Posted by: kubiakl | December 7, 2010

EL84, 12AX7, NOS, ANOS… WTF?

I’ve complained before about how many idiotic posts plague internet forums.  And I stand by that – generally speaking it’s hard to find useful information.

But when I went searching for information on tubes for my Blues Jr. I found some surprisingly good answers.  Apparently people who take the time to worry about those little glass valves in their amp are smarter than your average bear.  Which is good… because there’s a lot of things I didn’t know.

The main reason for replacing the tubes in my amp is to correct an issue:  after playing for a while the volume drops off.  From what I gather this is a power tube issue.  The other thing I found out is that the power tubes should have been replaced a long time ago.

See, these things are like light bulbs.  They wear out.  The more you play, the harder you push your amp, and the rougher it’s handled all factor in to how long the life of your power tubes will be.  Some tubes wear out quickly, others last a few years, but in general it’s a good idea to replace the power tubes every year.

I’ve had this amp for four years.  Someone else had it before that.  The stock tubes are still in place.

Once I realized that I had to go ahead and order new power tubes the question became what kind?  The Blues Jr. uses two EL84 tubes for its power section.  But there are many different brands, plus there are NOS and ANOS tubes available… it took some reading to figure some things out.  NOS means New Old Stock – these are tubes that have been shelved since their creation and are highly prized (and priced).  ANOS means Almost New Old Stock – slightly used but with most of their life still intact.

Since it’s only used around my apartment I decided not to spend the money on expensive NOS tubes.  New tubes (and reissue tubes) are generally made by one of the few companies still producing vacuum tubes like New Sensor.  There are many suppliers though.  Mojotone (the company I bought the reverb tank from) has a selection, as does Torres Engineering, Eurotubes,, The Tube Depot, and the place I bought from – Doug’s Tubes.

The Tube Store got quite a few nods, but they ship out of Canada and I just didn’t want to deal with that.  Bob at Eurotubes is supposed to be very helpful but… looks a little odd.  Mojotone was great about shipping my reverb tank but didn’t have the tubes I wanted.  Some people like The Tube Depot, and while almost no one mentioned Torres Engineering, they do have a good reputation for their tube amp kits.

In the end I went with Doug’s Tubes.  Doug is a three man operation out of New York who has a great reputation on the message boards for being helpful and responsive, as well as fast order fulfillment.  He tries to match tubes with the sound you want and even rates power tubes by how early they distort.

Mullard reissue EL84s sounded like the tubes for me.  According to a review at The Tube Store, they have a creamy distortion with little clean headroom.  Since I don’t play with clean tones they seemed to be good for me.

I’ll update when I get them installed.  For now I’m going to leave the stock preamp tubes (which are Groove Tubes 12ax7s – probably Russian made Sovteks), but those may get changed later on.  Preamp tubes don’t wear out as quickly as power tubes.

A few other things I’ve found while reading:  Different tubes will fit the 12ax7 slots and change the amount of preamp distortion.  5751, 12au7, and 12at7 tubes will all work.  There is also a 7025 designation but those are just low noise 12ax7s, and since all 12ax7s made in the last 50 years are built to low noise specs it is an outdated designation.

Stevie Ray Vaughan liked the 5751 tubes in the V2 (reverb) position.  A few people said that the 12at7 works well as a phase inverter (V3, next to the power tubes).  And of course there are many different brands of 12ax7 tubes, all with die-hard fans.

Tube rolling is another term I came across.  Since the V1 preamp tube has the most effect on tone it is recommended that you rotate the three preamp tubes until you find the combination that gives you the best sound.  Remember – when it comes to tone, no two things are ever quite the same.  Two Stratocasters with sequential serial numbers will sound different to the people who play them.  So even if you have three Electro-Harmonix 12ax7s, you should switch them out until you find the combination that works best for you.

Preamp tubes will come later for me, I just couldn’t bring myself to retube everything at once.  The price wasn’t terribly high, I’d just like to do it one step at a time.  But right now I’m looking at Tung-Sol 12ax7s and possibly a 5751 just to see how it sounds.



  1. Right on. I have a 2 yr old Bugera v22 w-2 JJel84’s, a used but good rca 12ax7a in v1, a Tung Sol reissue in v2 and the original chinese 12ax7b in v3. Articulate and powerful clean sound. Marshall amp sound in overdrive channel. Zz Top, Aerosmith. Klang, kerrang, crunch and great bouncy ‘feel’. Great compact amp. I’ve tried numerous preamp tubes- I like EH, jj low gain and certain nos. EH EL84s are smoother and not as dynamic as JJs. Amp is very different sounding with different tubes.

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