it turned out to be a kind of false start: I sent Igor a photo with the question "is it worth writing from this or is it not interesting?"
But it also worked out well - there are questions in advance that can be answered.

The fact that this is a power amplifier is obvious, at least by wires - power, input, output.
Circuitry UZCH on TDA7265 to discuss in general and there is nothing - everything is banal.
And there are some constructive ideas:
self-supporting structure without chassis and
cooling due to natural draft from the temperature difference in a long pipe (no fans, like in a fireplace).

Let's see what's inside!

Actually, the TDA7265 2x25W amplifier was purchased as an already soldered semi-finished product and installed on a 600 cm2 radiator to which everything else is attached. Power supply capacitors 47000 uF. Rectifier bridges with 0.1 μF shunt ceramic capacitors are soldered directly to the terminals of the power filter capacitors. The white brackets holding the radiator are bent from sheet polystyrene and glued to the transformer. The rest is visible and so.
The trim ring is a demonstrator of technologies, it was tried on whether it was possible to get in at all and twist the legs, etc.

The amplifier is connected to the S-30B speakers, for which everything was started - it was a pity to just throw them away, but now they will still work.

The body (as you already guessed) is a piece of a sewer pipe, left over after repair, with a diameter of 110 mm and a length of 1 foot (I took a round number in at least some system of measures). View before pasting:

Initially I thought to paste it over with self-adhesive "under the tree", but then I realized that "under the skin" is still better. "Under the tree" looks too fake - you can immediately see that the stump is not real. With black leather and a shiny grille, it turned out very solid IMHO.

The eye-catching shiny fan grille appeared just before completion, initially I wanted to cover the top with just fine mesh, but couldn't find a suitable one. By the way, this lattice is made from some very fragile muck - two brackets broke when bent, the fracture looks like a silumin.

The case is assembled (in this photo it is still empty and the connectors are not screwed on):

For both contact and view, it would, of course, be better to use screw clamps to connect the speakers, but they are fastened with nuts from the inside of the case, but I could not figure out how to get in and tighten them and took the clamp shown in the photo. It is easier to fix it. Although bringing wires to it is also a separate story.

Already worked as a mystery photo of the construction in operation:

Until the idea is completed, only a nameplate with a long handwritten inscription obliquely, such as "Marshall" or "Weltmeister", is missing, only some non-existent company with a furious German name, such as "Schwаrzenegger" or something like that.

To catch up, I give the network public a few more ideas for designing such a design:

"Glamor" - for example, when I bought a film, it was still under the "snake skin" with overflows, carry golden screws, glue the Schwarovski crystals into the slots, inside the backlight with blue LEDs.

"Military" - paint with protective or ball (for sailors) paint and cover with inscriptions in a stencil "charter" font:

PRODUCT 3-14-2-EC
BLOCK UM-2/25
WHEN TRANSPORTING BY AIR, CLOSE PLUG "B"

Etc., attach a military connector with a cap on a chain, etc.
Radiation hazard signs to taste.

"Tanuki or Dr. Sigmund Freud Presents" - use such an amplifier with

UMZCH on TDA7265 25 * W or 50W bridge circuit (mono)

The amplifier based on TDA7265 belongs to class AB and is intended for use in HI-FI technology. The TDA7265 microcircuit is equipped with thermal protection against overheating of the microcircuit crystal and protection against short-circuiting the outputs to the case or power bus. The microcircuit has a built-in MUTE and STAND-BY system, which allow you to eliminate noise and crackling when turning the amplifier power on or off.

Pin 5 in the microcircuit controls the MUTE and STAND-BY systems, if the voltage at pin 5 is -2.5V or higher (in the positive direction), then the microcircuit operates in STAND-BY mode, and if the voltage is in the range from -6.0 to -2.5V, then the microcircuit is in MUTE mode. At a voltage lower than 6V, the TDA7265 microcircuit operates in normal mode.

The amplifier based on TDA7265 (in stereo version) has the following main characteristics:

Supply voltage from +/- 5 to +/- 25V at nominal supply voltage +/- 20V
Quiescent current 80mA at rated supply voltage
output power at 10% THD and 8 Ohm load at rated supply voltage is 25W per channel
Slew rate 10V / μs
THD up to an output power of 15W at a load of 8 Ohm no more than 0.01%
The temperature of the crystal of the microcircuit at which the thermal protection occurs is 145 g. Celsius

When using a microcircuit in a bridge connection option, it is necessary to use a load of at least 16 Ohm (2 * 8 Ohm) or 8 Ohm but with a supply voltage of no more than +/- 16V .. Based on materials from the site rcl-radio.ru.

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The amplifier based on TDA7265 (in stereo version) has the following main characteristics:

Supply voltage from +/- 5 to +/- 25V at nominal supply voltage +/- 20V
Quiescent current 80mA at rated supply voltage
output power at 10% THD and 8 Ohm load at rated supply voltage is 25W per channel
Slew rate 10V / μs
THD up to an output power of 15W at a load of 8 Ohm no more than 0.01%
The temperature of the crystal of the microcircuit at which the thermal protection occurs is 145 g. Celsius

When using a microcircuit in a bridge connection option, it is necessary to use a load of at least 16 ohms (2 * 8 ohms) or 8 ohms but with a supply voltage of no more than +/- 16V.

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The TDA7265 microassembly is a fairly powerful two-channel Hi-Fi class AB amplifier in a typical Multiwatt case, the microcircuit has found its niche in high-quality stereo equipment, Hi-Fi class. Simple wiring diagrams and excellent parameters made the TDA7265 a perfectly balanced and excellent solution for building high-quality amateur radio audio equipment.

Reference on TDA7265 (DataSheet)

Features of using microassembly:

Wide supply voltage range (up to ± 25 V)
Bipolar power supply
Large enough output power 2x25W
No noise when turning off and on
There is a mute mode (MUTE)
Standby (STAND-BY) present
Low current consumption in STAND-BY mode
Short Circuit Guard and Thermal Guard

The limiting parameters of the microassembly and the main technical characteristics are presented in the reference book at the link above. The pinout of the TDA7265 pins is in the same place and in the figure just above.

ULF on TDA7265

ULF schematic diagram:

The location of the radio components on the printed circuit board assembly is shown in the photo below:

The drawing of the printed circuit board, made in the Sprint-LayOut radio amateur utility, has been added to the folder with the datasheet for the microassembly and you can pick up this entire archive using the link above.

Assembly option with alternative PCB layout

Collected from those components that were at the right time in the right place. The capacitors were still made in the USSR, soldered from old different boards. We have worked for 30 years and will continue to work, but just in case I checked them. The power supply provides power to the TDA7265, and also generates a bipolar voltage +/- 15V to power operational amplifiers (conventional repeaters). The dimensions of the board are of course impressive. she was going for strictly defined seats. I also added a self-induction pulse damper circuit (at the moment the transformer winding is disconnected from the network, a self-induction pulse appears in it, an arc discharge is generated between the contacts of the switch, and noise enters the network. Scheme below, the board in the photo above).

PCB in the same archive as above.