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Making a tube amplifier

When asked to come up with a "do it yourself" tube mic pre project, I thought long and hard about what topology to go with. The thought being, if you are going to spend the time to build it, then make it worth the effort. In my opinion, the transformers in a tube amp are just as important to the sound as the tubes, so building a transformerless tube amp would not provide much of the desired characteristics which people seek in tube gear. I stole the basic design from the tube mic pre that I build and sell, and tried to make carefully chosen "compromises" to get the cost down. The philosophy was to eliminate the very expensive components that make only subtle improvements, while putting money into the important things like high quality audio transformers.


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WATCH RELATED VIDEO: I built the Tiniest DIY Guitar Tube Amplifier!

How To: Tube Amp Biasing


A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the s and s.

Valve amplifiers can be used for applications such as guitar amplifiers , satellite transponders such as DirecTV and GPS , high quality stereo amplifiers, military applications such as radar and very high power radio and UHF television transmitters. Until the invention of the transistor in , most practical high-frequency electronic amplifiers were made using thermionic valves.

The diode conducted electricity in one direction only and was used as a radio detector and a rectifier. In Lee De Forest added a third electrode and invented the first electronic amplifying device, the triode , which he named the Audion. This additional control grid modulates the current that flows between cathode and anode. The relationship between current flow and plate and grid voltage is often represented as a series of "characteristic curves" on a diagram.

Depending on the other components in the circuit this modulated current flow can be used to provide current or voltage gain. The first application of valve amplification was in the regeneration of long distance telephony signals. Later, valve amplification was applied to the ' wireless ' market that began in the early thirties.

In due course amplifiers for music and later television were also built using valves. The overwhelmingly dominant circuit topology during this period was the single-ended triode gain stage, operating in class A, which gave very good sound and reasonable measured distortion performance despite extremely simple circuitry with very few components: important at a time when components were handmade and extremely expensive.

Negative feedback NFB was invented by Harold Stephen Black in , but initially little used since at that time gain was at a premium. This technique allows amplifiers to trade gain for reduced distortion levels and also gave other benefits such as reduced output impedance.

The introduction of the Williamson amplifier in , which was extremely advanced in many respects including very successful use of NFB, was a turning point in audio power amplifier design, operating a push-pull output circuit in class AB1 to give performance surpassing its contemporaries.

World War II stimulated dramatic technical progress and industrial scale production economies. Increasing affluence after the war led to a substantial and expanding consumer market. This enabled electronics manufacturers to build and market more advanced valve tube designs at affordable prices, with the result that the s saw the increasing spread of electronic gramophone players, and ultimately the beginnings of high fidelity.

Hifi was able to drive full frequency range loudspeakers for the first time, often with multiple drivers for different frequency bands to significant volume levels. This, combined with the spread of TV, produced a 'golden age' in valve tube development and also in the development of the design of valve amplifier circuits.

A range of topologies with only minor variations notably different phase splitter arrangements and the " Ultra-Linear " transformer connection for tetrodes rapidly became widespread. This family of designs remains the dominant high power amplifier topology to this day for music application.

This period also saw continued growth in civilian radio, with valves being used for both transmitters and receivers. From the s the silicon transistor became increasingly pervasive. Valve production was sharply decreased, with the notable exception of cathode ray tubes CRTs , and a reduced range of valves for amplifier applications. This reduced set of types remains the core of valve production today. The Soviets retained valves to a much greater extent than the West during the Cold War , for the majority of their communications and military amplification requirements, in part due to valves' ability to withstand instantaneous overloads notably due to a nuclear detonation that would destroy a transistor.

The dramatic reduction in size, power consumption, reduced distortion levels and above all cost of electronics products based on transistors has made valves obsolete for mainstream products since the s. Valves remained in certain applications such as high power RF transmitters and the microwave oven , and audio amplification equipment, particularly for the electric guitar, recording studios, and high-end home stereos. In audio applications, valves continue to be highly desired by most professional users, particularly in recording studios' equipment and guitar amplifiers.

There is a subgroup of audio enthusiasts who advocate the use of tube amplifiers for home listening. They argue that tube amplifiers produce a "warmer" or more "natural" valve sound. Companies in Asia and Eastern Europe continue to produce valves to cater to this market. Many professional guitar players use 'tube amps' because of their renowned 'tone'.

Most audio technicians and scientists theorize that the 'even harmonic distortion' produced by valve tubes sounds more pleasing to the ear than transistors, regardless of style. It is the tonal characteristics of valve tubes that have sustained them as the industry standard for guitars and studio microphone pre-amplification. Tube amplifiers respond differently from transistor amplifiers when signal levels approach and reach the point of clipping.

In a tube amplifier, the transition from linear amplification to limiting is less abrupt than in a solid state unit, resulting in a less grating form of distortion at the onset of clipping. For this reason, some guitarists prefer the sound of an all-tube amplifier; the aesthetic properties of tube versus solid state amps, though, are a topic of debate in the guitarist community. Power valves typically operate at higher voltages and lower currents than transistors - although solid state operating voltages have steadily increased with modern device technologies.

High power radio transmitters in use today operate in the kilovolt range, where there is still no other comparable technology available. Many power valves have good linearity but modest gain or transconductance. Signal amplifiers using tubes are capable of very high frequency response ranges — up to radio frequency and many of the directly heated single-ended triode DH-SET audio amplifiers use radio transmitting tubes designed to operate in the megahertz range.

In practice, however, tube amplifier designs typically "couple" stages either capacitively, limiting bandwidth at the low end, or inductively with transformers, limiting the bandwidth at both ends. See power amplifier classes. Some significantly different circuit topologies exist compared to transistor designs. The high output impedance of tube plate circuits is not well matched to low-impedance loads such as loudspeakers or antennas. A matching network is required for efficient power transfer; this may be a transformer at audio frequencies, or various tuned networks at radio frequencies.

In a cathode follower or common-plate configuration, the output is taken from the cathode resistance. Because of negative feedback the cathode-ground voltage cancels the grid-ground voltage the voltage gain is close to unity and the output voltage follows the grid voltage. Although the cathode resistor can be many kilohms depending on biasing requirements , the small-signal output impedance is very low see operational amplifier. Valves remain in widespread use in guitar and high-end audio amplifiers due to the perceived sound quality they produce.

They are largely obsolete elsewhere because of higher power consumption, distortion, costs, reliability, and weight in comparison to transistors. Telephony was the original, and for many years was a driving application for audio amplification. A specific issue for the telecommunication industry was the technique of multiplexing many up to a thousand voice lines onto a single cable, at different frequencies.

The advantage of this is that a single valve "repeater" amplifier can amplify many calls at once, this being very cost effective. The problem is that the amplifiers need to be extremely linear, otherwise " intermodulation distortion" IMD will result in "crosstalk" between the multiplexed channels. This stimulated development emphasis towards low distortion far beyond the nominal needs of a single voice channel. Today, the main application for valves is audio amplifiers for high-end hi-fi and musical performance use with electric guitars , electric basses , and Hammond organs , although these applications have different requirements regarding distortion which result in different design compromises, although the same basic design techniques are generic and widely applicable to all broadband amplification applications, not only audio.

Post World War II, the majority of valve power amplifiers are of the Class AB-1 "push pull" ultralinear topology, or lower cost single ended i. The basic moving coil voltmeter and ammeter itself takes a small current and thus loads the circuit to which it is attached.

This can significantly alter the operating conditions in the circuit being measured. The vacuum tube voltmeter VTVM uses the high input impedance of a valve to buffer the circuit being measured from the load of the ammeter. Valve oscilloscopes share this very high input impedance and thus can be used to measure voltages even in very high impedance circuits. There may typically be 3 or 4 stages of amplification per display channel.

In later oscilloscopes, a type of amplifier using a series of tubes connected at equal distances along transmission lines , known as a distributed amplifier was employed to amplify very high frequency vertical signals before application to the display tube. Valve oscilloscopes are now obsolete. In the closing years of the valve era, valves were even used to make " operational amplifiers " — the building blocks of much modern linear electronics.

An op-amp typically has a differential input stage and a totem pole output, the circuit usually having a minimum of five active devices. A number of "packages" were produced that integrated such circuits typically using two or more glass envelopes into a single module that could be plugged into a larger circuit such as an analog computer. Such valve op-amps were very far from ideal and quickly became obsolete, being replaced with solid-state types.

Historically, pre-WWII "transmitting tubes" were among the most powerful tubes available. These usually had directly heated thoriated filament cathodes that glowed like light bulbs.

Some tubes were capable of being driven so hard that the anode itself would glow cherry red; the anodes were machined from solid material rather than fabricated from thin sheet to withstand heat without distorting. Notable tubes of this type are the and Later tetrodes and pentodes such as and direct heated were also used in large numbers in especially military radio transmitters. RF circuits are significantly different from broadband amplifier circuits.

The antenna or following circuit stage typically contains one or more adjustable capacitive or inductive component allowing the resonance of the stage to be accurately matched with carrier frequency in use, to optimize power transfer from and loading on the valve, a so-called "tuned circuit". Broadband circuits require flat response over a wide range of frequencies.

RF circuits by contrast are typically required to operate at high frequencies but often over a very narrow frequency range.

For example, an RF device might be required to operate over the range to MHz just 1. Today, radio transmitters are overwhelmingly silicon based, even at microwave frequencies. However, an ever-decreasing minority of high power radio frequency amplifiers continue to have valve construction. From Wikipedia, the free encyclopedia. This article is about valve vacuum tube amplifiers in general. For a more detailed discussion on the use of valve amplifiers in specific applications, see Valve audio amplifier , Valve RF amplifier , and Valve audio amplifier technical specification.

For tube amps from the Valve company, see Valve Amplification Company. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources.

Unsourced material may be challenged and removed. Type of electronic amplifier. Main article: Valve audio amplifiers. Main article: Valve RF Amplifier. Magnetic amplifiers were limited to below roughly kHz.

Hydraulic amplifiers were not directly useful as electronic devices. Authority control. Integrated Authority File Germany. United States.


TUBE AMP BUILDING WORKSHOP

Well, yes and no. While tubes are no longer the technology of choice in the computer industry, they are very much alive and well when it comes to modern high-end guitar amplification. It is because of the electric guitar amp that vacuum tubes are still being manufactured today. Guitar amps with tubes are currently front and center in the high-end market because many guitar players find their sound characteristics to be superior to solid-state amps i.

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Alvenh Channe


For a first amplifier build you should consider a kit because it can be difficult to source all the correct components and shipping charges from multiple vendors can add up. Building a kit is also a great way to boost your understanding of electronic theory and tube amplification. I recommend Mojotone. If you are tight on cash consider building the chassis only and playing through an extension cab if you don't have an extension cab consider borrowing one. You can always buy a speaker and buy or build a cabinet after you successfully get it up and running. There's no better guitar amp to start with than the Fender 5F1 Champ. It has only 26 components but sounds fantastic.

Scratch building amps

making a tube amplifier

Once a discarded relic, over the years the humble vacuum tube has been rehabilitated in the arena of specialist audio. There are plenty of tube amplifiers now being manufactured, with a popular choice being headphone amplifiers that use a tube as a gain stage followed by an op-amp as a buffer with a low impedance output. The tube circuit is a very conventional anode follower using an EF95 pentode. An NE steps in for the op-amp buffer role, making for a very simple circuit. Power comes from a set of four Lithium-Ion cells with associated charger and balance boards, while a little switching boost converter provides the volt HT for the tubes.

Build your own great sounding valve guitar amp!

Class-A Push-Pull Tube Power Amplifier


Make sure your amp remains in great condition when traveling from gig to gig. As sturdy as many guitar and bass amplifiers are, many of them—especially tube amps—house fairly delicate electronics, and care must therefore be taken when transporting them. Transport the amp upright. Amp heads are especially easy to transport in their normal upright position. If you can manage that, great, and happy motoring. Set it on a blanket, foam or rug to provide extra cushioning from the unrelenting metal van floor or bouncing trunk that can shake valves loose.

DIY Tube Amplifier

We have been making all tube amplifiers for over 35 years. We hand wire our amplifiers to obtain the highest sound quality and to maintain the build quality that Quicksilver is known throughout the world for. Get the best performance from your quicksilver product. Please visit our vacuum tube section and see why Quicksilver tubes make a difference. Quicksilver Audio only offers the best in tube replacement. All parts in Quicksilver amps are chosen for their sonic performance in each product they are used in.

As a result, the guitar amplifier industry is one of the few that as long as guitar players want them, someone will keep making them.

Amp Maker kits contain everything you need to build your amplifier, from the input to the output. You get UK-made transformers, chassis and control panels, all the resistors, capacitors and every nut and bolt. All of the kits include a fully detailed online build guide that takes you through the process step-by-step.

For technical books, tube data, vintage data, transformer data, and McIntosh data, go to: www. I consider all the information that I post here to be in the public domain. So, you can use it however you want, for commercial or non-commercial use. That said, I would appreciate it if you at least let me know if you are going to use any of the circuits or especially PCB Gerber files to make commercial products, or to sell bare PCB's. There are some cases where products are being sold not only with my permission, but active involvement.

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For many, many years the SLI integrated amplifier has been the standard by which all other vacuum tube integrated amplifiers are judged…period! Thousands of music lovers all over the world have heard and seen the virtues of this spectacular vacuum tube integrated amplifier. Before we gloat about the sound of the SLI, just look at it. The open chassis showcasing the warm soft glow of the tubes only enhances its sonic beauty. It is a display piece for any setting, pure and simple. While only offering 15 watts per channel of pure class-A remote-controlled power, the CADSEI does things that almost no other amplifier today can achieve. Its careful attention to design and construction means that it is extremely quiet, allowing the tiniest musical details to float against a background of dead silence.

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