Preamp tubes come in different models, types and brands. The most popular for nowadays guitar amps is the 12AX7/ECC83. I've collected and tried a few preamp tubes, and noticed that different types and different brands do sound different. Different enough to write the umpteenth 12AX7 shootout, something nobody wants to read. So why did I write this story anyway? Simply because I needed a reference for myself, and my homepage seemed more organized than my desk.
I'm not striving for the ultimate sound. I've just made an inventory and tried some possibilities, not determined to go in a particular direction, but also trying out not so obvious combinations of tubes. Furthermore, I didn't care about measuring the tubes. Measurements can't tell a thing about the musical capability of tubes. It's all about what you hear, not about the characteristics that you see on an oscilloscope.
The guitar used was a Gibson The Paul SL with standard humbuckers. The neck pickup (490R) was used for the clean sounds (by turning down the guitar volume), the bridge pickup (498T) for the overdriven sounds. Both humbuckers are difficult to amplify, they have very compressed mids. Especially an overdriven rhythm sound - which doesn't sound mushy - is hard to accomplish. Lead and clean are a lot easier. The amp was a standard Rivera R100-212, it has two different sounding channels (Marshall and Fender). Lead, rhythm and clean were tested on both channels. So far only the gain hole (it uses five preamp tubes) was used for testing the tubes. The reference tubes used were one Sovtek 12AX7WA in the gain hole, four Chinese 12AX7s, and four Sovtek EL34WXT power tubes. These were also the tubes the amp came with.
Now before you read my results and start complaining about the low scientific value of this review: testing tubes by listening to them, as opposed to measuring, is prone to becoming highly subjective. Feel free to disagree with me. Please e-mail me if you decide to write your own review. Let your ears be the judge.
This is the tube the amp came with (in the gain hole). Lead playing sounds
very good, a little nasal (in a positive way). As stated before, the
humbuckers on my guitar are very hard for playing crunchy rhythm, and the
12AX7WA has major problems with this. The rhythm sound also tends to get hollow.
The clean sound is good, with enough richness and clearity. I'm not sure if
Rivera amps are still shipped with this tube, mine's a few years old.
The LP stands for long-plate, the S for spiral (for AC filaments). There are
stories about people returning this tube, because they didn't see the
filaments glow and thought it was defective. People, use your ears for
listening, not your eyes! But they were right, it is hard to see
if the tube's functioning, I had to stick my head in my amp to see some vague
glowing. And the sound? A lot like the 12AX7WA, but brighter, and that's
a plus with all types of sounds. The lead still has that nasal feeling (good),
the rhythm is still a little hollow (not so good) and the clean sound is
very rich and clear. One time during rehearsal I noticed that this tube
is more microphonic than the 12AX7WA. I bought a tube damper, but due to
the LPS's slightly bigger size it
wouldn't fit! The 12AX7LPS scores a better overall than the 12AX7WA,
but they both have problems with rhythm.
I bought this tube as a spare for holes 2 through 5 (actually I bought four,
because the Chinese factory doesn't make 12AX7 and 12AT7 tubes anymore). So
I also tried this one in the gain hole. The most noticeable fact was that this
tube sounds very direct, not exactly harsh or shrill, but loud, in your face.
It produces very good clean sounds, but when playing lead and rhythm the amp
sometimes doesn't sound like a tube amp anymore. The Audio-Voice may be great
for other positions, but certainly not for the gain hole.
I bought this one because it has a lower mu than a 12AX7 (60 as opposed to
80-100), to try it in the reverb follower or the phase inverter section, but
it's also nice to try it in the gain hole. It left me with the same impression
that the Chinese 12AX7A made: too direct and glassy but with less gain. Even
the clean sounds weren't very pleasing.
A friend of mine gave me a box full of tubes, including the Philips. All tubes
were used, and this one didn't seem 100% anymore. It didn't provide enough gain.
However, the tube tester indicated that this tube is alright. A second
listening test made clear that this tube is more than OK. I didn't like this one
in the gain hole 'though. Too many non-pleasing highs.
The Valvo was in the box too, and this one sounds a lot better. It provides
a lot of gain, even more than the Sovteks. This tube also has a pleasing
nasal sound when playing lead, but sounds better than the Sovteks when
playing rhythm. It lacks some character, but doesn't sound mushy. The extra
gain is especially significant when playing clean. I had to turn the volume
on my guitar down to get a clean sound, which sounded good.
This one was a surprise. It was also in the box, but I'd never believe this
was an ECC83 if it wasn't printed on. Too bad the print's got worse since
I got the tube (I apologize to all the purists).
The plates have single flanges, making
them look asymmetrical. The Brimar has the nicest rhythm sound, tight and
it doesn't suffer from being hollowish (like the Sovteks). The clean sound
is rich and clear. The lead sounds
rich, colorful and almost 3D, and yes, it has that nasal sound again.
The only thing that the Brimar lacks is
enough gain when playing thrash-like staccato power chords. This could be
a matter of age. I've ordered two Brimar NOS 12AX7s, and will check if they
provide more gain. If that's not the case,
then trying this tube in the second hole with another tube with a higher gain
(like the Valvo) in the first position could solve this problem (I had already
tried this tube in the second position, with a Sovtek 12AX7LPS in the gain
hole. This combination sounded as colorful as the Brimar in the first
position with a Chinese tube in the second). If that fails too, then using
some extra gain (like a, preferably tube-driven, overdrive pedal) might
provide enough crunch for playing those power riffs.
The CV4004 has the Brimar ECC83's asymmetrical
look, but mirrored! The CV4004 has more highs and is louder. It delivers that
extra punch to play staccato power chords. This one in the gain hole and
the Brimar ECC83 in the second hole was slightly disappointing. The sound got
too dark. What works well 'though, is using CV4004s in the first and second
position. It's slightly less 3D than the Brimar ECC83.
This tube was sold to me as an ECC83. It's stamped 12AU7A/ECC83! Notice the box, it has a 12AU7A/ECC82 stamp on it, with an ECC83 sticker over it. I bought it anyway, assuming the relabeling was done after measuring the tube and concluding that this 12AU7A had specs closer to a 12AX7. Well, that wasn't true, it's just an ECC82 (looks like an ECC82 too). The sound is very direct, almost solid state. Maybe I'll have it checked out by a harp player with a tube amp I know.
The Tungsram is the definite winner in several other 12AX7 shootouts, so
I was curious how it would perform in my setup. There are some things I
like about this tube, and other things that I don't. To start with
the latter, I don't like the clean sound, too much bottom. The rhythm
is a lot better, the mid's a little mushy but not hollow at all. The lead
sound lacks some character, but it too has that same pleasant nasal feeling,
and provides enough gain for playing staccato power chords.
I'm not sure if this tube is exactly the same as the JJ 12AX7A. According
to my information it is (same factory, just a name switch a couple of
years ago), some state that they do hear differences between the
Teslovak and the JJ. Anyway,
it's supposed to be a near exact copy of the Telefunken ECC803, a tube I've
never seen or heard, but the Teslovak surely looks like the Telefunken's
mechanical description I was given (ECC88 alike). And the sound? Well,
it has some nice transparent
highs, especially when playing lead and clean. The lead has that
nasal sound, but just like the Brimar it lacks some gain for playing power
riffs. The rhythm sounds a little hollow.
The EI factory was bombed by NATO, but not heavily damaged.
Because the city council of Nis is not run by the
government party but by the opposition, Nis is one of only two cities to
receive oil, but it may take years
before any shipment of tubes makes it to NATO countries, due to embargo
restrictions. Okay, enough about
politics, let's talk about the ECC83. It misses just that little extra gain
for power chords, but the weird thing is, it sounds almost as direct and in
your face as the Chinese tubes. Maybe a good contender for holes 2 through 5,
but not for the gain hole.
I've tested these tubes some months ago. In the meantime I've installed new pickups in my guitar, and new speakers in my amp, so the sound is totally different. I use the test as a reference now, to quickly look up which tubes deliver approximately what sound. I've discovered that playing around with different preamp tubes is still fun, but changing pickups had more of an impact, and changing speakers almost seemed like buying a new amp. I still try different tubes once in a while, and I will certainly write about the ones I'll buy in the future. Just don't expect me to give you advice on what tubes you should buy.
If you really need an expert's advice on buying tubes, try:
http://www.watfordvalves.com/ (opens in a new window).
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