[FullRangeMan]

Some symbols and abbreviations used in vaccum tube world to help tube fans understanding more about the hot valves.
A=amplification
B+=plate/anode battery positive supply(in the old days)
C=capacitance
E=voltage
eb=instantaneous total plate voltage
Eb=plate supply voltage
Eba=average plate voltage
Ebo=quiescent(no signal) plate voltage
Ec1=control grid plate voltage
Ec2=quiescent screen grid voltage
Ec3=quiescent(bias) suppressor grid voltage
eg=instantaneous value of alternating component of grid voltage
ek=voltage across cathode resistor
Emax=maximum value of plate voltage
Emin=minimum value of plate voltage
ep=instantaneous value of AC component of plate voltage
erp=instantaneous voltage across the plate resistor
G=grid
G2=grid 2
G=glass bulb
GT=a T9 straight side glass bulb + an octal base
Gm=transconductance
H=harmonic
H2%=percentage second harmonic distortion
i=instantaneous
I=current
Ib=plate current
Ic1=grid 1 current
Ik=cathode current
K=cathode
P=plate
P=power
Po=power output
Pp=plate dissipation watts
R=resistance, resistor
Rb=DC resistance of the plate load resistor
Rc=DC resistance of the grid load resistor
Rg1= grid 1 resistor
Rk=resistance of the cathode resistor
Rp=DC plate resistance
rp=AC plate resistance
u=amplification factor(constant)
umhos=unit of transconductance
X=a base composed of special low loss material
Y=a base composed of special intermediate loss material

Source:
Rider: Inside the Vacuum Tube, 1945.
GE: Essential Characteristics, 1973.

[FullRangeMan]

A, B, C electrical supplies operating Voltages are designated as below:
A supplie to filament heating or cathode heating if DHT.
B Positive supply to plate Tension (B+).
C Supply to Voltage grid (Bias), usually negative Tension.

[FullRangeMan]

Transconductance (Gm)
The GE book version of Transconductance is:
The transconductance (Gm) of an electronic tube is the ratio of a small change in the plate current to the small change in the grid voltage that produce it, with all other voltages maintened constant.

I have simplified a definition of transconductance to:
The ratio between a grid tension value to a plate current change, hence the preffix ''trans''.
Usually is grid1 to plate transconductance and other voltages are keep constant.

[FullRangeMan]

Amplification Factor (u)
Is the ratio of a small change in grid voltage to a small plate voltage change, when the plate current and all other electrode voltages are keep constant.

Plate Resistance (Rp, Ohms)
Is the ratio of a small change in plate Voltage to the corresponding changing in plate current with all other electrode voltages are keep constant.

[JakeJ]

Good idea, FRM!  Your topic is now a sticky.

[S Clark]

The characteristics that interest me are not the statistics, but the nature of the sound.  Is there a 6qb5 sound, vs a 6L6 sound?  How do 6dj8's compare to 12au7's ?

The tube electrical characteristics is just black magic for most of us.  Do they really contain smoke, if so, where is it before it gets let out?   

[Wind Chaser]

The characteristics that interest me are not the statistics, but the nature of the sound.  Is there a 6qb5 sound, vs a 6L6 sound?  How do 6dj8's compare to 12au7's?

I recently read an interesting article by Steve Deckert where he wrote, "I firmly believe that the art of amplifier design has very little to do with the tubes you use."

http://www.decware.com/paper16.htm

[FullRangeMan]

I recently read an interesting article by Steve Deckert where he wrote, "I firmly believe that the art of amplifier design has very little to do with the tubes you use."

http://www.decware.com/paper16.htm

As a manufacturer he is praising the tube circuits.

[FullRangeMan]

The characteristics that interest me are not the statistics, but the nature of the sound.  Is there a 6qb5 sound, vs a 6L6 sound?  How do 6dj8's compare to 12au7's ?

The tube electrical characteristics is just black magic for most of us.  Do they really contain smoke, if so, where is it before it gets let out?   

I found this comparative test:
https://www.youtube.com/watch?v=fKq8_aw4thw
For 6DJ8 vs 12AU7 there is various links:
https://www.google.com.br/search?q=6qb5+vs+6l6&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=wDuBV5TSGM7K8gfJka_ADA#q=6dj8+vs+12au7

[FullRangeMan]

BOGEY
An average characteristic value or a tube exhibiting these avarage values is termed a bogey tube.
CCS= Continous Commercial Service.
CCS= Constant Current Supply.
CCS= Constant Current Source.
CCSC= Constant Current Source Circuit.

[FullRangeMan]

GE-1973 five stars special quality tubes for critical applications.
Diodes
Low Current Rectifiers: 5726, 6919.
Full Wave Power Rectifiers: 6202, 6203, 6087.
Triode
Single: 6135.
Twin:5844,5670,5687,5814A,6189,6211A,6386,7861,5751,5965A,6201,6414,6829.
Pentodes
5654,6688,6136,6265,8425A,8426A,5749,5725,6005,5686,6216,7239.
Heptodes
5750,7036.
Thyratrons
5727

[FullRangeMan]

Class A
Audio Amplifier or Modulator
•Peak grid drive equal to or less than the grid Bias.
Grid Bias may be obtained from the drop across a resistance in the place current return or from a battery or rectifier supple.

Plate dissipation allowable for this type of service is generally lower than is safe for other uses since the energy is dissipated in the plate in smaller areas due to relatively high voltage drop in the tube.

The plate dissipation is equal to the plate voltage multiplied by the normal plate current. Performance data are based upon the use of a resistance load. Undistorted output is calculated on The basis of 5% second harmonic distortion.

Class B
Audio Amplifier or Modulator:
•Grid Bias practically at cut-off and grid driving voltage higher than the Bias
Two tubes may be used in balanced circuit. An adequate driving stage and an input transformer with good regulation must be used so that the grid current drawn during positive grid swings does not produce appreciable distortion.

Radio Frequency Power Amplifier or Oscillator:
The Class B radio frequency amplifier is used to amplify a modulate4d radio frequency carrier wave without appreciable distortion. It operates similarly to the Class B audio amplifier except that a single tube may be used, the tuned output circuit serving to  preserve the wave shape. The push-pull circuit however eliminated the even order harmonics and thus increases the efficiency slightly.

Class C
Radio Frequency Power Amplifier or Oscillator:
•Grid Bias below cut-off
Plate Unmodulated
This type of operation is suitable for telegraphy or the production of a continuous flow of radio frequency power for purposes other than communication.

Plate Modulated
This type of operation is used when the modulating voltage is superimposed on the plate supply voltage and to obtain good quality the output power should vary as the square of the plate voltage. For complete 100% modulation the voltage varies from zero to twice the applied direct value during a cycle of the audio frequency.

[FullRangeMan]

Vacuum Tubes Glossary For Musicians:
A.C. Abbreviation for “alternating current”. This is electricity that goes one direction and then reverses and goes the other direction. Your guitar signal is A.C. and so are the 120-volt wall outlets you plug your amp into.

ATTACK & DECAY ENVELOPE The rise and fall of volume levels that occur inherently in an amplifier when a note is played. This shapes the overall sound and is what gives the “breathing effect” of certain amps.

BIAS To adjust the operating level of a vacuum tube, much the same as you would adjust the idle on your car; The negative voltage relationship comparing the grid to the cathode.

CATHODE This is the part of the tube or semiconductor diode where the electrical current flow enters.

CATHODE-BIASED One of several ways a tube could be biased. This design uses a resistor between the cathode and ground to set the biasing. This cathode-biased design is almost always used on preamp tubes and sometimes used on output tubes. Though not as efficient as fixed-bias, cathode-biased output tubes generally “sing” more.

CATHODE RESISTOR This is the resistor that goes from the cathode to ground in a cathode-biased circuit.

CAPACITOR A device made from two conductors separated by a non-conductor. Whatever is between these conductors is called a dielectric. These devices store electricity.

CUT OFF A condition in which no current flows through a vacuum tube. This is achieved by having the grid potential so negative (with respect to the cathode) that current “cuts off”.

D.C. Abbreviation for “direct current”. This is electricity that goes one direction only. The tubes in an amplifier use “direct current”. All batteries are D.C.

DIELECTRIC The non-conductor substance that separates the two conductors of a capacitor. Paper, air, electrolyte, mica, Mylar, polyester & ceramic are some of the dielectrics that are used.

DISTORTION The difference between what goes into an electronic device & what comes out.

DYNAMICS The loud/soft quality of music that gives it character.

ENVELOPE The changing dynamics of a vacuum tube circuit that can be heard as an attack, decay & sustain volume level when a note or a chord is played through the amp.

EQ. Abbreviation for equalizer.

FIXED-BIAS A way to achieve bias in a vacuum tube in which a fixed amount of negative voltage is placed on the grid of a tube. This is almost done on output tubes and almost never done on preamp tubes.

GAIN The amount of voltage amplification in the preamp section of an amplifier. This voltage amplification ultimately drives the power tubes, which do not add any more gain. The power tubes add current (power).

GRID One of the internal parts of a vacuum tube. This is usually where the input signal connects.

HARMONICS The frequencies that are related to the fundamental frequency by being multiples of the fundamental frequency.

HEADROOM The volume level that is attainable before clipping occurs.

IMPEDANCE Sum of all resistance, capacitive reactance and inductive reactance.

INTERLEAVED A way of winding a transformer in which a little bit of the primary is wound, then a little of the secondary is wound, then a little primary, then a little secondary, etc. until the transformer is wound. The more interleaves, the better the efficiency.

K Abbreviation for one thousand.

MEGA – One million ohms or 1000K.

MICROFARAD – One millionth of a farad (.000001 farad). The abbreviation is “uF”.

MICROPHONIC – The tendency for a vacuum tube to pick up sound like a microphone.

NEGATIVE FEEDBACK – A small portion of signal that is taken from the output of an amplification stage and then reinserted to a previous stage at a point that is 180 degrees out of phase. This would phase cancel some of the louder frequencies and there would be little effect on the not-so-loud frequencies, thus the frequency response would become more even. Leaving a cathode resistor unbypassed can achieve the same effect.

NEGATIVE FEEDBACK LOOP – A circuit in which a small portion of the amplified signal is fed back to an earlier part of the circuit in which it is 180 degrees out of phase. This has the tendency of flattering out the frequency response.

OHM Unit of measure of resistance.

OUT OF PHASE If you consider that a vibration such as guitar note changes from positive to negative in its vibrations, then a signal is said to be 180 degrees out of phase if it is going positive at the same time that the original signal is going negative and of course it will be going negative when the original is going positive. This is also referred to as an inverted signal.

PENTODE A vacuum tube that has five electrical components. They are: cathode, grid, screen grid, suppresser grid and plate. The heater doesn’t count.

pF The abbreviation for picofarads.

PHASE INVERTER The circuit in a push-pull amplifier that feeds the power tubes signal. It feeds one power tube an in-phase signal and the other power tube an out-of-phase signal. The tube for this circuit is always located next to the power tubes.

PI FILTER A filter, called the pi filter because of its resemblance to the Greek letter Pi, is a combination of the simple capacitor input filter and the choke input filter.

PICOFARAD A very small amount of capacitance that is equal to a trillionth of a farad (.000,000,000,001). Sometimes also called “micro-micro-farads”.

PLATE The part of the vacuum tube that has high voltage on it. Except in a cathode follower circuit, the output is always taken from this part of the tube.

PLATE VOLTAGE The voltage that is applied to the plate of a vacuum tube. Higher voltages give more headroom and high end; lower voltages give more breakup and a “browner” tone. All tweed amps had relatively lower plate voltages.

POTS Slang for potentiometer, which is a variable voltage divider used in volume controls, tone controls, etc.

PREAMP The section of an amplifier whose function is to add gain. Preamps are always before the output stage.

PRESENCE Another type of high end, similar to treble that gives a biting edge to the sound. On Fender & Marshall amps and many others, the presence control is actually a tone control on the negative feedback loop.

RECTIFIER A vacuum tube with no grid, whose purpose is to change alternating current to direct current. Current flows from the cathode to whichever of the two plates that happen to be positive at the time.

RESISTANCE That which impedes the flow of electrons is said to have resistance. Resistance accounts for the fact that different conductors will allow more or less current to pass, given the same voltage present.

RESISTOR device used to add resistance to a circuit. This device is always used to either create a voltage drop or to limit current.

REVERB sound in which sound waves are reverberated. Passing sound through two or more long springs of different lengths and amplifying the resultant sound does this. The springs are in a small enclosure that is called a “reverb tank”.

RING MODULATOR An electronic device that generates the sum and difference of two or more frequencies and in doing so creates non-harmonically related sounds.

SAG The amount of decay in the envelope before a played note is sustained at a constant volume level. It’s caused by the resistance of the power supply and that resistance would include the rectifier tube resistance as well as the internal resistance of the power transformer.

SATURATION A condition in which maximum current is reached and no more current can possibly flow.

SCREEN RESISTOR The resistor that is placed in series with the screen of a vacuum tube. It is used to limit screen current.

SELF-BIAS A type of biasing arrangement in which a resistor is used to create a positive voltage on the cathode; this now makes the grid negative with respect to the cathode.

SOCKET The female conductor that a vacuum tube inserts into.

TRANSFORMER An electrical device made from two or more windings of wire wrapped around an iron core. These devices are primarily used to create power supplies and to match impedance’s between output tubes and speaker.

uF – The abbreviation for microfarads.

TRIODE A vacuum tube with three internal components not counting the heater. The three components are cathode, grid and plate.

VACUUM TUBE A device whose major components would include an anode and a cathode in an evacuated envelope. It performs as an amplifier, oscillator or rectifier in audio circuits.

VIBRATO The effect of pitch varying slightly higher and slightly lower than the fundamental signal.

[FullRangeMan]

Valve Codes by Eduardo Nartlof
Introduction:
Have you read Frankeinstein by Mary Shelley?
Anyone who has ever had contact with this magnificent work should remember the scene in Captain Walton's office, at the very end of the book, in which the creature is crying beside Dr. Frankeinstein's body. The captain asks, "Who are you?" The corpulent creature slowly raises his wet eyes and says,
-He never gave me a name!

The electronic valve is a creature of Frankeinstein in that detail. The device was never properly baptized. Instead, it has always been called something similar in form or function. In plain terms we call it simply a valve, there are several other meanings for word valve and its common use is in hydraulics or medicine! In Spanish or Italian the thing is called "lamp". In England it is called a "vacuum tube".

When the transistor was created, its inventors bothered to give a name to the piece. Something original and not to be confused with other things. They then joined the words "transmitter" and "resistor" by coining the term "transistor".

The electronic valve is not a lamp, it is much more than simply a vacuum tube and is far from a hydraulic component.

It is no wonder that it is a subject that generates great curiosity and doubts among those who begin to mount things with valves. You go to an electronics store, order a valve, and send you to a Decca hydraulic hardware shop. And when you finds what you looking for, you sees things like 6L6GC, 6L6WXT +, 6L6WGC, and countless other combinations. Or the famous question of 12AX7 versus ECC83. But what is the difference between all these types? Or is there any difference?

Coding systems:
Little attention was paid by those involved in developing the valve in properly naming the device. Less attention was still given by industry. In the beginning each manufacturer gave the name that would like well the piece that was producing. It took some organization to resolve to normalize the standards to be followed. When the norms appeared, they were mismatched and each followed the one that suited him best.

To the confusion of those now attempting to venture into valve electronics, there are four coding systems that have survived. There is the codification that today is called industrial, European, American and Russian. Each system has its own rules, but these have never been followed so strictly by manufacturers. Let's look at each of these systems separately.

Industrial System
This is the most obvious and simple system possible. Only a given number of sequential forms to designate each valve. The number says very little about what it is about and without a valve manual to translate it, the user has no clue what the part is. This system was largely applied by the military, precisely because it did not give clues to the component. A letter may come after the numeric digits to indicate version. Thus a 6146A valve is an improved version of the 6146 and the 6146B is an improved version of the 6146A. The suffix letter system has been enhanced and expanded in US codes.

Examples of these codes are: 42, 76, 80, 811A, 6146B, etc.

[FullRangeMan]

American system:
This is a system with a little sense. A sequence of numbers and letters that try to give some hint of what is happening inside the piece. The code itself consists of a number, one or two letters, another number and optionally but some letters.

First number:
The first group of numbers gives an indication of the working voltage of the valve filament. It's not the exact voltage, but a kind of nominal working voltage. Let's look at some examples:

    0 - Indicates cold cathode. There is no filament.
    1 - Indicates that the filament works with voltage from 1V to 1,9V. Usually 1,4V
    2 - Filament from 2V to 2,9V. Usually 2,3V
    3 - Filament from 3V to 3.9V. Normally 3.15V
    4 - Filament from 4V to 4.9V. Usually 4,2V
    5 - Filament from 5V to 5.9V. Normally 5.0V
    6 - 6V to 6.9V filament. Normally 6,3V
    7 - Here is an exception! They are filaments of 6.3V too!
    8 - Filament from 8V to 8.9V. Usually 8,4V
    9 - It's a mess here. It has some valves started by 9 that has filament to 6.3V. Others have to 13V. Do not trust too much.
    10 - Return to normal. Filament from 10V to 10.9V.
    11 - Filament from 11V to 11.9V
    12 - 12V to 12.9V filament. Usually 12,6V. Many valves with 12.6V filaments, such as 12AX7, 12AU7 or 12BY7 have filaments that allow for connection at 6.3V or 12.6V. Therefore, be careful when connecting one of these so as not to roast the filament.
    13 - Filament from 13V to 13.9V
    14 - Filament of etc...

Well, I think you got the idea! The normalization is that the filament voltage goes from X, 0V to X, 9V, where X is any number. However, there are several exceptions. You should always consult a manual to see the correct voltage before you call. Even so, the rule works and if you do not have another tip, liquefy at the indicated voltage. Hopefully it will warm up properly.

Main letters:
After the nominal voltage, comes one or two letters to differentiate the type. The letters are given in sequence and have no exact meaning. So the codes started with A, B, C ... V, AB, AC, and so on.

The letters X, Y and Z are reserved to indicate rectifiers, but this is not a rigid rule. The 6Z7G for example is a double triode.

The nomenclature rule also says that if there are two letters, they must be different. Therefore, there are no AA, or BB valves. The letters I and O are not used, not to be confused as one and zero respectively.

Second number:
The second number should be the number of elements inside the valve. I say should, because it is often not, or who told, told wrong. So let's look at some cases:

    6SN7 - It is a double triode with 7 elements. Two cathodes, two grids, two plates and one filament.
    12AX7 - Ditto! Two cathodes, two grids, two plates and one filament.
    6DJ8 - Two cathodes, two grids, two plates, one filament and one internal shield.
    6L6 - A cathode, a control grid, an auxiliary grid, a beam deflector, a board and a filament.
    6BM8 - Two cathodes, two grids, two plates, an auxiliary grid, a baffle and a filament. I counted 9!
    6CA7 - A cathode, a control grid, an auxiliary grid, a suppressor, a plate and a filament. I counted 6!
    6BQ5 - A cathode, a control grid, an auxiliary grid, a suppressor, a plate and a filament. I counted 6 again!

It's been more than 20 years since I learned this rule and I've been counting those valve elements. I wanted someone to tell me how manufacturers can get to those numbers! This rule is the worst, since the bulk of the valves do not fit.

Optional letters:
There's a lot here that does not fit, but fortunately those lyrics do not mean anything too serious. The current valve industry has created yet another portion of suffixes just for marketing, which adds to the confusion. Let's look at some suffixes:

    A - Represents an improvement in the original design. The 12AX7A has a controlled heating filament. It only makes a difference if you connect serially. Do not pay more for one of these!
    B - Represents an improvement over model with suffix A. The 5U4G admits a current peak of 800mA. The 5U4GGA supports 900mA and the 5U4GB supports 1000mA.
    C - Improvement over type B. I think you got the idea, right?
    E - Export version.
    G - Indicates that the valve has a glass housing. The first octal-based parts were produced with metal housings, which were smaller and allowed better heat dissipation. The glass envelopes of the time were bulbous.
    GT - Indicates tubular glass shell, as opposed to bulbous.
    GT / G - They are valves with GT casing but with the same characteristics of version G.
    X - Indicates ceramic base. In some high frequency applications bakelite is not suitable.
    Y - Robust Base. Between octal valves it is common to find some with loose base. In some applications this may be a problem, and a more reinforced base should be applied
    W - Represents a more robust type than the standard model. A 6AQ5W for example can have thicker glass and pass more stringent tests than a standard 6AQ5.

Suffixes can be combined to give various information about the part. A 6L6GC, for example, is a piece with bulbous glass housing and improved over 6L6GB.

There are other suffixes that have been used by the industry, but that do not find shelter in the traditional nomenclature. Sovtek introduced the 6L6WXT + and 12AX7LPS. I can not imagine a meaning for these suffixes and should be just marketing.

[FullRangeMan]

European System (Philips)
The European system was actually created by Philips to name its parts and gradually adopted by other manufacturers. It is a fairly simple system that gives a lot of information about the component. The code consists of a sequence of letters and numbers. The first letter gives information about the filament.

    A - Filament for 4V
    C - Filament for series connection in circuit of 200mA
    D - Filament for 1,4V coming from battery.
    E - Filament for 6,3V. Without doubt the most popular.
    G - Filament for 5V.
    H - Series connection in circuit of 150mA.
    K - Filament for 2V coming from battery.
    P - Serial connection in circuit of 300mA.
    U - Series connection in 100mA circuit.
    X - Serial connection in circuit of 600mA.
    Y - Series connection in circuit of 450mA.
    Z - Cold cathode.

The following letters give information about the part's function. If there is more than one inner element, the letters are repeated, identifying each one of them.

    A - Simple diode for radio frequency.
    B - Dual radio frequency diode (one cathode and two plates)
    C - Triodos, other than those of heading.
    D - Output triode.
    E - Tetrodo, except for output.
    F - Pentode, except those of exit.
    H-Hexode or heptodo.
    K - Octodo or heptodo.
    L - Outgoing pentode.
    M - Tuning indicator.
    P - Secondary emission valve.
    Q - Enode
    T - Unlisted type, miscellaneous.
    X - Full-wave gas rectifier.
    Y - Half-wave vacuum rectifier.
    Z - Vacuum complete rectifier.

After the letters, they follow two or three numerical digits. The last digit is simply a sequential number. The previous digits indicate the type of base.

Russian system:
А Б В Г Д Е Ё Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ъ Ы Ь Э Ю Я

[FullRangeMan]

Ballast Tube - current regulator.