Hiss question on a tube amp

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Marcello, Jan 14, 2005.

  1. Marcello

    Marcello Member

    Messages:
    1,633
    Joined:
    Jul 15, 2004
    Location:
    Montreal
    Of course do we discuss something else than tube amps here :D

    Well, it may seem like a stupid question but here i go. I got a small tube amp, 20W, and when i turn it on, i hear a slight "shhhhh" noise coming from the speaker, i guess its called a hiss. To what extent is that noise a normal thing ?

    I know that amps produce some background noise, but even with my volume on zero i hear it. When i play it's drowned, my concern is mainly for recording purposes.

    Thanks
     
  2. aeolian

    aeolian Member

    Messages:
    6,083
    Joined:
    Apr 5, 2004
    Location:
    Santa Cruz, CA.
    Mostly hiss is thermal noise from the resistors. The big debate is whether to use quieter metal film resistors or the carbon comp ones since that's what the vintage amps have. Randal Aiken has a great bit on his web site about this.
     
  3. kannibul

    kannibul Member

    Messages:
    239
    Joined:
    Apr 27, 2004
    It could also be a tube causing it.

    Try replacing them, and see if it goes away =)
     
  4. Lonely Raven

    Lonely Raven Member

    Messages:
    1,003
    Joined:
    Jun 29, 2004
    Location:
    Bolingbrook, IL
    Single ended amps also have an inherent hiss to them.
     
  5. Andy H.

    Andy H. Member

    Messages:
    83
    Joined:
    Nov 8, 2004
    Location:
    Amsterdam, Netherlands
    A slight amount of noise is totally normal / healthy. Your amp is working!

    Signal to noise ratios usually render it pretty insignificant for recording purposes. But with computer recording software you can simply sample the hiss, and remove it later if needed.

    Andy.
     
  6. spentron

    spentron Member

    Messages:
    1,305
    Joined:
    Aug 2, 2004
    Location:
    RVA
    With an amp with only one volume control, most of the amp comes after the control, so the hiss will only increase near max. volume. With a master volume, still part of the amp has to be ready to go wide open. It's less of a tube issue than a gain structure issue, exactly the same as a case I saw of a plasma TV hissing because the volume was all the way up on the TV and set low on the cable box, if you'd like a modern example ;) .
     
  7. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    If hiss is excessive the preamp plate loads may be getting tired or may be under rated. In addition to (or instead of) going for metal films, you can substitute a higher wattage part. Digi-key carries a line of 1W carbon comps, but they go $2/resistor. 1W carbon films are usually a good compromise and go a mere $0.14 at Mouser.

    Another big source of hiss is cheap potentiometers in the tone stack and volume control (reg'lar ol' 1/2w carbon comps usually). Unfortunately, replacing with 2 watt conductive plastic Clarostats (or similar) can be an expensive venture.
     
  8. JimLamme

    JimLamme Member

    Messages:
    115
    Joined:
    Jan 4, 2003
    Hey Marcello,

    I used to have a 20w amp like that also. Even at zero there a was very noticeable hiss. I sent it back after changing the tubes didnt help the situation.

    Just curious, what kind of amp is it?

    Thanks.
     
  9. AlexT

    AlexT Guest

    I got so used to hiss that Amps with no hiss now sound un-natural.

    If it bothers you, you can always use an attenuator at 3 dB. The hiss will be mostly gone, and it will probably also fatten the sound if you are playing at lower volumes.

    My .02c

    Alex
     
  10. Marcello

    Marcello Member

    Messages:
    1,633
    Joined:
    Jul 15, 2004
    Location:
    Montreal
    a traynor YCV,pretty cool amp.

    Thanks for all the answers
     

Share This Page