Preamp Tube Shootout

Forum member Dave_P recently sent Blarg and I a box of miscellaneous tubes that were surplus to his needs (mucho thanks Dave). I sorted through my half of the booty this weekend and found that (a) all the tubes worked 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.

If you performed that nice little melody for each tube, A+ for getting it exactly the same each time. The tone was very nice as well, in all five BTW.

I think all of them sound the same except #4 which does not sing as much after the initial attack. Otherwise even that one sounds similar to the others. Maybe the purported differences between tubes requires a range of conditions to expose. As for this setting it does produce a significant blip on the radar.

Last edited by Michael-GnL-Michael on Mon Sep 12, 2011 8:21 pm, edited 1 time in total.

I hear no differences. Can't say I'm all that surprised to be honest, internet myths are almost all complete BS. And as for NOS tubes - maybe they were built better and last longer but there's nothing that I'm hearing there to justify the extra $$$ over the standard EHX tubes.

Great job on the playing Phil, it sounds very sweet and makes me want to max out the Visa on a nice double-bound ASAT Special . The recording is nicely done too, sounds very professional.

Thanks Dave!

I am not surprised at your observations. I have found that substituting a different type tube (12AT7 for a 12AX7) can make a difference because of the gain difference. Great information guys.--Darwin

Can't say I'm all that surprised to be honest, internet myths are almost all complete BS.

I remember you told me that when I picked up the tubes! Now I've done the experiment, the scientist in me completely agrees.

Good luck on the quest for the Special. A double bound would be especially sweet. If I was going to get another one I'd have to go for a semi-hollow to justify it to my wife. Unfortunately they don't come up often on the Bay, even less so in shops.

From my experience, the cheap Chinese 12ax7 tubes that were not labeled that came with my stereo tube amp sounded a little thinner on my 18 watt guitar amp than the vintage 60s Sylvanias. The Sylvanias sounded more analog in a pleasing way. But the Chinese tubes still sounded very good though.

I find that generally I prefer the sound of vintage tubes especially on my home stereo amps. However, there are some new tubes being made that sound great like the new Sophia brand for example. I realise that I am straying away from the guitar amp topic. I think it also depends on the amp too.

Back to guitar amps: On my Fender amp clone, I found that the Electro Harmonix sounded just as good as a quality 60s RCA 12ax7 so I am happy with Electro Harmonix in my system if I need it. There was a noticeable difference though but subtle.

I agree that there are people who get too crazy about tubes. I see this with some hi fi stereo people. A quality transformer and power supply is more crucial than some new old stock over rated rare vintage tube even though they can be a good link in the chain.

Slightly off topic:

I have some good quality 6SN7 military tubes from World War 2 that I use on one of my stereo amps and it not only sounds good but it's also a part of some fascinating history. The cool thing about many of the new home stereo tube amps is that the tubes are visible so you can see them glow when relaxing with the music.

As much as I love guitar music, most of my music listening is non guitar jazz and classical music and IMO, a well designed (unfortunately expensive) stereo tube amp makes the music sound better than most solid state amps.

Interesting reading on tube testers here

http://boyercentral.net/ToneLounge/www. ... sters.html

Nice write up Phil! After all of my experimenting I'd have to agree that the sound difference is subtle in person for most preamp tubes and doesn't come through on recordings or in the mix. And as far as power tubes go the biggest differences I've heard have not been between different brands of the same tube type. They've been in compatible substitutes for the standard tube (i.e. 6L6wgb in place of 6L6gc) even then it's more of a headroom/early breakup thing rather than distinguishable tonal difference.

The 5751, AT7, and AU7 all have, progressively, lower gain than the 12ax7. Theoretically the 5751 or AT7 should give you a little more clean headroom in V1, 12at7 is usually called for in the phase inverter for Fender. The AU7 is generally too low for guitar use, if you know any bass players that have a tube amp (ampeg, etc.) they use 12au7 preamps, it's labeled Hammond but should be RCA (clear top) or Raytheon.

Hope it was still somewhat worth it, let me know if the 5751 helped with the top boost channel on your AC15


Jamie: sorry again about the el84's hope you got some useful tidbits out of the lot.

-Dave

Hope it was still somewhat worth it, let me know if the 5751 helped with the top boost channel on your AC15

It definitely was worth it! Thanks for going to all the trouble to post the tubes in the first place, Dave.

I really look forward to getting the 5751 and the Electro Harmonix tubes in my Vox.

I'll post up another comparison for the Vox if I get the time.

Also, good info on the Hammond labelled tube. It does have a clear top so is probably RCA. I'll try the 12AT7 in V3 (phase inverter) of my Blues Junior. It already sounds sweet in V1.

Edit: After reading this it seems I should have tried the 12AT7, 12AU7 and 5751 in the phase inverter for maximum effect.

It definitely was worth it! Thanks for going to all the trouble to post the tubes in the first place, Dave.

It wasn't any trouble at all once I found the time
I'm glad you're having some fun with them

-Dave

Philby... Thx for the above link.
Seems like a 12AT7 is the way to go for the PI.
Just got done doing the swap, will have to wait til morning to do a tone report....

Ciao...
BW

I've now got the 12AT7 in the PI and the JJ 12AX7 from the PI in V1. It sounds more 'Fender-y' in that configuration, but it's a subtle difference. There seems to be some natural compression going on now which I've never noticed before. It still doesn't sound dramatically different from any of the clips I posted above.

Interesting thread.

I just wasn't aware that Dave was a "former" member. ;+) - ed

I just wasn't aware that Dave was a "former" member. ;+) - ed

I thought I wrote "forum member". Oops, apologies if it slipped out as "former" member.

You did write "forum member."

Am I missing something? Ha! - ed

12AT7 for the phase inverter all the way baby!!... Now I have a tube amp....
I'll work on getting some pics and some sort of commentary on what I ended up doing shortly....
For now it's off to a gig. Early start 5pm central....

Go Brewers

BW