For many years, the output transistors were the limiting factor in the speed of audio power amplifiers. So a lot of claims were made about the superiority of this or that amplifier based on 100V/us slew rate or a frequency response extending up to 1mHz. The output device we use in GamuT is actually too fast, so we have to slow it down. It has a rise time of 200nS, that is 1/5 of a millionth second. The highest tone from a CD is 20,000Hz and has a rise-time of about 10,000nS. So we have spent a lot of time reducing the speed of this SINGLE MOSFET and keeping it under control. Slew rate is measured by feeding an input signal that is too fast for the amplifier to cope with, and then seeing the slew rate in Volts per uS at the amplifier output. So slew rate is in fact an overload condition, and it should not occur at all inside an audio amplifier. So being proud of a slew rate is very strange indeed. The input filter should prevent slewing from happening. The relevant specification is the rise time of the input filter. We have done a lot of practical test in recording studios and built our filter accordingly. Do not worry about this filter, the air around us also acts as a strong filter at 50-100kHz. This is due to the mass of the air molecules, so in humid weather the effect becomes extremely effective. Note how sound changes in foggy weather, and that fog horns on ships have a very low frequency. A middle or high frequency cannot be heard far away due to the filter formed by very humid air.