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Groovetubes 12AX7M and ElectroHarmonix 12AX7EH review

LoveThatBass

LoveThatBass

Supporting Member
Jun 28, 2004
5,177
3,566
Dallas/Fort Worth Metroplex area of North Texas
#1
I just got the tubes in and tried them out.
Compared to the standard Groove tube 12AX7R.
The 12AX7M is balsy, clear well defined low end, decent tone, low noise if shielded properly. They have more gain than the standard Groove tube.
Having said that..the 12AX7EH is a close second. Good gain, clear, nice well defined low end but not quite the balsy low end of the 12AX7M..close though...Good tone.

Having said that the 12AX7EH is a better buy at 1/3 the cost of the 12AX7M. Which will I use...12AX7M since I have it. The EH's will be my back up. I bought 2 of each while CE Distribution had them at 1/2 off till Christmas.
 
#2
I tried the Groove tubes 12AX7M too. Sounded as you described + not so good when breaking up. Didn't like the sound when I played harder and the bass growled accoustically. Sounded harsh with this tube. I since bought the Ei Elites 12AX7E which was just what I was looking for: Warmth, punch, clarity and breaks up nicely. A bit noisy but there's a gold plated version that should be more silent. Oh - and it's cheap too. Under 10 bucks.
 
#8
LoveThatBass said:
Carl-Anton , What amp do you have and does it have more than one 12AX7 tube? With the original tube or a Groove Tube 12AX7R I get preamp clipping on volume of 5. With the Groove Tube 12AX7M it does not clip until 7 or 8.
Click to expand...
I use the SWR Bass750. One tube. It clips around 3 o'clock with not much difference as to which tube I use. With the Ei tube the clip is softer, more continious whereas the GT M seems to break up the sound, if you know what I mean.
 
#9
Lovethatbass,

What does the M mean (in 12AX7M)? For example, I know that the R in the GT 12AX7R3 is for Russian.

Thus far, I've tried a variety of 12AX7 / 12AT7 / 12AY7 tubes including GTs, RCA NOS, Mullard, and Ruby brands in my Eden WT-550. They each have their own tone character and gain levels. The differences are subtle but noticable to the discerning ear. For playing the R & B / funk / top 40 cover material that I typically do, I found the original stock Ruby tube that came with my amp to sound best as far as overall tone, warmth, articulate bottom-end, headroom, and punch. I'd like to try the EH and the GT 12AX7M as well. Thanks for the review!
 
#11
Well, I had to go out and buy one of these GT 12AX7M tubes to try out in my WT-550, just because of this thread.

I brought it home and A/Bed it with the stock Ruby 12AX7A that comes in the Edens. At first impression, it has about the same volume as the stock Ruby, but it has slightly less low-end fullness. There also appears to be slightly more presence in the upper mids and treble ranges.

I'm a bit disappointed in the low-end response, but I found that I can dial it back in with the amp's EQ.

Can anyone comment on whether the tonal response of an amp will change after the tube as been running for awhile? if so, how many hours does it take to get the optimum tone out of the tube? I was thinking that maybe the low-end was lacking because the GT tube is brand new and needs to be burned-in?
 
#12
I A/B'd my SWR with a GT12AXM against a
  • Ruby Tubes 12AX7 labeled Mesa
  • NOS long plate 12AX7, origin unknown
    (pulled from a Fender, when new by a Mesa Tech).
  • JAN Sylvania 5751
  • Stock SWR GT12AX7 Chinese

Each tube produced different tones.

Describing them is dicey at best,
however I'm stupid enough to try...

GT12AX7M - Focus on the Mids. With Mids breaking up first.
Definitely a Guitar Amp tube.
Has a voice that would appeal to r'n'r guitars.
Ruby - had to roll back the highs. A little hissy.
Fender 'blackface' - had sweet mids.
JAN 5751 - was super low noise. Solid rump. Smooth highs.
Stock SWR GT12AX7C - that 'SWR Sound.' A bit "high" in the Hi-Fi.
 
#14
LoveThatBass said:
So, your recommendation would be the JAN 5751?
What brand?
Click to expand...

Sylvania black plate JAN, JHS, etc...
Sylvania Gold Brand black plate

I use a Green Print JAN Sylvania.
These usually cost less then a GTAX7M and will last much, much longer.

Disclaimer:
  • Suggestions are for clean tone,
    (dirt in the signal should be left to external devices designed for that purpose).
  • Claims made here are void if deaf, partially deaf, brain damaged, or ********.
  • Not responsible for those unable to recognize good tone.

Kurt Kurosawa said:


Link Removed

I recently bought a minty '98 SWR Bass 350. I hated the sound as soon as I
plugged up and hit the first note. No amount of knob twiddling could tame
the unruly sound, harsh up high, peaky in the mids, and big and blurry in
the bass. I figured the only part of the circuitry I could change was the
tube, and because my entire signal went through that one tube, I was
entirely at its mercy, so I started reading up on tubes, and considered
buying a Telefunken flat-plate diamond-base ECC83 (they go for $100 new and
$30-40 used). Expensive fix for a newish amp that I just paid $400 for! Then
I stumbled across this article (if you have a one-tube preamp in your amp,
like an SWR or Trace, you really need to surf over there):

Joe's Tube Lore

. . . and I learned all about the 5751 tube. It is an industrial tube with
only 80% of the gain of a 12AX7, and because it's not an audio tube, the
sound qualities differ greatly not only from make to make, but from lot to
lot. So who needs the hassle? Well, first I learned from Joe's FAQ that the
12AX7 is noisy and blurry. Actually, I knew that already, but it's good to
hear it from an expert. Then I learned that the three-spacer 5751 was
designed for toughness and survivability in B-52s and other nuclear war
weapons systems. Cool. Then they ought to do just fine sitting on top of a
thundering bass speaker. And lastly, I learned from the FAQ which ones to go
hunting for.

I went to a local electronics supply and they had piles and piles of tubes.
All the 5751 tubes were 10 bucks and new and used ones were all mixed
together, 13 in all. The Sylvania JHS 5751 gold print was pure magic. It
took
every bit of the harshness out of the highs on Pyramid Gold flatwounds (the
harshness of these strings makes a SansAmp PS-1 into a Stewart World 1.2
into an Epifani 410 sound bad). The sound of this tube was the sound of the
bass itself without the coloration of the "hand selected" Groove Tubes
12AX7A that came in the amp. I flattened all the EQ (actually, my EVM 15L
needs +6 dB bass, but really, the only thing EQ should be used for is to fix
the speakers and the environment, not the amp itself). I turned down the
Aural Enhancer all the way. And without any coloration masking my sound,
what I heard was the voice of my bass, the pure muttering growl of the
P-sound.

By the way, it doesn't matter to me that the 5751 only has 80% of the gain
of the 12AX7. The Bass 350 manual says to turn up the preamp gain knob until
the clipping light flickers as I play at my normal volume. For me, that's
about 2 o'clock for flatwounds or 1:30 for roundwounds, so the 5751 has
plenty of gain for my purposes. Maybe if you had a Dano or some other
low-volume axe, you might run out of gain. Maybe. But if you're doing like
the manual says and the light is flickering and the knob isn't maxed out, I
don't think you're going to notice the lower gain. Besides, the purpose of
higher gain is to increase the S/N ratio, and 12AX7 tubes are so much more
inherently microphonic than military three-spacer 5751 tubes, I think the
S/N advantage probably lies with the 5751.
Click to expand...

Kurt Kurosawa said:


You've got a raft of great choices in preamps with offerings from SWR, Demeter, Eden, and others. I have most of my experience with SWR preamps, both built into integrated amps and rackable, so I'll talk about the essential aspects of those--the others are fairly similar. The SWR preamp has a wonderful direct interface built right in, and whether you go direct or line, your bass goes through the tube first. One is all you get and one is all you need. The caveat is this: you're totally at the mercy of the sound of that one tube. So you're going to have to take the time to find the right tube. Although you have probably experienced the generality that tubes sound warm (because they generate even-order harmonics) and that solid-state devices sound cold (because they generate odd-order harmonics), while I would take a good tube sound over a good solid-state sound, I'd take even an average solid-state sound over a bad tube sound--the debates about tubes vs. solid-state devices per se make no sense to me.

I listened very critically to a decent 12AX7 and as raucous and loose-sounding as it was, I was sure I could do better (no amount of EQ-tweaking helped; in fact it made things worse). Then I ran across Joe's Tube
three-part FAQ about substituting the 5751 for the 12AX7. I lucked into a good one and tried it (a 1959 three-mica, black-plate, gold-print Sylvania JHS 5751). Pure magic. The bottom tightened up to a nearly unbelievable extent. The mids were vibrant yet not peaky at all. The highs were smooth and sweet. The gain is noticeably lower, but the quietness of the tube more than makes up for that loss (since a good S/N ratio is what the 12AX7's extra gain aims at in the first place, even if it misses).

Essentially, this particular tube added nothing to the sound it was fed, so the P-bass' characteristically vocal low-end growl was able to shine through in spades. I believe the tube would do even better by the J-bass' main strength, its famous mid-range howl (to me, nothing good can come of adding EQ to fix problems with tone--EQ only masks the instrument's strengths, so what I'm after is a good sound gotten by stripping away everything that sounds bad). Anyway, I've been feeding the board my bass through a tube ever since. No theory can beat hearing a fact with one's own ears

LINK:
Summary of 12AX7 vs. 5751 taste test with all the gory details.
Click to expand...
 

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