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Opinions on EHX 12AX7

G

Gonzo476

Mar 1, 2009
726
10
Madrid, Spain
#1
I'm going to buy a Bugera Infinium (guitar head, I know, but sounds really nice with a bass) and, from what I've heard, the stock tubes aren't great. I was checking out some tubes and I found these Invalid Link Removed

Are they any good? I don't want the preamp to overdrive at low volumes and I was wondering if the EHX could do that.
 
#2
I'm not a fan of E-H branded Russian 12AX7s. Or any other Russian 12AX7s for that matter. But tube quality doesn't have a lot to do with whether they will stay clean. A modern amp with cascading gain stages in the preamp is designed to allow you to dial in preamp distortion. A quality preamp tube will certainly provide distortion under those circumstances. If it didn't, it would be putting out less than spec output, and so it wouldn't be a quality tube.

All you need to do is not dial in any distortion in the preamp - how exactly to avoid that depends on the design, but basically, given the choice, you want to select the channel with the least number of preamp gain stages (not counting tubes or individual triodes used for post EQ makeup gain). Then, if you have separate controls for the later gain stages, you want those off or as low as possible, and you want to use the first one as your real volume control. The master volume pot - which is, in nearly every case, in reality part of the preamp circuit and not the power amp - should be all the way up - unless the amp gets noisy when used this way, as some designs do, in which case you'll need to split the difference and back it off.

High input signals (whether due to active pickups, onboard preamps, hot passive pickups, or pedals) will make this harder.

If you're doing all of this and it's still an issue, you might try subbing some of the preamp tubes for lower output equivalents. There are lots of threads that go into this. Personally I favor clear top RCA 12AU7 for this purpose, which do the job, are very common and last a very long time. Sometimes a 12AT7 will work better. Impedance as well as gain differences come into play with these different dual triode tubes that share the 12AX7 pinout.
 
#8
hudpucker said:
They're *okay*...but nothing special. Good gain but somewhat scooped and bright. Not even close to good NOS.
Click to expand...
This would apply to the few EHX tubes that are not excessively microphonic noisy or only function for a couple of months.
Let new old stock or known good pre used be your watchwords in tubes.
Other than that "Don't be a dullard! fit a Mullard".:bassist:
 
#10
(In General) I think people really need to look at tubes in two ways when comparing tubes; Current Production and Old Production.

If asking on that current production EHX 12AX7 tube, it is ok but there are better options for approx same price or depending on what you need it to do. It will do its job but may not suit your flavoring. It is rather a boring tube in tone for me and tends to get muddy like a JJ ECC83S. I would pick this tube over a JJ ECC83S because that JJ is one of the muddiest tube out there IMO. But hey, if that is what you're going for, then a JJ ECC83S maybe your tube.

However, here are a few of my "go-to" current production 12AX7 type tubes:

Tung Sol 12AX7 Reissue (well rounded tube, adds a touch of brightness, and opens things up). I usually always run this in V1 but will throw this tube in any preamp section without thinking about it). I've only had one microphonic issues out of approx 20 of these (if that).

JJ ECC803S Gold Pin (little bigger bottom end with a nice top end sparkle. I usually run this in the V2 or any position that may be in the EQ section). Some guys or gals really like this tube in V1. IMO, its ok in this position but since I slam the front end with a lot of dirt, it usually doesn't react well to me. The downside to this tube is that it will go microphonic over time (due to larger plates). Also, I say Gold Pin because it will produce a slightly smoother tone to it over the non-gold pin.

Sovtek 12AX7LPS (this is great 12AX7 type phase inverter tube. Works well in other positions but IMO it isn't that exciting in tone).

Sovtek 12AX7B (surprizing I have found this tube very useful. Its an OK tube and reacts well. I like to use these in V1 or V2 applications (depending on circuit) or effects loops).

Shuguang 12ax7 9th gen (not the most exciting tube to talk about since it is Chinese but it functions well. It also serves well in effects loops or reverb positions).




I can keep going on but honestly, most people (or musicians for that matter) won't even hear the difference. You could slam your whole front end with those EHX 12AX7's and the crowd wouldn't know the difference. Also keep in mind for everything I have posted here, someone will say the exact opposite.
 
#11
Old production and NOS are different things. Old production includes used valves, which means they can be burnt in and tested, NOS means not tested and burnt in (because then wouldn't be new). Lots of people call used valves NOS though, "I have NOS valves in my amp", being in an amp makes them neither new or stock, any old valve used to be new, and stock once. I'll take tested used old valves over NOS any day, not least because anyone selling valves as NOS when they are used is dodgy for a start.
 

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