What are tube amps?

Tube Amps, also known as Valve amplifiers, are those amplifying devices which use electronic components called “Vacuum Tubes” or “Electronic Valves” for amplification purpose in the circuit instead of solid state components like transistors, FETs, ICs etc..

WHY do guitarists favour tube amps?

Take a look at any major guitar player in history from any genre and you will see two things in common with all of them. First is passion and second is the fact that they used tube amplifiers to forge their signature sound. Be it David Gilmour from Pink Floyd, Eddie Van Halen, even the late great Dimebag Darrell switched after years of using solid-state amplifiers to tube amps to achieve and better his sound.


So the question arises why did all these players use tube amplifiers instead of solid state or hybrid amplifiers?


The answer is simple.


Tube amps sound and feel REAL….The reason for this is the way the tubes amplify the guitar signal in a very specific manner. This allows the sound to breathe and release the rich harmonic content. So when the amp is overdriven due to the natural compression, midrange emphasis…compressed soft clipping occurs with even order harmonic distortion so much preferred by the guitarist against the odd order you hear on solid-state amplifiers.


Companies have tried for many years to emulate the tube amp sound quality on solid-state or digital designs, without much success. No advanced circuitry or endless number of pedals or variations will ever provide the rich warm sound that tubes produce. Furthermore, they are extremely sensitive to your touch…Take a well-designed tube amp and crank up the gain channel all the way. The best ones will still maintain a clean sound when the guitar is played with the lightest of touches and burst with distortion when struck with force.

What drives a tube amp?


The tone is honestly in your hands and tube amps reward dynamic playing. The very manner in which you strike a chord or pick a note changes the way it sounds. It is the Holy Grail for guitarists as it allows them to express themselves with absolutely no filters. They are finally able to hear themselves in the rawest form and learn to create their own signature sound.


Every guitarist has different hand texture and frets notes in a certain manner. There is an old Van Halen story that illustrates this beautifully. Right around the time Van Halen was starting to become popular they were opening for Ted Nugent. Like all other guitarists Nugent was blown away by Eddie’s sound and wanted to plug into his rig to see what gear he was using to get his sound. Unsurprisingly, he still sounded like Ted Nugent. There were no magic pedals or fancy modifications to the amps that made his sound. Eddie learnt how to strike the guitar in ways people never thought possible. All because he practiced day in and day out with a tube amp to constantly refine his playing and develop his unique sound.

Why choose Calor tube amps?

We craft some of the highest quality Tube amps in the world, and this has been testified by artists who have personally tried our amp. We use only the finest materials from international markets. We are not that Indian company that wants to enter a market because we think we can make it cheaper. We are extremely passionate about high quality guitar tones and wish to provide that gift to those who seek it. We understand that every guitarist wants to sound great and unique and our tube amps allow you to do just that.

What are our valve amps designs based on?

Building an amp is an art form much like writing music and we respect the intellectual property rights of the original designer.  Almost all other brands in themarketplace are trying to replicate American or British tones. We design Calor amps that put a smile on your face the moment you plug your guitar and strike the first note. The cleansound has to linger with sweetness and sustain, and the Drive channels should scream and roar, scream depending on how you play your instrument. Extensive studies, calculations and many hours of tweaking have gone into designing each of our valve amps. We have designed our valve amps to get the best American Clean and British Drive sound and we know that you will not be disappointed.

Why are all tube amps expensive?

The main reasons are raw material costs in tube amps are more than those used in solid state amps plus of course…the labour and time involved to build tube amps, especially hand-wired ones.

Why is there a STANDBY Switch on most of the tube amps, what does it do? Is there a method to properly turn on a tube amp with Standby Switch?

Standby Switch is a common sight on a tube amp and is given for this reason. Guitar amps are designed to practically abuse the tubes by giving them more than rated voltage like 350-450 volts or even more when they were expected to be used at around 200-350 volts in a hi-fi amp. When such high voltages are given to tubes before they are warmed up, cathode stripping takes place in other words tubes get degraded and the life is reduced. By properly using a standby switch we ensure that these high voltages are given to tubes only after they warm up by turning on just the heater, so prolonging the tube life.

Recommended Method…First you must ensure that both the Mains and Standby Switch are in OFF STATE – Universal symbol…’0′, then turn on only the Mains switch – Universal symbol being ‘l’. After 30-60 seconds the Standby Switch could be turned on. When turning off, turn off the mains switch, this will help the voltages to bleed. Standby Switch can also be used when you are taking a break during a set or rehearsal.

What do Single ended tube amps do?

Single ended tube amps sound and feel very different to their 50 and 100 watt counterparts. They are loved because they sound like higher powered amps at non-deafening volumes. Don’t expect a very big headroom and loud tight cleans. They have a signature sweetness and rich harmonic content which cannot be achieved by their bigger counterparts. The 50 and 100 watt amplifiers sound balanced only when cranked up to a certain level which may be undesirable in many situations

18 watt push-pull amplifiers?

18 watts of clean power is channeled through a pair of EL84 (or 6V6) tubes in a push-pull configuration. The power stage is more or less the same through various 15 – 20 watt amps built by various brands. These amps can be driven further to get clipped overdriven sounds that could easily produce up to 30 watts. People not used to hearing tube amps can find 18 watts too low on paper but too loud in reality. With modern music reproduction technology no one ever needs more than 18 watts for small to medium sized venues. Just ask our artists who have been touring with the 18 watt models here and overseas

So what kind of Tube amp should I go for, there are so many in the market?

With many valve amps in both combo or head and cabinet configurationfrom the lower powered up to 100 watts available, it depends on the style of music you play and where you play. For example an 18 watt will be enough for home and band practice, recordings and mediums sized gigs, howeverremember you can use them in larger venues by simply micing up and sending the signal to a P.A. System. So review your needs carefully,your unique sound is your dream.

Why does a 50 watt Tube Amp sound louder than a 50 watt solid state?

The reasons are very simple, the conventions for writing the output power of a tube amp was the wattage the power tubes could deliver when they are at clipping, that means when you turn the volumes past clipping, it pushes out even more power.


Guitar Amps are designed to practically abuse the tubes into the clipping region and this is where we get the typical valve overdrive. For example, a 50 Watt Marshall head like JCM800 could produce around 50 watt of power at clipping but when driven hard into the overdrive region can produce up to 90watts RMS! The circuit components are carefully chosen to handle the extra load.


So, a 15 watt tube amp can be significantly louder than a 15 watt solid state amp. It is actually, closer to a 40 watt solid state amp.

What are Class A and Class B and Class AB, does it mean Class A is better than Class B?

NO. Different amplifier Classes and Configurations serve different purposes and styles. One is not better than the other. The classes depend on how the power tube configuration and voltage supply is arranged. In terms of tone, the following is noticable :


Class A or Class AB

Pros: Chimy pleasing tones even at low volumes, Smooth Distortion avoiding the harshness of crossover distortion of class B(class A has no crossover distortion, class AB has some).


Cons: Loose or Flabby Bottom End, Inefficient in terms of Output Power(no matter what tube is used, it will definitely be less powerful), Heat Dissipation and Electricity Consumption, No matter what volume you play they always run in the hot region and hence wear out a lot quicker than those running in Class B(they may last around 1-3 at moderate usage in a guitar amp), Lack the “Sagging Quality” (compression due to heavy current consumption causing dip in voltage at high volumes) of Class B. Technically speaking, class AB amps stay in the class A region at lower volumes and transit into the class B at Higher Volumes.


Class B


Pros: Punchy Tones and a Tighter Bottom End, Nice Sag Quality providing musical compression much more than Class A or AB, Very Efficient in terms of power output(they produce more power than class A from same number of tubes), Heat dissipation, Electricity Consumption and have a longer life than those tubes running in Class A or AB(at moderate use they may last from 2-5 years).


Cons: Class B amps suffer from crossover distortion which sounds harsh that doesn’t exist in class A Amps, they tend to sound good only at Higher Volumes.

What are Point to Point Wired amps and why are they expensive than PCB Based Tube amps?

In a Point-to-Point Handwired amp each component is connected to a tube pin or solder lug or jack. PCB Construction includes everything soldered to a PCB, including pots and tube sockets. This makes it easier and cheaper to manufacture, but harder to service and modify, and there is some question about the reliability of the PCBs holding the sockets of the extremely hot power tubes. A Hand wired point-to-point amp sounds a certain way that people like because all amplifiers in early era were built in the similar traditional way and they seem to stand the abuse of decades and have worked to the liking of the guitarists.


Calor utilizes a specially designed board, which acts as a turret board found in amplifiers of the classic Hiwatt/Harry Joyce style or the classic Fender and “plexi” construction methods. Here although a board is used, there are absolutely no signal traces on the PCB. Some of our Amplifiers are built on well designed dual sided PCB with thick traces and carefuly planned component layout with only preamp tube sockets, power tubes sockets are mounted to chassis and are hard-wired. This allows us to maintain the qualities of a Point-to-Point construction methods hence avoiding signal loss compared to total PCB based construction methods where signal traces on a PCB suffers from signal degradation.


The amps constructed in traditional methods are durable and are easy to modify and repair. Poorly built PCB based amps suffer from cracks in traces when it undergoes long periods of stress especially in combo amps.


Since a lot of expertise and labor is required to build a hand wired point-to-point amplifier, they are significantly more expensive than a cheaply built PCB based amp. The durability and tone of hand wired amps make them an attraction much like handcrafted guitars.

Why are there so many types of tubes?

Just like other electronic components, tubes are of different types too, in fact, there are tubes with different model numbers which are exact equivalents of each other.
Most commonly used PRE AMP TUBE in a guitar amp is the 12AX7 also known as ECC83 (ECC83 is the English name for this valve, 12AX7 is the American), lower gain tubes like 12AU7/ECC82 or 12AT7/ECC81 are also used in some amps like Fender. Other rare varieties like EF86(used in matchless and vox amplifiers) and 6SL7, 6SN7(used in Ampeg) were also used in some amplifiers.


Most commonly used POWER AMP TUBES are EL84, EL34, KT66, 6L6, 6550, 6V6, 5881 each with their own sound and output power limit.


Types of Tones Produced by Different Tube.


EL84 and 6V6 are low power tubes a pair of which can produce around 15-18 watts at clipping and more when driven, a quartet is used in 30 watt amps.


EL34, 6L6, KT66, 5881 etc. will produce around 50 watts of power from a pair and 100 watts from a quartet.
EL84 tubes are known for bright chimy sounds and are the backbone of the famous Vox AC30 sound and are used in Matchless and Orange Amplifiers as well.


6V6 has an extended low end than EL84 tubes and were used in low powered Fender Amps and gives them THE Fender Sound.
EL34 is famous for it’s midrange crunch instantly creating Hard Rock nostalgia made popular by Marshall Amps.


6L6 have a tighter bottom end than EL34s, they are relatively clean sounding Tubes that don’t distort that easy and hence are used in lot of Bass Amps and Boogied or Hot-Rodded Amps where the tone is heavily driven and reclipped in many preamp stages itself.


KT66 are expensive and old production KT66 are getting rare. They are known to be the best sounding tubes for Guitar Amps, used in Early Marshall Amps used by Hendrix and Clapton.


Most tubes have variations in names like 12AX7A, 12AX7WA, 6L6G, 6L6GT, etc..they are more or less the same tube with the other version being more rugged, or has larger dissipation, might have gold plated or silver plated components, etc. check for the manufacturer’s tube datasheets for more details.

Do tubes burst or explode on their own under normal operation?


How long can tubes last?

This is the best part about tubes, they have an indefinite shelf life. That means if you take a tube keep it in some corner of your house forget about it and a 100 years later your great grandson finds it and tries to use it in a circuit, it will still work!


Under normal usage in an amp, life of tube depends on the type of tube and how hard you drive them. Hard usage means how hot you are running them, for example, amps played at lower volumes will not run the tubes so hot but if played at higher volumes in order to get the power tube distortion means you are running the tubes pretty hot. Pre-amp tubes like 12ax7, 12au7, 6sl7, etc..can last decades irrespective of how hard they are run.


Power Amp tubes are another story, they need to be replaced more often. A power tube say el84 in a class A operation in an amp which is played 8 hours a day at moderate to loud cranked up volumes will start degrading in as little 6-8 months! But the same tube in a class AB or Class B amp will last for 2-4 years at similar usage at moderate volumes.

How do i know if the tubes are worn out and it’s time to replace them?

Tubes will not just stop working in a day indicating you need to change them. The best guides are your “EARS”. Worn out tubes may not sound they way they did when you first bought them, most noticeable is the high end or presence in the sound, worn out tubes will sound dull, and some of them might even become noisy.


How do i replace them just pull them out and put in new ones?

Most of the amps have power tubes in even numbers like 2, 4 ,6 or 8, small amps might have just one. Replacing power tube is not that simple, just swapping them with new ones might make the amp work, but it may not sound right, the reason is power tubes need to be biased(setting idle current) in most of the amplifiers to produce the right tone, and this has to be done to new tubes that are used.


Hence, it is recommended that you take your amp to an amp technician for replacing your tubes. Some amplifiers need not be biased in which case you can replace the tubes with a matched set. Pre-Amp tubes when replaced with equivalent ones will work and don’t need to be biased, if you have a bunch of pre amp tubes of different brands, you can try each one of them to hear what sounds best.

Getting the most out of the tube amp ?

When approaching a tube amp a player must understand that it will behave very differently when compared to its solid state counterparts. A well-designed tube amp will produce every little nuance of what you put into it. We design our amps to be as transparent as possible so an artist can hear his own expressions through the amp.


To be honest, the amp sounds great if you play great. For beginning players the amp may feel demanding to play as it highlights every little mistake. This actually is a blessing in disguise as it forces the player to acknowledge their faults and learn to better their technique.

Are the Tubes or the output transformer the most important component in a tube amp?

There is no single important component in a tube amp, everything has a major or minor effect on sound, different tubes have a different sound, one interesting fact is that the same tubes manufactured by different brands sound different. Output transformers also play an important part in shaping the tone, the pre-amp tubes, resistors, capacitors, Connectors, wires and wiring method, component layout in the amplifier, voltages given to each tube, idle current set for tubes, even the type of rectifier(tube or solid state diode)used in the power supply affects the sound in some way or the other.

So you mean if i buy one of the tube based preamps, or overdrive pedals, i will sound as good as playing through a tube amp?

No, definitely not if you are using a solid state amplifier for the final output. In tube based overdrive pedals and preamps, the tubes that are driven hard to attain clipping are preamp tubes, which produce harsh clipping sounds, which more or less sounds the same as the solid state clipping circuits. You need to drive a valve amp driven hard to produce “Power Tube Distortion”.


Tube preamps have been overhyped and oversold, most of the artists who have a great tone used a simple solid state overdrive pedal in their signal chain driving a tube amp for their sound.


The real magic or warmth of a tube amp is achieved from it’s final equation of Power Tubes Connected to an Output transformer Connected to a Speaker which is  mic’d in a traditional manner for recording! It’s how the POWER TUBES break up that creates a very musical overdrive.


Power tubes and Pre-amp tubes distort in different ways, that’s why a tube amp sounds best when played at loud volumes, that is where it sounds fat, chimy, very touch responsive and distorts musically. In a solid state amp we don’t have an output transformer in most of the cases, D.I. boxes don’t give good results because the speaker sound is missing! All of this cannot be compensated in a small pedal where a preamp tube is clipped, and processors can only apply algorithms to your signals which can only come close, but nowhere close enough.