This configuration similar to many of this site was found in 1965 General Electric documentation. Modern equivalent transistors can be used. LEDs can be used.
We found this circuit in a publication from the 1970s. The circuit has a logarithmic gain...
This circuit was found in an Electronics World of 1966. It has a range of 5 to 25 000 Hz at 1 dB...
Found in Linear Technology documentation from the 90s, this circuit uses an operational amplifier...