The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This simple 3-channel passive mixer can be used with low-intensity signal sources but requires...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...
July 2017 - Texas Instruments' new 3 A bq25601 single cell battery charger can be found on Mouser...