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Why Every Tube Guitar Amp Owner Is Using The Wrong Sized Tubes

guitar-amp-modification

I never could quite achieve my dream tone, even when purchasing world class vintage amps… until I uncovered the secret to a perfect tube/amp pairing. It may surprise you that the amp industry has adopted inherently flawed tube choices which are still employed on most amps made today.

Amp builders are mostly stuck in the past, putting either too much voltage or too little voltage into the amp section design for these tubes. There’s so much going on with a tube amp there is so many things it could be causing your amp to sound like farts. However, there is one secret that very few amp owners, techs and builders are aware of that changes the whole game. 12AX7 tubes (the “12” denoting the 12 volts they consume) is in an amp circuit that only requires 6 volts! For those of you bad at math, your amp is using only half of each 12ax7 tube causing noise and microphonics… but why would amp builders do this and why haven’t they changed? Let’s get to the bottom of this.

We caught up with Walt Burger, tube store owner and Blues Jr Mods online shop to discuss why the industry standard still hasn’t changed. He suggests that back when a lot of amps were designed in the 50’s, we used different types of preamp and output tubes but by the 60’s we’d found 12ax7 and 6L6’s and EL84’s etc lying around in TV’s, Radios and in other electronics (prior to solid state tech). Now the use of the 12ax7 was because it was backwards compatible to 6v and stereos were 12v and used 12ax7’s. So it made sense for one type of tube to be used to make it easier for the consumer. But that doesn’t mean it was the best choice for sound, it’s just what was popular and readily available at the time, which became the standard like the dissonant and ear piercing frequency A440 we all suffer with today.

Now another reason the 6n2p and the 6p14p’s were not used is because they were built for the military. They never released these tubes to consumers. In the USA we had JAN tubes, (Joint Army and Navy), but we also had consumer versions of these tubes. Over in Russia they did not so up until the end of the cold war, these tubes (even into the mid 90s) were very hard to get your hands on, mostly because they are simply not susceptible to microphonics and sound incredible. When a tube is made for the military, it has to be a more durable tube, last longer and operate to more exact specifications of voltage. So the Military or JAN tubes are like Gibson guitars and the consumer grade tubes are like Epiphones, to use a common reference.

The US stopped production of tubes rather quickly and moved onto solid state technologies. Other counties utilized tubes for much longer than we did and over that time, as we stopped evolving in tubes, other countries continued to evolve their tubes.

In a few years already the 6p14p-eb tubes which are the holy grail of EL84 style tubes went from around $5 per tube to now about $30! Word has gotten out. But the standard and -k versions are still reasonable (when you can find the right person to buy them from who tests them and matches etc). The 6n2p has picked up steam in the past few years too. Companies like Mesa and Fender have to overbias the heck out of their amps to get a 12v tube to perform in a 6v circuit and they’ve done a decent job of this to keep the standard alive and keep selling cheap Chinese tubes. JJ, Ruby, EHX, Groovetube… once beloved tube manufacturers, who one by one, have been bought out by companies who own the industry like Fender who make them in China now but don’t mark them Chinese and charge you $30 a tube! Ouch.

Remember to always buy matched tubes for any amps that use multiple power tubes. Very important. If they are not a good match, the amp will sound like it has no balls. Be careful who you buy from that claim they match tubes, the equipment to be able to do this is very expensive so cross-check your source!

So which tubes should we be using and why? A 6n2p is a Military Spec 6.3v version of a 12ax7. In 99% of guitar amps the 12ax7 tube is under totally utilized. A 12ax7 tube can handle 12.6v. The number 12 in the name 12ax7 stands for 12v yet the circuit only uses 6v! Take for example the new Marshall Origin amp head. It will never ever push more than 6.3v from the socket that takes your precious vintage NOS mullard blackburn 12ax7… the horror! This can often be an issue because the entire gain structure of the tube is not being used! The 6 in 6n2p stands for 6v. So this tube is more ideal to use in a preamp section of a guitar amp. These tubes are used by the fabled amp builder Train Wreck and a few other companies that realized this but for some reason we are wasting a lot of money on 12v tubes that we don’t even use the entire gain structure from. This can cause noise. A lot of it. Microphonic bands wont do anything to help the problem either and are basically useless. But they sound like something that would/will work so people buy them. There’s a guy on YouTube called Psionic Audio and also the Guitalogist that get into this.

“We should have stopped using 12ax7 and EL84 tubes a LONG time ago with the knowledge we have today, yet the industry has adopted this inherent flaw as standard.”

– Walt, owner of geekarooit.com and premier tube supplier

Your amp wants a 6v tube and you have a 12v tube in it. What do you do? Well the 6n2p tube should solve this issue, clean up your amp and provide a much better overall tone. Because 6n2p tubes are Military spec these tubes are rated for about 5,000 hours on the low side but we’ve seen over 10,000 hours off many many 6n2p tubes. These are also structurally more sound than a 12ax7, especially current production 12ax7 tubes. Don’t get e started on new vs old Mullard Blackburn tubes. Why a Russian company (Sovtek) who makes wonderful tubes feels the need to whore out the old Mullard name in the name of profit is plain sad. Instead of making a name for themselves in Russia, they feel they need to piggyback on the coat tails of the legacy of Mullard by making inferior Mullard tubes. The fact is, the new Russian branded Mullard tubes are actually great Sovtek tubes and shuld be proudly touted as such. I digress. Ive found that the 6n2p solve a lot of noise issues and sound MUCH more full than even some of the nice expensive 12ax7 tubes available today.

The most significant change between the two is the pin-out is different. They are both 9 pin tubes, but 4 and 5 are not attached ground-wise so you would need a simple $10 adapter, which is easily found anywhere online. You plug the tube into the adapter and the adapter into your amps tube socket. That is it, no adjusting anything in the amp. Its that simple.

Current production tubes are rated at around 2,000 hours but a lot of the older 12ax7 tubes like the expensive Black plates etc wont last long the way a lot of the voltage is supplied from newer amps. We’ve experienced a lot of issues with older preamp tubes and power tubes running in newer amps. You have to remember the older amps were designed for 110v. Most current outlets put out at least 120v if not closer to 128v so that means the amp is literally cooking those old tubes! If you want to stick to 12ax7 style tubes and the good older NOS stuff everyone wants, you would want JAN NOS. JAN = Joint Army and Military. These 6n2p Reflektor tubes are the same thing but they are usually Russian military tubes and they will call these “Military Spec”.

Keep in mind 90% of the tube sellers on the internet that say their tubes test “new” are NOT new. Just because a tube tests new, doesn’t mean it’s new. Be careful with buying reflector tubes off eBay, Reverb, etc. Also be careful of over priced NOS stuff and be careful of people selling used tubes that test new as NOS, there’s more snake oil in the tube industry than in the actual snake oil business, which apprently is still a thriving legitimate business by the way. We’ll save that for another blog post.

The most expensive guitar amp for sale in the world today, the Dumble Special, which utilizes 6v tubes!

These 6n2p tubes (standard and -ev models) sound like vintage Black Plate RCA or GE tubes. As I’ve said, these last on the low side 5000 hours at least! I love these tubes and I use these in all my 12ax7 sections of my amps and our recording studio owns a LOT of amps. I have not used a 12ax7 tube in years as they are problematic and in almost every guitar amp. Even though 12ax7’s are not really the best choice, they became the standard for better or worse and like ancient fiction that becomes truth, 12ax7’s remain in every new amp to this day.

Another example of this quandary is the 6p14p power tubes. The same company over in Russia that makes the best 6n2p tubes also make the 6p14p which sound 10x better than a EL84. EL84’s are noisy and cheaply made tubes that cannot handle the voltages they are given in an amp circuit. These don’t require an adapter and once you try them you will be blown away! We should have stopped using 12ax7 and EL84 tubes a LONG time ago with the knowledge we have today. But it’s a standard and it’s hard to get people to open there mind. Maybe the amp companies are trying to make a buck off these cheaper inferior tubes, who know?

I’d say its worth trying these 6n2p tubes with adapters if you’re having microphonics or noise issues. It is the least expensive way to do this and get the best tone you can get out of your amp. It’s a very simple process and now your amp should be good for decades rather than months or a short year.

If you have any more questions we recommend you reach out to Walt at Geekarooit.com to get you set up with some new tubes and adapters.

Don’t forget to add a helpful comment if you have questions or feel you have additional information to share. Check out our other interesting blog posts here at Lutz Media too!

Still want more tube talk? Head on over to Walt’s website or watch this great video on how to clean your tubes properly!

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