The KTBK filter is a very precise Altec 9069B replica adapted for the modern studio including new controls, a mode selector and a resonance leveler.


8 in stock

An Equalizer with Vintage Flavour for the Modern Studio

For music-quality-conscious people who enjoy the character of a Variable Passive High Pass 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 music production workflow. Moreover, it is DSP validated to guarantee the Altec sound signature and the best conditions for stereo pairment.

KTBK1B Operational Diagram


Passive filters are very sensitive to the impedance matching. Originally, the Altec 9069B was designed to perform with a 600Ω impedance IO. However, our unit includes a mode control switch to be adapted to any kind of 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
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. 

KTBK1B Frequency Curves

BELL, 600 and NOTCH are the three different KTBK1B modes and they convert the KTBK1B into a unique piece of gear increasing its versatility in the different stages of the music production. The 600 mode recovered the original Altec 9069B response. The BELL mode reacts as the King Tubby’s sound signature, a peak resonance HPF without insertion loss, ideal as sweeping effect for dubbing with a recognized phasing effect. The NOTCH mode is an entire Audio Merge contribution, it was never available in other gear, it is just a modern classic mode made for the synth enthusiasts and subtractive analog EQ lovers. 

Recover the original
Altec 9069B response
The only top NOTCH EQ
in the world.
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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 provide 18 dB/oct slope with 10 steps for low frequency cutoff to reproduce unmatchable sound permutations. Originally, the 9069B, next to a Variable Passive Low Pass Filter unit (9068B), is part of the Altec 9067B 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.

Before 1972

The King Tubby’s Sound Signature

King Tubby, a Jamaican producer is considered as the dub music and remixing inventor. Tubbs 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 Reggae music created in Jamaica in the late 60s, 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.


A Modern 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: damping factor control (BELL) and mode selector (MODE).


KTBK Around the World

More than 300 producers, musicians and engineers enjoy the KTBK1B sound signature in different corners of the globe. Dub community around the world already has heard about this precise gem. At this time Soundgas LTD becames the only Audio Merge distributor. After the participation in the startup program in Barcelona Activa to support startups, Audio Merge’s Team decided to continue with their approach to build new modern classic equipment combining analog and digital tech and a new release in 2u rack format is planned for 2024. More info here