Lamp UMZCH entry-level (work on the bugs). Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Tube Power Amplifiers

 Comments on the article

The time that has passed since the assembly of the first working UMZCH layout has shown once again that, in principle, there is no such design that could not be improved. If for each change in the circuit it was necessary to manufacture a new amplifier, then at least half of the city's population would be "happy" with them. However, this is hyperbole :-)

In reality, several changes in the scheme were tested, contributing to the "more correct" use of lamps, but without requiring significant alteration of the design.

Schematic diagram one channel of the modified amplifier is shown in fig. one

Rice. 1 (click to enlarge)

The newly introduced elements first of all violated their usual numbering on the circuit diagram, so be careful - hereinafter the new numbering will be used.

About the scheme

First of all, on the strong recommendation of real audiophiles, capacitors were introduced into the auto-bias cathode circuits: C4 and C7 for the VL1 and VL2 tubes, respectively. Thanks to these capacitors, the influence of cathode resistors is eliminated (in fact, local current feedback is eliminated) on the output resistance of the amplifier stages (without these capacitors, it is noticeably higher). And, if for the cascade on VL1 this is not so obvious, then the introduction of the capacitor C7 into the cathode circuit of the output pentode VL2 made it possible (albeit quite a bit) to increase the maximum output power of the amplifier.

The chain of supplying the general OOS (R4, R7) to the cathode circuit of the first lamp (R5, C4) is somewhat complicated. This was done in connection with the desire to reduce the influence of the parameters of this chain on the VL1 lamp mode. Now the bias voltage of the VL1 lamp is almost completely determined by the resistance value of the cathode resistor R5, as a result of which there is no need to select it after changing the feedback depth.

Another two-position jumper JP2 has been introduced, which increases the degree of convenience for those who like to experiment. The jumper allows you to switch the output lamp from pentode mode to triode mode and vice versa. (The diagram shows a pentode connection - when the screening grid is connected to a power source. In a triode connection, the screening grid is connected directly to the anode, which ensures a sufficiently deep local voltage feedback, while the current-voltage characteristics - I-V characteristics - lamps become very similar to I-V characteristics of triodes , which is why such a name arose.) It should be noted that the use of this feature requires special care from the experimenter - changing the lamp mode often leads to the need to correct the offset value on the first grid, which means that it is also necessary to change the value resistance R10.

Printed circuit board has been updated to reflect the above changes. It was possible to keep its former size and mechanical parameters. But since the installation has become denser, when assembling, you need to pay attention to the dimensions of the electrolytic capacitors used.

The printed circuit board version with the JP2 jumper, however, does not seem to be entirely successful due to the excessive number of additional conductors, which significantly increase the mounting density (the voltage between the jumper contacts can reach 300 Volts - therefore, you need to be careful about observing the gap between the tracks of the board to avoid breakdown).

PCB with JP2 [gif, 300dpi, 122 kb]
PCB without JP2 [gif, 300dpi, 119 kb]

About heating capacitors

Many have noticed that during the operation of the amplifier, the electrolytic capacitors heat up. Heating occurs due to the thermal radiation of the lamps and, in my opinion, is not at all dangerous - capacitors C3 and C6 heat up to a temperature of about 40-45 degrees, and this is very little. However, it should be noted that the layout of the printed circuit board of the amplifier is designed for an open design and, if the amplifier mounted on the proposed printed circuit board is placed in any case, it is possible that heat shields will have to be used to reduce the degree of heating of the capacitors.

About replacing lamps

The closest in parameters to the 6P14P lamp is 6P18P. In fact, the lamps are very close (in the absence of markings, they cannot be distinguished at all) and differ only, according to the reference book, in the nominal voltage at the anode, which for 6P18P is 170 V at the maximum allowable 250 V. However, 6P18P works fine even at higher voltages and can be installed instead of 6P14P without any changes in the circuit. Unfortunately, this is where the list of lamps suitable for such a replacement ends - for the rest of the lamps, the selection of a cathode resistor is necessary. The closest parameters to 6P14P lamps:

It is possible to use a 6P1P lamp (with a 240 ohm cathode resistor), but it has a different pinout, which entails the need to change the printed circuit board pattern. It is difficult to use a 6P43P lamp (although the pinout is the same) due to the large value of the bias required for its operation (for this lamp it is more profitable to use the so-called fixed bias from a separate source).

Lamp 6N3P without any alterations is replaced by a lamp 6N26P. Without changing the circuit, it is possible to use 6N1P, but it differs in the pinout. 6N2P and 6N23P are of little use due to the low anode current of 6N2P (only 2,3 mA) and the strong microphone effect of 6N23P, but you can try to use them, also taking into account their pinout (similar to pinout 6N1P) /

Author: Andrey Kovalev, Tyumen; Publication: cxem.net

See other articles Section Tube Power Amplifiers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Improving Quantum Computing 11.07.2021 The computational capabilities of today's supercomputers may be staggering, but quantum computers are expected to outperform even the most powerful of these machines. Thanks to the huge amount of memory and speed of operation, quantum computers will be able to solve problems that are currently beyond the power of any processor. European researchers working within the EU-funded Magnum and microSPIRE projects have developed a potentially new qubit system using the rotation of so-called "holes". Semiconductors consist of artificial quasi-particles, which are a collection of electrons and holes. Holes are usually called carriers of a positive charge equal to the elementary charge in semiconductors. Although holes are not true particles, they share many properties with electrons. They interact when they come close to each other, and they also have the quantum mechanical property of spin. Holes in materials such as metalloid germanium are excellent candidates for spin qubits. The scientists built a nanostructure from various layers of germanium and silicon, which allowed them to confine the holes to a two-dimensional region. Scientists at L-NESS stacked several different mixtures of silicon and germanium just a few nanometers thick on top of each other. This made it possible to limit the holes with a germanium-rich layer in the middle. Tiny electrical wires, called gates, were added on top to control the movement of the openings by applying voltage to them. As a result, electrically positively charged holes responded to the voltage and could move very accurately within their layer. The research team used this technique to bring the two holes as close to each other as possible, which would help them interact as they rotate and form a spin qubit. More importantly, they were able to create a qubit from two interacting hole spins using less than 10 millitesla of magnetic field strength.

Other interesting news:

▪ Cooling electronics with jumping droplets

▪ Molecules stopped at absolute zero temperature

▪ Overweight people are happier

▪ Smart milk carton lid

▪ Sony a42 II full frame 99MP camera

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section And then an inventor (TRIZ) appeared. Article selection

▪ article Freeze the worm. Popular expression

▪ article Do all people lie? Detailed answer

▪ article Triple braided knot. Travel Tips

▪ article Dyeing stockings. Simple recipes and tips

▪ article Scanning pattern. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024