Practical equal loudness control circuit

Figure 1-91 is a practical circuit with an equal loudness volume control circuit added . It is inserted between the preamplifier and the tone control circuit
, and can be connected to the main amplifier circuit such as OCL. Practical results have proven to be effective. Even when the volume is turned up very low,
clear and soft bass can be obtained. The output stage of the preamplifier uses an emitter output device with a constant current source, thus ensuring low
output impedance and good following characteristics. Its operating current is adjusted between 4 and 6mA. Even when the load is small,
it can have sufficient signal level output and ensure minimal distortion (when the volume is zero, the load of the preamplifier is
It is a low-resistance Ri)o
    loudness volume controller that uses a field effect transistor, and has a high input impedance and a very low noise figure. This circuit
does not require high compensation. If the treble is insufficient during use, you can add high frequency compensation according to the dotted line in the figure and adjust the resistance to change
the degree of compensation.