This source was originally suggested by Delco in a 1969 documentation to power amplifiers up to 50 W. The transistors are of the time admitting modern equivalents.
We found this circuit in an 80's Radio Electronics. The circuit uses a PTC sensor and an LED...
In this circuit a 12 V lamp or LED blinks with the music signal applied to the input. R depends on...
Using a period sensor, this circuit was found in the February 1986 issue of Radio Electronics...