The mini but mighty underdog, 12AX7’s are one of the most important devices ever made, yet players and listeners alike consistently overlook them when considering how to improve the performance of their gear. Whether you are replacing the preamp tubes in your amp for the first time or are a certified tone snob (like us), here is our list of the best 12AX7 vacuum tubes ever made to help improve the performance of your gear:
Made in England through the heyday of valve electronics, Mullard 12AX7’s are seldom rivaled in both sonic quality and longevity. What really sets these tubes apart, however, is that Mullard preamp tubes are the most consistent valves ever made. That, coupled with their legendary tonal complexities, balance, low noise floor, and longevity make the Mullard 12AX7 the best 12AX7 ever made.
At Fuzz Audio, we test lots and lots of tubes, and with Mullard valves it is not uncommon for every tube in a batch to test nearly identical to one another (with balanced triodes as well). Even more remarkable, when we have lots of used tubes come in, the rejection rate of used Mullard 12AX7’s is much lower than for any other manufacturer. For an example, for every twenty low noise RCA 12AX7 black plate tubes we test, we probably throw away 2-5 tubes. With Mullard 12AX7’s, it would not be surprising to have zero rejects in a twenty-tube lot. Moreover, the Mullard 12AX7’s have the longest average lifespan of any preamp tube we know of, and they rarely go microphonic.
Mullard tubes are extremely well made, but they also sound extremely good in both audio and guitar amplifiers, which cannot be said about all high-quality tubes. In guitar amps, Mullard tubes are punchy, responsive and robust with a midrange kick. In audio applications, they are defined, full, and balanced with a slight emphasis in the midrange. All of these qualities combine to give us the best, most precise 12AX7’s history has to offer.
Notable brands who used vintage Mullard tubes:
You could easily make the argument that Telefunken 12AX7’s deserve the number one spot on this list and in our opinion the only reason why they come in second is because of Mullard’s freakishly consistent build quality. Otherwise, Telefunken tubes are superior to all others, no question.
What truly sets Telefunken preamp tubes apart is the way they sound. Of course, like Mullard, Telefunken’s build quality is top notch, and they too have lower rejection rate and longer life span than most tubes. But what really makes a Telefunken 12AX7 special is its tonal quality.
There are two main types of Telefunken 12AX7’s, smooth plates and ribbed plates. Smooth plates are legendary for their smoothness in tone, and this coupled with their dynamic range, balance and low noise floor makes smooth plates the best choice a listener could make for any HiFi amplifier. Furthermore, because smooth plates sound so smooth compared to any other tube, they are also a top choice for compressor/limiters and microphone preamps. However, the downside is smooth plates can sound a little sterile in guitar and bass amps, and thus they are application dependent.
Ribbed plates on the other hand are a better all-around tube and they sound great in any application. Unfortunately, they are not as smooth sounding as their smooth plate brother, but what ribbed plates lack in smoothness, they make up for in warmth, depth and punch, making them perfect for both guitar and HiFi amps. Beyond that, ribbed plates are an incredibly well-balanced tube with no real emphasis for high, lows or mids. They are also tight, punchy and responsive making them a great choice for bass guitar!
Notable brands who used vintage Telefunken tubes:
What do Teletronix LA-2A compressors, Fender Champs, and McIntosh monoblocks have in common? Well… they all relied heavily on RCA tubes through the glory days of their product lines, and because of this, some of the iconic tone we get from these devices can be directly attributed to the classic RCA tubes they used.
In many ways, RCA 12AX7’s are the opposite of Mullard and Telefunken examples. Mullard tubes have a robust midrange, while RCA versions highlight bass and treble. Telefunken tubes are smoooooth or even sterile sounding with a low noise floor. RCA tubes are warmer and tonally more complex, but they are also noisier on average.
RCA 12AX7’s are perfect for any guitar or music production device but they sound specifically good in American made guitar amplifiers. Whether you are looking to retube a Supro, Fender, Danelectro, Silvertone, Valco, Gibson, or a modern emulation/clone the first tubes you should consider are always RCA! If you are needing more information on specifically what tube types are best for you, check out our Buyer’s Guide and Plate Cheat Sheet.
Notable brands who trusted vintage RCA tubes:
Very similar to Mullard 12AX7’s, Amperex 12AX7’s are incredibly well built, but instead of the classic Mullard “pushed” mid-range, you get a balanced tube with more clarity and definition. These tubes are great for guitarist and bassist who like to play clean, or for audiophiles who are looking to add more clarity and definition to their system.
A great tube, that is becoming harder and harder to find as they grow in popularity, the Ei 12AX7 might just be the vintage tube you are looking for. These tubes sound stellar in both HiFi and guitar amp applications, and they have good lifespans. But what really makes them interesting is their uniquely warm and dark tone with an emphasis on the low ranges. If you have a shrill system, these tubes can help!