High Pass Filter Circuit | Rumble Filter

An electric filter or simply a filter is an electric network that passes or allows without loss, the transmission of electric signal within a certain frequency range but stops or disallows transmission of electric signal outside this frequency range.

The three most-popular filters found in audio equipment are the High Pass Filter (rumble filter), Low pass filter (scratch filter), and speech filters. The rumble filter is a high-pass filter, used to suppress the low-frequency rumbling sound associated with old and worn-out turntable and tape deck mechanisms. Here we explain to you how a high pass filter or rumble filter works with a circuit diagram and description.

We also define a high pass filter or rumble filter circuit as it passes all frequencies above a specified frequency, called the cutoff frequency f_c, and rejects all frequencies below f_c.

Circuit description of High pass filter or Rumble filter using LM387

The circuit of the high pass filter is built around general-purpose op-amp IC LM387. Input from the amplifier is given to the inverting input pin 2 and pin 7 through coupling capacitors C₁ and C₃. Unwanted frequency is filtered by capacitor C4. Where capacitor C₂ is used as a feedback capacitor connected from output to input. Output is taken from pin 4 and pin 5 through capacitor C₇. Non-inverting pin 1 and 8 is connected to the ground through capacitor  C_5.

F₀ = 60Hz,

Butter worth Q = 0.707

A₀ = 1

SLOPE = -12dB (OCTAVE)

The working of the circuit high pass filter using LM348/LM741 is the same as circuit 1 (High pass rumble filter using LM387). Capacitor C₄ is only connected when IC lM348 is used not while using LM741.

PARTS LIST OF HIGH PASS FILTER USING LM387 (CIRCUIT 1)

PARTS LIST OF HIGH PASS FILTER USING LM741/LM348 (CIRCUIT 2)