12AX7 Amplifier Valve Reviews

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The humble 12AX7 ECC83 Valve is the most commonly produced and used Vacuum tube available today and still in current production by several large tube manufacturers. Largely renowned for its versatility, fantastic warm tone that valves are known for and an ability to produce pleasing overtones and distortion when overdriven in guitar amplification. This site has several audio reviews of four of the most commonly available and most popular valves currently available. Please click on the side links to read reviews of Tungsol, Sovtek, JJ and Electro Harmonix. More reviews may be added as and when in the future.

Sovtek

This is the most commonly produced and most popular 12AX7 valve in current production. The valve is produced in the large Russian Sovtek Factory. The valve is very good value for money and for that reason chosen by many leading Guitar amplifier manufacturers as stock tubes used in their equipment and often re-branded with the manufacturers logo. Sovtek also manufucture a 12AX7WB which is a high gain version of the WA.

The Valve offers a full warm tone with emphasised lower mid range frequencies. During our batch testing the gain factor tends towards the lower end of the spectrum coming in with an average gain factor of around 94. Sovtek do offer the higher gain 12AX7WB as an alternative but the price is significantly higher for the B variant.

Bass is plentyful and Treble is slightly rolled off. They sound reasonable in Guitar amps and Hi fi amps alike but in our opinion are generally out performed by the higher grade valves mentioned in our other reviews. 

Tungsol

The Tungsol 12AX7 is a high grade Russian valve. The valve is very well engineered and ruggedized using thick glass and firm internal supports. On test we very rarely see failures after burn in indicating good long term reliability. The gain factor of the valve is slightly lower than the average 12AX7 coming it at around 97 compared with the average 12AX7 valves tested which test out with a gain of around 100.

We found on audio test that Headroom was greater than other 12AX7's compared against and also that Noise floor was very low coming in at an average of 83dB compared with normal average noise figures for 12AX7 coming in at around 79dB. The valves sonic signature leans towards a slightly scooped mid range but very detailed and extended high frequency response and extended bass also. In Guitar application when the tubes are overdriven they respond with oodles of harmonics and really cut through the mix.

Like the EH 12AX7 the Tungsol valves show no heater glow when powered up. The heaters are concealed within the plate structure and do not show the familiar warm soft red light often associated with valves when lit.

In Hi Fi applications the valve shows excellent high end detail with fantastic separation. Stereo image is defined and life like. The bass is extremely controlled and tight which is a bonus with Hi Fi tube gear. Very musical and pleasant tone from this fantastic valve. We liked this one a lot.

JJ

The JJ ECC83 S is modelled around the original Telefunken boxed plate valve available in the mid part of last century and made famous by its clear mid range and articulate tone. The valve is manufactured by JJ Electronics (Former JJ Tesla) in Slovakia Europe. These valves are favoured by both Guitarists that use Valve amplification and Hi Fi enthusiasts. The tone is distinctly different from the Russian valves.

The Valve offers a slightly pronounced, clear and detailed mid range. During our batch testing the gain factor tends towards the higher end of the spectrum coming in with an average gain factor of around 104.

Bass and Treble are slightly rolled of which emphasises the clear and warm mid range. They sound great in clean Guitar amps such as the Fender line. When over driven the valve is very focused and tight which really lends itself nicely to sweet singing sustain in solo work with very little splatter and unpleasant overtones sometimes found in some valves when overdriven.

In Hi Fi applications the valve is good for taming down over bright and harsh loudspeakers. Detail in the high registers is slightly rolled off but the valve still shows plenty of detail and offers a good stereo image.

Electro Harmonix

The EH 12AX7 is a mid to high grade valve manufactured in Russia. The valve is well engineered and employs thick glass envelope and rugged internal supports. The valve has a similar double finned anode structure rather than the more commonly found box plate structure. These valves are used in most Electro Harmonix rack systems and guitar tube effects pedals.

In audio tests the valve produces a slightly scooped mid range frequency response. Bass is tight low and clear. Treble is extended bright and detailed. During our batch testing the gain factory tends towards the average value of 100.

They sound very different to the JJ ECC83s and in our opinion furthest removed from the tone that the JJ tubes offer. In Guitar amps such as the Fender line the tubes really shimmer. A lot brighter than the JJ valves and good for cutting across a loud drummer or Bass guitarist. When over driven the valve offers rich harmonic content and really cuts across.

In Hi Fi applications the valve offers great detail and tight bass.

Both the EH and the Tungsol valves have been manufactured with very tight and almost sealed finned plates which house the heater elements. The latest generation show little to NO familiar tube glow when in use. This may be an issue for High end Hi Fi users where the Glow coming from the tubes emphasises the beauty of the valves on show. If looks are important to you and you like to see the soft warm orange glow of the valves then the Tungsol or EH tubes may not be for you. Our opinion, Tubes are largely for listening to so we like these and give them a good rating.