and (b) there were a variety of 12AX7 type tubes from different manufacturers. I researched the interweb and found it full of claims about how different tube makes and models can radically change the tone of your amp, so I decided to do a simple scientific comparison and waited to be amazed. I recorded the same riff over a hastily recorded backing track using my G&L ASAT Special into a ’95 Fender Blues Junior. I chose the Blues Junior because tube changes take about 10 seconds compared with my Vox which would take about 5 minutes per tube.
Each take was recorded with a different tube placed in the V1 stage of the preamp. This is the amplification stage where the tube character is likely to show the greatest effect. Everything was recorded clean as the Blues Junior doesn’t really do dirty very well. No effects were applied. The preamp volume was adjusted to compensate for the lower output of some of the tubes, but everything else was kept the same.
Here’s a list of the tubes tested:
1) JJ 12AX7 (my own tube, already in the amp)
2) Electro Harmonix 12AX7
3) JAN GE 5751
4) Hammond 12AU7
5) TungSol 12AT7
The JJ 12AX7 was near new, but I have no idea about the history of the others. The Electro Harmonix was quite noisy with nothing plugged into the amp, but the others seemed OK.
Here are the sound clips.
JJ 12AX7
EH 12AX7
JAN GE 5751
Hammond 12AU7
TungSol 12AT7
Can anyone hear a huge difference? I can’t. I noticed subtle differences while recording the takes, and these are still audible in the recordings despite the mp3 compression. I’d say you could make the tubes sound almost identical to each other by applying some subtle EQ.
My first impressions while playing the riffs are below.
1) JJ 12AX7 – I like JJ’s. They’re bright and punchy without being shrill. They’re also very quiet when idle.
2) EH 12AX7 – I enjoyed this tube the most while I was playing. It was kind of warm and spongey and broke up really early. It was also the noisiest tube when idle. It may have seen better days. It didn’t record as well as I remember it sounding.
3) JAN GE 5751 – I really liked this tube too. It wasn’t as high in output as the 12AX7’s so needed a bit more preamp gain. But it stayed warm and clean.
4) Hammond 12AU7 – I disliked this tube. It was the lowest output of the bunch and sounded cold and sterile to my ears. There was virtually no response to picking dynamics. It made my tube amp sound like it was a solid state. I was surprised to find that it recorded rather well.
5) TungSol 12AT7 – I enjoyed this tube. In fact I left it in. Not quite as high gain as the 12AX7’s, but delivered a round, clean, velvety sound.
So there you have it. I think some of the internet myths about certain tube types giving a holy grail of tone are probably exaggerated. Other factors such as the amp, speaker, guitar and player are likely to be FAR more important IMHO. But it was fun doing the experiment. Aside from the 12AU7, I'd be happy to have any of the tubes in my amp.
. The recording is nicely done too, sounds very professional.
Ha! - ed