Broughton Audio High Pass Filter

The Broughton Audio High Pass Filter is a compact utility pedal for cleaning up the low end of a guitar or bass signal. It is a 12 dB per octave low frequency filter: everything below the cutoff point you set is rolled off, while everything above it passes through untouched. Broughton Audio describes it as "the perfect utility pedal for cleaning up the low end"¹.

For a bass player, that means removing subsonic content that eats amp headroom and muddies a mix without touching the fundamentals you actually play. For a guitar player, it clears out rumble below the instrument's range. The single knob sweeps the cutoff continuously from 25 Hz to 190 Hz, so you can set it anywhere from a gentle subsonic cut to a tighter roll-off that thins the bottom of the tone¹.

What a high pass filter does to your sound

A high pass filter is the mirror image of a low pass filter: instead of trimming the treble, it trims the bass. The Broughton High Pass Filter cuts at a slope of 12 dB per octave, which means the signal is attenuated by 12 dB for every octave you go below the cutoff frequency. Broughton Audio describes it as a utility pedal for cleaning up the low end¹.

The practical uses are straightforward:

• Removing subsonic rumble and stage noise that a bass amp would otherwise reproduce
• Freeing up headroom in an amp or PA by cutting frequencies below the instrument's range
• Tightening a bass tone by rolling off the lowest content
• Cleaning up a signal before it hits overdrive or distortion pedals, where low content can cause flubby low-end response

The pedal works with active or passive instruments, and with other devices such as pedals, preamps, or effects loops, a flexibility Broughton also cites for its Low + High Pass Filter².

The cutoff knob: 25 Hz to 190 Hz

The single control is the cutoff knob, which ranges continuously from 25 Hz to 190 Hz¹. At the low end of the range the filter acts mostly as a subsonic cut, removing content below what most instruments produce. As you turn it up toward 190 Hz, the filter increasingly shapes the audible low end of a bass, which is where it becomes a tone-shaping tool rather than just a utility.

For comparison, the same 25 Hz to 190 Hz range appears across Broughton's filter line¹²³:

Power and connections

The High Pass Filter accepts 9 to 24 volts DC through a standard Boss style barrel connector with center negative polarity. The power supply is not included. Current draw is approximately 10 mA, light enough that it places little demand on a pedalboard power supply¹.

The stock input impedance is 1MΩ, the standard value for a passive instrument, and the output impedance is 100Ω¹.

Custom input impedance for acoustic pickups

Some acoustic pickups need a different input impedance than the standard 1MΩ to sound right. Broughton handles this directly: if you have an acoustic pickup that requires a specialized input impedance, you write the requirement in the notes during check-out and Broughton accommodates the request at no extra cost¹. The same offer applies to the Low + High Pass Filter².

The High Pass Filter in Broughton's filter line

Broughton Audio makes several filters built around the same circuit ideas, and the differences come down to what is added or removed:

• Always On High Pass Filter: a variant of the Broughton high pass filter built for players who want the cut engaged at all times.
• Low + High Pass Filter: combines a high pass filter and a low pass filter in one pedal, for shaping both ends of the frequency range.
• High Pass Filter DI: the high pass filter in direct box form⁴.

Warranty

Broughton Audio products, including the High Pass Filter, are covered for one year to the original owner. Warranty repairs are handled by emailing sales@broughtonaudio.com⁴⁵.

Questions