Valves, Vacuum tubes and Valve Amplifiers

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3

valveamplifier — Sun, 13 Jun 2010 21:23:12 +0000

From our last post (part 2), you may be able to guess now what a class AB amplifier is - this is one that is biased partly between Class A and Class B in its operation using the method described above.
Class AB1 and AB2 are only relevant in valve (tube) amplifiers and relate to the output impedance of the driver stage of the amp. In class AB1, this has a high output impedance, leading to clipping on the onset of a current flowing in output tube grid. In class AB2, it has a low output impedance allowing greater output power for a given bias current.
In the real world amplifier, all this tends to mean that Class A amplifiers have lower output due to the efficiency penalty, but many audiophiles feel that they produce a sweeter and smoother sound and are better at driving typical loudspeaker loads than class AB designs.

Ultralinear Operation

You may see the term ultralinear bandied about when discussing valve amplifiers - what does it mean? In essence, the screen grid in the valve is connected to a tap on the primary windings of the output transformer, so that the voltage at the screen grid varies in proportion to the signal at the plate (or anode). Why is this done? It is in effect a local negative feedback loop and gives characteristics somewhere between those of a triode and a pentode. Some audiophiles and designers believe this gives an amp combining the best features of the triode and the pentode tubes. This being Hi-Fi however, others believe it has the abilities of neither. Why use ultralinear mode? Simply because it represents the cheapest way to get both good performance and high power output from a pentode amplifier design

Characteristics Of Triode and Pentode Amplifiers.

That last section may make more sense if we consider what the characteristics of the two tube types are (to find out more about the types of tube, there is another article on my site explaining the different types of valve). The triode is a low power, low efficiency design contrasted with the higher power and efficiency of the pentode. The triode uses more power at idle and its sonic characteristics are usually described using words like sweet, pure and rich - having a very natural sound conveying vocals and instrument timbre very well. It also has very benign clipping charcteristics when over driven. Of course, to others it is coloured with low output power, a restricted bandwidth - and in many cases - overpriced. This is especially true of the 'classic' single ended triode designs featuring triode tubes like the 845, 300B and 2A3. These tubes are expensive but very simple, having directly heated cathodes -where the cathode is both the heater and electron emissive element. You will often see amps using these being referred to as DH-SET amps - Directly Heated Singe Ended Triode. For aficionados, these DH-SET amps represent audio nirvana - frequently with equally enlightening prices...Cheaper triode amps actually use pentodes like the EL-34 in a triode configuration. The pentode in contrast is usually described as being analytic in its sound - or harsh if you are a triode lover! It can also clip more sharply than a triode. At the end of the day - only your ears can decide!

JJ Tesla 300b pair
£50.00

Bewitch 300B x 2 Stereo Valve Tube Integrated Amplifier
£460.00

MA 2010 New Model XD 850 2A3 2A3300B Power Amplifier
£356.00

Music Angel King Tube 300B x 2pcs Stereo Integrated Amp
£288.00

YAQIN MS 300C 300B Vaccum Tube Integrated Amplifier New
£459.00

MA XDSE 2A3300B Hi End Vaccum Tube Power Amplifier NEW
£369.00

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 2 What is Amplifier Output Class and what is meant by...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 For those new to the world of valve audio or...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 2

valveamplifier — Fri, 11 Jun 2010 09:13:31 +0000

What is Amplifier Output Class and what is meant by 'Push-pull' operation or 'Single Ended' operation?

You will often see reference to an amplifier being a class A design - indeed one of several classes (Class A, B, C, AB, AB1, AB2). What does this all mean? The amplifier class refers to its mode of operation. As nearly all active electronic devices (e.g. valves or tubes) pass current in only 1 direction (a direct current) but audio signals are in alternating current form, there is a need to resolve this difficulty to allow an audio signal to be amplified - to make 1 way devices amplify 2 way signals. Two basic circuit topologies are used to achieve this, push-pull and single ended.

Push-Pull

This makes use of one or more pairs of amplifying devices (valves or tubes in our case - but it applies equally to solid state designs), one of which deals with the signal when it swings positive, the other with the negative swings of the signal.

Single Ended

In this method, a direct current of suitable size is superimposed on the AC signal to ensure that the overall signal remains positive even at the negative signal peaks - hence there is never any actual reversal of the current flow, so a single output device (valve) may be used rather than the pair of the push-pull topology. The superimposed direct current can then be filtered out of the output using a blocking capacitor or transformer.

Amplifer Class

Where does this leave us with regard to class of operation? If you consider the audio signal as a regular sine wave with positive and negative peaks, due to the nature of single ended operation (converting this to larger and smaller positive only peaks) it can be seen that the output device is always 'on' and passing a signal. This is known as class A operation, where the output device passes (conducts) during 100% of the signal cycle.

Looking at the push-pull circuit, it can be seen that one of the pair of devices is 'on' for positive swings of the signal, the other for negative swings - with our sine wave again they each conduct for precisely 50% of the signal cycle. This is Class B operation.Class C operation refers to circuits where the output devices conduct for less than 50% of the signal cycle - but these designs are generally not used in audio amplification and won't be considered further.

Of course things are never quite that simple. When looking at the class B push-pull amplifier and considering our sine wave again, it can be seen that there is a point when the positive signal crosses over to the negative part of signal - here the positive output device will be switching off as the negative is starting to switch on. At the precise crossover point, there should be no current flowing in either half of the circuit. Now amplifying devices tend to be 'nonlinear' in their operation at these low current cut off points - this introduces distortion at the cross over point referred to as crossover distortion (surprise!). The solution to this is to introduce a bias current that flows when the amplifier is idling so the output devices don't actually reach their low current cut off points and introduce crossover distortion. Perhaps you can spot where this is going? As the bias current increases it increases the conduction time for each half of the circuit to more than 50%. When the bias current reaches a value of half of the maximum output current, the devices in both halves of the circuit are conducting 100% of the time. So, in this case the amplifier is operating fully in Class A on both halves of the signal cycle. The downside to this is that the bias current flowing when there is no signal leads to the output devices dissipating this energy in the form of heat. This is why a Class A amp will run hot, even if just idling with no input signal - Class A operation in this case is not as efficient as class B.

In part 3, we'll continue our look at amplifier classes with the class AB amplifer.

Quad 22 Vintage Valve Preamp FM1 Tuner
£147.00

HFA 12 VALVE AMPLIFIERS AKA EDISON 12S ERIK ANDERSON
£100.00

YAQIN EL84 6P14 ClassA Valve Tube Integrated Amplifiers
£189.00

SV 2A3 Class A Valve Tube Integrated Amplifiers
£269.00

EAR 834P Phono Stage Tube Valve Preamp de Pavaricini
£486.00

Rogers Cadet mk3 Stereo Valve Amplifier
£99.00

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 2 is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 For those new to the world of valve audio or...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1

valveamplifier — Tue, 08 Jun 2010 20:03:55 +0000

For those new to the world of valve audio or hi-fi amplifiers it can be tricky to decipher some of the terminology you may read about in magazines, on the web or in manufacturer's brochures. The next few posts will give you a whistle-stop high level overview of some of the terms you are likely to come across when researching a potential tube amplifier purchase. So, if you've ever wondered what Class A operation is, about single ended or push-pull output stages and even what on earth ultra-linear means in an amplifier design, read on.

What is a Valve or Tube Amplifier?

A valve amplifier is a device for amplifying the power of electrical signals. These signals are most often at audio (sound - as in a guitar or Hi-Fi amplifier) or radio frequencies (in radio and radar transmission). It uses the ability of the thermionic valve to control the flow of current through the device in response to a signal applied, amplifying this signal in the process. The first valve to possess the ability to electronically amplify a signal was the triode valve invented by Lee De Forest in 1907. A triode valve has three electrodes - a cathode, an anode (frequently referred to as the plate) and the control grid located between the two. The cathode is heated electrically (directly or via a separate adjacent heater element) until thermionic emission begins when electrons are emitted. The Anode is positively charged with respect to the cathode and attracts these electrons, leading to an electron current flowing between the cathode and anode. A 'conventional' current is said to flow the other way. The control grid is biased negatively with respect to the cathode (i.e. it is 'more' negatively charged when compared to the cathode). This creates an electrostatic repulsion effect of the electrons emitted from the cathode and shields the plate from them, reducing the current flow. The effect of this negative bias is thus to control the flow of current through the device - the more negatively biased the control grid is, the less current flows. In broad terms, apply a signal to the grid and the current flow through the device will be regulated in proportion to the signal - bingo! - an device whose output is regulated in proportion to a signal applied, otherwise known as an amplifier.Lets now have a look at some of the terms you may come across when reading about tube amplifiers.

Output Transformer

Although a very good amplifying device, the valve or tube has one problem - it has a high voltage / high impedance / low current output unsuitable for directly driving many real world loads. In the specific case of audio amplifiers, the output is unsuitable for directly driving the typical low impedance load presented by a loudspeaker, which is obviously a bit of a problem in an audio amplification device. Two main techniques are used to overcome this - negative feedback to reduce the output impedance and matching transformers to match the output of the valve power stages to the load supplied by the loudspeaker. The transformers are very specialised, heavy and expensive - significantly adding to the weight and cost of a valve amp. The quality of these transformers is also very important in the sound quality produced by the amp.

OTL Amplifier

OTL - or output transformerless amplifier designs do away with the bulky output transformers in favour of running many tubes in parallel. In this design, as many as 12 or more tubes are connected in parallel (electrically connected side-by-side, rather than one after another) to reduce the output plate (anode) impedance to more closely match that of a typical loudspeaker load(4 to 16 ohms). The design was pioneered by Julius Futterman and such designs are often referred to as Futterman OTL amplifiers. OTL designs are renowned for running hot, having lots of tubes and a rather unique sound quality.

In part 2 of this article, we will go on to look at amplifier class and what is meant by 'Push-pull' operation and 'Single Ended' operation.

Quad 22 Vintage Valve Preamp FM1 Tuner
£147.00

HFA 12 VALVE AMPLIFIERS AKA EDISON 12S ERIK ANDERSON
£100.00

YAQIN EL84 6P14 ClassA Valve Tube Integrated Amplifiers
£189.00

SV 2A3 Class A Valve Tube Integrated Amplifiers
£269.00

EAR 834P Phono Stage Tube Valve Preamp de Pavaricini
£486.00

Rogers Cadet mk3 Stereo Valve Amplifier
£99.00

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 2 What is Amplifier Output Class and what is meant by...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...

Valve / vacuum tube types – what are they?

valveamplifier — Sun, 06 Jun 2010 15:21:42 +0000

There are a number of different type of vacuum tube or valve, with complicated sounding names like 'Triode'. This article provides a brief introduction to the various types of tube that you may commonly encounter. The tube naming convention is actually very simple - the name refers to the electrode configuration found in the valve or tube - hence 'ode' in the name. The first part of the name refers to the number of electrodes used - Di (two), Tri(Three) and so on.

Diodes

Diodes have two electrodes - a cathode and an anode, often referred to as the 'plate'. They allow the flow of current in one direction only. They can be used as rectifiers to 'rectify' or convert AC (alternating) current to DC (direct current).

Triodes

A triode has three electrodes (tri - three) due to the addition of another 'screen' electrode known as the grid between the cathode and anode. As the charge on the grid is varied from positive to negative, it affects the flow of electrons from anode to cathode controlling the flow. This makes the triode an amplifying device as the current flows in proportion to the signal applied. To make the triode 'linear' in operation (it is significantly non-linear in its behaviour at low volumes, giving rise to harmonic distortion) a standing current is applied to the grid to keep the valve working in the range where it operates linearly. This is called 'grid bias'.

Tetrodes

A potential problem was discovered when Triodes were used in the first radio sets - there was a tendency for them to oscillate due to capacitance effects. The cure for this was yet another electrode (the secondary grid) - and the four electrode tube or tetrode (tetra - four) was born. This had the welcome side effect of also increasing the tube's gain (amplification) at high frequencies. The beam tetrode is a further refinement of the tetrode design, using special design techniques and shaped electrodes (plates) that focus the electrons emitted into a beam, focusing this beam onto special spots on the anode. This improves the efficiency of the design and hence power output capabilities. This was first seen in the 6L6 tube and the KT66, KT77 and KT88 series of valves which are still widely used today in guitar amplifiers and Hi-Fi amplifiers.

Pentodes

The pentode evolved to overcome problems with the Tetrode. In this case, electrons released from the anode (caused by by the anode being energetically struck by electrons from the cathode) are captured by the secondary grid, reducing the current flow and hence amplification. This is not an issue in the triode as these electrons cannot reach the cathode or grid as they have insufficient energy to do so. The answer as always was another electrode called the suppressor grid - is biased negatively with respect to the positively charged anode and as such repels the electrons that have escaped from the anode back towards the anode, allowing them to be recaptured.
Other tube types exist including the heptode and even octode, but in the context of audio valve amplifiers, the tubes types described already are what you are likely to find in any tube amplifier, modern or vintage. To reduce costs, it became common practice to include more than one set of elements in the single glass envelope (tube) - a common example of this being the 12AX7 (or ECC83) valves which combine two triodes in a single tube. These are still extensively used today (despite being a 1940s vintage design) in Hi-Fi audio preamplifiers, the preamp stages of integrated amplifiers, output stages of tube CD players and guitar amplifiers.

A1834 Osram double triode Boxed believed NOS Tested
£4.99

GEC VALVE TUBE CV4079 A2293 TRIODE 2 PCS NOS NIB
£14.99

Pair NOS NIB TUNG SOL 12SN7 Medium Mu Twin Triode tubes
£6.47

RCA 6AV6 EBC91 tube valve double diode triode NOS 11]
£.99

2X Thorn ECC82 NOS tube valve double triode 12AU7 {6}
£.99

2X Thorn ECC81 tube valve NOS double triode 12AT7 {8}
£2.71

Valve / vacuum tube types – what are they? is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 For those new to the world of valve audio or...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...

A quick history of the valve (vacuum tube)

valveamplifier — Fri, 04 Jun 2010 20:19:46 +0000

The late 19th and early 20th centuries were a golden age of science and technological research, laying the foundations of the modern world and the electronic age. The list of scientists involved with research into evacuated tubes reads like a whos who of the great innovators of the time - Guthrie, Edison, Tesla, Flemming. Thermionic emission was first reported in 1873 by Thomas Guthrie, but it wasnt until 10 years later in research by Thomas Edison into the Edison Effect that this was really noted - Edison patented the effect, never being backwards in considering the commercial potential of any of his work. Apart from giving us the light bulb these researchers paved the way for John Ambrose Flemming to develop what he called the oscillation valve in 1904 whilst working for the Marconi company. This became known as the Flemming valve or later, the diode. With this seemingly simple innovation, John Ambrose Flemming gave birth to the electronics age and ushered in the modern world. This simple valve was used initially as a rectifier and a radio detector.

In 1907, Lee De Forest added a screen to the valve and the triode was born, the first valve signal amplifying device - he named it the Audion. Valve amplification was first used in amplifying telephone signals for long distance use and later in the burgeoning wireless market after the first world war.

This triode design was revised subsequently by Eric Tigerstedt in 1914, Irving Langmuir in 1915 (the Pilotron) and closely followed by the French type R valve in 1916 which was extensively used in radio communications during WW1. These last two were probably the first proper valves with hard vacuums and laid the foundations for everything that came after.

The inter-war years were the time when electronics first really invaded the home, with the growing popularity of the wireless and in the late 1930s the development of television - the valve being integral to these first mass market electronics.

The second world war again drove technological advances, with radar and the first computer - the Colossus code breaking machine at Bletchly Park in England. This machine used hundreds of vacuum tubes and was vital to the war effort in cracking German military codes.

The post war consumer boom of the 1950s and 1960s brought further advances in valve design, with the tetrode, pentode, miniature tubes, specialised tubes, rugged tubes and many more being developed - frequently with development being driven by military requirements. The rise of the gramophone and the rapid spread of TV kept the tube manufacturers busy. This period saw the birth of the first real Hi-Fi amplifiers capable of full range reproduction. The 1947 Williamson audio power amplifier typified this new breed with an advanced circuit topology incorporating negative feedback to reduce distortion (Negative feed back having first been proposed by Harold Stephen Black in 1927). Designs continued to evolve, leading to classics like the Quad II series in the UK.

By the late 1960s and early 1970s, time was running out for the valve due to the rise of solid state electronics with the transistor and latterly ICs (Integrated Circuits) taking over. Valves became limited to more specialist applications including high power radio transmission and specialised military communications (especially in the Soviet Bloc) due to their inherent resistance to the effects of EMP (electromagnetic pulse) from a nuclear detonation.

Tubes were continually popular in guitar amplifiers and began to enjoy a renaissance in the Hi-Fi world in the late 20th century with the development of many new valve amplifiers catering to the high end hi-fi world and appealing to a whole new generation of audiophiles (myself included!). With the advent of the iPod generation, valves have got in on the act again with tube powered amplification in the iTube docking station. Valves have even left the solar system on board the Pioneer series of spacecraft in nuvistor format.

Today, this is largely where the vacuum tube is - in a few niche markets, where it still does very well. Tubes are still manufactured around the world, especially in China (Shuguang), Russia (Svetlana and others), Slovakia (JJ-Electronic) and even the USA (Westrex Inc.) - they will be around for many years to come.

RS1003 SIEMENS TUBE VALVE NOS 1 PC
£101.00

Laney Valve Amplifier 100W Vintage
£125.00

Limit Valve Amplifier 100 50 20W switching Vintage
£125.00

CX1154 EEV THYATRON VALVE TUBE
£1,250.00

CX1191 EEV THYATRON VALVE TUBE
£450.00

E810F CV5809 MULLARD VALVE TUBE
£25.00

A quick history of the valve (vacuum tube) is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...
A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 For those new to the world of valve audio or...

A quick guide to valves Part 2 – Construction

valveamplifier — Mon, 03 May 2010 20:30:44 +0000

Basic Construction

As mentioned previously in part 1, the valve or tube consists of an arrangement of electrodes inside an envelope containing a vacuum or various low pressure gases, the latter being described as 'soft' valves. This envelope is frequently tubular in shape and is classically constructed of glass. Other materials are also used, including metal and ceramics. The electrodes are usually connected to pins on the base of the envelope which then plug into a valve socket, this arrangement having been designed to facilitate easy replacement of the tube if required. A number of different electrode arrangements exist, with extra electrodes being added to improve performance.The vacuum in the tube must be a very 'hard' vacuum - as near a perfect vacuum as is possible. This is because if any molecules of gas remain in the valve's envelope they may ionise and interfere with the tube's operation - possibly causing catastrophic failure and certainly poor performance. A special process is used in manufacture to alleviate the problem of any remaining gasses in the tube. A "getter" is used to absorb the remaining gas. In modern tubes this is usually a trough filled with a metal that oxidises rapidly (usually barium). After the tube has been sealed the getter is heated by RF induction until it vaporises and reacts with any gas still in the tube. This leaves a silvery deposit on the inside of the tube. The getter will continue to react with and remove any gas that leaks into the tube in its life, turning white as it does so. As an aside, if looking at a tube white deposits can be seen inside it, it is likely to be failing or has done so. Also, contrary to popular belief, black spots on the inside of the tube are not bad news and don't indicate failed getter and a valve on the way out.

Reliability

Tubes are perceived as unreliable which was seen as being one of the benefits of solid state electronics. Valve sockets were developed to facilitate easy changing of tubes. However, a modern power tube such as an EL34 should last 1000 - 1500 hours of use, pre-amp tubes longer still. One of the possible causes of failure is air leakage into the tube, although getters can help as described above. The heater filament may also break like that in a light bulb, though as the heaters are run at much lower temperatures than a light bulb this is less of an issue - the heaters tend to be most stressed by the switch on process. Interestingly, the Colossus electronic code-breaking computer used to crack German cyphers during the second world war was valve based and was left permanently switched on as the designer felt the tubes were more reliable that way (despite it consuming 1.5kw!). The cathode efficiency is also slowly reduced due to contamination by atoms from the other elements in the tube, restricting its ability to release electrons.Despite this, there should be little to worry the owner of a modern valve amplifier, tube preamp or tube guitar amp.

Valves and Tubes Today

Valves today are mostly used in specialised applications, but have been replaced by solid state electronics in everyday use. Today they are commonly used in audiophile high-end Hi-Fi for music reproduction, guitar amplifiers (where the valve sound is still sought after) and certain high-power radio frequency uses - where ceramic power tetrodes are still used in transmission for military and commercial purposes. Why? Because of their high power handling capabilities - a modern water cooled power tetrode is capable of handling 1.5 megawatts (1.5 million watts) of power - a 2 megawatt power amplifier could be constructed from two of these. In contrast, the highest power that can be dissipated by a transistor is about 1 kilowatt (1000 watts) - so a high powered transmitter requires and array of many transistors and bulky associated cooling equipment to do the job a single vacuum tube can! The humble valve has come a long way since the early 20th century - mostly replaced in modern electronics it still has its place to play in specialist applications not least high-end audiophile amplifiers - it is no coincidence that the most expensive amplifier in the word is a valve design. They are also still very widely used in the music industry - some of the characteristic guitar sounds of the last 60 years are due to the overdriven valve sound. There is even a PC motherboard that uses a valve in its audio output and a new docking speaker set for the iPod uses tube output too. Widely manufactured still, especially in China (Shuguang), Russia (Svetlana and others), Slovakia (JJ-Electronic) and even the USA (Westrex Inc.) - they will be around for many years to come.

HFA 12 VALVE AMPLIFIERS AKA EDISON 12S ERIK ANDERSON
£100.00

Rogers Cadet mk3 Stereo Valve Amplifier
£99.00

QED A240 CD STEREO QUALITY VALVE LIKE AMPLIFIER
£149.99

LEAK STEREO 20 VALVE TUBE AMPLIFIER PRE AMP BRONZE
£599.00

Leak Stereo 20 Valve Tube Power Amplifier Project
£165.00

FIRESTONE AUDIO VALVE MONO BLOCK AMPLIFIERS DEM PAIR
£495.00

A quick guide to valves Part 2 – Construction is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 2 What is Amplifier Output Class and what is meant by...

A quick guide to valves Part 1 – How does a thermionic valve work?

valveamplifier — Mon, 03 May 2010 19:57:02 +0000

What is a vacuum tube or Thermionic Valve?

A Thermionic Valve (also referred to as a vacuum tube or electron tube especially in North America) is an electronic device consisting of electrodes in an evacuated or low pressure envelope, frequently of tubular glass form - hence vacuum tube. Most valves do indeed have a vacuum inside the tube envelope, but there are many specialised forms of valves that use inert gasses in the envelope. Developed initially in the late 19th and early 20th centuries, they are still in use today despite the rise of the transistor and integrated circuits. Why? Well, for some uses because they can handle very high power and in the case of Hi-Fi, because there are still plenty of audiophiles that rate the valve / tube sound above all others - myself included!

How does a Valve or Vacuum Tube Work?

The simplest valve has two electrodes - a filament and a plate (called the Anode) - and resembles nothing more than the humble light bulb in operation. When a current is applied to the filament, it heats up (as does the filament in a light bulb) causing it to emit electrons creating a negatively charged cloud of electrons in the vacuum envelope - this process is known as thermionic emission. In the case of the light bulb, that's as far as it goes. In a valve however, the second electrode (a plate called the anode) if positively charged with respect to the filament will attract these electrons. So, there will be a flow of electrons from the filament to the Anode called the electron current. As the anode plate is not heated in any way, it cannot emit electrons itself, so the current can only flow one way. A device that shows this property (only allowing current to flow one way through it) is called a diode - di (two) electrode. In later valves, another electrode was introduced called the cathode which was heated by the filament. The cathode became the source of electron emission and the filament was then referred to as the 'heater'. This scheme reduced the effects of 'hum' if an alternating current was used to heat the filament. As they were originally designed to be operated from batteries (e.g. in the earliest military radio sets) much of the associated terminology still applies - in the US the power supply for the heater is called the A battery; that for the plate the B battery or today B+. These are more commonly referred to as the LT (low tension) and HT (high tension) supplies. You may sometimes see reference to the C battery or grid bias supply as well. Valves are not the most energy efficient devices due to the heat required to start the thermionic emission process. In addition, they must not become too hot or thermionic emission will start from the anode also - they rely on the temperature difference between the cathode and anode to work.

In part 2 of this article, we'll have a look at how a valve is physically constructed and have a look at how valves are used today.

YAQIN EL84 6P14 ClassA Valve Tube Integrated Amplifiers
£189.00

SV 2A3 Class A Valve Tube Integrated Amplifiers
£269.00

YAQIN MC 100B KT88 Tube Vaccum Integrated Amplifier SV
£339.00

Bewitch 6550 KT88 Tube Hi End Integrated Amplifier New
£349.00

YAQIN EL34 x2 Tube Headphone Integrated Amplifier bk
£249.00

MENG YUE 6P1 6BQ5 Push Pull Valve Integrated Tube Amp H
£109.00

A quick guide to valves Part 1 – How does a thermionic valve work? is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...
Valve / vacuum tube types – what are they? There are a number of different type of vacuum tube...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 1 For those new to the world of valve audio or...
Valve / Vacuum Tube Amplifiers Demystified – a layman’s guide – Part 3 From our last post (part 2), you may be able...

Valve Sockets

valveamplifier — Tue, 02 Feb 2010 00:24:27 +0000

Ebay Results For Tube Sockets

Ceramic Tube Socket for 3-500 and 4-400 Tubes

GBP 16.16 (0 Bid)
End Date: Saturday Sep-04-2010 9:52:32 PDT
Buy It Now for only: GBP 19.40
Bid now | Buy it now | Add to watch list

Cinch 7 pin miniature tube sockets with shield base

GBP 3.85
End Date: Saturday Sep-04-2010 12:26:42 PDT
Buy It Now for only: GBP 3.85
Buy it now | Add to watch list

Amazon Results For Tube Sockets

Regal Tu1910B Tube Rail Sockets Chrm X2

Price £1.60

Regal 1538Mspb Tube Rail Sockets Brassx2

Price £1.60

Yahoo Answers For Tube Sockets

Question How to install a fluorescent light bulb into tube socket?
How do I install the light bulb? I need instructions on how to install the bulb into the tube socket because I can't seem to get in there correctly. The light bulb has two-prongs and it's a ceiling light. A diagram would be helpful. Yes, I already tried howstuffworks. It doesn't say how to exactly install the light bulb though.

Best Answer line up the 2 pins at each end so that they are in a vertical line straight up, push bulb up into the pin socket, but don't force it, do both ends at the same time, when the bulb' s pins appears to be all the way up into the socket then turn it 1/4 turn and you should feel the pins slip into place. That should do it, good luck.

Question Know of any sites for DIY tube amp kits?
I'm looking to build a DIY tube amp and I've already got an empty 1x12 combo with tube sockets, and now I have just the electronics left to buy. I've heard of tube amp kits which supposedly includes all the electronics necessary to complete the project, but I haven't been able to find any kits below $200. Does anybody out there know of any decently priced kits?

Best Answer http://www.tubedepot.com/tubeampkits.html

Valve Sockets is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...
A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
Valve Bases Ebay Results For Tube BasesRATHEON RAYTEL 2 -- TUBE BASE...
Valve Dampers Ebay Results For Tube DampersSet of 3 NOS 6CD3 /...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...

Valve Dampers

valveamplifier — Mon, 01 Feb 2010 00:00:00 +0000

Ebay Results For Tube Dampers

Set of 3 NOS 6CD3 / 6CG3 Diode Damper VACUUM TUBES

GBP 5.15
End Date: Sunday Sep-05-2010 16:31:25 PDT
Buy It Now for only: GBP 5.15
Buy it now | Add to watch list

Top Hat Tube Dampers (Right-Way Audio)

GBP 29.15 (0 Bid)
End Date: Sunday Sep-05-2010 17:58:18 PDT
Bid now | Add to watch list

Amazon Results For Tube Dampers

ORIGINAL PRINTED APPLICATION NUMBER 10.234 FOR IMPROVEMENTS IN DAMPERS FOR WATER TUBE BOILERS. [1910]

Design of Fluid Dampers for Tube Drawbenches

Yahoo Answers For Tube Dampers

Question Harley 41mm front fork tubes?
Anyone out there know if '84 & later 41mm fork tubes/dampers etc will work in '81 fxwg sliders?

Best Answer NO, 84-up fork tubes will not work on earlier bikes. 80-83 FXWG had their own tubes.......... http://www.vtwinmfg.com/Catalog1/VTwinCatalogIndex1.htm

Valve Dampers is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

A quick guide to valves Part 1 – How does a thermionic valve work? What is a vacuum tube or Thermionic Valve? A Thermionic...
A quick history of the valve (vacuum tube) The late 19th and early 20th centuries were a golden...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...
Valve Bases Ebay Results For Tube BasesRATHEON RAYTEL 2 -- TUBE BASE...
Valve Sockets Ebay Results For Tube SocketsCeramic Tube Socket for 3-500 and...

Shanling MC-30

valveamplifier — Sun, 08 Nov 2009 00:41:02 +0000

No items matching your keywords were found.

Shanling MC-30 is a post from: Valve amplifier the place to find out more about the magic of valves (vacuum tubes) and buy valve amplifiers, spare valves (tubes) and much more.

Shanling CD-S100SE US Auctions Australian Auctions Austrian Auctions Belgian Auctions Canadian Auctions...
Shanling CD300 US Auctions Australian Auctions Austrian Auctions Belgian Auctions Canadian Auctions...
Shanling CD-T1000se US Auctions Australian Auctions Austrian Auctions Belgian Auctions Canadian Auctions...
Shanling CD-T100 US Auctions Australian Auctions Austrian Auctions Belgian Auctions Canadian Auctions...
A quick guide to valves Part 2 – Construction Basic Construction As mentioned previously in part 1, the valve...