The Dynaco Tube Audio Forum

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


    Hummmmm from double hockey stick

    Share

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Hummmmm from double hockey stick

    Post by Brutus63 on Sat Jun 07, 2014 7:52 pm

    scratch finally got my st-120 built, set bias, playing straight into tube amp out of iPod works great.
    When I hook up to BOTH marantz and pioneer receiver ,,, buzz city.
    The preamp out works,,,and is fine because that is what I had my old dynaco st70 hooked up to and had no problem.
    Sooooo iPod good,,, vintage receiver bad.
    Any hint of another direction I can go?
    VERY DISAPPOINT RIGHT NOW.
    Tom

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: Hummmmm from double hockey stick

    Post by stewdan on Sat Jun 07, 2014 9:41 pm

    Hi Tom --- can you please clarify your configuration ... "preamp out works fine"?  
    Which unit Marantz or Pioneer?  Do you have a Stereo Receiver and a Stereo Preamp or an integrated amplifier or some other hardware combination?

    If your receiver or integrated amplifier has Pre Out and Main In connections, you should be able (with all the power off) to pull the jumper wires from the Pre OUT and Main IN and go from Pre Out directly into the ST-120 Amp (bypassing the amplifier stage of the receiver or integrated amplifier), just like you did with your IPOD.

    Are all the power cords 2-wire or do you have a 3-wire power cord somewhere which is causing a ground loop, thus the buzzing you hear.

    Best I can do with the limited info.

    Please let us know more details,
    Stew

    j beede

    Posts : 328
    Join date : 2011-02-07
    Location : California

    Re: Hummmmm from double hockey stick

    Post by j beede on Sat Jun 07, 2014 9:43 pm

    Nothing to be disappointed about... We have all been there. If any of your pieces utilize a three-pronged mains plug, try inserting a 3-prong to 2-prong adapter and see if the hum vanishes. You have a ground loop meaning that you have more than a single ground reference in your system.

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Hmmm

    Post by Brutus63 on Sat Jun 07, 2014 10:01 pm

    Marantz is a two prong,
    St-120 is two prong
    I did go preamp out of marantz directly into tube amp
    Buzz city
    iPod same way, no buzz
    I'm using a marantz 2330b as a preamp (preamp out)



    j beede wrote:Nothing to be disappointed about... We have all been there. If any of your pieces utilize a three-pronged mains plug, try inserting a 3-prong to 2-prong adapter and see if the hum vanishes. You have a ground loop meaning that you have more than a single ground reference in your system.

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: Hummmmm from double hockey stick

    Post by stewdan on Sat Jun 07, 2014 10:13 pm

    Hi Tom --- if you still have your ST70 can you try the Marantz Receiver again and see if its PreOut is still Buzz-Free?

    Is your Pioneer also a receiver or something else?

    Stew

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Re: Hummmmm from double hockey stick

    Post by Brutus63 on Sat Jun 07, 2014 10:22 pm

    My old dynaco is in Nashville.
    Pioneer is a 5580 (sx-1050)

    stewdan wrote:Hi Tom --- if you still have your ST70 can you try the Marantz Receiver again and see if its PreOut is still Buzz-Free?

    Is your Pioneer also a receiver or something else?

    Stew

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Re: Hummmmm from double hockey stick

    Post by Brutus63 on Sat Jun 07, 2014 10:24 pm

    We tested the marantz preamp out to another receiver
    It worked fine so the preamp out works fine



    stewdan wrote:Hi Tom --- if you still have your ST70 can you try the Marantz Receiver again and see if its PreOut is still Buzz-Free?

    Is your Pioneer also a receiver or something else?

    Stew

    stewdan

    Posts : 161
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: Hummmmm from double hockey stick

    Post by stewdan on Sat Jun 07, 2014 11:05 pm

    Ok -- Marantz PreAmp Out works driving another receiver but buzzes when hooked to the ST-120. And both the Marantz and the ST-120 have 2-wire power cords.

    I have one of Bob's ST-120's and I drive it with just about anything, tube unit or solid state unit or IPOD and no Buzz..

    To me this sounds like a grounding issue between the Marantz and your ST-120 .... ???

    Or an impedance mismatch between the Marantz and the ST-120 .... no, can't be since you could drive you old ST70 with the Marantz.

    Sorry, I am out of ideas ... maybe Bob or one of the other guy's can suggest something.
    Stew

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Re: Hummmmm from double hockey stick

    Post by Brutus63 on Sun Jun 08, 2014 5:13 pm

    Update and solution.
    It was an assembly error on my builders part, not bob
    It wasn't really anyone's fault,, just a slight sodder drip that caused a short.
    Thanks Bob for all your help
    Tom

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Hummmmm from double hockey stick

    Post by Bob Latino on Sun Jun 08, 2014 5:42 pm

    Hi Tom,

    Glad to hear that your amp builder and you have got the issue under control. Sometimes just a little excessive solder can drip into places and cause a problem. The thing that was really strange is that the loud hum/buzz did not occur when you used the amp with your Ipod miniplug to dual RCA connector ? Maybe the RCA side of that connector was a hair smaller and did not short to the solder drip inside center pin of the RCA jack? Can't say for sure ?

    Bob

    Brutus63

    Posts : 7
    Join date : 2014-06-07

    Thanks

    Post by Brutus63 on Sun Jun 08, 2014 5:57 pm

    Bob,
    I appreciate your help and patience with me and my builder.
    Look forward to breaking this boy in
    Listening to some remastered zeppelin as we speak
    Thanks
    Tom

    Sponsored content

    Re: Hummmmm from double hockey stick

    Post by Sponsored content Today at 2:24 pm


      Current date/time is Sat Dec 10, 2016 2:24 pm