This balance indicator for stereo amplifiers was found in an 80's Elektor. The components used are common. Zeners are 1.8 V or close to that value.
The integrated circuit used in this configuration for noise reduction on FM radios is not common...
The presented circuit provides an output voltage proportional to the input current, according to...
The low-pass filter shown in the figure uses two operational amplifiers with JFET at the input to...