Tube Characteristics

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FullRangeMan

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Tube Characteristics
« on: 9 Jul 2016, 01:37 am »
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.
« Last Edit: 10 Jul 2016, 01:05 pm by FullRangeMan »

FullRangeMan

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Re: Tube Characteristics
« Reply #1 on: 9 Jul 2016, 01:38 am »
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.
« Last Edit: 5 Aug 2016, 11:36 am by FullRangeMan »

FullRangeMan

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Re: Tube Characteristics
« Reply #2 on: 9 Jul 2016, 01:38 am »
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.
« Last Edit: 28 Aug 2016, 01:29 am by FullRangeMan »

FullRangeMan

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Re: Tube Characteristics
« Reply #3 on: 9 Jul 2016, 01:38 am »
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.
« Last Edit: 7 Sep 2016, 06:25 am by FullRangeMan »

JakeJ

Re: Tube Characteristics
« Reply #4 on: 9 Jul 2016, 01:22 pm »
Good idea, FRM!  Your topic is now a sticky.

S Clark

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Re: Tube Characteristics
« Reply #5 on: 9 Jul 2016, 02:35 pm »
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?   :wink:

Wind Chaser

Re: Tube Characteristics
« Reply #6 on: 9 Jul 2016, 04:40 pm »
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

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Re: Tube Characteristics
« Reply #7 on: 9 Jul 2016, 05:23 pm »
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

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Re: Tube Characteristics
« Reply #8 on: 9 Jul 2016, 06:06 pm »
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?   :wink:
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

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Re: Tube Characteristics
« Reply #9 on: 6 Sep 2016, 11:20 am »
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.
« Last Edit: 3 Oct 2016, 01:21 pm by FullRangeMan »

FullRangeMan

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Re: Tube Characteristics
« Reply #10 on: 6 Sep 2016, 11:40 am »
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

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Re: Tube Characteristics
« Reply #11 on: 11 Sep 2016, 05:14 pm »
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.
« Last Edit: 13 Sep 2016, 08:39 am by FullRangeMan »

FullRangeMan

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Re: Tube Characteristics
« Reply #12 on: 5 Nov 2017, 12:57 am »
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.
« Last Edit: 5 Nov 2017, 04:08 am by FullRangeMan »