Our low pass filters (LPFs) can be built into Single-ended or Balanced cable assemblies (Analog-Precise), or installed into certain equipment chassis such as DAC and PrePros (LPF Mods) , but they are best applied in the cabling since this serves a broader picture, read below. Our LPFs reduce noise that is inherent in the analog amplifier / driver amplifier Our LPFs reduce noise that is coupled into the analog amp output from the power supply busses Our LPFs reduce the considerable conversion noise caused by the DACs in digital audio equipment This "DAC noise", though higher in frequency than the human ear can hear, does materially result in "hearable" noise through the amplitude modulation that occurs on the interfering carrier. Assume that there is some 300 kHz noise from a DAC in the analog output of a digital audio processor. This may seem like "no problem" because people cannot hear 300 kHz. Some, though, discriminating audiophiles claim that they can hear it. Are they crazy? Nope! Any competent EMC engineer will tell you that it is common for interfering energy to have some degree of amplitude modulation on it. This is often 50/60 Hz but it can be any lower frequency that is available "in abundance" including high frequency hiss. In the case of our example this means we have a 300 Khz carrier with 60 Hz on it. So what? You still can't hear 300 khz. The problem lies in the ease with which an amplitude modulated signal is demodulated. any non-linear circuit will demodulate (detect) such a signal and suddenly you have the 60 hz right in your pass band, i.e. you can hear it. But, you say "wait, my circuits have tremendous linearity, no non-linearity's" That true at 20-20khz. but at 300 khz it is quite non-linear. This whole area also very much applies to the need to filter-out environmental energy at higher frequencies. Cabling will pick up various energies and pass it into the receiving audio device and by the same mechanism, anything from 60Hz to high frequency hiss will be heard by the listener. this is especially true in any environment that has a great deal of signals: any medium to big city, any nearby factories, any nearby RF equipment from broadcast stations to wireless internet, etc. Our LPFs have tremendous filtering, from the 100 Khz region into the Ghz spectrum.