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My name is Stu. Stu Pid.

Okay--I think it will be obvious that even though I simply worship tubes (even though I have one and am about to get another SS amp) I don't know much about the theory behind them.

I'm getting a Vox Valvetronix amp. Probably the AD60VTX, and probably in about an hour hopefully. When I change the preamp 12AX7 that comes stock with the amp, can I just plug in the new tube and go or does it have to be biased or something. I just don't know if biasing means matching tubes to tubes or tubes to amp or whatever.

No biasing just plug and play. FWIW, an easier way to get the tube out is to remove the rubber ring around the hole and then use good quality packing tape to tape to the end of the tube, allowing a few inches to hang out. Then GENTLY rock the tube while pulling up with the tape. You will find out just how tight of an area the tube is in. There is physically no way for an adult sized hand to fit into this space.

Thanks for the tip. I've got a chubby hand, so that is a much appreciated bit of wisdom. Now if I could only get deadbeat relatives out of the house using the same method, LOLOLOL!!!

Unless the tube is bad, you may as well leave the stock tube in there. Putting in a different preamp tube will do next to nothing to improve the tone. I did some experimentation with different tubes in my Cambridge 30...no noticable change to my ears.

The tube or tubes in the Valvetronix amp are for the REMS technology.This technology is for the output stages of the amp.I'd only replace the 12AX7 if you're worried about reliability issues with some of today's preamp tubes....I use sparkplug wire removal pliers to pop my tubes out after removing the rubber ring like JM mentioned...

I read this in an ebay auction--

quot;WHEN I BOUGHT THIS AMP I UPGRADED THE TUBE TO A NOS MULLARD 12AT7TUBE. THE SOVTEK THAT COMES WITH THESE AMPS ARE CHEESY AND HARSH IN THE MIDS AND HIGHS. THE MULLARD TUBE MADE A TREMENDOUS DIFFERENCE I WAS ABLE TO PULL OUT THE SWEET SILKYNESS FOUND IN BOUTIQUE AMPS COSTING THREE TIMES AS MUCH AS THIS. ON THE DISTORTED MODELS THIS AMP WILL CRANK WITH A LOT OF MIDDLE WARMTH. ON THE CLEAN SIDE YOU GET A SMOOTH REACTION TO DYNAMICS.quot;

I just picked up the AD60VTX and one of the salesman had done the same with his and said it really improved the sound. He didn't put in a Mullard but he did change the Sovtek to I think a JJ 12AT7. The quote above was from an auction on the AD30VT


Originally Posted by 75lespaul
quot;WHEN I BOUGHT THIS AMP I UPGRADED THE TUBE TO A NOS MULLARD 12AT7TUBE. THE SOVTEK THAT COMES WITH THESE AMPS ARE CHEESY AND HARSH IN THE MIDS AND HIGHS. THE MULLARD TUBE MADE A TREMENDOUS DIFFERENCE I WAS ABLE TO PULL OUT THE SWEET SILKYNESS FOUND IN BOUTIQUE AMPS COSTING THREE TIMES AS MUCH AS THIS. ON THE DISTORTED MODELS THIS AMP WILL CRANK WITH A LOT OF MIDDLE WARMTH. ON THE CLEAN SIDE YOU GET A SMOOTH REACTION TO DYNAMICS.quot;

He is trying to sell the amp is he not? Try it for yourself and see, but I doubt you will hear any difference.

I swapped out the Sovtek 12ax7 for a JJ and really couldn't hear any difference. That said, it doesn't hurt to try different ones if you already have them. But I wouldn't go out to buy some nice expensive NOS tube expecting big changes.


Originally Posted by big_blackHe is trying to sell the amp is he not? Try it for yourself and see, but I doubt you will hear any difference.

Exactly--that's why I didn't bid on that amp, LOL. I should have put that in the post. I like to putz around a little with stuff so I'll try a few different tubes and in the end if there's no sound difference then I'll have spares for the future. I'm not that educated on tubes so I would of course believe you guys before A) an ebay auction and: B) a salesman--although I had already paid for the amp when I brought it up, and it wasn't the guy who sold me the amp.


Originally Posted by 75lespaulI read this in an ebay auction--

quot;WHEN I BOUGHT THIS AMP I UPGRADED THE TUBE TO A NOS MULLARD 12AT7TUBE. THE SOVTEK THAT COMES WITH THESE AMPS ARE CHEESY AND HARSH IN THE MIDS AND HIGHS. THE MULLARD TUBE MADE A TREMENDOUS DIFFERENCE I WAS ABLE TO PULL OUT THE SWEET SILKYNESS FOUND IN BOUTIQUE AMPS COSTING THREE TIMES AS MUCH AS THIS. ON THE DISTORTED MODELS THIS AMP WILL CRANK WITH A LOT OF MIDDLE WARMTH. ON THE CLEAN SIDE YOU GET A SMOOTH REACTION TO DYNAMICS.quot;

I just picked up the AD60VTX and one of the salesman had done the same with his and said it really improved the sound. He didn't put in a Mullard but he did change the Sovtek to I think a JJ 12AT7. The quote above was from an auction on the AD30VT

Sounds to me like some selling hype! I Put a set of NOS RCA 12AX7s in mine,but only because I had the tubes and could...I did it for reliability and long term mindset,but I can't say the amp took on a whole new personna with the RCAs? There was this placebo effect to where I thought the amp was warmer(maybe stronger though)after I switched the tubes...These RCAs are still in the amp and the amp is still working and sounding great...Guess it was worth it then?


Originally Posted by 75lespaulExactly--that's why I didn't bid on that amp, LOL. I should have put that in the post. I like to putz around a little with stuff so I'll try a few different tubes and in the end if there's no sound difference then I'll have spares for the future. I'm not that educated on tubes so I would of course believe you guys before A) an ebay auction and: B) a salesman--although I had already paid for the amp when I brought it up, and it wasn't the guy who sold me the amp.

Those tubes are a SOB to pull out of the bottom of that amp and you risk breaking the tube! Be careful and take your time...Remove the rubber ring around the tube first and quot;carefullyquot; find someway of pulling that tube out...I use Sparkplug wire pullers...It's a nice rocking while pulling motion in an effort of not breaking the glass tube..My amp had 2 like this!

Cool--I'll be careful, if I ever do it. I just bought two Mullards off ebay. Hopefully they're real. The seller had a feedback of over 3000 and tons of good feedback about Mullard tubes so what the heck. I'll toy around and hopefully I can hear a difference but I'll tell ya, It's sounding really good already. I don't know if anything I do will make it sound quot;betterquot;, only different. Well, maybe the speaker.


Originally Posted by 75lespaulCool--I'll be careful, if I ever do it. I just bought two Mullards off ebay. Hopefully they're real. The seller had a feedback of over 3000 and tons of good feedback about Mullard tubes so what the heck. I'll toy around and hopefully I can hear a difference but I'll tell ya, It's sounding really good already. I don't know if anything I do will make it sound quot;betterquot;, only different. Well, maybe the speaker.

The speaker will make the amp even smoother and less tight and hi fi sounding if you're comparing to the Celestion Neo-Dog speaker? Both of mine are currently for sale on E Bay and the V30s smoke these speakers!

Just took the back off the amp. Holy crap! I'm gonna see if you can just take the amp apart and pull it normally. More screws, more time but maybe it will be easier. At least the cabinet is wood, although the back is still the MDF or whatever you call it. Particle board.


Originally Posted by 75lespaulJust took the back off the amp. Holy crap! I'm gonna see if you can just take the amp apart and pull it normally. More screws, more time but maybe it will be easier. At least the cabinet is wood, although the back is still the MDF or whatever you call it. Particle board.

Even after you pull the chassis there's this metal shield around and in the way of the tubes....Stupid setup.I just carefully pulled the tubes out the bottom with a sparkplug wire puller with rubber tips....

Don't do anything right now to void your warranty in case you run into a problem with your amp..Hopefully you won't,but ya never know?

I changed out tubes in my preamp and noticed a significant change in tone, versus the stock tube. I would figure to have a decent ear. It was Sovtek. I ended up getting a Ruby ECC83, which is only $15, but incredibly smooth. Maybe it's just a higher treble cut, but as well, the mids were rich and full. I think this may have to do more with quality control, than actual difference in brands. Given a well made tube, the brand is probabily insignificant. But, unfortunately, it isn't always this way, although I wish it was.


Originally Posted by remingtonbo2001I changed out tubes in my preamp and noticed a significant change in tone, versus the stock tube. I would figure to have a decent ear. It was Sovtek. I ended up getting a Ruby ECC83, which is only $15, but incredibly smooth. Maybe it's just a higher treble cut, but as well, the mids were rich and full. I think this may have to do more with quality control, than actual difference in brands. Given a well made tube, the brand is probabily insignificant. But, unfortunately, it isn't always this way, although I wish it was.

If you're talking about the Valvetronix series the preamp tube(12AX7) isn't used as a preamp tube,but it's used to drive the power amp section...Read about the Valve Reactor technology in your manual or on the Valvetronix site...I always read through my owner's manuals at least twice so I get a full understanding of all the workings of my gear. REMS technology is used in the preamp section of these amps..Read about both,pretty interesting and new technology..

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