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What is a Tube Amplifier? 8 Questions People Concerns the Most



For so many years, tube amplifier has always been a “controversial” component in the electronic field, people are attracted by its premium sound quality but discouraged by its price.

 

Today we are going to talk about tube amplifiers, to understand what this device is, why its price is so much higher than other amplifiers, what are its advantages and disadvantages compared with other amplifiers, and so on.


Catalog

I. What is a Tube Amplifier?

II. Pros and Cons of Tube Amplifier?

III. How Does the Tube Amplifier Work?

IV. Tube Amplifier VS Solid State Amplifier?

V. Tube Amplifier VS Transistor Amplifier?

VI. Things Needing Attention While Using a Tube Amplifier

VII. Why is Tube Amplifier So Expensive? Is It Worth It?

VIII. How to Extend the Life of   the Tube Amplifier?   

FAQ


I. What is a Tube Amplifier?


The tube amplifier is one of the earliest electrical signal amplifiers.

 

The cathode electron emission part, the control grid, the acceleration grid, and the anode (panel) lead enclosed in a glass container (generally a glass tube) are welded to the tube base.

 

The electric field is used to inject an electronic modulation signal into the control grid in the vacuum, and the signal data of different parameters after signal amplification or feedback oscillation is obtained at the anode.

 

Tube amplifiers were used in electronic products such as televisions and radio amplifiers in the early days. In recent years, they have been gradually replaced by amplifiers and integrated circuits made of semiconductor materials. However, in some high-fidelity audio equipment, tube amplifiers with low noise and high stability coefficient are still used.


II. Pros and Cons of Tube Amplifier?


Pros:

1. The tube amplifier has a large input dynamic range and a fast conversion rate.

 

2. Electronic tube amplifiers mostly use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. This is especially obvious in developed countries.

 

3. The open loop index of the tube amplifier is better than that of the transistor amplifier. It does not need deep negative feedback and can work stably without adding phase compensation capacitors, so its dynamic index is better.

 

4. The sound quality of the tube amplifier is generally soft and pleasant. More specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of human voice is its strong point.

 

5. The treble of the tube amplifier is smoother, has enough air, and has a sound coloring that quite a few people like. The soft and slightly fuzzy sound is very beautiful.

 

6. The tube amplifier mainly causes even-numbered second harmonics. This harmonic component is very pleasing, just like adding rich overtones and beautifying the sound.

 

Cons:

1. The service life of the tube amplifier is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use.

 

2. The tube amplifier consumes high power and often works in Class A state, which reduces the efficiency. However, there are basically no harmful sound quality factors such as transient intermodulation distortion, switching distortion and crossover distortion.

 

3. The tube amplifier is not at all superior to the transistor amplifier in terms of weight, efficiency, and lifespan.

 

4. In use, the tube amplifier should have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube amplifier, so it is necessary to keep the temperature of the tube amplifier as low as possible.

 

5. Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible.


III. How Does the Tube Amplifier Work?

This is a basic overview of some of the components of a tube guitar amp and how they work, without getting too technical.


IV. Tube Amplifier VS Solid State Amplifier?


A solid-state amplifier converts an electrical signal into an audio wave using transistor circuitry. Instrumental amplifiers have two amplification stages: the preamp stage at the beginning of the circuit and the power amp stage at the end. 

 

The physical difference between a solid-state amp and a tube amp is that a solid-state machine employs electronic transistors for amplification, whereas a tube amp employs vacuum tubes (also known as valves). Transistors differ from tubes in that they do not deform pleasantly when pushed to their limits.

 

The key difference between tube amplifier and solid state amplifier is: solid-state amplifiers are ideal for guitarists that require a lot of power (a.k.a a loud, clean, undistorted signal). However, without any natural distortion, an electric guitar can sound brittle. As a result, solid-state amplifiers are more popular among bassists and keyboard players than guitarists.


Compared with tube amp, solid-state amp has several advantages:

1.    They are less expensive. Almost all solid-state amplifiers are less expensive than tube amplifiers. They have fewer parts and the ones they do have are reasonably inexpensive. 


2.    They are less bulky. Weight can be an issue if you're a gigging musician who needs to transport an amp around town. Tube amplifiers are almost always heavier than solid-state amplifiers. This is due to the circuitry necessary to operate the glass tubes, not the glass tubes themselves (which are hollow).


3.    They require less maintenance. Tube amplifiers need routine maintenance. Most gigging guitarists replace their power tubes once a year and their preamp tubes every two years. Solid-state amplifiers, on the other hand, do not require part switching. They can function for decades with all of their original components.


V. Tube Amplifier VS Transistor Amplifier?


A transistor amplifier, as the name implies, is used to amplify power, voltage, or current signals. It has a common emitter amplifier, a common collector amplifier, and a common base amplifier. This is the most basic. There are also differential, push-pull, and so on. The audio is actually a power (transistor) amplifier.


The difference between transistor amplifier and tube amplifier:


1. Working characteristics and circuit structures are different

Transistor amplifiers work under low voltage and high currents. The working voltage of transistor power amplifiers is within tens of volts, and the current reaches several amperes or tens of amperes. In the circuit design, direct-coupled (OCL, BTL, etc.) non-output transformer circuits are mostly used. The output power can be very large, up to several hundred watts, and the various electrical properties are very high.


The tube amplifier works under high voltage and low current conditions. The screen voltage of the final power amplifier tube can reach 400-500V or even thousands of volts, and the current flowing through the electron tube is only tens of milliamps to hundreds of milliamps. The input range is too large and the conversion rate is fast.


Most of the tube amplifiers use discrete components, manual wiring, and welding, which are low in efficiency and high in cost. Transistor amplifiers mostly use a combination of transistors and integrated circuits, and printed circuit boards are widely used, with high efficiency, stable soldering quality, and high electrical performance indicators.


2. Power reserve and anti-overload ability are different

The dynamic range of the high-fidelity amplifier should be 120dB, so as to meet the needs of the sound from the slightest to the peak of the climax, the amplifier output is not clipped, so the amplifier must have sufficient power reserve.


If the dynamic range of the audio voltage is 3:1, since the power is proportional to the square of the voltage, the power dynamic range is 9:1. That is to say, a power amplifier with a power of 90W can only be turned on to 10W to achieve high-fidelity playback.


Therefore, the transistor amplifier needs a large power reserve to avoid overload distortion. Once the ground is loaded, its distortion will almost rise in a vertical line, which can damage the transistor in severe cases.


The anti-overload capability of the tube amplifier is far stronger than that of the transistor amplifier. In case of overload, the peak of the music signal only becomes slippery than the normal waveform, and the sound is not deformed much. For transistor amplifiers, clipping will occur at this time, and the sound quality will deteriorate significantly.


3. Efficiency, life, and cost are different

Tube amplifiers are not superior to transistor amplifiers in terms of weight, efficiency, and lifespan.


The service life of the electron tube is relatively low, and some technical indicators will drop significantly after one to two thousand hours of use. The lifetime of transistors and integrated circuits is much longer.


In addition, the tube amplifier consumes high power and often works in the Class A state, which reduces the efficiency. However, there are no harmful sound quality factors such as transient intermodulation distortion, switching distortion, and crossover distortion.


In terms of cost, for the same grade of amplifiers, tube amplifiers are generally significantly higher than transistor amplifiers. The main reasons are the high cost of electronic tubes and output transformers, and the production process of electronic tube power amplifiers is not easy to automate, and the production efficiency is low.


4. Different sound quality

The sound quality of the tube amplifier is significantly better than that of the transistor amplifier.


Transistor power amplifiers have a sense of overwhelming when listening to high and medium and high frequencies, and less low frequencies. Transistor power amplifiers sound hard, especially low-frequency sounds are not soft enough, and high-frequency sounds are sharp and dry. Sometimes it sounds like there is crossover distortion in the high-frequency range. These phenomena become more obvious when the frequency increases and the volume is louder.


However, the transistor amplifier has large dynamics and high speed, which is especially suitable for music with greater dynamics. As for the sound effects of guns and lightning, it is certainly better than a tube amplifier.


Generally speaking, the sound quality of the tube amplifier is soft and pleasant. Specifically, the low-frequency sound of the tube amplifier is soft and clear, and the high-frequency sound is slender and clean. The performance of the human voice is its strong point, and therefore it is more valuable.


All in all, the choice of amplifier varies from person to person. If you like orchestral music, especially chamber music and vocals, then tube amplifiers should be your first choice. If you like jazz, rock, and modern music, then transistor amplifiers are the choice.


VI. Things Needing Attention While Using a Tube Amplifier?


1.    The tube amplifier must be used under the limit parameters. Although it can still work normally under the limit parameters, the life of the tube amplifier will be shortened quickly. Therefore, the tube should be used under the rated parameters.


2.    The location of the components in the device should be conducive to the heat dissipation of the tube amplifier. To control the temperature of the tube case of the tube amplifier, the allowable temperature of the glass case of various tube amplifiers is different. For example, the allowable limit temperature of the power output tube during operation does not exceed 90°C in principle.


3.    Except for the high-reliability tube amplifier with a special structure that can work at higher accelerations, other receiver amplifier tubes can only withstand small shocks for a short time. Therefore, pay attention to the shock absorption of the tube when using it.


4.    When using small tubes (thumb-finger type) and other tubes without tube bases (but with tube needles), use tube sockets specified by the Ministry of Electronics Industry. Prevent cracking or damage to the glass shell. When plugging and unplugging the tube, its direction should be perpendicular to the plane of the tube base. When inserting an electronic tube, prevent damage to the normal position of the contact reed in the socket socket of the tube socket, and avoid using the empty foot of the tube socket as a connecting pad.


5.    When using an indirectly heated tube amplifier, the potential difference between the cathode and the filament must not exceed the specified limit. For this reason, a dedicated filament transformer is often used for power supply. In order to eliminate the effect of leakage current instability, under the condition of not hindering the operation of the circuit, a shunt resistance of about several ohms can be connected between the cathode and the filament.


VII. Why is Tube Amplifier So Expensive? Is It Worth It?


In short, tube amplifiers are costly because they use pre and power tubes as their primary amplification source. Each tube costs approximately $50 and can have up to four of them in a single unit. Second, these amplifiers have more expensive components, larger casings, and more complicated circuitry than solid-state amplifiers.

 

Whether tube amplifiers are "worth it” or not, well, that’s more of a subjective question.

 

If your goal is to build a pristine audio chain that cleanly reproduces the input signal you give it, a tube amplifier is definitely not worth it.

By spending extra money to put a tube in your signal chain, you are intentionally distorting the sound.

 

Note that modern high end A/D/A conversion equipment (which aims for perfect signal reproduction) never uses tubes. The marketing pitch on tube equipment is that it does change the sound that you give it. Don't buy a tube amplifier unless that is what you want.

 

Now, if your goal is not to amplify signal accurately, but rather to make a sound that you personally find pleasing, a tube may yield some benefits.

 

You can listen to some tube amps at different levels to decide what you personally prefer. Does this make a tube amp worth it? Bear in mind that there are many ways of creating harmonic distortion (in the analog domain, or emulated with digital techniques), and many are cheaper than tubes, which are expensive to produce.

 

The high cost of tubes is not a function of the fact that it was difficult to engineer their particular audio qualities. The way tube amplifiers color audio is a historical function of the fact that engineers were not able to compensate for the changes they introduce.

 

Many people have now decided that this is a valuable property - but the production of tubes is becoming relatively more expensive as demand for them diminishes and they require specialty, limited-run manufacturing (compared to transistors, demand for which is growing).

 

In all, thinking from your practical needs before jump into any conclusion, whether tube amplifier is worth it or not, there’s no absolute answer to this question.


VIII. How to Extend the Life of the Tube Amplifier?   


The problem of short life of the tube amplifier is often criticized, but this is often not a problem of the tube amplifier itself, but a defect in the circuit design and a problem in use. It should be noted that a good quality tube amplifier must have a correctly designed circuit, sufficient heat dissipation, and thoughtful shock absorption.

 

In use, the tube amplifier must have good ventilation and heat dissipation. Overheating of the temperature will inevitably shorten the life of the tube, so the tube amplifier should be kept as low as possible.

 

Vibration is not good for tube amplifiers, so it is important to take anti-vibration measures to avoid vibration as much as possible. If these two can be achieved, the service life of the tube amplifier can be at least doubled. For this reason, there should be a proper space around the tube amplifier equipment, especially above it, in order to have good convection ventilation, if possible, a fan can be used to help dissipate heat.

 

When the cathode of the tube amplifier has not reached the required temperature, the high-voltage power supply is immediately applied, and its cathode will be damaged, which will also shorten the life of the tube amplifier.

 

Therefore, if the tube amplifier equipment has a preheating device, it must be used. For example, first turn on the filament low-voltage power supply to preheat, and then turn on the high-voltage power supply. If there is no preheating device, don't rush to connect the input signal, you can turn the volume down to the minimum, wait for 20-30 minutes to warm up the machine before using it.

 

If the indirectly heated rectifier tube is used to supply the high voltage of the whole machine, it just provides a simple and effective high voltage delay. In addition, do not switch the power supply frequently during normal use.

 

Of course, if the tube amplifier circuit is designed correctly and the wrong use is avoided, the tube amplifier will not "die young". It should be normal for the tube amplifier to use thousands of listening hours.

 

The most common mistakes in circuit design are:

1. The potential difference between the filament and the cathode of the tube amplifier is too high

2. The screen or screen grid voltage of the tube amplifier is applied to the maximum value

3. The filament voltage of the tube amplifier is too low or too high

4. Improper installation position of the tube amplifier causes the electrode to overheat and the high-voltage power supply does not have a delay device, etc.

 

Therefore, these problems should be avoided when designing the circuit to effectively extend the service life of the tube amplifier.


FAQ


1. Why is a tube amp better?

Tubes, like analog recordings, have a more full-bodied sound than transistor gear. There's a "roundness" to tube sound that solid-state gear never equals. Tubes are less forgiving about mismatches, so to get the best out of a tube amp it must be used with just the right speaker.


2. What is tube amplifier used for?

Tube amplifiers, or tube amps as they're commonly called, are tiny electronic or electromagnetic components that are used to boost electric current in devices to improve their performance. It's what makes your hearing aid pick up sounds through a microphone from all around you.


3. Are tube amps worth it?

In many cases, tube amps do not require the amount of maintenance that they have a reputation for. As long as you properly take care of your gear, owning a tube amp is simple and very well worth it for the tone.


4. How long should a tube amp warm up?

20 to 30 minutes. As a rule of thumb, your tube amp needs to be warmed up for 20 to 30 minutes at least before you can start playing your guitar.


5. Why are tube amps louder?

When tubes are driven outside their linear region, for the first 12db or so of overdrive the harmonics that they produce trick the human ear into thinking that the sounds are getting louder, when in fact the sound is getting progressively more distorted.


6. How does a tube amplifier work?

The power transformer and rectifier work together as an electron pump which pulls electrons out of the amp circuit creating a positive voltage (electron scarcity = positive voltage). The amplifier's electronics need DC to amplify. The amp is powered by DC but the guitar signal moving through the amp is AC.


7. What's the difference between a tube amp and a regular amp?

The physical difference between a solid-state amp and a tube amp is that a solid-state machine derives amplification from electronic transistors, while a tube amp uses vacuum tubes (also known as valves). ... Solid-state amps are great for players who want maximum headroom (a.k.a a loud, clean, undistorted signal).


8. Which is better tube amp or solid state?

Tube amps are generally more expensive in initial cost and to operate (because you need to replace the tubes occasionally), and solid-state amps are generally less delicate and more reliable. Many players, however, feel that tube amps yield a warmer, more musical tone and more musical-sounding distortion.


9. How often should a tube amp be serviced?

15 years. If its a well made amp, recap every 10 or 15 years, retube as needed. Fenders might go many years without needed a power tube replaced.


10. How many watts do I need in a tube amp?

100 watts. You'll need a solid state amp that has around 100 watts, or a valve amp that has around 50 watts. This will usually give you enough volume that you can be heard over the drummer, without having to push your amp's volume too hard so that the distortion becomes overbearing.