The HLF-3C completes the Passive EQ Collection. This plug-in has 12 dB per octave low and high cut filters, providing broad retro-tonal sculpting or bygone-era special effects, without the inconvenience of insertion loss found with the unamplified passive hardware. You can easily subtract the unnecessary frequencies in any instrument and sub-group so they stay wonderfully musical in the mix. The original HLF-3C hardware unit is a true passive design: there are no input/output amplifiers and it does not require any external power. As a result, there is an inherent loss of signal level when using the HLF-3C hardware. The RRS HLF-3C plug-in compensates for this inherent signal loss for simplified use in the modern era: it has unity gain upon insertion (there is no insertion loss until one or both of the cut filters is engaged). The HLF-3C interface is very simple and includes only three controls: • Enable — This toggle switch is the plug-in bypass control. When in the down position (bypassed), plug-in processing is disabled altogether. The plug-in is engaged with the switch is in the up position. This switch can be used to compare the processed settings to that of the original signal; • Low Cut — This rotary switch specifies the cutoff frequency of the low cut filter. Ten frequencies are available: 50, 80, 100, 150, 250, 500, 750, 1000, 1500 and 2000 CPS; • High Cut — This rotary switch specifies the cutoff frequency of the high cut filter. Ten frequencies are available: 1.5, 2, 3, 4, 5, 6, 8, 10, 12 and 15 KCS. To use HLF-3C as a plug-in, you need an AUv3-compatible host app like GarageBand, Auria, AUM, Cubasis and more — HLF-3C will appear in the list of Audio Unit extensions for effect plug-ins in the host app.