All Portaphile amplifiers are built using strictly Metal Film SOIC resistors inside the amplification circuitry that have a 0.1% tolerance. Resistors come in different tolerances such as 20%, 10%, 5%, 1% and 0.1%. What the 0.1% tolerance means is that the resistor is rated by the manufacturer to vary only +/- 0.1% from it’s stated value. This means that a 1K resistor used in the right channel will only vary +/- 0.1% or a value +/- 1.0 different than the equivalent 1K resistor used in the left channel. This ensures that the right channel is matched as close as damn near possible to the left channel, and every resistor used in the amplification circuit of our amplifiers is a Metal Film SOIC with a tolerance of 0.1%.
Our goal is the build the best portable headphone amplifier and that requires that we match the left and right channels as close as possible. This improves stereo separation. This improves instrument placement. This improves soundstaging. This improves the realism of what is being amplified.
This is the reason we only use 0.1% Metal Film SOIC resistors in the amplification stage of our amplifiers.