This circuit is from 1999 documentation. The integrated circuit used is not very common today. Both transistors are used if the motor current is greater than 500 mA.
The transistor of this remote preamp can be the BC549. We found this circuit in a 1976 technical...
Although it is a common configuration today, these circuits were taken from an old publication. The...
We found this circuit in a 1982 publication. This source allows an adjustment of the output...