New VOX AC4TV owner; Do I need to bias when I change tubes?

Discussion in 'Amp Tech Center' started by Kloun, Aug 28, 2020.

  1. Kloun

    Kloun Tele-Meister

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    Sorry if this is a dumb question but if I want to change tubes in a Vox AC4TV, do I need to do any biasing or is it just plug the new tube in and play? I was searching the internet and it appears that no biasing is necessary, but wanted to double check. Thanks.
     
  2. Wayne Alexander

    Wayne Alexander Friend of Leo's Silver Supporter

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    Cathode bias. No need to adjust or change bias if you stay with the same type of output tube.
     
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  3. Dacious

    Dacious Poster Extraordinaire

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    Its worth just running the amp with the back off for a few minutes just to check the power tube doesn't redplate. It's very, very unlikely but always a slight possibility to get a tube that's bad out of the box.
    images (1).jpeg
    Just keep an eye out for this - the plate structure in EL84s you can see in the tube on the left is starting to overheat. Normally you will get horrible hums and/or buzzy staticky sounds. The tube on the right it's the heaters glowing which is normal and fine

    If it doesn't do this, and the amp is otherwise quiet with nothing plugged in and sounds normal when playing guitar you're good to go.
     
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  4. Kloun

    Kloun Tele-Meister

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    You guys are awesome. Thanks very much.
     
  5. El Marin

    El Marin Tele-Afflicted

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    Hi

    I would like to make you a question. I am in need of a small amp to carry everywhere... Does the AC4 has enough volume to play with a drummer?
     
  6. Jon Snell

    Jon Snell Tele-Holic

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    Depends how professional your drummer is. The more professional the drummer is, the quieter they can play and still retain a good feel.
     
  7. Kloun

    Kloun Tele-Meister

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    It's certainly small and easy to carry. If the drummer isn't John Bonham or intentionally tries to drown you out, I think it would work. It's pretty loud. Also, the amp is rated at 4 watts, but it is actually an 8 watt amp. Vox put in 16 ohm speakers to reduce the power of the amp, but if you use an 8 ohm speaker or an 8 ohm extension cabinet (which is what I have) you can use the full 8 watts. See this thread

    https://www.tdpri.com/threads/cool-information-about-the-vox-ac4tv-series.230846/
     
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  8. gusfinley

    gusfinley Tele-Afflicted

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    I built a little AC4 for myself with top boost channel and EF86 channel.

    I took it to band practice because it was easy to lug around.

    At the second band practice, the drummer said to me "That amp sounds great, but can it go any cleaner?" My response was "Not at this volume!"

    I brought my AC15 to the next practice.

    Of course at the show, the sound guy was mentioning how loud my AC15 was (as was the drummer). He asked how many watts it was and was surprised when I mentioned it was only 15 watts. I also mentioned that I only had the master volume turned up to 3.
     
  9. DougM

    DougM Friend of Leo's

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    I used to have a PV Classic 20 combo that I used to keep my bass player and drummer in check. If they started to creep up too much, I'd just tell them I was already dimed. But, they were very sensitive and professional players with great sense of dynamics, so it wasn't often a problem.
     
  10. Chiogtr4x

    Chiogtr4x Poster Extraordinaire

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    And to keep your gigs and get more of them!

    We ( now) know how to make our guitars and other electric instruments sound, whatever way we like them (for the music we play), at ANY volume, including quiet.

    At least this is my 'gig universe', and I love it. And venue managers/patrons do too!

    A good mature, dynamic drummer is the key, makes it all happen.
     
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  11. El Marin

    El Marin Tele-Afflicted

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    Good info, thanks

    Anyway, I have tried some 5Watters and I cannot use them with my drummer. I am using a 20Watts and will keep it
     
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