2023-07-17 16:01:00
When buying a tube amplifier, whether for headphones or speakers, probably, over time, the owner will realize that it is not enough to just plug it in for it to work perfectly. The reason for this is the operation of thermionic valves, also known as “vacuum tube” or “vacuum tube”. Learn how to make the best choice to use in your headphone tube amplifier in this article!
Currently, there are few valve production factories for use in audio systems. The reason for this is that the vast majority of amplifiers today are transistorized, also called Solid State (SS). However, there are those who like the sound result obtained when using tube systems and that’s why this content came, to help you know how to choose a good set of tubes and make it possible to extract the best from your amplifier.
How to look for the best tubes for your tube amp
Check out tips below to make it easier to find the best tube for your tube amp.
NOS valve boxes (New Old Stock). Source: Vitor Valeri
1 – Read your amplifier’s manual or visit the manufacturer’s website
The first thing to do is to find out which tubes are compatible with your amplifier (“amp”). Once this is done, note that each of the types (example: 6DJ8) has equivalent codes (6DJ8 = 6922 = 7308 = ECC88) and consequently will serve in your “amp”. However, please note that there may be differences in build quality for each of these nomenclatures.
Woo Audio WA3 Amplifier. Source: Vitor Valeri
In the case of the 6DJ8 tube, called ECC88 in Europe, we have the equivalent 6922 which are an improved version of the 6DJ8. The 7308 (CV4108 in Europe) is the highest quality version possible for this valve model, where the best quality materials are used and tests to check the quality after production. This also occurs for several other models, so it is recommended that you research these differences.
2 – Buy in stores or from sellers that offer some valve measurement
It is important to buy from sellers or stores that provide measurements on the valve you are interested in trading. The reason for this is that this information says about the state in which the valve is. As the best options are those that were manufactured before the 90s, you will see that there are many NOS (New Old Stock) models sold, which are valves that were never used, although their production has been stopped for decades.
Philips Valve 6DJ8 JAN NOS. Source: Vitor Valeri
To measure the operation of the valves, “pipe testers” are used, where data on their “health” and “quality” is obtained. Example:
– 14.8/14.3ma
– Gm=4000
Screenshot of the tubeworldexpress website. Valve Tester. Source: eBay
The closer the values in “ma” are, the smaller the difference between the transmission of the valve channels and the better the quality (if they are equal, it is perfection). The “Gm” informs the “health” of the valve, saying if it is weak or still has enough “vigor” to continue working for years. There is an ideal range of “Gm” for each valve, so it is worth researching what the average is for the specific model.
3 – Look for valves made for military purposes
The valves identified as JAN (Joint Army Navy) are those that were manufactured for military purposes, that is, they were used by the army and the navy. The reason for choosing these is simply due to the strict requirements that were made for the production of these models.
Sylvania valve box 6DJ8 NOS JAN. Source: Vitor Valeri
4 – Combined valves (matched)
The matched valves are used in amplifiers when there is a need for duos, quartets, among other sets, in the amplifier. Generally, in more “simple” designs of tube “amps”, you have a pair of smaller tubes, called “driver” [1]and a larger one, the “power” [2]. In the case of the mentioned project, where there are 2 “driver” valves, it is necessary that the measurements of the two are close so that they are combined and there is no great distortion in the signal.
Observation: There are also cases of tube amplifiers that use more than one “power” tube.
Sylvania matched valves. Source: Vitor Valeri
The greater the number of combined valves, the higher the price charged by sellers and stores. This causes many to opt for simpler valve models due to the high cost of matched valves.
[1] Driver tubes, also called input tubes or gain tubes, are generally used at the input signal of the amplifier and are generally responsible for providing the increase in signal level (gain). Usually they are small and don’t handle a lot of power, have low distortion and low noise.
[2] Power tubes, also called output tubes, are tubes with great power and are usually larger than “driver tubes”. They are responsible for giving the final gain to the output of the headphone amplifier.
5 – Whitish silver cover
The silver coating that is in certain regions of the valves helps to indicate when they are close to reaching the end of their useful life. Usually a valve like this makes a lot of noise or doesn’t work. So always ask for detailed pictures before buying a used valve.
Valve at the end of its useful life. Source: Vitor Valeri
Bonus 1 – Top tube amps: Table with compatible tubes
Check below a table (under construction) with the main tube amplifiers on the market and their compatible tubes.
Amplifier
Type
power valve (power)
Preamp tubes (preamp)
Darkvoice 336SE
OTL
6A7S, 6N5P
6N8P, 6SN7GB
Little Dot I+
Hybrid No EF95, EF92 and 408A
Little Dot MK2
OTL
6N6, 6N6P, 6H6N, E182CC, 5687, ECC99
6J1, 6AK5, 6AK5W, 5654, EF95, M8100, 6AK6
Little Dot Zero
Hybrid No 1K2, DF91, 1T4, W17
Woo Audio WA3
OTL
421A, 5998, 7236, 6080
6922, 6DJ8, 7308, E188CC, E88CC, ECC88
Xduoo MT-602
Hybrid None 6J1, 6AK5, 6AK5W, 5654, EF95, M8100, 6AK6
Xduoo TA-26
OTL
6A7S, 6N5P
6N8P, 6SN7GB
Related news
Bonus 2 – Where to buy tubes for your tube amp
Below is a list of the main reliable online stores to buy tubes for your amplifier:
This article is made in partnership with Grupo Fones de Ouvido High-End:
1689614373
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