Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups

Worthwhile retubing single tube Vox?

Discussion in 'Glowing Bottle Tube Amp Forum' started by Michael A., Jan 6, 2016.

  1. Zipslack

    Zipslack Tele-Meister

    Jun 8, 2011
    The Valve Reactor used a transformer with the tube as a mini-power tube and then amplified that up for the output. The Valvetronix did away with that and just use the tube as a starved-plated preamp to help filter the sound to be more tube-like (check the Valvecaster DIY pedal for's not a bad thing). It is not like the the Reactor and swapping will not have as much effect. Not sure which system your amp used.

    It's only a 12ax7....swap it and see. No need to go Telefunken or Mullard...find a cheap, common one like RCA. If it sounds better to YOU, then it's worth doing.

  2. Michael A.

    Michael A. Tele-Holic Silver Supporter

    Jan 12, 2013
    Virginia Beach, VA
    Thanks for the many replies, more than I expected.

    It does not sound like anyone has tried a swap in this particular amp. I guess I need a specific recommendation before I try a change. From the little bit I have seen, even RCA tubes are $40+, which is more than I want to spend in a $90 amp without an emphatic confirmation of an audible improvement.

    Thanks again, I'll do a bit more Googling to see if I can find someone who has upgraded this exact amp.

  3. john_cribbin

    john_cribbin Tele-Afflicted

    Nov 26, 2014
    You could do a lot worse than go onto www.valvetronix,net and post the question there. Very helpful group when I had a VT30, bet someone there has been down the same road with your amp.

  4. JD0x0

    JD0x0 Poster Extraordinaire

    Feb 22, 2009
    New York
    You dont need a NOS tube to improve over the stock Chinese tube, IMO. You could try a $10 JJ or a $16 Tung Sol and achieve results.

  5. mRtINY

    mRtINY Tele-Afflicted

    May 7, 2015
    You are mistaken.

    I have an older VT15. It definitely has the valve reactor circuit. There is a "Valve Reactor" series which doesn't have the digital effects (and they have analog pre-amps, I believe).

    I don't know if Vox was being obtuse to keep people from figuring out how to replicate the technology, or just figured most guitarists weren't savvy enough about electronics to bother being clear.

    ...really, what is starved-plate operation? Is there a voltage threshold for the bias voltage?

    ...does the phase inverter and center-tapped output transformer make it into a "mini" power amp? I have some Navy Radios that used 12ax7 tubes like that to drive the RF amplifier in a different box.

    Does anybody use their ears to decide if an amp is good or not anymore?


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