【 Weak current College 】 vacuum characteristic specifications---Power By 【 China power house network 】

Vacuum tube characteristics specification terminology:

Design an expansion of the machine, we must first understand the various features of the vacuum tube, because the vacuum characteristic specifications specifications can let us know all the parameters related to the vacuum tube and the information, and then on the basis of these data to design the circuit, in addition to the specifications of the vacuum tube characteristics are the specifications of the vacuum tube, and also data of instance data, we can select one of the action instance completely accordingly.

If you do not want to follow the example of the vacuum tube Guide to design, they will carefully study the manual of the various parameters to design an expansion of the machine.

However, if you want to vacuum tube with a thorough understanding of the characteristics must be evacuated, following specifications, the characteristics of the WE300B specifications:

Filament voltage and current

Provide vacuum tube filament lamps of the voltage, the DC or AC available, each of a vacuum tube filament current is not the same, we actually used to close this value too high, too low will have a negative effect, as a general rule, slightly lower than the manufacturer specifications of filament voltage is allowed, but will not exceed the manufacturer, or it will shorten the life of vacuum tubes.

For example the 300B of filament voltage is 5V (DC or AC), the current is 1.2A, we actually used, the value you want to close this, too high, too low will have a negative effect.

Maximum screen voltage

Vacuum up the screen voltage, in actual use, not to exceed the screen pressure value.

For example, the maximum screen 300B voltage not exceeding the screen very 450V loss is 40W, general practice, when in actual use, not to exceed the maximum value of 70 ~ 80%, that is, the screen voltage 300B do not exceed the 350V, screen loss do not exceed the 30W.

Maximum screen loss

E impact screen makes the screen very hot, the heat said a power loss, each of a different kind of vacuum tubes each have their own different screen loss, we use the vacuum tube, apart from voltage and current, you should be careful not to exceed the maximum loss value and the actual use, the screen consumption will not exceed the most large consumption of 70%-80%, otherwise the vacuum will soon be damaged.

How to calculate the screen loss?

Very simple, that is, the vacuum tube voltage supply screen and screen current product: the P = EI

Of which:

P = the screen loss

E = the screen voltage

I = the screen current

For example, most large screen extreme loss 300B 40W, suppose we design the screen voltage 300B is 350V, current 80mA, phase product is approximately $ 300B 28W, most large screen extreme loss of about 70% of 40W, so it is very safe.

Most large current

Another project is the large current, if the current flowing through the vacuum tube, once it exceeds the maximum value, the vacuum is possible in two cases, one is the screen because of too many electrons colliding and hot, the second is due to excess emission cathode. Playing valves have seen vacuum tube of screen red experience that exceeds the screen and makes the screen consumed red.

In the data, 300B 300B most large current there are two different provisions, i.e. use fixed bias, most large current to 70mA, use self-sufficient bias, to 100mA. So we designed the work point must not exceed this value.

Appearance and pipe, block

Next we'll look at 300B appearance, structure, dimensions, and pipe, block a, 300B appearance as long as the photos on the line, in the middle of the glass tube, shape a bit like a pear-shaped tube called "ST" (generally straight tubular glass tube as EL-34 or 6550, called the "GT" pipe), 300B is larger ST tube. As for the factories of internal structure but 300B are not the same, this will be a comparison of the various 300B and when you hear the details.

The original data in the external WE300B FIG1 is dimension, the tube is 300B FIG2 bottom pin size figure, we can see FIG1 tube base part has a prominent needle-like metal plug, this is used for vertical pipe, block the card stud, as long as the vacuum tube of card stud alignment this card stud-type of socket insert, and then to the right you can get the vacuum tube card firmly, like 211 and 845 vacuum tubes are used to insert the vacuum tube socket, but a comparison of the pipe, block 300B smaller only. But in General most of use generally 300B four feet of pipe, block.

We can see the four foot 300B common pipe, block, two large jacks and two smaller Jack, including two large Jack "1" and "4" is a filament, two smaller Jack "2" and "3" are the gate and the screen. Also use this pipe, block of vacuum tube is called "UX-Type", there are a lot of vacuum tube with the pipe, block, UX-Type like 2A3, 26, 45, 50, 71, direct thermal-triode, or 80, 83, direct thermal-rectifier diodes are used to this kind of pipe, block of UX-Type.





Interelectrode capacitance

In table a has a very important parameter is the 「introduction interelectrode capacitance 」, vacuum tube very and very capacitance between.

Vacuum tube in the pole is conductor, also often have a potential difference, so they have the role of capacitance, transistors had 「introduction gate-screen "," gate-Yin (silk) "and" screen-Yin 」 three interelectrode capacitance, for example, three-pole WE300B between capacitance between the gate and the screen is 15pF, gate and filament is 9p betweenF, screen and a filament between 4.3pF, although these interelectrode capacitance are very small, but these small capacitor will affect the high-frequency response, interelectrode capacitance, the greater the more high frequency response. These parameters can be as long as generation PSPICE mostly allow usto estimate the frequency response.

Original factory recommended action instance

All vacuum manual has original factory provides the recommended action instance tables, different jobs, different, has different output power as well as different distortion rate. If you do not want to own in accordance with the characteristic curve design vacuum tube, diameter reference originally recommended action instance according to the dress code.

Vacuum-tube, three-parameter

Gm-μ-rp (dynamic characteristics of vacuum tubes)

We know that use extended machine aims to enlarge the sound signals, and vacuum tube in practical work, the input of the music signal is not a set of values, but as signals and change of voltage, so we will need to know the vacuum tube to the subtle changes in the response, this is the dynamic characteristics of vacuum tubes (DynamicCharacteristic), decide the parameters of the dynamic characteristics of vacuum-tube, three, namely 「introduction transconductance "," zoom factor "and" screen resistance 」.

For example, 300B of filament voltage Ef = 5.0V, Eb = the screen voltage 300V, Ec =-61V under negative pressure, this time the screen is very current, zoom factor to 60mA 3.85, screen resistance to 700W, the gate to the screen the transconductance is 5500 mho. With zoom factor, the screen resistance and conductance is a vacuum tube of the most important of the three parameters, so we will need to first understand the meaning of the three parameters and mutual relations.

-GM (Gm)

Gm=DIp/DEsig

-GM (Gm) is equal to the screen current change quantity divided by the gate voltage variation (the screen voltage fixed).

Of which:

DIp = screen current change

DEsig = gate signal voltage change

The vacuum tube in the gate voltage change, caused by the relative to the screen very current generated by the change, the gate voltage variation, and the screen ratio of the current changes,that 「introduction transconductance 」 (Transconductance), also known as 「introduction interconvertible 」 (MutualConductance), the symbol for the "Gm", transconductance is in mho "mhos".

It is necessary to pay attention to this "mhos" and "ohms of resistance", we know the conductivity is the reciprocal of resistance, voltage, equal to the current divided by a unit is mho.

But in practical, because the unit is too large to do mhos, usually with one millionth mho, μ m o s h.

Magnification factors (μ)

μ=DEp/DEsig

Magnification factors (μ) equal to the screen voltage divided by the gate voltage change (screen current fixed).

Of which:

DEp = the screen voltage change

We know that a small change of signal voltage from the vacuum tube of gate input, the output from the screen into a large change of signal voltage, this small change grid input voltage lead to big changes the screen output voltage ratio, is called the zoom factor to Greece "μ", or also known as "mu".

The magnification factors determine the transistors in vacuum tube mechanical structure, near Gate from the cathode, on the screen of current in the greater the thus amplifying factor μ is the greater; on the other hand, if the mesh is spaced grid, grid on the potential of small, smaller magnification factor.

For example, 300B is designed for power amplification and design of the tubes, power tube screen higher working voltage, current, cathode space (or silk pole) and the screen is better than voltage amplifying tube is bulky, and the gate of the mesh also needs to be adopted by a large, high-current, thus amplifying factor will not be high.

Screen resistance (rp)

(Here the so-called screen resistance means vacuum tube internal resistance, not the screen load resistor)

rp=DEp/DIp

Screen resistance (rp) is equal to the screen voltage divided by the screen current change (gate voltage is fixed).

Vacuum tube ofcurrent from the cathode (direct thermal transistor filament that cathode) launch, transmitted through space charge, gate, to the screen, there will be loss of energy is converted into heat, in other words, the vacuum inside the screen from the cathode to the paths to the current resistance is called the screen resistance, rp unit and resistance, as OM "W" or "ohms.

The relationship between the three parameters

The above three parameters of transistor is very important that the relationship is between:

μ=rp∩Gm

This third argument is not a hard and fast, we can consist of original data FIG4, FIG5, FIG6 figure seen in the mutual relations between them.

　

WE300B of allusions

The expansion of our Pack 300B machine, you will need to thoroughly understand the Yuan zu-300B WE300B of allusions.

Who invented the 300B?

Is the United States in the West to the company (Western-Electric hereinafter referred to as WE) want to know in the first world war, many specialized manufacture vacuum tube manufacturers, including most of the manufacturers we haven't heard of, it will be in a future article will gradually, and West to the company, is one of the family, but also is the world's oldest manufacturing one tube manufacturers.

United States from the West to the company in early before the production of many different types of vacuum tubes, and 300B or laterProduct, in fact, most of the vacuum tubes are for the purpose of the military or address, rarely is specifically designed for audio purposes, from the West to the company's nature is no exception.

But it is specifically intended to 300B audio purpose, why? because after the war, the military needs of the vacuum tube to reduce significantly the number of vacuum tube factory and even the factory are received, but WE have at this point to 「introduction audio uses 」 developed vacuum tube.

Why? because WE already have plans for the company specialized in film sound developed by expanding machine, vacuum tubes in 1930 developed 300A of vacuum tubes, but did not get used until 1934 to 300A use in their expanding machine 「introduction WE-1068 」 audio movie playback system, system expansion machine number 「introduction WE-86 」, although this WE-86 expanding machine only 8W output power, but it is a push-pull amplification design, mainly because the output power 300A is too small, you will need to use the push-pull circuit to output power of 8W. But later, XD and launches expanded 「introduction WE-91 」, you have to switch machines, single tube design, this expanded machine while WE-91 took only a single output 300A do, but the screen voltage increase so that the output be the twin 「introduction WE-86 」-pull of 8W.

Why the West to the company will raise the voltage to design their WE-91, previous WE-86 without high voltage?

The reason is mentioned, because the West to the company was originally designed for military use of vacuum tube manufacturing company, the production of vacuum tube must be resistant against prolonged use and performance, high-stability requirements. To this end, in addition to manufacturing requires particularly stringent, the use of the screen voltage than the rated voltage value is much less in order to durable until after using several years 300A, they found the 300A of vacuum tube as durable, many years after the performance will remain unchanged, 1936 to 300A of increased by-consuming screen to 40W and 30W so that in their 「introduction WE-91 」 expand machine, turn the screen voltage 300A, make it output power increases, found still remains very durable, visible at the time of the specification is very conservative.

To change the 1937 40W screen consumption 300A renamed 300B, 300A earliest design of prototypes, the screen voltage value to 300V, after long-term use to find stability without problems, the time changed to 400V and third then heightening to 450V.

Inaddition, the film uses 300B have been NASA large as military machine power supply voltage.

WE want to know the company developed by 300B is designed specifically for audio WE film playback system, at that time, WE are the United States largest film equipment manufacturers, their expanding machine only rented to the cinema, so the market is not buy 300B expansion machine, not to mention the 300B vacuum tube, and therefore may want to now how much happiness for person, who was in search of scrap of Japan 300B for expanding machine, of course, the end-of-300B in some inventory product, so it is available in case of non-300B, therefore apart from Japan's few audio player, the world's few people used to make expanding machine 300B, not to mention is the audio manufacturers use to produce their 300B expand machine.

Until 1989 the continent began to produce 300B, this is a United Kingdom company PM Peter ran to the continent to continent made, later also own mainland 300B of vacuum tube production, since then, the world's vacuum tube manufacturers have adopted the design of your expanded-300B, until now, production of at least more than 300B STW 10 above.

　

　

Super voltage amplifying tube 5842/WE417A

Decades of sound career, I have installed acre expand machine, and heard and seen expanding machine, whether imported or original (one might be called 「introduction original 」 not?), it may be more numerous than was there any expansion machine designers have more experience than they, of course, are abundant.

From experience, I think one expanding machine no matter how good the circuit design, or the use of vacuum tube characteristics better, but most important is the vacuum tube of STW, although in theory, the same number of vacuum tube characteristics are the same, but actually voice does is not the same, but the difference is enormous. So I need to pick the vacuum tube to the selection of vacuum tube of brands, this is mydesign expanded machine and other designers maximum difference.

Of course, to design a non-negative feedback for the expansion of the machine, or to choose the frequency response of the vacuum tube, wide enough for non-negative feedback expanding machine frequency response not by negative feedback to gain, but rather to choose their own frequency response is enough width of vacuum tubes.

So I designed this expanding machine driver level and input level, the first requirement is to pick the low-vacuum tube screen internal resistance, the lower the resistance because of the screen, the more wide frequency response.

To pick a type of vacuum tube?

Let us first take a look at the audio sector most common voltage amplifying tube, as well as their internal resistance of the screen:

The most commonly used vacuum tube voltage amplifier transistor is ECC83/12AX7 tube, the internal resistance of up to 62 screen, 500 Ω (raw frequency response characteristics of a very narrow), if not a lot of negative feedback, it cannot be used with no negative feedback-expansion machine.

With 12AX7/ECC83 on similar medium voltage amplifying tube is 6SL7, screen internal resistance 44, 000 Ω, bare of bandwidth.

ECC81/12AT7 in screen lower internal resistance, about 10, 000 ΩThe raw properties of bandwidth is still available.

12AU7/ECC82 is also often used as drive pipe, the internal resistance is low, the screen is 6, 7 Ω, bare of bandwidth is also good.

12AU7/ECC82 and similar vacuum tube with 6FQ7, 6CG7, 12BH7, internal resistance to both screen before 7, 7 Ω, the latter is lower internal resistance, about 5, 300 Ω. The other and considerable 12AU7/ECC82 medium-voltage amplifying tube is the internal resistance is 6SN7, screen, 7 7 Ω, bare of bandwidth is also good.

There are also lower? has the most recent popular 6DJ8/ECC88, low internal resistance on the screen, about 2, 640 Ω or so (which is why recent vacuum tube expansion machine will ECC83/12AX7 fleet ECC88/6DJ8 reasons).

There is a vacuum tube is Japan's recent amateur circles commonly-6463, screen internal resistance Ω 3, 850.

Addition of a vacuum tube overlook is that dual triode 5687, recently some factories expanding machine use, screen internal resistance only about 2, 000 Ω.

There are also lower?, I searched through RCA and GE's vacuum tube manual, all available voltage amplifying tube specifications are read and recorded the results list, find a lower internal resistance of the vacuum tube, only 1, 800 Ω, 5842.

In addition the second branch of the vacuum tube is also very low internal resistance of the screen, one is E188CC/7119/7004 of 1, 750 Ω and E288CC/8223 of 1, 400 Ω.

All vacuum tube is searched, then to decide I want to use that type of vacuum tubes, the screen is the lowest resistance E288CC/8223, and E188CC/7119/7004.

After all the characteristics of vacuum tubes, I selected the 5842 vacuum tube for two reasons: first, 5842 is a single transistor, while others are double triode, to know two transistors packed in the same glass tubes double triode, there will be mutual interference effects, find a single transistor today since, of course with a single transistor. Second, there WE pipe 5842 is WE417A, of course, WE had better listen to the voices of vacuum tubes.

It used to do 5842/WE417A properly driven? or do input voltage amplifying tube well?

A look at the characteristics of 5842/WE417A, I decided to drive-level and input are 5842/WE417A, but I also decided to use only the level of magnification, which is the driver class and the input level is level.

5842 features specifications

5842 characteristics very similar with the specification, including WE417A data the most complete is Raytheon's 5842WA, therefore we to Raytheon's 5842WA illustration.

5842 is a smaller "MT" pipe, so-called MT tube is "MiniatureTube" means, like ECC81, ECC82, ECC83, 12BH7, 6FQ7 ... and so on are, but the smaller pipe 5842, not the shape of small, but this 5842/WE417A pipe special short, short, represent the inside material is small, the vibration of course also on the small, standing at 「introduction sound hygienic 」 standpoint, is very 「introduction health 」, 5842/WE417A glass tube height only 3.8 centimeters, really cute.

Its pin map shown in Figure 1, figure we can see 5842 is a 9 foot tube filament is 3, 9, 6 feet, the cathode grid 4, 5, 7, 8 are connected, the screen is 1 foot.

This vacuum tube of grid very close to the cathode, Gm values as high as 25, 000mhos, is the highest in the transistor, and μ values as high as 45, screen internal resistance only 1.8 K Ω. Low internal resistance, Gm screen higher, this vacuum tube of very low output impedance, frequency response particularly wide.

From table 1 we know the razor wire voltage 5842 is 6.35V, current is 0.3A, the maximum may not exceed the screen voltage 200V, most large screen extreme loss up to 4.5W.

See the interelectrode capacitance 5842, screen to the cathode and the filament of the capacitor is 0.55pf, cathode to the grid and the filament is 9.0pf, screen to the grid and the filament is 1.75pf.

We can no matter the tubes of the interelectrode capacitance problem because it is the first level of amplification, in front of the signal source is not a front-stage expansion machine is CD sing-up, or e-newsletter of the damper, these sources are very low output impedance, there will be ineffective without, not to mention Cascode circuit interelectrode capacitance is only about half of General enlargement, not hell interelectrode capacitance.

Table of typical action instance to screen pressure 150V, cathode resistance 60 Ω, screen flow 23mA, sequestering is 1, 800 Ω, Gm value 25, 000mhos, μ value is 45.

We can calculate the energy consumption of the screen appears:

P=EI

150 × 0.023

=3.45Wr>
Figure 2 is the characteristic curve of 5842, we can see the gate voltage from 0V to begin until + 6V curve interval is very average, so we get by-0.5V corruption-3V bias can, if you want to be lazy, for example, we direct use table typical original action instance that screen pressure 150V, cathode resistance 60 Ω, screen flow 23mA to work, in which case the bias by:

Ec=R×I

= 60 × 0.023

= 1.38V

The bias is-1.38V.

　

　

5U4 series comparison of rectifier tubes

Rectifying tube I prepared a lot, although different diode rectifier out of voltage is different, but also not be too big, like 5AR4, CV378 like Pong thermal diode, the whole out of voltage is higher, like 5U4, 5R4, 5Z3, direct thermal-rectifier diodes, the voltage is lower, different brands and different, new and old pipe will be different, various rectifier voltage tube whole out about corruption in 420V 450V.

But as far as I know, special diode as 83, mercury vapor tube, the whole out of voltage is particularly high; another type of rectifier tubes such as 81, 281, 381, classical rectifiers, whole out of voltage is particularly low, and both types of rectifying tube filament, pipe saddle also are different, replace the cumbersome, so we cannot compare the two types of rectifiers, just compare the transfer can be directly inserted, nevertheless, rectifying tube also spent a lot of time, because each change a rectifier tubes will take some time to wait until the voltage rises to stability, these differences in rectifying tube sounds as follows:

United States RCA5U4G:

Sound grandiose, open, transparent, energetic enough wide frequency response.

United Kingdom Mullard5AR4/CV1377:

Voice clarity, detail and more wide enough, frequency response, but sounds thinner, less charm.

United Kingdom MullardCV378:

Sound clear, rhyme, frequency response, but not wide enough RCA5U4G sound strong.

United Kingdom GECCV378:

Sound than MullardCV378 clearly, frequency response is wider, more rhyme, but sound is thicker.

United Kingdom EMITrade5U4G/U52:

There are more than the 5AR4 Mullard rhyme, but resolution is not high, the bass more Mullard.

United Kingdom BrimarU52:

Need than MullardCV378 rhyme, clarity is also good, high and low ends of the extended slightly lost to GEC's CV378.

United States KenRad5U4G:

Frequency response, clear, transparent, tone lighter.

United States Tunsol274:

Frequency response w, transparent, open and energetic than the rectifier tubes of audio and music are good.

United States WE274B:

Is this ever more rectifier diodes in the best of a team, and the sound than Tunsol274 also good on a big Festival, sound, sound field up to broaden the largest, most transparent, most energetic and rhyme, sound and thick, frequency response also widest is the comprehensiveness is fine, but unfortunately I only have two, but could not find the third branch.

300B when rectifying tube?

The sound is too good not to say that we were both excited for a while, after listening to many record labels, find details, frequency response also wide, most, most important is the low-frequency resonant problems solved.

When I suddenly realized that this kind of positive and negative are plus resistance to flow ring filtering method voltage will not change, so hurry to measure, this volume, Hey can be unnerving, voltage suddenly took off after about filtering 40V voltage 400V only!

This filtering mode sounds very nice, but the voltage is lost too much visible output power will be reduced a lot, but my transformer secondary coils are used to the maximum of 380V, also high up, what to think a thought, on! different rectifiers whole out of the voltage is different, why not try a change of rectifying tube voltage rises? immediately pull down of 5U4G RCA, replaced the GEC CV378 rectifier diodes, power up, and sure enough voltage to rise up, but the voltage only after filtering to 420V, still not enough.

What to do, GEC of 378 rectifying tube voltage rectifier it has very high, if the heat exchanger 5AR4, high not to go there. I suddenly thought quickly, think only of internal resistance 300B 700 ~ 90 wells, if used for when pipe, I wonder if the rectifier voltage will not be raising some, by the way, you can try to sound 300B rectifier, 300B is the transistor, diode original used is also very simple, as long as the screen and connect a diode triode, but is a single screen of triode 300B and, therefore, necessary to use two to do full-wave rectification, that is not difficult, since I'm more than ready-300B.

Turned over vacuum tube of the same tray, 300B factories are only two, the only mainland graphite screen has four 300C, use this four rectifiers 300C to when to use it.

But problems again， 300B of pipe, block is four feet, and if you want to swap to change 300B pipe, block, and the entire machine parts location to large moving, but that is no we, together, one person, one, soon adapted well, immediately plug four graphite screen 300C try rectifier voltage value out. Sure enough, it use 300C rectifier voltage after anti-flow ring voltage rise after filtering to voltage 440V, just good, listen to the sound, Hey, it's just too good, sound thicker, denser, more meat, warmer and more transparent, more clearly, the most difficult to play the sound is clear and warm, it is difficult to eat it, but use 300C when rectifying tube, have your cake and eat it, and I were both very happy.

Then plug the other 300B tube only on one computer, take a look at a different voltage, the result is changed several 300B,, Rectifier voltage is almost out.

Use 300C when rectifying tubes, sound presses WE274 of rectifiers, really good, he knows the continent a graphite screen 300C only three thousand dollars, than my WE274B cheaper too much, but there is a singular WE274B price, but also the one-tube-hard to find, let alone the rectifier voltage ratio of high, consistent with the balance WE274B on flow ring filter circuit, will have the opportunity, you can change WE300B when rectifying tube sound.