The Real Difference In Guitar Power Tubes

Guitar amps that use tubes are still great, and even after all these years, digital modeling amps still emulate the character that these amps possess. After a while these tubes start to “lose” their sound and then it is time to replace them. There are many opinions on which tubes are best and have the greatest tone, but it is not really that complicated. There are three basic tube types (by purpose) that an amp has and I will go over each one, its alternatives, and its tonal benefits. This will go much faster than you would expect.

Preamp Tubes

The preamp tubes are the first tubes in the electrical signal path. These are the smallest tubes in the amp and are technically two conjoined tubes, a dual triode. Most common is the 12AX7, alternatives are the 12AU7, the 12AY7, and some other 12**7 tubes. They last longer than the power tubes so you won’t need replace these as often. Their differences can be explained best here.

For guitar and bass, I would stick with the 12AX7, it is easier to find since it comes standard on everything! You might think the alternatives would be a great candidate for a reverb channel or an effects loop, but no one would really notice a difference. If anything, you might have to convince yourself that it was worth the experiment.

Power Tubes

This is what most people look for. These are usually the first to fail and the subject of much argument. Common types are 6L6, EL34, 6V6, KT88, EL84, and KT66. The first two in the list are in 90% of all amps, and bass amps usually go for the KT types. All have pentode sockets, with the exception of the EL84. You should only get the type your amp needs, or you can damage your amp. For example, if you are replacing KT88 tubes with 6V6 tubes and don’t have the ability to adjust the voltage, you may melt something.

These tubes are very voltage dependent and their output differences are mistaken for tonal variation. Buying  matched sets is highly recommended if your amp has multiple sockets for power tubes. These tubes must be biased to work properly, that means they have to have their voltage “regulated” by a little knob so thy can be used to their full or desired potential. When the voltage is low, they are said to be “running cold”, and when the voltage is high, they are said to be “running hot.”

Rectifier Tubes

These tubes are the not something you want to do wrong. Replace these with the same type, or if you want to really experiment, check this site here for some basic info, and here for the hard data. If you are changing to some Webber Copper Caps, like I did, then use something comparable.

The rectifier tube can change the feel of your amp, but as I was told by an amp builder– once you crank the amp to make it loud, the whole “sag” thing kind of disappears because the voltage hitting the tube is so constant.

A Note on Brands and Different Manufacturers

You are going to see people say that JJ tubes are the best, and that Ruby Tubes have the best tone, some say that the NOS (New Old Stock) is the way to go. Before you dredge the forums and tear your hair out at Ampage looking for a solid answer to which tube brand sounds the best, ask yourself this question: which sounds better? A Sylvania light bulb or a Phillips light bulb?

Tubes are basically designed to do the same thing, so don’t expect one brand to eclipse the other in terms of tone and sound quality. They all are designing their tubes for the same voltage requirements, not tone. “But cathode bias is the best on a XYZ tube!” No. Unless you have a magic ear, you wont hear it. My friend swapped out all of his Sovtek tubes on his Laney VH100R with JJ tubes because he heard they had great tone. When he got them all in, it sounded terrible because it needed to be rebiased and he had a bad 12AX7. Once he had it all up an running, it sounded exactly the same! Let me end with this, tubes are designed for voltage, not tone.

The best instrument cable in the world!

Everyone wants the best of the best, even if you can’t afford it. Is it Mogami, Canare, Monster, LiveWire, Planet Waves, or some generic thing you find in an alley? The answer is simple and rather dumb: the one that works the best for you is the greatest cable. What you should ask instead is, “what makes a great cable, and what would work for me?” If you are impatient and just want a name to go buy, then skip to the end and you can see my personal favourite. For the rest who want to make an informed decision, continue on…

What is a guitar cable? Typical Guitar Cable

A guitar cable is a length of wire, which is shielded and protected, that conveys an electrical signal from one end to the other with phone plugs on each end, just like in the picture. There are four main parts of importance:

  • Phone plug/ connector
  • Core wire
  • Shielding
  • Insulation/Cover

Before we get into the depth of these, lets talk about materials. These cables are made of metal and plastic rubber. The order of conductivity in metal (that is how well it transmits electricity) from best to fair is, Silver, Copper, Gold, Nickel, and Aluminium. There are others, but this list is pertaining to common metals in guitar cables. Plastic is an insulator, which means that electrical signals do not easily pass through it. PVC, Polypropylene, Vinyl, Polyethylene, and Rubber are also insulators and have different qualities. The exterior of most cables are usually made of PVC.

Phone Plug

Typical Guitar Plug

The typical guitar connector is a relic of the days when phones used switchboards and operators.

It was a job that women usually did until they were replaced by robots. There are different types of phone plugs, but the type that is used in instruments and speaker cabinets is the 1/4″ TS (Tip Sleeve) phone plug. You will notice that the tip is insulated from the sleeve by a piece of plastic or rubber, and that there are no other bands on it. If you look at the plug for your headphones or ear-buds, you will see an extra band. That is for stereo only! Do not use it on guitar or bass or it might short, maybe. Some of these are at right angles, but as long as it is a TS connector, phone plug, guitar plug of 1/4″ in diameter, it will work. Most connectors are made of nickel even though it is not quite as conductive. Nickel has excellent resistance to corrosion and will withstand all the sliding that goes on when plugging in your gear. Like Nickel, gold has excellent resistance to corrosion and has great conductive properties, but it normally doesn’t survive all the friction from sliding in and out of receptacles. After the signal travels through the gold, it will still have to go through the nickel to get to the cable. Only one company that I am aware of uses copper tips in their plugs, and while they are great, copper does corrode and oxidize (rust), but it is not difficult or impossible to clean. As far as silver and aluminum are concerned, I have not run across a plug made from these materials. Be wary of cryogenic treated plugs and strange and fancy alloys. These do not always work the way they are advertised, or the cryogenic treatment was done wrong. Cryogenic treatments are good for strengthening the metal, and there is some evidence that it will help resist corrosion and with plating some metals.


Mogami Cable

Most cables are are made in similar ways. This example of a quality Mogami cable, diagrams the insides quite well. The center wires are what conduct the signal and the copper shielding protects the signal from EMI and RFI.

The Core

Before we get into all that, lets start at the center. This is usually made of copper in differing qualities and gauges. The larger the gauge, the more of a signal can flow easily, but there is a limit. If you remember our list of metals you would see that silver would be best as the core of the cable. This is cost prohibitive  but there are some tutorials on making cables from gold and silver. Oxygen free copper is good because it is more pure and will resist corrosion better. Some manufactures will stick what looks like a strand of fishing line or dental floss down the middle for added strength, it won’t degrade anything. Cable capacitance is how much signal is going to be put through the conductor before it builds up too much and comes out in pulses, sort of. Measured as pF/ft, lower is usually better, and this is what the expensive cables brag about.


The best cables are useless without proper shielding. This is kind of a complicated subject and it is best explained here. What you want is a cable that is shielded from EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference). The efficacy of the shielding is measured in db (decibels) where the higher the db, the better. Most companies will not divulge this information though. Materials used for this are mainly copper, but nickel wire and aluminum wraps are sometimes used. Conductive foam and rubber can also be used to protect the signal. The shielding also acts as a ground for the phone plug

Protective Cover and Insulation

The outside of the cable is often ignored. This is the part that protects it from scrapes and physical damage, along with noise that can get introduced from bumping and dragging. There is also insulation and protection between the conducting core wire and the shielding. While  PVC and polypropylene are common, Nylon mesh and cotton weaves are also used to protect against bumps and to cushion impact. Fabric has a nice feel and can perform better than plastics when it comes to impact.

The Results?

A good cable with nickel plugs can give you a warmer more vintage sound, adding gold plating will open up the sound a bit, and copper will really translate well and sound very open. The best cable at transmitting a signal is going to be one from Lava Cables, called the Ultramafic. It is silver plated copper wire, with a low capacitance and a silver core plug. For a second place, I would choose their Blue Demon cable with the copper core plug from G&H, and third would be any other company that specs out well. Remember that many companies will spend more money marketing their wares than building quality stuff, and that some features are really unnecessary and more of a gimmick, like spark plug connectors. Choose wisely, and rock on!