Hello and welcome to this week's article! Today we're going to talk about TUBES! How to choose them? I have made many researches throught the last few years and tried many of them on my own amps, plus I've made treasure of the experience of other people I've known (for example the guys of my forum, Guitartribe, which is in italian), so today we're going to see and introduction on how to choose them, which are best suited for certain amplifiers and genres, and how to obtain the right sound.
Let's start by saying two words about vacuum tubes: A vacuum tube consists of two or more electrodes in a vacuum inside an airtight enclosure, and these electrodes are attached to leads which pass through the envelope via an airtight seal. On most tubes, the leads, in the form of pins, plug into a tube socket for easy replacement of the tube (tubes were by far the most common cause of failure in electronic equipment, and consumers were expected to be able to replace tubes themselves).
Tube-based electric guitar amplifiers are also preferred to solid state or digital ones by many guitarists, because in this application users are not seeking the most accurate reproduction of an original sound, but rather for the equipment to add its own characteristics. The sound produced by a tube power amplifier when overdriven has defined the texture of some genres of music, starting from classic rock and blues, and spanning through all the music spectrum. Rather than the hard clipping characteristic of solid state power amplifiers, a tube amplifier and output transformer produces audibly different and distinctive distortion. Guitarists often cite the sound of tube amplifiers for the "warmth" of their tone and the natural compression and eq cut that results when overdriven (as guitar amplifiers routinely are). (Wikipedia).
First off let's give some general advice: If you want to replace Power tubes on your amp, after the replacement you should adjust the Bias (or have it adjusted by someone who can do it without risking his life), in order to use it at their best and avoid to ruin your power amp. If you want to learn more about how to set the bias, check out This Page. Preamp tubes instead cannot be biased or adjusted, you can just replace them. Also you don't need to use (except for exceptional cases) preamplifier tubes of the same brand, you can use a different brand for each position, if you wish.
A low gain amp cannot be turned to a hi gain beast just by replacing tubes, although the tube that you put in the first position may change a bit the general sound of your preamplifier: a 12AT7 will make it more dynamic, a 12AX7 will make it more overdriven and gainy, a 5751 will make it cleaner, and a preamp tube will last more or less 2 or 3 sets of power tubes.
Now, according to the Tube Town Map, we can give some general advice in choosing the right tubes for your amplifier, keeping in mind that obviously these are not rules (and many more tubes than these, which are just the most common), so the only real way to choose the right tube for you is to do some test.
Preamp tubes (sorted by music style, these are the most commonly found on online stores, at a reasonable price):
Acoustics - Clean guitars: Electro Harmonics 12AY7, GE 5751, Fender 12AT7
Blues - Classic rock: JJ 12AX7, TTE 83CC, Mesa Boogie 12AX7
Grunge - Classic metal: TT 12AX7, Tung Sol 12AX67, JJ ECC83S
Thrash Metal - Extreme metal: SOVTEK 12AX7LPS, JJ ECC83S, TT 12AX7
(And here are some of the most sought-after, rare/boutique/vintage):
GE 12AX7WA: clean, dark sound.
GE JAN 5751: 30% lower gain than a 12AX7, bright sound.
RCA 12AX7A: hi gain, american fat sound, good for crunch
RCA 7025: lower gain, very good for clean tones.
RAYTEON 12AX7: lower gain, enhanced higher frequencies, great dynamics.
MULLARD 12AX7/ECC83 modern/old logo: hi gain, enhanced mid frequencies, suggested for british amps (beware of the price!).
BRIMAR 12AX7: similiar to the Mullard, but slighly less gainy.
TELEFUNKEN ECC83: high definition, bright sound, less gainy than a Mullard. Very expensive!
TUNGSRAM ECC83: Balanced sound, enhanced mid-lows,high definition, high headroom.
RFT ECC83: strong lower frequencies and good for crunch, lower headroom and break up level, suggested for blues.
TESLA ECC83S: good amount of gain, suggested for british sounding amps.
Power tubes (sorted by type):
EL84: JJ EL84 for a Standard sound, Sovtek / Electro Harmonix for an all around tone, JJ EL844 For a tight, low power sound.
EL34: JJ EL34, Electro Harmonix EL34 for a sound ranging from blues to hard rock, TT EL34 and Tung Sol EL34 for Heavy Metal, SED EL34 for dropped tuning and Bass.
6L6: JJ 6L6 and TT KT66 for a sound ranging from blues to hard rock, TT 6L6, Tung Sol 6L6, Sovtek 6L6 WXT+ for heavier tones up to the extreme metal, and SED 6L6 for dropped tunings and bass.
JJ 6V6 are lower power tubes, which leads to a lower output and a softer overdrive.
KT88 / 6550: JJ KT88, are basically good for every genere, Electro Harmonix KT88 are suggested for Bass amps, while SED KT88 are rich of lower frequencies.
Have fun trying all of the combinations!!
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