This circuit, to add the ambience effect, was suggested by National Semiconductor in documentation from the 90s. The amplifier needs an appropriate power source.
This step-down converter with 10 to 60 V input produces a 5 V output with a maximum current of 5...
Found in an old American documentation, this step has as input and output transformers coupling. Two...
This circuit was found in a 1963 magazine, but can still be easily assembled with some current...