The Dynaco Tube Audio Forum

Would you like to react to this message? Create an account in a few clicks or log in to continue.
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


2 posters

    intermittent hiss problem.

    baddog1946
    baddog1946
    baddog1946


    Posts : 319
    Join date : 2010-02-03
    Location : Costa Rica
    • Post n°1

    intermittent hiss problem. Empty intermittent hiss problem.

    Post by baddog1946 Sun Feb 17, 2013 5:03 pm

    A couple of days ago my ST-120 started to make a low level hiss on an intermittent basis. It disappears irregularly and there is no noise whatsoever when its gone, even with the volume jacked up.
    It seems completely normal but in a minute or so it begins again and cuts in and out. Before I pull it apart to check it out do any members or Bob have some suggestions on where to look first or some tests to eliminate the most common issues and a drawn out trial and error process? Any members help would be appreciated.
    Baddog
    • Back to top
    OnlineBob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3276
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by Bob Latino Sun Feb 17, 2013 5:22 pm

    Baddog,

    As a first try to remedy the issue ... Replace the CENTER driver tube with another tube and see if the hiss goes away . ...

    Also you didn't mention whether the hiss was on one or both channels ?

    Bob
    • Back to top
    baddog1946
    baddog1946
    baddog1946


    Posts : 319
    Join date : 2010-02-03
    Location : Costa Rica
    • Post n°3

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by baddog1946 Sun Feb 17, 2013 5:23 pm

    Both channels.
    • Back to top
    baddog1946
    baddog1946
    baddog1946


    Posts : 319
    Join date : 2010-02-03
    Location : Costa Rica
    • Post n°4

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by baddog1946 Sun Feb 17, 2013 5:32 pm

    Ok I swapped the center tube and it made no difference.
    Amp came on with the hiss steady but after a minute or so it became intermittent again.
    I am using 3 Mullard 4024 tubes in there which all test fine on my tube tester.
    • Back to top
    OnlineBob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3276
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°5

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by Bob Latino Sun Feb 17, 2013 7:44 pm

    Hi George,

    Your amp is about 3 years old .. It could also be a dirty tube socket on the driver board. Try cleaning the pins with some WD-40 and reinserting the tube a couple of times.

    Do a full voltage check on the amp as outlined in the manual. Listen to the amp as you make the voltage check. When the amp makes the hiss noise, see if possibly one of the voltage check points changes its voltage slightly during the hiss.

    Bob
    • Back to top
    baddog1946
    baddog1946
    baddog1946


    Posts : 319
    Join date : 2010-02-03
    Location : Costa Rica
    • Post n°6

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by baddog1946 Sun Feb 17, 2013 8:13 pm

    roger that thanks!
    • Back to top
    Sponsored content

    Sponsored content


    • Post n°7

    intermittent hiss problem. Empty Re: intermittent hiss problem.

    Post by Sponsored content

    • Back to top
      Current date/time is Mon Nov 25, 2024 11:54 am