiency speakers like your VOTTs, you should only be able to hear a slight hiss (if that) with your ear up close to the horn.
    I can't find any efficiency specs for VOTTs; there are many models. My Klipsch at 102dB (high!) efficiency speakers exhibit noise like I stated earlier with my VTA 70. Almost none!
    There is something wrong with your amps if there's noise; what is the noise like?
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    Bryans12v
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    Bryans12v


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    • Post n°3

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Bryans12v Sun Dec 09, 2018 9:54 pm

    My apologies. They are mkiii kits with the octal tubes 4 hifi driver boards. I swapped tubes but still buzzing. Tonight I pulled the Inputs and popped in shorting plugs and it went away. I'm using a marantz receiver as a preamp and as soon as I plug in the input the noise is present even with the receiver off and gets louder when the marantz is turned on. It can only be heard with the volume all the way down. It did this also with a marantz 3800 preamp as well.

    It's a buzzing sound like a guitar amp.
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°4

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Bob Latino Sun Dec 09, 2018 10:06 pm

    Bryans12v wrote:My apologies. They are mkiii kits with the octal tubes 4 hifi driver boards. I swapped tubes but still buzzing. Tonight I pulled the Inputs and popped in shorting  plugs and it went away. I'm using a marantz receiver as a preamp and as soon as I plug in the input the noise is present even with the receiver off and gets louder when the marantz is turned on. It can only be heard with the volume all the way down. It did this also with a marantz 3800 preamp as well.

    It's a buzzing sound like a guitar amp.

    If either the Mark III's with the VTA driver board or the Marantz preamp or any other piece in your music system has a 3 wire cord, try floating the ground on that piece with a 3 to 2 wire "cheater plug" on any piece that has a 3 wire cord. If the amp does not hum/buzz with the inputs shorted, then the amp is not the cause of the hum/buzz.

    Bob
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    Bryans12v
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    • Post n°5

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Bryans12v Sun Dec 09, 2018 10:24 pm

    Will try that. Now that I realize it, the mkiiis are the only components that have a 3 wire cord. Will try floating them.

    I really appreciate the advice.
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    Bryans12v
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    Bryans12v


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    • Post n°6

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Bryans12v Mon Dec 10, 2018 8:01 pm

    So I picked up the cheater plugs today and gave it a whirl, it sounds better now, not perfect. Here's a video if it.

    After this I finally got around to pairing them with a pas3x and the noise is all but gone. Now, however, I'm getting a wicked snap when powering off. In any ideas?
    Here's the video
    https://youtu.be/xCsn69292yI
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    Bob Latino
    Bob Latino
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    • Post n°7

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Bob Latino Mon Dec 10, 2018 8:23 pm

    Bryans12v wrote:Now, however, I'm getting a wicked snap when powering off. In any ideas?

    Either try a new power switch OR try placing a small .022 uF @ 250 volt film capacitor across the two terminals on the power switch.

    Bob
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    Peter W.
    Peter W.
    Peter W.


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    • Post n°8

    VTA MKIII noise floor. Empty Re: VTA MKIII noise floor.

    Post by Peter W. Tue Dec 11, 2018 10:27 am

    Bob Latino wrote:
    Bryans12v wrote:Now, however, I'm getting a wicked snap when powering off. In any ideas?

    Either try a new power switch OR try placing a small .022 uF @ 250 volt film capacitor across the two terminals on the power switch.

    Bob

    That capacitor must be X-rated if across the terminals.
    That capacitor must be Y-rated if from one of the terminals to-ground (chassis).

    https://www.mouser.com/new/Kemet-Electronics/KEMET_XY_Film_Caps/  

    The MKIII OEM did not have a grounding cord. Installing such is a recipe for trouble. They should be replaced with two-conductor, polarized cords with the hot side to the switch. Check for any stray current from the chassis to a known-good ground. And, make sure that the RCA-jack grounds (shell) are properly connected, and that the patch-cord shell is making good contact - both ends.

    Then, check your wallplate to make sure it is wired correctly. You would be shocked (pun intended) to learn how often they are miswired.

    https://www.homedepot.com/p/Receptacle-Tester-400-029/206303234?MERCH=REC-_-PIPHorizontal2_rr-_-206212329-_-206303234-_-N  

    One of these should be part of your go-to toolkit.
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