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Written by: Grzegorz Makarewicz
Category: Uncategorised
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A website dedicated to various topics that interest me. Retro electronics – primarily devices using vacuum tubes, forgotten old corners of Warsaw, playing with artificial intelligence, and other topics that strike my fancy at the moment.

I'm also trying to recreate the device descriptions I once posted on the now-defunct FonAr and Trioda website. These descriptions are not only mine but also those of my friends, primarily from the Trioda Forum. To enhance the site's content, I've included illustrations in various sections that I found in old books, usually from the 1950s, on topics broadly related to radio engineering (these are books or excerpts from books from defunct publishers, often without identifying the authors).

Where possible, I add information about the author to the drawing.

As promised, on January 10, 2026, I added another diagram to the book (there are already 132 of them)

 

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QUAD 22 Preamplifier (QUAD 22 Control Unit)

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Written by: Grzegorz Makarewicz
Category: Gallery
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Grzegorz "gsmok" Makarewicz (2018-01-08), This email address is being protected from spambots. You need JavaScript enabled to view it.

The QUAD 22 preamplifier was designed to work with one (mono system) or two QUAD II amplifiers. Its capabilities, and in particular the replaceable external modules, predisposed it to act as a control device for an audio system. This was reflected in the name of this device, which described it not as a typical preamplifier but as a control unit (the full, original name is: "The QUAD 22 Control Unit".

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Hi-Fi Devices - Hi-Fi Amplifier with 36W Output Power (Ultra-Linear)

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Written by: Jan Różycki
Category: Articles
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Eng. Jan Różycki, 1st Edition,
Państwowe Wydawnictwa Techniczne, Warsaw 1959

4.4. Hi-Fi Power Amplifier Circuits

4.4.4. Hi-Fi amplifier with 12 W output power (Ultra-Linear)

Read more: Hi-Fi Devices - Hi-Fi Amplifier with 36W Output Power (Ultra-Linear)

Mains tube power supply

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Written by: Jerzy Kurpiewski
Category: Books
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Engineer Jerzy Kurpiewski,
Biuro Wydawnictw Polskiego Radia (Polish Radio Publishing Office), 1952

CONTENTS

  • Introduction (5)
  • Transformer (12)
  • Rectifying electron tube (19)
  • Cuprite and selenium rectifier (26)
  • Voltage rectification (32)
    • unidirectional rectifier (35)
    • bidirectional rectifier (37)
    • bidirectional rectifiers in a bridge circuit (39)
  • Smoothing of rectified electrical voltage (45)
  • Filter elements (64)
  • Stabilization of rectified voltages (66)
  • Power supply circuit (69)
  • Power Supply System Overview (69)

INTRODUCTION

  A fundamental aspect of a radio technician's work is having adequate power sources. They primarily use AC power; they illuminate their work area with electric bulbs, use an electric soldering iron for assembly, and often employ an electric drill when making enclosures and sheet metal structures for audio amplifiers, radio receivers, simple but essential measuring instruments, and so on.

  However, to operate a tube circuit that lacks its own power supply or whose power supply is malfunctioning, it requires DC voltages. This voltage can be conveniently obtained by converting the electrical energy of the 50-cycle AC lighting network into DC energy. This can be accomplished using AC rectifiers, such as vacuum tubes (rectifiers) or selenium or copper stacks.

  A device that supplies regulated direct and alternating voltages, powered from an alternating current network, is called a mains power supply.

  A power supply provides DC voltages, for example, up to 350 V at a current load of 200 mA, and AC voltages regulated in increments from 1 to several volts for filament operation with AC currents of up to several amps. The power supply can therefore serve as a source of anode voltage and filament voltages for vacuum tubes. More sophisticated power supplies may also incorporate a separate rectifier, providing a negative voltage, and a rectifier, which allows for filament operation with DC current. It's worth noting that the DC voltage at the power supply output will still have a certain percentage of AC component, despite the use of a smoothing filter. In practice, however, this ripple can be reduced to a low value so that it doesn't interfere with the power supply's operation. The additional option of using the power supply's transformer alone can significantly expand its usability.


Rys. 1.

A typical laboratory power supply will consist of:

  1. a transformer that converts the mains voltage to the same value to obtain the desired DC voltage at the power supply output after rectification, as well as the filament voltage found in vacuum tubes;
  2. a vacuum tube rectifier;
  3. a filter that smooths the ripple after the rectifier.

  All voltages are regulated either in steps or continuously. When discussing various power supply systems below, we will also mention voltage regulation methods. Generally, a power supply can be a less complex device than previously mentioned, for example, when it serves a specific purpose: powering a radio receiver, an audio amplifier, or a transmitter. They may differ in their AC input methods, rectification or filtering methods, and finally, the power they are supposed to deliver. The most common power supply system is the power supply for radio receivers.

Fig. 1 shows one of the systems:

  • C1 = C2 = 16 µF
  • R0 = 7 kΩ

The mains transformer has taps for 220 V and 110 V on the primary side. Bidirectional rectification with a Π-type filter. Instead of a voltage-smoothing choke, a real resistance is used. The rectifier tube is heated from a separate winding of the tube from the second circuit.

A more complex arrangement is shown in Fig. 2. 


Fig. 2.

The input from the mains transformer to the AZ1 rectifier tube. The filter has two elements, plus an input capacitor C.

The first filter is a choke, the second a resistor. DC voltages are taken at points <a>, <b>, and <c>, with the negative voltage additionally filtered using resistors and capacitors R1 and C1.

The half-wave rectification circuit is shown below in Fig. 3.


Fig. 3. Filter with input capacitor and resistance in the series branch

Positive voltage is obtained at points <a> and <b>, negative at <c>.

  It's also possible to create a power supply without a mains transformer by using the circuit below with a tube that has a high filament voltage. The rectifier tube is connected directly to the mains. The filament of this tube and the external circuit's tubes are in series. Resistance R reduces the filament current to the appropriate value.


Fig. 4.

  The L1 and L2 coil system with capacitor C1 acts as a high-frequency filter, preventing it from reaching the rectifier tube, where it could be modulated by low mains frequencies and produce a humming effect that could interfere with broadcasts. A 1000 pF capacitor, C4, shunts the high-frequency voltages and prevents this harmful phenomenon. The resistance r, approximately 50 Ω, prevents excessive current pulses when the tube operates as a rectifier. At the output, we have a standard filter circuit with an input capacitor and a filter choke.

  The power supplies discussed here deliver relatively high voltages at low load currents. This is typical for powering receivers, as the load currents in these cases vary only slightly during operation, so they do not affect the output voltage of the power supply.

  When we want to maintain a constant voltage that is not very dependent on the load, we use filter systems with an input choke, e.g. the one shown in Fig. 5.


Fig. 5.

  The power supply provides a DC voltage of 250-300 V, with higher voltages achieved by connecting the input capacitor C1 and a negative voltage of 75 V from a separate vacuum tube rectifier operating on half of the secondary winding of the mains transformer. This circuit can be used for a small radio transmitter. We'll also cite an example of a power supply for a cathode-ray oscillograph. Power supplies for oscillographs combine two requirements:

  1. providing DC voltage to power amplifiers and the so-called time base generator;
  2. providing high voltage but low current to power the oscillographic tube.

For reasons of material and space economy, we often connect both of these power supplies together to obtain one combined power supply.

  A schematic of such a power supply is shown in Fig. 6. We can see that the low-voltage portion of the power supply is designed as usual. Full-wave rectification is achieved using a 5Y3 rectifier tube. The filter used to smooth the rectified voltage is interesting in that the filtering capacitances consist of two capacitors connected in series. While the total capacitance of this branch will be halved, this overcomes the lack of capacitors for a higher operating voltage. By connecting two identical capacitors in series, we create a circuit that can withstand twice the operating voltage of a single capacitor. The high-voltage portion of the power supply is typically designed as a full-wave rectifier, as filtration is not an issue with low current consumption. Therefore, the filter is very simple. The capacitors used are small, 0.25 µF, and a resistor is used instead of a choke. Therefore, we do not use electrolytic capacitors, but rather ordinary paper capacitors with an appropriately high operating voltage.

  The high-voltage winding consists of two parts: we use half of the low-voltage transformer winding and then add enough turns in series to achieve the desired voltage for the tube. This reduces the total number of transformer turns compared to making the high-voltage winding separately.


Fig. 6.

  

Since the high-voltage positive is connected to ground, we also use a constant voltage from the low-voltage rectifier. This, collected from a 22 kΩ resistance, is added to the voltage from the high-voltage rectifier, thus increasing the positive potential of the oscillographic tube's anode relative to its cathode.

The voltages required to power the individual anodes and the grid of the oscillographic tube are derived from a resistive divider, placing appropriately rated potentiometers across it, as shown in the diagram. A separate filament winding is provided for the oscillographic tube, which should be well isolated from the transformer ground and the filament winding of the circuit's tubes, as this winding is at a high potential relative to the device's ground, which is usually connected to ground.

Unbalanced tube amplifier on a 300B tube

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Written by: Grzegorz Makarewicz
Category: Tube equipment
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Photographs: Grzegorz Makarewicz, This email address is being protected from spambots. You need JavaScript enabled to view it.

At one time, fascinated by the 300B triode, a cult device in the audiophile community, I decided to build an amplifier based on this tube. As I decided, so I did. The amplifier has the form of two monoblocks. Below is a photo of one of them. I have to disappoint the purists - the monoblocks are not "visually" symmetrical, they are really identical. When you put them next to each other, they can arouse a certain distaste among aesthetes. I found out about it personally. My answer in such situations was always the same: we should listen to these monoblocks as they work together, not as they "look together". And it turns out that sometimes it helped.

Read more: Unbalanced tube amplifier on a 300B tube

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