DC•BLOCK is an in-line device that is located right at the DACs coaxial signal input. It's a 2nd order Butterworth filter integrated in a BNC adapter that blocks DC leakage and filters RF noise below 1Mhz. DC (and low frequency AC) may be caused by symbol correlated fluctuations in the signal, degradation of the source blocking capacitor, transfer of energy along the dielectric or EMF from proximate components inducing currents in the coax cable itself. (The latter is a reminder to keep coax cables ultra short and well shielded).
LP•FILTER is an in-line BNC adapter device that contains a RLC low pass filter with a 100MHz cut-off frequency. It can be coupled in series with DC•BLOCK or located at the source output.
The combination of DC•BLOCK and LP•FILTER is highly recommended as a cost-effective way to get a noticeable improvement in transparency. Zero unwanted current flow and reduced RF noise outside the S/PDIF passband will help DACs sound better. For an even more dramatic improvement, consider the addition of OPTO•DX which adds optical galvanic isolation from the source plus improved RF noise attenuation. For truly remarkable transparency, add RF•STOP EXTREME SE Signal Filter which extends filtering from 100Mhz to well beyond 1Ghz.
Refer to the connection drawings below. Order two DC•BLOCK+ LP•FILTER for dual-coax connections.
Source Coax to DAC:
Recommend DC•BLOCK. Add LP•FILTER if your source is noisy -or- if you want to ensure maximum filtering.
SRC•DX to DAC:
Recommend DC•BLOCK. Add LP•FILTER if your source is noisy -or- if your USB is not well isolated -or- if you want to ensure maximum filtering.
OPTO•DX to DAC:
Recommend DC•BLOCK. Add LP•FILTER if you want to ensure maximum filtering. OPTO•DX optical modulation is a low-pass filter.