Designed to bridge the considerable gap between an upright bass and a solid-bodied fretless, the Hollow33 is a highly versatile, hollow-bodied fretless bass with a warm, mellow, woody acoustic tone.
The Hollow33 is lightweight, yet balanced and comfortable to play. Thanks to its two switchable pickups, the bass can produce a whole palette of sounds, making it suitable for a wide variety of musical styles.

Standard features


Mahogany hollow body
Proprietary full hollow body construction
Mahogany back with maple veneer


Fretless fingerboard
33" scale length
String spacing at bridge 4-string: 19 mm
String spacing at bridge 5-string: 18,5 mm
String spacing at bridge 6-string: 18 mm
5-piece neck from straight grained aged neck blanks
European Maple, mahogany and hard maple neck
Two way quality truss rod
Angled headstock strengthened with a volute
Matching wood headstock plate
white sidedots


Adamovic basbars pair
Pick-up covers matching to fingerboard wood
Series / single coil / parallel switch for each pick-up


Wooden bridge stringed trough body
High quality Hipshot ultralite tuners
Schaller security Locks

Additional information


Price calculator

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Sound samples

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The design

The design

The Hollow33 is based on the Jupiter design and features a completely hollow body which is very similar in construction to an acoustic or steel-stringed guitar. However, instead of having traditionally bent sides, the body is cut out of a solid piece of wood, with sides measuring 5/8” (15mm) in thickness.

The top and back of the Hollow33 are free to resonate and are designed to minimize feedback and maximize the acoustic sound when the bass is amplified. Due to its lower-rigidity design, the Hollow33 generates a warmer sound with more overtones and more complex notes.

Supported only partially by the body wood, the Hollow33’s bridge absorbs the vibrations from the strings and transfers them to the top and back. This absorption of string energy makes the strings vibrate in a specific pattern, which is registered by the pickups, creating a unique, upright-like acoustic sound with long-sustaining notes.

Because the body is cut out of a solid piece of wood, we are able to round its edges for a much more comfortable feel. The average weight of the Hollow33 four-string is under 3kg (6.6lbs), making it a breeze to play.

The woods

The woods

We selected woods that complement the Hollow33’s acoustic timbre. The body is made of warm-sounding mahogany, with the perfect stiffness to support our proprietary full hollow-bodied construction.

The back plate is also made of mahogany, and is supported by maple veneer and bracings. For the braced top, you can choose between maple, walnut and camphor burl.

For the stable five-piece neck, we use straight-grained, aged neck blanks consisting of European maple, mahogany and hard maple, ensuring the perfect weight-to-stiffness ratio.

The Bridge and scale length

The Bridge and scale length

The sound of the Hollow33 is largely determined by the bridge, which is glued directly to the top in a traditional manner. In this way, the largest part of the bridge, which includes the saddle, is not supported by the body, leaving it free to transfer the string energy into the top wood.

Passing through the body, top and bridge, the strings place the optimum amount of pressure on the saddle. This construction maximizes the absorption of the string vibrations, creating a unique, upright-like acoustic sound with long-sustaining notes.

The solid bridge and saddle are both made from a solid piece of wood. You can choose between Pau Ferro or ebony, which will be matched with the fingerboard, pickup cover and knobs. Alternatively, you can opt for the adjustable bridge, which has adjustable brass and steel saddles.

The Hollow33 has a 33” scale. This shorter scale length produces a warm, woody tone with a strong fundamental. In addition, the lower string tension produces a fuller low end and more “bloom” at the end of the note.

The Pickups

The Pickups

For many years, Nikola ran a repair shop in the Netherlands. During that time, he repaired many semi-acoustic and acoustic guitars and basses, most of which were equipped an active piezo pickup system under the bridge saddle. Many of these instruments had feedback issues and differences in output from string to string, which is typical of piezo pickups because of their pressure sensitivity.

One of the main goals for the Hollow33 was to make an acoustic-sounding bass with regular magnetic pickups. Consequently, the acoustic sound had to come from the construction of the bass when amplified.

A major advantage of regular magnetic pickups is that there are no feedback issues or volume differences between the strings. The Hollow33 can be strung with any type of electric bass string and can be played in full passive mode. Each pickup has three different switching options, offering nine sound combinations when the blend is set in the middle. This makes the Hollow33 a unique, versatile fretless bass.