Other methods for improving sound quality
Earth’s magnetism affects the performance of equipment that implements magnetism (transformers, speaker systems, etc), so it is important to align the magnetic axis of devices with Earth’s South-North polar axis as much as possible. If you do not know the magnetic direction of your transformer, try slowly moving it while looking for S/N ratio improvement and distortion decrease. Speaker units, network coils, MC transformers, CD line transformers, power supply transformers and other kinds of transformers all have optimal orientations for the best sound.
Typical coaxial interconnecting cables (signal code type) should be grounded at the exit, to easily protect the signal from external induction. This will improve S/N ratio and decrease distortion.
Tone quality improves if a speaker matching transformer is connected between amplifier and speaker unit. The matching transformer should have a large core or multiple winding in order to handle frequencies as low as 10 Hz and produce high inductance and distortion-free sound. If the matching transformer does not meet these specifications, it can produce the opposite result and actually make sound worse.
Commonly used transistor amplifiers implement negative feedback (NFB) to tweak parameters such as frequency response and distortion characteristics. Such amplifiers in effect have a negative influence on sound depth, width, timbre and localization, producing colored, unnatural sound, with strong characteristics. Some vacuum tube amplifiers also utilize NFB or connect the resistor parallel to a transformer to forcibly rectify impedance. As a result, their sound lacks the distinction typical of tube amps, sounding instead more like transistor amplifiers.
A good amplifier should not employ NFB to tweak its parameters. For natural sound and musicality, choose vacuum tube amplifiers with a transformer connection circuit over ones with C-R connection circuits or SRPP circuits.
For a good amplifier, a quality transformer and push-pull circuit are most vital.
With use, an amplifier gradually becomes magnetized and should be demagnetized every 1-3 months. This is highly beneficial for vacuum tube amplifiers, especially single-ended amplifiers. To demagnetize, first remove speaker connections. Turn the volume down to minimum and connect pink or white noise into a PHONO terminal. Slowly turn up the volume, and then slowly turn it down. Sound distortion should decrease.
Because of a transistor amplifier’s large output, extra care is advised.