“They are magical little bottles of joyful tone that allow us to express ourselves in a way that no other device on the planet can…”
Or a more proper definition:
“A valve amplifier or tube amplifier is a type of electronic amplifier that makes use of vacuum tubes to increase the power and/or amplitude of a signal”
Basically, vacuum tubes are used to increase the power of a guitar amp to an audible level. Tubes have been in use for decades in audio equipment, TVs, military applications (radar), and transmitters. Tube amplifiers were largely replaced in the 1960′s and 70′s with solid state amplifiers which use transistors to produce the sound. A solid state amplifier is more reliable (since the transistors don’t degrade over usage as tubes do) and for portability: tube amps are heavy!
Tubes, while seemingly an archaic technology, are still widely used in certain applications such as high power RF transmitters, microwave ovens, and audio amplification equipment: particularly for the electric guitar, recording studios, and high-end home stereos. It’s widely accepted that the tonal characteristics of tubes (also called ‘valves’) are more pleasing to the human ear than transistors.
The problem is that they do not last forever and will need to be changed. There are two reasons someone will change the tubes in their amp:
- They die:Its not a question on if they will fail, but when they will fail. Tubes, much like batteries have a limited life. We push them into distortion and make them scream their little heads off… they can only take that abuse for so long before they begin to loose the ability to drive your rig. As you can see from the picture at left, these are tubes in action. When properly biased (meaning adjusting the amount of voltage the tubes are drawing while ‘idle’) the amp will get nice and HOT!
2. To completely change the sound of your amplifier:
The type of tube used can DRAMATICALLY impact the sound of your rig! I had a Peavey Triple XXX back when my band began playing out a few years ago. I almost returned the amplifier. It was my first high gain all-tube amplifier (I did own a Fender Hotrod Deville, but thats hardly metal) and it was really just… missing something. So I did a little research on tubes. I come to find out that each different type of tube has different gain structures and harmonic and EQ responses. I thought, “why not? Let’s give this a go…” I ordered a set of KT77s for the power amp and some high gain 12AX7s for the preamp and hoped for the best. Long story short… I dropped these puppies into the amp and fell in love with it. It was a completely different amplifier.
Guitarists are notorious for “tone chasing”. Well, what is tone? Thats one of those things that we all seem to understand as guitarists but lack the ability to really put in words. If refers to timbre and pitch color and a whole myriad of things that have a direct effect on the sound coming out of your speaker cabinet. It’s a lot like trying to explain to someone how sugar tastes… And don’t use the word “sweet”.
Alright. Take a look at this picture on the left. You should notice two distinct type of tubes.
The smaller set of tubes is part of the preamp section of the amplifier. The preamp does the basic tone shaping for your amplifier (its also the part of the amp most responsible for gain or distortion). The larger set of tubes belongs to the poweramp section of the amplifier. This is the power house that drives the whole thing. It basically ‘amps’ up the preamp so it has enough ‘oomph’ (these are technical terms here…) to drive the speakers. BOTH sections of the amp are responsible for your overall tone (equally so), so you will need to replace all of them if you really want to change the sound of your amp.
Ok, so tubes can completely change your sound, right? So how do you know which ones to go for. Well, you can ask an expert. Or use Google. I don’t want to get into too much here, as this article is meant to be more of an introduction on tubes, but I will go over the basic types:
PREAMP – 12AX7
This is a preamp tube (one of the little guys from the picture above). You have different version such as the ECC803 S, ECC83 S (including versions where the pins are made from gold) There are other preamp types, such as the 12AT7 and the 12AU7. It is beyond the scope of this article to go into too much detail, but each tube has different gain structures, EQ response and will react differently to your playing. At the end of the article I will provide some resources you can do your own research with
POWER AMP – EL34
The EL34 is the tube responsible for that “Marshall crunch”. For guitarists that should require no description! They do make updated types, such as the E34L and the KT77 that tighten up the low end while still maintaning that nice sizzle in the top end without making your ears bleed! If you want that British amp sound, but with a bit more complexity and low end ‘oomph’ try the KT77.
POWERAMP – 6L6
This is the last tube I will cover for this article. These tubes provide BIG low end compared to the EL34 style tubes. They also have much more complex mids and the highs aren’t anywhere near as brittle as an EL34 (but it certainly doesn’t ‘crunch up’ the same… less aggression in this tube).
This barely scratches the surface on what’s available on the market today. I recommend that you do your research on the different types of tubes before making a purchase. They have a HUGE impact on your overall tone and are a rather large piece in the never-ending quest in the pursuit of tone. Oh, and here’s another thing: As long as the tubes draw the same voltage… you can mix and match them for even more tonal possibilities! You will need to get them from a pro, like Eurotubes, to make sure the tubes are MATCHED. If they aren’t, you can end up with a less than stellar performance from them.
So what do I have in that Carvin V3? I have an integrated quad of 6L6′s and E34L’s (Matched of course!) for the power amp and a set of high gain ECC83S’s for the pre amp. I am definitely digging the tone!
They can be expensive, but try and have some fun trying out different types. Happy shredding!
Oh, one last thing. Check out my friends over at Eurotubes. There, you can find comprehensive information about tubes, not to mention these guys have some of THE BEST customer service in the industry and will help you choose the right tubes for your amp and you as a player!