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Tube amplifier on g 811. Powerful single-ended amplifier on an affordable element base

Today:

On this page of your site
I decided to talk about my G-811 tube amplifier
which was made by me in 1998.

For all my practice of working on the air, I have previously manufactured and adjusted various amplifiers using various radio tubes I have, such as GU-50, (2xGu50,4xGU-50), 2x6P45S, GI-7B, GU-74B, GU- 43
All amplifiers worked perfectly, covering all amateur radio bands, and like any product had its minuses and pluses, whether it was purely design flaws (and where without them?), And purely energy ones, requiring their own, certain conditions, depending on the installed radio tube.

Over time, I came to the conclusion that the use of ceramic-metal lamps in amplifiers up to 500-600 watts is not justified at all, due to the fact that ceramic-metal lamps need power supplies of increased complexity, where it is necessary to use screen voltage stabilization, an anode, to introduce a bunch of automation with by switching on power and cooling sources in series, where sometimes at the output, we still have approximately the same order of output power, and the spread plus or minus 100 watts essentially does not affect anything, but on the whole it significantly complicates the entire design and not only ...

Thus, sorting through all the lamps available at that time for me, I decided to make an amplifier on "glass", which, in terms of its parameters, would be close or similar to one GU-74b lamp, but much simpler and more economical than the latter.

The ready-made case I had from an old GI-7B amplifier was taken as the basis, where 4 G-811 lamps were placed. The box turned out to be quite cramped, which is always a minus in PA, but nevertheless, push the lamps there, -contour, fan and incandescent transformer, I still managed ...)))

The amplifier contains input P-circuits and a tuning capacitance at the input, for ideal matching with a transistor transceiver and on all ranges and provides an SWR between the transceiver and the PA input, not more than 1.2
There is a button to turn on the "PA bypass", and it can also work automatically in FM mode, if there is a carrier with a level of 3-4 W at the input. Built-in three pointer devices, show the OUTPUT level when matching with the load, the degree of matching at the input (small device) and the anode current (full deflection of the needle - 1 A)
A small 110 volt motor from an old turntable is also used, which works absolutely silently and cools the lamps with an air stream.

The amplifier is made according to the classical scheme. I did not consider it necessary to draw a complete amplifier circuit, since in fact, the circuitry of such amplifiers is almost the same and is well known to radio amateurs. Just for clarity, I will give the circuit of the Ameritron amplifier on the 3-G811.

My power supply for the amplifier is made according to the classical scheme and in a separate box, a case from the old Soviet C1-19 oscilloscope and was conceived as a universal power supply unit for the UMS, where the anode transformer is very well located, made on a toroidal ring from LATRA for 2 kW. The anode contains a secondary winding of 1.2 mm wire and can deliver a switchable voltage of 300 volts up to 2.2 kilovolts, providing good current, sufficient for more powerful amplifier. Also in this PSU, a number of additional voltages are issued, such as + 24v, - 100v (with voltage regulation), + 12.8v and + 5v, which are not used in this amplifier.
As filters, 2 oil containers for 6KV / 100 microfarads are used. USM and PSU are connected using two cables. One cable with thick insulation (automobile, high-voltage, candle) through which the ANODE and the second cable are connected, brings the 220v network and a number of low voltages - 22v, + 24v to power relays, circuits, and control lamps.

Main technical characteristics:

Anode current, in the maximum, maximum power mode - 800mA, with anode 1500v
- Anode current, regular mode work - 650mA, with an anode 1300v
- Anode voltage drop under load, no more than 5 volts.
- Glow, serial lamp supply - 12.8v / 9A
- Power buildup, from 30-65 watts.
- Quiescent current (total, for 4 lamps), no more than 80-120 mA (depending on the anode voltage).
-Output power, at anode 1500v, buildup 40w, 80m-600w; 20m-550w; 10m-450w;
-Ranges -80m-40m-20m-15m-11m-10m

Features of building and setting up an amplifier on the G-811

top cover

The second feature is that the G-811 lamp is a triode. The property of this lamp is a VHF boost! As it turned out later, everyone who assembled the amplifier on such lamps, one way or another, faced this problem. This fate has not bypassed me either. What measures did I not take to get rid of this scourge ...

Well, the last. Since I never managed to find ready-made panels for these lamps, I had to make a home-made version, based on 4 lamps at once. As a basis, I used a plate of thick fiberglass, 12 mm thick, in which I had to drill holes for the lamp legs exactly in size. In the leads themselves, pieces of copper tubes are inserted and flared on both sides of the plate. Everything turned out to be quite reliable and during operation, no problems were noticed!

Outcome

Compared to the amplifier on the GU-50, in versions of 3-4 lamps, this amplifier wins in power, almost twice and significantly in terms of power output at 28 MHz. I liked the amplifier so much that over the years, I got a triple set of spare, new tubes. In my thoughts, there is a desire to make a miniature amplifier in one case with only 2 G-811 bulbs, with an output power of about 250-300W for field work.

Power supply and amplifier for 4xG-811

I will make a reservation right away that I have nothing to do with the creation of this amplifier. I got it for repairs from one Oryol club. This amplifier is interesting not only for its output power (more than 100 watts), but also for its design. There are only two lamps in it (G-811), they are swayed by the TDA7294 microcircuit, the connection between the cascades is a transformer. The power of the interstage transformer is approximately 50-60 W, as an output it is used, miraculously, rewound TSA-270. OS is missing. Output lamps, which is natural for G-811 triodes, work with grid currents. The amplifier also has a tone control on the microcircuit, but I will not touch it for well-known reasons. An approximate amplifier circuit is shown below.

Capacitors are especially striking. more precisely - their small capacity. 4 electrolytes at 180 microfarads. Only. Connected in series for high voltage. A resistor is installed in parallel to each electrolyte. There are no chokes in the power filter of the amplifier.

Lamps in the dark.

Actually, the amplifier itself.

So, with the help of two lamps and a microcircuit, as well as WITHOUT huge electrolytes in the power filter, a really powerful amplifier works great.

Comments on the article:

In a single-ended amplifier on the 811, you can make an amplifier of 15 watts per channel with a band of 20 Hz 80 kHz and a low level of distortion and output impedance< 0.4 Ом. Но это не радиолюбительская работа.

Threat And light bulbs are good, probably with tungsten anodes.

The lamp is funny - a triode with a pentode characteristic,
extreme right, with incredible amplification.
Get ready to work with grid currents (A2): read the theory on interstage trances or cathode followers for buildup.

Schemes at: //www.metaleater.narod.ru/s_se.html

my experiments with this lamp, and with A2 in general,
convinced of the prospects of such a path - the sound is very strong, dense, "meaty".
I took the circuit from RCA as a basis, but remade it into a single-cycle: 6E5P + 2A3 + interstage.

And at first he trained on 6N1P "reinforced SRPP" +
6P7S (in triode) - sound, compared to conventional SRPP,
became “meaty”, the power increased (of course, a slight increase in the gain of the cascade also affected). Professional musicians were delighted to listen (classical).
Among the shortcomings - some confusion on very heavy music (groups like "Throne of Chaos", "Your Shapeless beauty"). In addition, 6N1P-EV worked with serious
exceeding the nominal parameters - they were enough for
six months.

Most experts do not advise contacting, but
I was intrigued by N. Shishido's scheme - if he decided to do it on 811, then for a reason!
Toropkin

>Has anyone done an amp on such a lamp

>how does it sound

>Load resistance

It's up to you.
Anton

At 3: it will not be enough! 10-12 kOhm

the lamp is terribly right at 700 volts at the anode and 0 on the grid, the lamp is locked. starts to open at + 20-35 volts on the grid. I do not remember exactly.
But probably at 3000 on the anode it behaves differently.

Used in telegraph transmitters in class C.

In sound, her project will be at the level of hm 70 at a price for power is weaker.

> > >I had always heard that the Svetlana 811A"s were the most rugged of them

> > Rumor has it that Svetlana is dropping production of the 811A due to low

> > sales, Charles.

> > - Rich..., 805.386.3734, www.vcnet.com/measures.

Charles, I wouldn't be surprised if it's Svetlana. Ameritron uses
811s" in both of there 811 amps. The only other 811 amp that I know of
is made by Ten-Tec and I "m not quite sure what tube they use. Cetron
BTW, also makes a good 811, but Svetlana is probably the best, high
gain, good fit and finish. Quality workmanship and tolerances. 73"s de
Phil W2GE

Svetlana also.......in the Ten-Tec Model 411 Centaur.

73 de Mike, W9WIS

I'm here again with the stupid idea of \u200b\u200bthe first (in the corrector) to put the G811 with a bias of -3V and anode 1300-140 0V. efforts to develop such a cascade.
And the sound of a light bulb without grid currents is simply wonderful!
Rezvoy

I would say for all such direct filaments with a tungsten cathode
Vasyanin

What are our realities? We take the 811th Marshall, with ribbed anodes under the horizontal, 100 dollars a matched square, and enjoy life ...
KAA

Why “at least”?.. An ideal (or close to it) current distribution in a triode, when the electric field lines inside the electrode system are most rectilinear and the input characteristic is as close as possible to a straight line, is in principle achievable only in the mode with grid currents. ..
KAA

I tried this scheme (I took it out of my head; just in case, I don’t claim authorship):
Two sources. The first is 190v, better stabilized. An 800 V, ordinary, is successively attached to it. So, only a kilovolt. From the plus of a large source down: wire, primary output trance, anode 811th. The 811th cathode (through an artificial middle point) is connected to the 6P9 anode. Grid 811 is connected to a source of + 190V, the 2nd grid 6P9 sits there.
1st grid 6P9 at the input, in the RC cathode. R is chosen so that the current through both lamps (and they are connected in series) is 40-45 ma. At the anode 6P9, about 200V is obtained.
That's the whole scheme. Sensitivity 1 ... 1.5v, depending on the specimens. 5-6 watts is easy, with 1-2% distortion. A very favorable spectrum (2-3 harmonics and, perhaps, everything). With a class 34 lamp, the measurements are better, but the sensitivity is very low (the high source here should be 600 volts, the current is under 70 mA). The sound is quite decent (obviously better than the 811 fed by the cathode). Plus schemes - extreme simplicity. Minus - the need for a good output trance with a reduction of 8-10 kOhm (the random copy I had played, strictly speaking, more than the middle). And one more minus is a very large "plus" on the anode sticking up. Fearfully...
Evlampy

Message from Alexey Shalin

> But there is also such a moment: a non-sprayed getter with its “apparent absence” often

>cheats beginners and they reject perfectly good lamps

I agree, the G-811 has a non-sprayable getter, you can immediately see a ring on the anode. But it needs to be known.
shi

I agree with Evgeny about 572\811. Indeed, after (according to my observations) 600 ... 650V they give a somewhat simplified sound, which, in general, has its own physical justification - the overall dimensions of the anode and the geometry of the electrode system are such that edge effects at a grid-anode field strength above 1.5...2MV/m are strong enough and lead to the formation of "virtual" triodes with high permeability from the bottom and top of the anode. In GM70, the interelectrode distances are larger and similar effects take place at much higher voltages. From this point of view, 350...400V for 811/572 approximately correspond to 1.2...1.5kV for GM70.
Lynx

One time ago I listened to CE on 811, the mode is such that it does not climb out of positive biases on the grid at all, the buildup of the pentode through a powerful (on 6L6) cathode follower. Great, fast, detailed sound! With all my prejudice against both 811 and A2, and against a lot of things in this device! But - the ears vote "for"!
HRYUN

The G811 lamp looks similar to the widespread G807 beam tetrode, although it is slightly larger. But the G811 is a completely different lamp. Worse or better? This is a rhetorical question. But the fact remains that this is a direct-heated triode. With regard to direct heating, there are many different fabrications on the network that justify the special sound quality. But in fact, direct heating does not have any objective advantages over indirect. The case is just the opposite. Since it is necessary to apply galvanic isolation of filament circuits, this is reflected in the weight and size indicators of the entire structure.

An example of a tube amplifier circuit is shown in the figure below. Given the good controllability of the triode, a simple implementation with a single tube in the preamp assembly can be used to build a push-pull circuit. You can start right away with a phase inverter. Or you can use the Williamson scheme. Who likes what. The main thing is to ensure decoupling from the incandescent circuits of the output lamps and make autonomous sources of symmetrical supply voltage, right on alternating current industrial frequency. The filaments will have to be wound, and you will need 4 toroids of 25 watts each or a pair of toroids of 50 watts, respectively. There is no standard solution here and you will have to use assault. The wires from the filament transformers are high current, so they need to be run in twisted pair over a short distance directly from the toroidal filament transformers located in the basement. Intersections with signal wires should preferably be avoided.

Since the anode voltages of the G811 output lamps are relatively large, the supply voltages of the anodes of the preliminary stage should be limited. To do this, it would be nice to use a parametric stabilizer. A stable voltage will significantly improve the mode of operation of the phase-inverted stage. And since the own consumption of the anodes of a small double triode is small, the stability will be extremely high. It is convenient to use a differential pair as output transformers, designed for small currents and high voltage. Output lamps have allowable cathode currents not exceeding 150 mA. So don't run too far here. A pair of matching transformers in the size of about 60-80 watts will be quite sufficient.

G811 triodes are pretty nice appearance. Their number is limited. But they can be bought here in proven pairs, at a price 25% lower than in Istok. You can also buy a tube amplifier for such beauties here on a prepaid basis. But it will cost quite a lot, from 100K and above. To purchase, just contact me by mail, discuss the price and terms of delivery, self-pickup is possible. After that, the person who wishes should call the phone number indicated on the website to discuss the details, and only then make an advance payment of 20% of the contractual amount to my account in Sberbank. Having received the transfer, I send a notification and within two weeks I will call back myself with confirmation of the proper packaging of the product and readiness for shipment, and I will send photos of this particular unit, open and packed, by mail. For shipment, the buyer is obliged to transfer the remaining amount, after receiving which I carry out the shipment and send a copy of the receipt to the mail. If the circumstances of the buyer in the specified period of time have changed, then the purchase can be abandoned. The listed deposit is non-refundable. Warranty for the amplifier 12 months from the date of delivery. The warranty does not apply to glass in terms of postal shipment and transportation by a transport company. Sincere wishes of good health and success to all.

Evgeny Bortnik, Krasnoyarsk, Russia, November 2017

The linear amplifier for a category I radio station transmitter is designed for linear amplification of single-sideband, telegraph and AM signals in the ranges of 10 ... when pronouncing a long “a” in front of a microphone) is also 200 watts, while the peak power input can reach 400-500 watts. Amplifier efficiency 65-70% depending on the operating range.

The amplifier uses four G811 lamps connected in parallel according to the OS scheme. The total dissipation power on the anodes is 160 W, so it is possible to carry out rather long transmitter tuning sessions with an input power of 200 W.

Due to the small output capacitance of the G811 lamp (6 ... 7 pF), several lamps can be switched on in parallel. In this case, the anode current increases in proportion to the number of lamps, which is equivalent to using a lamp with a large anode current pulse at a not very high anode voltage (1000 V). The anode load resistance is small. This, along with the low output capacitance of the G811 lamps, contributes to the high efficiency of the amplifier in the ranges of 10 ... 15m, where it is difficult to create a circuit with a large equivalent resistance and high efficiency.

The similar resistance of the amplifier depends on the number of lamps connected in parallel. With four lamps, it is 75 ohms.

When receiving signals, the amplifier lamps are locked with a voltage of -27 V supplied to the grids through the winding of the K1 antenna relay. The contacts of this relay connect the antenna to the X3 socket, where the receiver input is connected. When transmitting signals, the grids of lamps are connected to the transmitter housing by switch S1 or an external contact (for example, in a transceiver) through socket X5. In this case, relay K1 is activated and connects the antenna to the output of the transmitter. A tuning indicator is connected to the output of the amplifier, the sensitivity of which is regulated by resistor R6.

The inductor L9 in the heating circuit is wound simultaneously with three wires on a ferrite rod with a diameter of 12 mm and a length of 140 mm from the F-600 material. The number of turns is 40. The diameter of the extreme wires of the inductor through which the filament current passes is 1.5 mm, the diameter of the middle wire passing the cathode current is 0.51 mm. The incandescent transformer T1 provides a voltage of 2 X 6.5 V at a current of 8 A. Its overall power is 110 watts. Coils L1 ... L4, wound on resistors RI ... R4 of the MLT-2 type, contain 5 turns of PEV-2 wire with a diameter of 0.62 mm. The anode choke L6 is wound with PELSHO-0.35 wire on a porcelain frame with a diameter of . 20-25 mm and 150 mm high. The number of turns is 150, the 50 turns closest to the anode are wound with a pitch of 0.5 mm. Chokes L7 and L8 of any type.

A P-loop is used at the output of the amplifier. Capacitor C12 must have a gap between the plates of at least 1.2 mm. Capacitor C13 is a built-in unit of variable capacitors from an old-style radio receiver (with a gap between the plates of at least 0.3 mm). The rotating coil L5 is wound with a wire with a diameter of 2 mm and is equipped with a coil counter. Since the output P-circuit has three adjustable elements, in order to correctly tune the amplifier in the range of 80 m, it is necessary to set the maximum capacitance of the capacitor C12 (250 pF); when working on a coaxial feeder and low SWR, the capacitance of the capacitor C1 should also be close to the maximum. The circuit is tuned to resonance by rotating the coil L5, the connection with the load is regulated by the capacitor C13. In the range of 40 m, the capacitance of the capacitor C12 is 120 pF, in the range of 20 m-50 pF, in the range of 15 m it should be close to the minimum, in the range of 10 m it should be minimal.

When mounting the amplifier, the input circuits must be separated from the output circuits by a screen, for example, the input circuits should be placed under the chassis, and the parts of the anode circuit - above the chassis. The conductors of HF circuits should be as straight and short as possible.

Right assembled amplifier starts working immediately. With self-excitation, the resistance of resistors R1..R4 should be reduced by 1.5-2 times. When amplifying a single-sideband signal, to achieve an anode current envelope of 400 mA at the peak, an excitation power of 25 W is required.

G811 lamps can be replaced with GU50 type lamps in triode switching. To maintain the same input resistance (75 ohms), three GU50 lamps are switched on in parallel. Since the GU50 lamp has a heated cathode, excitation must be applied to the cathode. The middle wire of the filament choke is connected to the cathode.