VoxAC15's steady "shhhhhhhhh" = new tube time, yes?

Discussion in 'Amp Central Station' started by RoscoeElegante, Apr 19, 2019.

  1. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Sounds okay otherwise. But a very steady shhhhhhhhhhhhhhhhh = new tube time, yes?

    Had it five years and still on the stock ones, so I guess this question is as dumb as its asker.

    But is shhhh'ing a common symptom of shoddy/worn-out tubes? It's always done this to a degree, but is now much more prominent, especially if any EQing is done to boost its mids.

    And it runs apace w/ vibrato. Turn that up, and the shhhhhh'ing becomes shhSHHshhSHHshh, as per the vibrato speed setting.

    So, put a whole new set in (as I'm inclined to do), or do the one-by-one to see if it's only one or two tubes that need replacing?

    Thanks for your advice.
     
  2. Dacious

    Dacious Poster Extraordinaire

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    Depending on how hard you ran it tubes can last a fair while - if it changes with gain and EQ it might be a preamp tube, maybe it's cocked over and just needs reseating.
     
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  3. AJBaker

    AJBaker Friend of Leo's

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    Did you try turning off the volume on the channel you're not using?

    (Silly I know, but has happened to me)
     
  4. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Yes, I have. It occurs even then. (Just occurred to me: it would be a good effect if I had a steady-wind-at-the-shore song that needed an ending.)
     
    Last edited: Apr 19, 2019
  5. 1300 E Valencia

    1300 E Valencia Friend of Leo's

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    Unless there are other symptoms, this all sounds rather normal, especially if any control knob is over "5". The louder, the more noise. The more the knobs are turned up, the more noise.
    Still, EL-84 powered amps tend to run the EL-84s hard. If you don't have a matched pair of EL-84s for spares, now's a good time. Hiss might be one or more 12AX7, too, but pre-amp tubes don't wear out like power tubes, and may last many thousands of hours.
     
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  6. TheMindful

    TheMindful Tele-Meister

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    Some amount of shhh shhhould be normal. But my ac30 made some crazy noises as a precursor to needing a tube replacement (rectifier, as well as power, iirc)
     
  7. michiganguitar

    michiganguitar TDPRI Member

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    My AC15 is the noisiest of all the amps I’ve recently owned. Just bought a Morgan AC20 which is hard to tell if it’s even on sometimes whereas the Vox def has a hiss going on. The tubes are relatively new, btw.
     
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  8. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Plate resistors can cause hissssssssss.

    Esp carbon comp types.
     
  9. BobbyB

    BobbyB Tele-Afflicted

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    Swap the 1st pre-amp tube with another see if the hiss goes away.
     
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  10. SPUDCASTER

    SPUDCASTER Poster Extraordinaire Silver Supporter

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    Turn off your phase shifter.:lol::D
     
  11. DaveTone

    DaveTone Tele-Meister

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    Yup. Had this exact issue in my HRDx. I ended up replacing it with a 12AY7 and my mids are even more sparkly under drive.
     
  12. Mike Eskimo

    Mike Eskimo Doctor of Teleocity Ad Free Member

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    AC15 and AC10’s are hissy/white noise amps.

    New tubes or not.

    I dig em and currently own a 10 but quiet they’re not.
     
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  13. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Thanks for the feedback, everyone.

    Given the AC15's inherently hissiness/white noise-ness, how do people record 'em, and effectively-enough dial out/play over the white noise factor?

    I love the amp--it really is like another instrument--but the friend who manages our recording/producing keeps insisting that the amp is too noisy in the studio. He wants to go all straight-in and add effects/room qualities from there. Any suggestions that I can convey on how we can record w/ the Vox sometimes, too?

    Thanks again.
     
  14. 3-Chord-Genius

    3-Chord-Genius Poster Extraordinaire

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    Yeah, this exact same thing happened to me when I first got the AC15C1 and hadn't figured it out yet!
     
  15. Dismalhead

    Dismalhead Poster Extraordinaire

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    My AC15C1 had very fizzy tubes from the factory. I only heard it on note decay though. I replaced them within a month of getting it with Tung Sols and JJs. Now it sounds awesome. Yep, replace them. It'll sound a lot better than it ever has with the stock tubes.
     
  16. ce24

    ce24 Poster Extraordinaire

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    Yep had some hiss but with new JJs quiet as a mouse....along with some NOS RCA preamp tubes.....
     
  17. Les Paul lover

    Les Paul lover Tele-Meister

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    This is only partially true, re: a certain level of noise is to be expected.

    I used to accept it too, in all my amps.
    I've recently started to revalve all my amps with NOS ECC83, ECC81, 6P14P EV as substitute for EL84, and EL34.

    What has been astounding, beside the very noticeable improvement in sound richness, fullness and response, is how silent my amps are when running idle.

    Even with heavy gain and high volume, they are near silent when you stop playing. I wasn't expecting that as a bonus. A degree of hum isn t normal, though I used to accept it with modern valves.
     
  18. chet again

    chet again Tele-Meister

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    My AC15 is quiet. I put NOS EL84s in it when I got it. I think the preamp tubes are NOS too.
     
  19. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    You have a spare set of power tubes on hand and one of each preamp tube - right?

    If not - you should. EVERY tube amp owner should - tubes are fragile, glass items that can break. This is a question you should be able to answer yourself! It's as basic as jeeping a spare fuse on hand. Or guitar cord.

    First thing that came to mind here as well.

    To the OP - if tube swaps - and only swap out preamp tubes ONE AT A TIME and ALL the power tubes at once, separately - don't solve the problem you'll need to get the amp in to a qualified tech. It's not uncommon for AC15's and 30's to develop his from bad preamp plate resistors.
     
  20. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Thanks for your replies and advice, everyone!
     
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