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Vacuum Tube Basics

Please ask us if there's a question we haven't answered here.

1. What do the numbers and letters in a tube's name mean?

There are several different tube numbering systems that you may see on tubes, which generally are a result of where they were built. Most commonly the numbers contain digits only (e.g. 5751), or are some combination of numbers and letters (12AX7, ECC83, CV4004). These different numbering systems may be from the American or British military, or from American or European industrial or consumer use, and then of course there are many strange exceptions. But to use the notation commonly seen in the United States, here is the meaning of "12AX7":

       12 - the filament voltage

       AX - an arbitrary model number

       7 - the number of internal elements, including the filament

      To make things more complicated, many tubes have letters after the name, such as 6L6WGB, 6L6GC. Sometimes these letters mean functionally nothing (design revisions) and sometimes they refer to different voltage capabilities of a given type.

      The bottom line for buying tubes for your amp: we list types together that will work in your amp without problems. There are many different tube substitution possibilities for those wishing to push the limits in the quest for unique performance, but our site is straightforward for those who just want to re-tube their amp without any extra concerns.

2. Why do some types have many different names?

As mentioned in the answer to the previous question, some types (usually the popular ones) are referred to by different numbering systems. For instance, what is a 12AX7 in the U.S. is an ECC83 in Europe is also a 7025 to Fender owners because for a while Fender sold tubes labelled 7025 that were a low noise 12AX7. These tubes are all the same thing.

3. Does any tube that fits in the socket work okay?

No. If you aren't sure why some weird tube is in the clearly labelled socket of the amp you just bought, ask us or pick up a handbook and check for yourself. There are thousands of tubes with identical basing, and the vast majority of them won't work in your amp.

4. Why are some old types more expensive than others?

Mostly, it's supply and demand. These tubes aren't being made anymore, and lots of vintage amp owners like to have a purely vintage rig, tubes and all. Also, much like vintage amplifiers and guitars (or vintage tuners and stereos), certain items achieve anointed status and their demand is even higher than usual, which also pushes the price higher.

5. I've got some old tubes. Would you like to buy them?

If they're in new condition and are old stock, send us your list.

6. Are new tubes from Russia and China as good as old tubes?

Yes. No. Maybe. This is one of those questions that answering can be problematic, because the answer is up to your ears. There are many good tubes being produced right now, and every company in the business has had difficulties with certain types. This has led to a bum rap for an entire industry that works very hard to reproduce tubes from "the good old days". It's also true that people with a garage full of vintage tubes tend to think they sound better, no matter what they hear. Most modern amps are designed around current production tubes for the good reason that they know you will be able to re-tube your amp in the future, and so these modern designs tend to sound best with current tubes.



7. How often should I change the tubes in my amp?

Like the previous question, this is a difficult one. A simple guide is to replace the power tubes twice as often as the preamp tubes, because they wear out more quickly. An amp that is used every day should expect to replace its power tubes every one or two years. If you notice lower output, strange noises, or a "muddier" tone, your tubes probably need replacing.

8. I can't find a certain tube on your site. Do you have it?

Probably not. Our website is updated every day, and new stock is added quickly. If you're desperate, send us an email and we'll see if we can find it for you.

9. Do you have brands like Siemens, Telefunken, or Mullard?

If we do, they're on our site. Many of these types are impossible to find in large enough quantities to do tube matching, but we do get them occasionally. If you see them available on our site, they usually won't be in stock for long!

10. My amp has a 7025 tube in it. Do you have it?

The 7025 was a tube that was sold by Fender as a low noise 12AX7. It hasn't been made for years until recently. Most current 12AX7 tube types will work however we now stock a 7025 that meets the noise specification and provides great tone.

11. What does "JAN" in a tube name mean?

The JAN designation is found on many American made new old stock tubes, and stands for "Joint Army Navy". It means they were originally built for the military, often with improvements in their construction and quality control.

12. What is "New Old Stock"?

Commonly known as "NOS," New Old Stock simply refers to tubes that were made years ago but have never been used. Much like antiques, "NOS" tubes are currently not being manufactured and this means their supply is dwindling while the price continues to rise.

thetubestore.com has over 1000 NOS tube types available. We have a few specially selected NOS tubes available as NOS Treasures.

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