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13 comments / Posted by Bruce Ohms

EL84 Power Tubes

When you bought your tube amplifier a major factor was probably how good it sounded! You worked it hard for a long time and made a lot of great music with it, and then one day you noticed it just didn’t seem as awesome as you remembered it sounding. Or perhaps you were playing and one of the tubes died, leaving you wondering what it would take to bring it back to life? Sooner or later, every tube amplifier aficionado will have to face the confusing task of choosing replacement tubes for their amp. Let’s look at how you can sort through the hype, get the great sounding tubes you need and avoid paying more than you have to for them.

From groovy sounding brand names to ones that sound like rare jewels and precious metals, the tube marketing industry loves to sell us their quality. But are those expensive boutique brands that sell tubes from the same factory worth the extra money? Well, it depends. In order to make the right choice for your situation you’ll need to know a little bit about how tubes work, and a little bit about the tube industry. Let’s take a look inside the world of tubes.

Preamp tubes:

Choosing the right preamp tube is a subject all of its own. They do not have to be the same brand as your power tubes, nor even from one to the next. Since they are self-biasing in the circuit you don’t need them matched. With basic electronic safety skills most guitarists can learn to change their own preamp tubes without a technician. The fancy tube companies many times are not making the tubes, but they are doing secondary testing and separating the tubes into more categories for gain, output, microphonics and other characteristics. Different brands direct from the factory distributor will have different characteristics of gain and output also. You can save some money and buy a few different models and manufacturers to try out through the factory distributor. Then if you want to compare to a “higher end” tube you can try one of them. Carvin Audio sells the same tubes that come stock in the amplifiers, so if you want the same tone replace your Carvin amp with the same tubes. Note: Carvin Audio uses two different pre amp tubes, the 12AX7C which is a high gain tight low end preamp tube and the 12AX7JJ tube, which is a lower gain more broken up preamp tube at high gain settings.

Power tubes:

Now what is important for your power tubes is that they are reasonably well-matched, which is an industry term for selecting tubes in sets that draw the same amount of current under a given bias voltage. This matters because most amp designs do not have individual tube bias adjustments and the amp design relies upon both sides of the circuit amplifying part of the signal accurately. A mismatch will create distortion (of a type most musicians do not find appealing). While the fancy brands offer matched tubes, the factory distributors do too and sell them for a lot less. Either way you will still need your amp adjusted to the optimum bias voltage by a qualified technician.

So what advantage do the boutique tube companies offer? You can order matched tubes from the factory distributor, but they don’t distinguish between how much current those matched sets draw in the circuit (which is why the tech has to bias it). So the next set of power tubes you order from the factory may have an entirely different draw, and you’ll need to pay your tech to bias your amp all over again. Boutique distributors often sort their tubes by current draw (or “hardness”) and mark it on the package so you can ask for the same ones next time and put them straight in the amp without a tech adjustment. This can be convenient for the hobbyist who can afford it and an important advantage to a working musician that might need to replace damaged tubes on the road without test equipment or a technician.

There will always be lots of mystique and hype around tubes and tube products, but much of it is just that, hype. This does not mean that a particular company does not have a great product or new testing technique, but you will just have to dig in and do the research. For those just looking for a new set of tubes to get your amp back up and running, look into the tubes the amp came with and start from there. If you want the same sound, get the same or very similar tubes. If you want to experiment, try other brands or styles of the same type of tube.



  • Posted On August 26, 2016 by Brian

    Good article. Felt like it ended really early. Maybe cover tube power ratings and things of the sort in a different article.

  • Posted On August 24, 2016 by Monty Cole

    Well ok article.. Sort of left out what sound differences happen with different power tubes, or how bias affects the sound, or any effects they have, and why should we worry about biasing power tubes.. So I would say less flowery talk and more down to tacks talk. Maybe cause I’m sort of a teky . and the author is writing for melenials. but I think they too could appreciate some more detailed and dry Teck talk… good article thanks

  • Posted On August 24, 2016 by Richard H Mahan

    I have the V3M- head 50watts with all the bells and whistles I use my effects board for all the distortion & gain just use-ing the clean channel straight out of the front amp when I gig this work’s best for me because the preamp channel has two much compression causing feedback , not using direct box !Just mic-ing in front of four by four cab with vintage30’s and it work’s but I still get feed back at times if I’m to close to the amp is only set volume on two or two-n-half whats your sugestion?

  • Posted On August 24, 2016 by Edward Leverich

    I have a Carvin V3m.If ,and when, I need power tubes and purchase a complete set from you,Do I have to them Re-Biased? Thank’s Eddie

  • Posted On August 23, 2016 by Freddie

    I read the post about tubes and i have a question
    Ive own legacy 3 for about 2 years and i think its time to change the tubes, the tube stock now its PM el34 and 12ax7 china. It feels boomy on the low end and its not that i dont like but its not the type of tone what im looking for.

    If i want to change with another brand what the most fit for chunky growl and tight tone like slash tone type. Whats ur recomendation?


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