The KTBK filter is a very precise replica of the Altec 9069B adapted for the modern studio with new controls for impedance matching and resonance. It was designed through Reverse Engineering techniques and validated with DSP to achieve the most accurate cutoffs utilising a customized multi-tap coil.


3 in stock

The KTBK unit includes two additional switches, a mode selector and a resonance leveler which allows to modify the filter response for adapting it to the modern studio for different phases of the music production workflow.

An Equalizer with Vintage Flavour for the Modern Studio

For music-quality-conscious people who enjoy the warm character of an analog filter. The King Tubby’s Big Knob (KTBK) provides the same genuine tone as an Altec 9069B, a vintage equalizer, designed in 60s, which enable a great control over the sound tone. The KTBK unit includes two additional switches, a mode selector and a resonance leveler which allows to modify the filter response for adapting it to the modern studio for different phases of the music production workflow.

Let's Design the Sound

Tweak the Big Knob to get different tones, textures and an unrivalled sound effect. Allows to remove rumble noise, the parasitic frequencies and muddy sound effect in order to reducing the masking effect and achiving a clear sound. The KTBK Variable Passive High Pass Filter has stepped frequency selection with ten unequally spaced cut-offs offering a crossover type action – 70, 100, 150, 250, 500, 1k, 2k, 3k, 5k and 7.5k. A need when it is required an accurate control of the sound tone.


Passive filters are very sensitive to the impedance matching. Originally, the Altec 9069B was designed to perform with a 600Ω impedance transfer standard and currently modern audio equipments require other values. Our unit includes a mode control switch to be adapted to any equipment, allows to reproduce the original HPF response, or to generate a resonance bell over the cut-off frequency.

Sweep the Sound like
a Dub Master

Sweep and layer your sounds with the KTBK filter to get unmatched sound signature. Perfect gear to create a dynamic mix with LO-FI tones! The digitalization has changed the way to record, produce and process music. It is time to explore new ways, taking the best of analog and digital domain.

Handbuilt with Love and
a Customized Features

The assembly and subsequent validation of each unit is manually done in our workshop, sited in Barcelona. The multi-tap inductor is a custom-designed element based on various frequency response and phase distortion analyses using different cores and coil winding techniques, in order to get the most accurate cut-off frequencies. The customized stepped rotary switch offers a very smoothed rotation resistance to guarantee the creative freedom during the performance. High quality ELMA rotary switch with proven solvency in the world of professional audio equipment.

The Altec 9069B,
The Influencer of the Big Knob

At the 60s, Altec Lansing launched the 9069B, a variable high pass filter designed by Arthur Davis. The 9069B was a passive inductor based T-network filter, with toroidally winded inductances which provides 18 dB/oct attenuation with 10 positions for low frequency cutoff to reproduce unmatchable sound tones. Originally it was part of the Altec 9067B unit with the LPF 9068B unit.

1950 – 1965

A Program Equalizer’s Creator

If we speak about vintage equalisers, Art Davis is our man. He designed Graphic and Program Equalisers like the Altec 9069B, the Langevin EQ255a and the Cinema Engineering 4031 for different brands.


Altec 9069B Passive
Program Equalizer

Originally comprised the class of sound effects filters used to simulate distant sounds, radiophonic voice, and other such spatial effects in radio and cinema sound design.


The King Tubby’s Sound Signature

King Tubby, a Jamaican producer is considered as the dub music inventor and remixing. Tubby achieved an outstanding sound signature experimenting with recordings at his MCI mixing desk using an Altec 9069B, recognized as his secret weapon, in combination with reverb and tape delay effects.

Since 70s to 1989

The Big Knob, a Secret Weapon

“It was a red knob, slightly bigger than the others—hence its name Big Knob—, in the right top corner of the MCI console. The strongest characteristics of the filter’s sound are the discrete steps, the clicks and crunches when the frequency is switched, and the phasing effect heard when filtered signals are mixed with the unfiltered originals.” Extracted from Tubby’s Dub Style thesis.

Since 1990

Dub Around the World

Dub Music is a form of music created at 70s, that gave birth to and influenced many genres of music for years, including Rock, Punk, Pop, Hip Hop, Disco, Folk and later House Techno and other EDMs. Indeed, Dub has become a basis for genres like Drum and Bass, Jungle and Dubstep. Nowadays, dub culture continues to grow and attract new generation of fans and followers.


The New Vintage Program Equalizer

Audio Merge, a very small startup sited in Barcelona-Terrassa, builds three KTBK prototypes to get a very accurate and robust Altec 9069B replica, using a handmade customized small coil and adding two new features to the original Altec’s design: resonance control and mode selector.