Check the listing for details. Triton Audio FetHead Filter In-line Microphone Preamp. Condition: New. Listed at 84.95 USD. In-line Pre and HPF for Your Dynamic and Ribbon Mics Triton Audio FetHead Filter is primed and ready to elevate the performance of your gain-hungry dynamic and ribbon microphones. This in-line mic preamp utilizes top-quality Class A FET technology to yield you up to 27dB of clean boost. The result is a cleaner signal with lower noise, greater sensitivity, and improved transient response. FetHead Filter also includes a built-in highpass filter with a 220Hz cutoff for taming excessive low-frequency mud and rumble. What's more, FetHead Filter protects your delicate ribbon mics by isolating them from phantom power. If you want to get the best out of your dynamic or ribbon microphones, stop cranking your mic pres past their usable range.