Audio Circuit:

TDA7245 Datasheet

Turn on/off circuit:
Dave Jones EEVblog #262 - World's Simplest Soft Latching Power Switch Circuit

"https://www.youtube.com/watch?v=Foc9R0dC2iI"

Power supply:
External 16 to 24 Vdc power adapter.

Basic operation:
Pressing the soft latch on/off button turns on/off small Relay that powers the amplifier and ventilation fan.

Components and materials:
Glass dome HÄRLIGA from Ikea was offered from a friend.

All components, wires, pins, connectors are scrap from old electronic equipment taken from local disposal e-bins.

Adjustments, connectors and switches:

— Turn on/off button is an old electrolytic cap.

— Volume control knob is an old electrolytic cap.

— Fan speed is controlled by a variable resistor.

— Audio output connectors from old hifi with outside knobs made of Cupressus lusitanica wood.

— Audio input connector from old CD player.

Costs:

Ikea HÄRLIGA Dome: 12€

Wood:

— Base of Ikea wood: Unknown
— Five base wood blocks: Unknown scrap wood

Wood finish:

— Tung Oil

Time taken:

+/- Three week's