What are the best tubes for my amp?

When you are choosing new tubes to put into your amp, there are a number of different tubes and a number of different brands to choose from.

The two main considerations for new tubes for your amp are:

1. Which tubes you need to make your amp work
2. Which tubes you want to make your amp sound better

Which tubes do I need to make my amp work?

Of all the different amplifiers available, most amps will be designed with preamp tubes and power tubes.

Preamp tubes take the signal from the input – this might be a guitar, bass, microphone, audio signal etc. – and then amplify that signal to a much higher voltage that can then be used by the amplifier.

Power tubes take the signal that has been tone shaped by the preamp section, and then amplifies it to drive the speaker.

One of the easiest ways to work out what tubes you need for your amp is to use our easy select tube sets on our website. Find the brand of amp you use, then the model, and our drop down selectors will tell you which type of tubes you need and how many of each.

You can also look “under the hood” and look at what tubes are currently in your amp. Typically the tubes will be found at the back of the amp and can be seen, but some amps may require a back cover to be removed before you can visually inspect them.

Amps start as simple as one preamp tube and one power tube, and can go all the way up to 7 preamp tubes and four power tubes, as well as a rectifier tube. The Blackstar HT1 has only two preamp tubes, with the 12AU7 preamp tube being used as a power tube!

TIP: in some circumstances you can use different preamp tubes to the ones designated, however typically you cannot use different power tubes. As an example, you could substitute a 5751 or 12AT7 for a 12AX7 if you were looking for lower gain, however you can’t just plug in EL34’s if your amp is designed to use 6L6.

The 12A*7 family of preamp tubes are designed similarly, in that they use the same voltage and have very similar characteristics, whereas the different power tubes run on different voltages and have much different electrical characteristics.

If you were to use different power tubes without any changes to the amp, you are very likely to destroy the tubes, or blow up components in your amp – you have been warned!

Of course, there are always exceptions to the rule, and that is where the amp is designed to take different types of power tubes. Usually in these amps there will be a switch that will be flicked between say EL34 and 6L6, and then you can put the other type of tube in. The amp will need to be biased properly after changing between tube types, but this can make the amp quite flexible in getting different tones.

Which tubes do I want to make my amp sound better (or different)?

Once you have worked out which tubes you need to use in your amp, then there is the choice of tube brands.

How do I know which brand tubes are the best?

A lot of the choice in tubes comes down to preference. The style of music you are playing, whether you play on the clean channel and use pedals or use the overdrive channel, and most importantly what type of amp you are using.

Regardless of what tubes you choose, you won’t get that 5 watt Fender Champ with its 1 x 12AX7 preamp tube and 1 X 6V6 power tube sounding like a fire breathing high gain Peavey 6505 or Mesa Boogie Triple Rectifier.

Keeping that in mind, there are options with tubes that will add different flavours to the sounds you can get from your amp so you can tweak it to your tastes.

Preamp Tubes

The most common preamp tube in guitar amps is the 12AX7. This tube is used for both the musical sound it produces, but also because it has the highest gain rating out of the most common preamp tubes used. The gain rating scale of the most common preamp tubes is:

12AX7 = 100
5751 = 70
12AT7 = 60
12AY7 = 40
12AU7 = 17

However, even amongst different brands of 12AX7 there are differences in the actual gain ratings that are measured. Typically we measure the following gain ratings for each brand of 12AX7:

JJ – 100-105

Sovtek (12AX7LPS) – 100-110

Genalex 12AX7 – 95

EH – 90-95

Svetlana – 90-94

Mullard – 95

Tung Sol – 90-95

The higher gain 12AX7s will give more overdrive and amplification, which can be useful for high gain amps. It can also be useful for smaller amps that you want to drive harder. In those instances you would want to use a JJ or Sovtek 12AX7LPS for the high gain

Conversely, if you want to keep the signal a little cleaner then you would lean towards a Tung Sol or EH. The Tung Sol 12AX7 is our favourite for retaining some clarity in any amp, on both clean and gain channels.

Power Tubes

Power tubes operate differently to preamp tubes, and so the choice of tubes is also different.

The power tube will typically be a fixed choice i.e. EL84, EL34, 6L6 etc. You generally can’t swap in different types of power tubes like you potentially can with preamp tubes, unless your amp is specifically designed to take say both EL34 and 6L6. Even then, you have to ensure that the switch on the amp is set correctly so that you don’t blow the tubes, or worse still the amp itself.

Once you know what type of power tubes you need, then the choice just comes down to brand. This is a personal choice, and can be a combination of brand loyalty or choice of tone.

The overdrive on power tubes won’t typically be noticeable until the tubes are pushed harder, which means high volume i.e. normally 8+ on the volume dial. The louder you push the amp, the more the power tubes will overdrive, but at lower volume levels this won’t be as noticeable, so the choice of tube doesn’t have as much impact.

When your amp has either a pair (2), quad (4) or even sextet (6) of power tubes, then the power tubes should be matched.

All power tubes sold by AmpTubes are sold in matching pairs, quads and sextets by default. We know they need to be matched, so that is how they are setup in our store.

Conclusion

Choosing tubes can be either easy or hard, depending on whether you are searching something particular to influence your tone, or you just need new tubes to get back to shredding as quickly as possible.

One of the best way to get know your favourite tubes is to try our preamp tube sample set. Swap the tubes in and out of your amp to find your favourite tone amongst the options.

That is part of the fun of owning a tube amplifier. Try the different options and tweak the amp to find that tone that you are looking for – your distinctive tone.