1 to 2 kHz Audio Oscillator

A 1 to 2 kHz audio oscillator using  the easily available EI14 600 ohm audio transformer and 2 transistors in a long tail pair configuration to provide negative resistance.  An increase in the voltage at the collector of Q1 results in extra current flowing into the base of Q2, causing Q2 to conduct more and Q1 to conduct less. 

An increase in voltage at the collector of Q1 causes less current to flow through Q1 which is negative resistance.

The variable resistor R2  interpolates between the 2 tuning capacitors C1 and C2 which resonate with one winding of the audio transformer.  R2 causes some loss in Q (quality) of the LC resonant circuit but it is still far higher than the Q of an RC based audio oscillator such as a phase shift oscillator or a Wien bridge oscillator.