Archive for the ‘Tubes’ Category

Orange Amplification Announces DIVO VT1000 Valve Tester

Thursday, January 31st, 2013

Orange Amplification has released the DIVO  VT1000 Valve Tester, an automatic valve tester that performs a host of diagnostics on both preamp and power amp tubes. The unit has one octal and two nine pin valve sockets to fit pe-amp and EL34 valves. Once inserted, the user presses the start button and the tests are run.

Vt1000 valve tester

VT1000 Details:

Tests run:

  • Heater filament test: Short circuit
  • Heater filament test: Open circuit
  • Heater filament test: Tolerance check
  • Heater cathode insulation: Leakage
  • Heater cathode insulation: Short Circuit
  • Tests for heater current abnormalities
  • Amplification factor
  • Voltage gain
  • Power gain
  • Screen grid test
  • Mutual conductance test
  • Dual test for double triodes
  • Emission
  • Inter electrode leakage
  • Inter electrode short circuit
  • Flash-over (arc detection, high voltage breakdown)
  • Gas ionisation test

Compatible Valves:

  • EL34/6CA7
  • EL34L
  • 6L6
  • 6V6/6v6GTA
  • KT66
  • KT77
  • KT88
  • 6550
  • 5881
  • EL84/6BQ5
  • ECC81/12AT7
  • ECC82/12AU7
  • ECC83/12AX7
  • ECC99
  • 12BH7

Does Plate Dissipation Affect Valve / Tube Life In Practice ??

Thursday, November 8th, 2012

In general, the obvious connection between higher anode dissipation and shorter tube life holds good, however,  many other factors affect tube life, including accuracy of heater voltages and the efficiency of tube cooling within amplifiers.

The tube leaves the factory with a known amount of cathode coating material which is the source of all the electron emission. In use, this material is used up as it emits electrons when heated by the filament and plate current is drawn.

If plate current is drawn before the cathode is at operating temperature, the surface of the cathode can be damaged (so called ‘cathode stripping’).

This is why the Standby switch should be off when the amplifier is warming up. If, however, the tube is operated for long periods with the filament hot with little or no plate current being drawn, then an oxide-like coating can form on the cathode, effectively blocking the emission of electrons even when normal operation is required (known as ‘cathode poisoning’). TubeSync takes care of this by automatically controlling the bias at both start-up and run conditions.

vacuum tube EL34 valve

Plate dissipation is generally quoted by the manufacturer as a maximum value which, if exceeded could cause damage to the tube and should not generally be used for ‘normal’ operation. The relationship between tube life and plate dissipation follows an exponential curve. Tubes operated correctly at around 30% maximum dissipation can have lives in the region of tens of thousands of hours and can last several decades of years. This figure decreases rapidly as the dissipation increases, in some cased down to hundreds or even tens of hours as they approach or exceed their maximum plate dissipation rating.

Cooling is extremely important as running tubes very hot also increases the risk of arcing and a condition known as thermal runaway, which can instantly destroy the cathode material, making the tube useless. Conventionally biased tubes are most at risk when biased towards ‘Class-A’ operation, as they experience maximum power dissipation when no audio signal is present.

TubeSync_225

Electro Harmonix Guitar Valve / Tubes EL34 s etc..

Tuesday, March 30th, 2010

Electro-Harmonix is a New York based company that makes electronic sound processors. The company was founded by Mike Matthews in 1968. They are most famous for a series of popular guitar effects pedals introduced in the 1970s and 1990s.

EL34EH Electro-Harmonix

buy

Electro-Harmonix was founded by Mike Matthews in October 1968 in NYC, USA.

Himself an R&B keyboard player, he had traded his passion of music for a job as a salesman for IBM in 1967. Shortly afterwards he realized that his job at IBM no longer suited him, and he was interested in trying once again to make career for himself as a keyboard player. Concerned he may not be able to support his (now ex) wife while being unemployed, he aspired to save some money to support her before embarking on his journey to stardom. Partnering with an acquaintance of his, Bill Berko, an audio repairman who claimed to have his own custom circuit for a fuzz pedal, they jobbed construction of their new pedal to a contracting house, and began distributing the pedals under a deal with the Guild Guitar Company Fuzzboxes were in demand following a trail of hits involving their sound, including “(I Can’t Get No) Satisfaction ” by The Rolling Stones two years prior, and recent popularization of Jimi Hendrix. The latter connection resulted in the pedals being branded the ‘Foxey Lady’.

Following the unexplained departure of his partner, Matthews was introduced to inventor and electric engineer Robert Myer through IBM colleagues.

Together the two began conceptualizing a circuit designed to emulate Jimi Hendrix’s use of a distortion-free sustain. While testing a prototype of the Distortion-Free Sustainer pedal, which Matthews did by simply plucking the strings of an electric guitar, as he did not play guitar, he noticed another small box connected to the prototype. When asked, Myer explained this box was a line booster, designed to boost the guitar’s passive signal to an appropriate level for the prototype. Matthews listened as the guitar’s volume increased greatly as the booster was turned on, and asked Myer what was involved in manufacturing the pedal. The pedal consisted of a simple circuit and used just one transistor (This would later become know as the Linear Power Booster (LPB-1), a pedal still manufactured today.Shortly afterwards, Matthews founded Electro-Harmonix to produce this and other pedal designs throughout 1960s, 70s and early 80s.

The first Electro-Harmonix product was the Axis fuzz pedal, which was also sold under the name “Foxey Lady” for the Guild guitar company. While working with Bob Myer on the early Big Muff design, Mike Matthews used a booster circuit Myer had incorporated into the design and marketed it as the LPB-1 or Linear Power Booster in 1969. This massively boosted a guitar signal to provide gain by clipping the signal, dramatically changing the sound. The new device provided a raw distorted sound, full of sustain and harmonics.

Several similar devices followed such as the Treble Booster and Bass Booster. The new devices were extremely popular with guitarists.

Electro-Harmonix stopped making pedals in the mid-1980s, and in the early 1990s started selling vacuum tubes re-branded with their name for guitar amplifiers, which they had also been making since the 1970s. However due to demand, and the high prices guitarists were paying for old 1970s pedals on the vintage market, they reissued the more popular old pedals in the mid-1990s, the Big Muff Pi and Small Clone included. In 2002 they started designing new pedals to add to their range. Company policy is that all reissued effects remain as close as possible to the original, vintage designs. This means however that casings, knobs and especially the old-fashioned mini-jack power plug are not up to modern-day standards. This all changed in 2006 with their smaller and more standardized “micro” and “nano” effect lines.

Guitar Amp Tubes / Valves The History Of .. EL34 s etc

Thursday, March 18th, 2010

Until the introduction of the germanium transistor in the late 1950’s, there was no alternative form of high quality audio amplification to the thermionic valve (American terminology was always ‘Tube’). The 1960’s, 70’s and 80’s saw a steep decline in the usage of valves for all purposes except audio amplifiers, to the point that, with a few exceptions, they were almost entirely replaced by transistors and integrated circuits. However, since the late 1980’s, valve amplifiers have experienced a renaissance which has, in the last decade grown rapidly year on year.

The unique character of the ‘Tube Sound’ has once again attracted both amateur and professional interest in the areas of High Fidelity (HiFi) amplification, Musical Instrument (MI) amplification (notably the electric guitar) and Audio amplification. The dominance of digital technology now, means that the valve amplifier is seen as new to younger people and as nostalgic to the older generation. Please note it is estimated, that the electric guitar amplification market consume as many as three out of four of the world’s production of audio tubes.

EL34 Valve

EL34 Valve

Many arguments have been put forward as to why tube amplification ‘sounds’ better than digital. Some differences can be proved using measuring instruments, whilst others are down to the nuances of the human ear. Whatever the reason, evidence shows more and more listeners appear to prefer the sound of a tube amplifier.

The demand for tube amplifiers is rapidly growing, with products ranging from a few hundred pounds to several thousand pounds, depending on quality and output power, with tube sales worldwide currently standing at over $100,000,000. Today vacuum-thermionic devices hold sway over the US $100 million worldwide guitar amp business. One rough estimate shows a 10-percent-per-year growth in demand for tubes used in MI instrument amplifiers and high-end audio since the late 1980s, with no apparent slackening.

However, the problems with existing tube amplifier technology is that the circuits used are based on ‘classic’ designs developed in the 1940’s and 50’s and, although more modern technology has occasionally been applied, this is usually confined to regulating the power supplies. One of the principle disadvantages of existing tube amplifiers is that they are very inefficient in converting electrical power into audio power. This is largely due to the ‘classic’ methods of controlling them. All analogue high power amplifiers require a system known as ‘Biasing’ to be applied to them. This controls the output devices and prevents them from ‘Thermal’ overload and eventual destruction. It does, however, incur a heavy cost in loss of output power and increased heat dissipation. In addition valves also need to be used in ‘Matched’ pairs, in order to control distortion of the output signal. This process is time consuming and expensive when carried out on a commercial basis.

THE SOLUTION IS ……..

EL34

EL34

The Advantages Of TubeSync In Guitar Amps

Thursday, September 3rd, 2009
Eliminates tube matching

Eliminates the need for bias current matching of amplifier output tubes,this increases manufacturing efficiencies, due to reduced testing.

Reduced tube cost

Eliminates the need to purchase tubes in ‘matched pairs’ and replaces conventional biasing components.

Increased tube life

Automatically micro-adjusts the bias on each tube to ensure the full potential of each tube in the system is realised throughout its working life.

Reliability assurance

Replaces conventional tube testing methods by performing an ‘in circuit’ test every time the amplifier is powered up.

Half power back-up

If TubeSync® detects a faulty tube, it can automatically ‘switch out’ the offending tube and run the amp at half power, until the defective tube can be replaced. tubesync rendering white

Maintains optimum performance

Dynamically measures the amplitude of the drive signals supplied to the grids of each output tube and optimises performance accordingly.

Simultaneous distortion

Maintains the classic warm sound of the amplifier by ensuring tubes distort symmetrically.

Reduced power consumption

Reduces quiescent power consumption when compared to conventional amplifier biasing techniques by an average of 20%.

NEW ‘ Hot Anode’

TubeSync® knows the optimum operating temperature of your tubes, so there is no need to warm up your amp. TubeSync® will get you to where you need to be just as soon as you start playing.

Customisation

Unique algorithms can be incorporated to tailor optional performance characteristics and features to customer requirements.

Tube Failure Modes, Within Amplifiers

Tuesday, August 11th, 2009

Catastrophic Failures. These are failures that occur suddenly, without warning, making the equipment unusable.

Examples of catastrophic failures are: –

  • Glass failure, loss of vacuum due to mechanical damage or thermal stress.
  • Heater failures open circuit or partial short circuit due to excessive heater voltage or high initial surge current and normal on off cycling over many thousands of hours.
  • Arcing, due to low cathode temperature, causing damage to the cathode and grids.
  • Bias failure due to component leakage or valve characteristic spreads using fixed or auto bias.

Degenerative Failures. The slow but eventual, deterioration of all tubes, which can contribute to the end of life of the tube.

Examples of degenerative failures: –

  • Gas is present in all tubes and if the tube is used within its characteristics should not be a problem, however excessive dissipation can liberate gas from the tube structure and lead to eventual premature failure.
  • Getters are patches of evaporated metal, which are deposited on the inside of the glass. The purpose of the getter is to absorb any gas that may be evolved during the life of the tube and work best at normal glass bulb temperatures.
  • Spurious emissions are uncontrolled unwanted emissions usually caused by gas released due to excessive dissipation and elevated temperatures.
  • Inter electrode leakage. This is current, which flows between the electrodes of the tube, which are not connected in any way. The cause is metallic vapours released by the hot metallic structure of the valve being deposited on the insulating micas and eventually leading to a conductive path.
  • Cathode depletion can occur due to arcing, which can strip the cathode coating reducing the active area of the cathode. Arcing will vaporise the cathode material and generate gas, which can poison the cathode material. This can also be caused, by passing excessive cathode current before the heater has reached its normal operating temperature.

Subjective Failures. These are tubes, which will normally pass tests but do not perform satisfactorily due to for example: – hum level, microphonics and noise.

Examples of subjective failures: –

  • Hum is an unwanted mains frequency signal, which is superimposed on the wanted signal.  It can be caused by heater to cathode leakage or due to electrostatic or electromagnetic fields within the equipment.
  • Microphonics is defined as a signal originating inside the valve caused by mechanical vibrations being amplified by the tube.
  • Noise is a signal originating from inside the tube, but not due to hum or microphonics. It can be due to intermittent short circuits, open circuits or arcing due to leakage paths between the electrodes.

Characteristic Variables. These are variations or spreads in the tube characteristics, due to manufacturing tolerances and follow a normal distribution curve.

Examples of characteristic variables: –

  • The Standard is usually a tube that complies with the manufactures published data. The Upper and Lower limits are values that any tube within these limits can be considered acceptable for normal use.
  • Characteristic Spreads is the degree of deviation from the standard tube.
  • Design Tolerances is the normal variations of standard parts, which a well-designed piece of equipment will operate correctly.

The Solution Is ……….TubeSync!

TubeSync Amp Biasing

TubeSync Amp Biasing


www.kbodynamics.com

Thermionic Tubes & Tube Amplifier Operation

Friday, June 12th, 2009

Thermionic tubes

Thermionic tubes are very tolerant if their specified operating conditions are temporarily exceeded; unlike most semiconductors which tend to suffer from ‘catastrophic’ failure (defined as a failure mode which causes instantaneous and irreversible damage).Unlike semiconductors, tubes do however, ‘wear out’, which means that they have a finite operating life.

NN-M-EL34Operating them under unfavourable conditions or beyond the manufacturers working specification, usually results in a reduced lifespan, although this may not be audibly apparent in their operation. In audio applications, the majority of seriously damaging problems lie in the power output stages.

Introduction to Tube Amplifier Operation

The majority of amplifiers use at least two output tubes in a circuit configuration known as ‘Push-Pull’. Basically, this means that the audio signal is split into two halves by preceding circuits. Each of the two ‘Split’ signals now drives one output tube.

The signals then undergo power amplification by the output tubes and are re-combined by a special audio grade transformer which also drives the loudspeaker.  Please note that, although there are many different types of tube for various applications, the vast majority operate on the same basic principles.

Tubes & Their Internal Construction

Thursday, June 11th, 2009

Tube Internal Construction

Tube Construction

Tube Construction

Cathode – this is the ‘power house’ of the tube as it is coated with a material which, when heated, releases electrons. The entire operation of the tube relies on controlling their movement (hence the term ‘Thermionic’).

Heater – this is an electrically heated filament which provides thermal stimulus to the cathode.

Grid – depending on the type of tube, their may be one or more grids present, each with a specific function, however all audio tubes contain at least one control grid. The control grid is made negatively charged with respect to the cathode in order to restrict or prevent the flow of electrons in the valve.

Anode – this electrode is made positive with respect to the cathode (usually by a few hundred volts), and serves to collect the electrons which are allowed to pass through the grid.

Vacuum – audio grade tubes will only operate satisfactorily if there are virtually no air or gas molecules in the envelope. To achieve this, the glass envelope is evacuated to a very high degree during manufacture, which is known as a ‘hard’ vacuum. If small amounts of gas are present, their molecules will ‘ionise’ due to the high voltages present and can give rise to electrical noise or overheating in worse cases. Under these conditions, the valve is said to have ‘gone soft’. Each valve contains a small amount of a reactive metal such as barium (known as the ‘getter’), which is burnt inside the envelope after evacuation in order to ‘mop-up’ the last remaining gas molecules. If the envelope is cracked or broken, air will enter and cause the heater to oxidise and ‘burn out’; it will also disrupt the electron flow and the tube will cease to conduct current. It will be seen from the description of the control grid that if an alternating potential audio signal is applied to the grid, it will modulate the flow of electrons to the anode. Electrical current is defined as electron flow; therefore the signal applied to the grid will produce a modulated current in the anode circuit. Under ideal conditions, this current will be an exact replica of the input signal, but of much greater amplitude. Power valves are optimised to produce large current swings at the anode for relatively small control grid signals. This large output current is used to drive a loudspeaker via a matching transformer.