Chasing a hiss in a Hayseed 30

Discussion in 'Amps and Cabs' started by deluxeman, Apr 14, 2016.

  1. deluxeman

    deluxeman Member

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    I have a Valvetech Hayseed 30 with the EF86 channel. It has developed a hiss that gets louder as you increase the volume. I have retubed it completely with new tubes, Power, preamp and rectifier tubes. Anyway, it was better but not as quiet as it was, so I email Rob at Valvetech to see if I could get it in to him to check it out. He sends me back a reply stating that a hiss is normally a tube issue. This sounds reasonable to me so now I get to try to find a bad tube.

    So I am looking for a good, fast way to find the culprit. I am sure many of you have done this same thing, I am looking for any hints, tips or tricks to make this as painless as I can. I have a few known good 12ax7's and a good EF86. I am not sure I have 4 EL84's though.

    Thanks for the help.
     
  2. s360guitarist

    s360guitarist Silver Supporting Member

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    Original owner? Was all good then the hiss started? All outlets? With/without pedals? All guitars? Etc...

    Guessing an entirely new tube set could rule out tubes?
     
  3. deluxeman

    deluxeman Member

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    It will hiss with or without anything being plugged in.
     
  4. Dr.Picklebottom

    Dr.Picklebottom Member

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    if it was hissing, you replaced all the tubes, and its still hissing that would suggest its not the tubes. the varying level of hiss would be a function of the new tubes having different specs and operating at different levels. of course you could have happen to acquire 2 faulty tubes that have the exact symptom but thats beyond unlikely.
    based on that i wouldnt waste anymore money buying new tubes.
     
  5. misa

    misa Supporting Member

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    What tubes does your amp use? I'm guessing an EF86 preamp, two 12AX7s for the second channel preamp, a 12AX7 phase inverter, a GZ34 rectifier, and a quad of EL84s for the power section.

    If you pull all of the preamp and the PI tubes out and its still hissing, then you can pinpoint it to the rectifier and power tubes or the circuitry around that. If the hiss is gone, then you know its in the preamp section. You can then pop the PI tube in and check. Then the EF86 tube and check. The second 12AX7 preamp tube and check. And finally, the first 12AX7 preamp tube and check. Some people may prefer to leave all the tubes in and then work backwards, pulling only one tube beginning with the PI. The benefit I find with removing all preamp tubes is that you witness the absolute minimum hiss you're going to be able to achieve without mods and part changes (and there usually is a little bit).

    It isn't always a tube's fault, but it is a good place to start. Here is some more troubleshooting info for hiss: http://www.geofex.com/ampdbug/hiss.htm
     
    Last edited: Apr 15, 2016
    csweldon, deluxeman and 71strat like this.
  6. deluxeman

    deluxeman Member

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    Thanks for the great info. That is why I am a member here!!!
     
    misa likes this.

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