Tips for buying headphones

The tube headphone amplifiers on the market all use cathode output devices as the final amplifier. This type of circuit structure is very reasonable. Therefore, it is adopted by most manufacturers. However, this circuit has high output impedance and can only be used with headphones above 200 or 300 ohms. The higher the impedance, the smaller the distortion.
The final stage of the transistor headphone amplifier uses an OTL circuit, which has no strict requirements on impedance. Moreover, the lower the impedance, the greater the output current and the greater the power. Therefore, transistor amplifiers can handle high, medium and low impedance, but it is better to drive medium and low impedance headphones.