The 12AT7 might not be the first tube you think of when determining which tubes to upgrade in your amp, but underestimating their importance is a huge mistake. 12AT7 tubes can control things like how rich your reverb or tremolo is, or define your amp’s headroom and distortion characteristics through the phase inverter (PI). Whether you’re a seasoned tone chaser or just embarking on your tube amp journey, selecting the right 12AT7 can make a world of difference in your rig’s overall sound and performance. In this guide, we’ll dive into the key factors to consider when choosing the best 12AT7 vacuum tube for your setup, helping you unlock the full potential of your amplifier and achieve the tone you’ve been dreaming of.
A Brief Overview of the 12AT7
The 12AT7 might not be the first tube you think of when determining which tubes to upgrade in your amp, but underestimating their importance is a huge mistake. 12AT7 tubes can control things like how rich your reverb or tremolo is, or define your amp’s headroom and distortion characteristics through the phase inverter (PI). Whether you’re a seasoned tone chaser or just embarking on your tube amp journey, selecting the right 12AT7 can make a world of difference in your rig’s overall sound and performance. In this guide, we’ll dive into the key factors to consider when choosing the best 12AT7 tube for your setup, helping you unlock the full potential of your amplifier and achieve the tone you’ve been dreaming of.
Determining the Role of Your 12AT7 Tube
A 12AT7 tube serves various critical roles in audio amplification circuits. As a reverb driver, it amplifies and shapes the reverb effect, determining its richness and character by controlling the echo’s size and warmth. In the phase inverter position, it converts a single-ended input signal into a balanced, phase-split output, essential for driving push-pull amplifier stages, improving power efficiency and reducing certain types of distortion. Additionally, as a gain stage tube, typically placed at the start of the signal chain, it amplifies weak electrical signals, preserving audio integrity, maximizing dynamic range, and contributing to cleaner and faithful audio reproduction, especially in high-fidelity applications where tonal balance and low noise are critical. Before we can say what 12AT7 is best, we need to know its function.
Unfortunately, there is no trick to discovering what your specific 12AT7/ECC81 is doing within your amp. Your best bet is to google your specific amp model and for mostly any major brands like Marshall, Fender, Vox, McIntosh, Marantz etc. you are likely to find your answer on a blog or website article. However, there are many amplifiers out there where this will not be the case and you may not be able to find a blog with the correct information. If this happens, you either need to find the schematic and investigate how the tube is being used in the circuit, or even experiment by removing the tube to see what happens. If all else fails give us an email at support@fuzzaudio.com and we can take a look at a schematic and help troubleshoot.
The Best 12AT7 for Reverb Drivers
A reverb driver tube in a guitar amp makes the reverb effect louder and sends it to the reverb tank, which is where the echo is created. Imagine it like this, when you pluck a guitar string, the tube takes that sound, makes it bigger, and then throws it into a room where it bounces off the walls to create an echo before it comes back to you. This echo is what you hear as reverb, and the tube helps decide how big and rich that echo sounds. This is why picking the right reverb driver is so important.
Great reverb is deep, wide, warm, and natural. So naturally, these are the qualities we look for when picking 12AT7 tubes for use as a reverb driver. Beyond tonal quality, reverb drivers need to be robust, strong, well built tubes. This is because reverb drivers operate under a relatively intense load, which can lead to tube failure over time if the tube is not of a high enough quality. Furthermore, because reverb drivers are somewhere in the preamp stage of the amp, a microphonic 12AT7 will ruin the sound of your amp.
1. RCA and GE 6201/12AT7 Black Plate
Because reverb drivers need warm, natural, robust sounding tubes we typically recommend vintage American made black plate 12AT7. You can read more about black plate tubes in our “Plate Cheat Sheet” but in short, black plate tubes are known for their deep, warm, natural tone so they are a perfect fit. There is only one catch with black plate tubes, if you are moving your amp around often black plate tubes, depending on type, can be sensitive to movement which can lead to failure. This is why top of the line black plate options like the RCA and GE 6201, with plate suspension rods, are superior to all other tubes ever made for driving reverb.
2. Vintage Telefunken and Mullard 12AT7/ECC81
After USA black plate tubes, vintage Telefunken and Mullard 12AT7 tubes are top choices for lush and warm reverb. With a vintage Telefunken 12AT7 you can expect a very similar sound to an American black plate tube, where you will sacrifice some depth and warmth for an extra low noise floor and a more forward reverb sound. Similarly, Mullard 12AT7 may lack warmth compared to the USA black plates, but what they lack in warmth they make up for in loudest and strength. If you think your device has weak sounding reverb, adding a Mullard 12AT7 will bring it back to life.
3. Vintage USA Made 12AT7
If the above tubes are out of budget or seem like overkill, pretty much any vintage US made 12AT7 will be fantastic in the reverb driver position. Many tube junkies might recommend tubes like the RCA black or grey plate 12AT7, and these are indeed great options, but so too are the equivalent examples made by GE, Sylvania, Tung-Sol and Raytheon. If you are stuck not knowing which of these many options to choose, we like Sylvania black plates and GE grey plates over more popular options like RCA and Tung-Sol for this application.
Choosing the Best 12AT7 Tube for Your Phase Inverter
A phase inverter tube serves to convert a single-ended input signal into a balanced, phase-split output. It essentially creates two signals, one that is in phase with the original input and another that is 180 degrees out of phase. This phase-splitting is crucial for driving push-pull amplifier stages, where each signal phase drives a separate set of power tubes. By doing so, it enables the efficient amplification of both halves of the audio waveform, improving power efficiency and reducing certain types of distortion. Additionally, because the phase inverter is still a gain stage tube, it plays a role in defining the overall tonal characteristics and dynamic response of the amplifier.
1. Vintage European 12AT7
European tube manufacturers are really good at producing tubes that are both durable and balanced, so it’s no surprise that brands like Amperex, Telefunken, Mullard, Mazda, Brimar, and Siemens lead the pack when it comes to picking the best tubes for your phase inverter. Phase inverters have the important job of splitting the signal into two parts, and that means the tubes have to be super strong and balanced to get it right. You won’t find any tubes tougher and more dependable than the ones made in Europe, because they’re all about that consistency. This dedication to quality is what puts European-made tubes in a league of their own, especially in high-precision tasks like phase inversion.
2. Sylvania and Philco 12AT7
For the discerning ear of a musician or audiophile, especially when budget is part of the equation, Sylvania and Philco 12AT7 tubes make amazing phase inverters. Unlike their European counterparts, which come with a premium price due to scarcity, these North American tubes are readily available and won’t stretch your finances. These American made tubes are known for their robustness and stability, which translates to reliable performance and quality sound from your amp. So if you’re looking to upgrade or replace your phase inverter and want to do it without significant expense, Sylvania and Philco tubes are a no-brainer! If you are looking for clarity and headroom go for grey plates, if you would like more warmth and a richer overdrive sound go with black plates!
3. RCA, GE & All Other US Brands
RCA is one of our top selling tubes for the phase inverter position, especially in Fender amps. They offer excellent warmth and clarity that can really help give your tube amp some depth and richness. But there is a catch with RCA tubes, they are rare and popular. Therefore, their price is inflated due to demand and scarcity. Are they great tubes and do they make excellent phase inverters… yes! Yet, on the other hand, Mullard and Mazda are supior options for the PI position and they are nearly the same price. Moreover, Sylvania/Philco options are cheaper and will do the job just as good, if not better as well. Beyond all that, brands like GE, Tung-Sol, Raytheon, and Westinghouse all make fantastic sounding options that are very comparable to RCA examples.
(Please note: this logic does not carry over to 12AX7 or other valves. This advice is specific to vintage made 12AT7. Vacuum tube manufacturers each had their stregths and weaknesses when it comes to making particular valves.)
4. Modern 12AT7
Just kidding… There is never any reason to by a modern 12AT7 tube when you can find a vintage 12AT7 for the same price. Try a vintage Japanese 12AT7 if you are still looking to explore reverb driver options.
Best 12AT7 for Gain Stage Tubes
Before delving into the best gain stage 12AT7 tube, it’s crucial to understand what a gain stage tube is and what it does. In essence, the preamp gain stage, typically placed at the start of the signal chain, amplifies a weak electrical signal and boosts it to a suitable strength for further processing through the remaining chain of tubes. This initial amplification is essential for preserving the integrity of the audio signal and ensuring that it can be effectively manipulated and shaped by subsequent components in the audio system, such as equalizers, compressors, and mixers. By adding the right tube at this stage we can control the character of the entire amp, like while maximizing the signal’s dynamic range, ultimately contributing to cleaner and more faithful audio reproduction.
• The Optimal 12AT7 for High-Fidelity Stereo Amplifier Gain Stages
It’s worth noting that while it’s not a common practice, the use of 12AT7 tubes in the gain stage preamp section of high-fidelity stereo amplifiers can have a significant impact on sound quality. European-made 12AT7 tubes are particularly recommended for these units because they excel in delivering the essential qualities required in high-fidelity audio systems. In the realm of hi-fi, where dynamic range, tonal balance, and low noise are paramount, the choice of the right tube can significantly influence the overall sound quality of the entire audio system. Vintage European valves stand out as the top choice for this application due to their ability to provide a broad dynamic range, tonal balance, articulation, and maintain an exceptionally low noise floor, ultimately contributing to a cleaner and more faithful audio reproduction..
• The Optimal 12AT7 for Guitar Amplifier Gain Stages
If you want to add headroom to your guitar amp or just trying to tame it out a bit, installing a 12AT7 in place of one of your 12AX7’s could make you fall in love with your amp all over again and ultimately save you hundreds in not having to buy a new amp just to get some clean tones. If you do decide to go down this route, and you want to add a 12AT7 into the gain stage of your amp, we recommend Vintage USA 12AT7 for the job. Specically, you want to try black plates for extra warmth and depth or grey plates for a little extra twang.
Why vintage USA tubes? In our opinion modern made 12AT7 sound shrill and have too shirt a life span to justify their price. While European 12AT7 on the other hand are just too sterile sounding. This leaves the natural warm and rich sounding American tubes as almost a no brainer choice for most guitar amp gain stage applications. Try brands like Tung-Sol, GE, Raytheon, and Westinghouse… an maybe you have heard before… RCA is pretty good too.