The Rycote Tac!T (pronounced "Tas-It") filter is an in-line, active "third-order" (18dB/octave) filter with a "knee" at approximately 60Hz. This enables it to pass, unaffected, virtually all of the desired audio, while massively reducing wind and handling noise, and floor transmitted vibrations. The energy in these extreme low frequency and infrasonic sounds can be very high, and if not attenuated, would otherwise cause overloads and disturbances across the entire audio spectrum.
The Tac!T filter draws its power from the P48 phantom supply while also passing power on to the microphone. It is electronically symmetrical and does not disturb the intrinsic balance of the microphone circuit, nor does it introduce any signal loss for normal programme frequencies.
A key feature of the Tac!T filter is that it fits entirely within the body of a Neutrik XX-series XLR connector. It is not switchable, and the electronically buffered circuitry ensures that its performance is consistent for almost all phantom-powered microphones and preamplifiers in general use.
Tac!T is a fully symmetrical balanced 3rd order filter. It is has a DC path through it so that it can couple phantom power as well as signal.
Current draw is necessary for the circuit to operate - the device will not work with dynamic microphones that do not pull current. The actual current draw varies with the load used so it is not possible to give a specification figure for it. The circuit demands are very low and with IEC 26815 compliant P48 supplies it is very unlikely to cause any problems. With excessively hungry microphones (eg those that suggest they need the full 10mA available, such as Earthworks), and phantom powering that cannot deliver adequate current, or is significantly under-voltage there might be problems. The likely outcome is under-performance of the microphone in terms of max SPL etc, or increase in self-noise rather than failure.
Front-end filters on mixers are usually 6 or 12dB/octave, and these give a greater loss of wanted higher frequencies for a given cut of infrasonic or extreme LF noise. The steeper 3rd order filter (18dB/oct) is more effective. This is why the Schoeps Cut 1 and similar filters are liked by many recordists. In some cases internal filters are also fitted after a transformer and/or first amp stage - in that case these parts of the circuit can be overloaded before the internal HPF can act. Transformer inputs are particularly susceptible to infrasonic overload.
Tac!T can be used in conjunction with internal mixer filters to give a dual slope HPF, but is perhaps of greatest value in applications such as camera inputs where no LF tailoring is provided at all.