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The AC-Signature fretless has been developed in collaboration with Canadian jazz legend Alain Caron since the mid 1980’s. This series was inspired by Alain’s desire to have one fretless bass that could do it all—anything from acoustic to modern electric tones, a big clear voice to hold down a groove and an extended range fingerboard with easy access for soloing. Al often refers to playing fretless as a second language, so it was imperative that this instrument be highly expressive and sensitive to playing dynamics. This is achieved through our original semi-chambered design, procurement of premium lumber used in traditional upright bass builds, our handwound F Bass single-coil pickup, RMC Piezo saddle pickup system, and our natural & transparent F Bass preamp. This is a highly refined instrument and has been dubbed by our players as the “King of Fretless”!

Features – click for details

Upright Inspiration & BIG Tone

Our AC’s are made with the same wood combination used in traditional upright basses and include: a lightly figured Maple semi-chambered body, Canadian Spruce top, Hardrock Canadian Maple neck, and dense Gabon Ebony for the handmade bridge and extended range 28 fret fingerboard. This combination offers a beautiful resonant tone that produces rich low end and midrange, a warm yet articulate high end, an attack that has each note blossoming to full volume with loads of that fretless “muah” expression.

We love a big bass sound though can’t stress enough that it has to be focused and controlled. That’s why our 5 & 6 string AC’s are made with a 34.5” scale length. This 0.5” scale length extension adds clarity to the low B while maintaining a thick and musical G & C. To control these lower frequencies even further, we string up our AC’s with custom F Bass exposed-cores made for us by LaBella. These exposed-core strings were developed in tandem with our AC’s and have been continually improved since their inception in the mid 1980’s. The steel core is completely exposed over the saddle for maximum contact producing excellent clarity, a clean fundamental, and piano-like sustain.

F Bass Stacked Single-Coil Pickup

Our pickup takes the Jazz Bass single-coil a few steps further. While the focus is still a strong midrange and clear high end, the overall tone is thicker, smoother, and with none of the grit or grain in the higher frequencies. To eliminate 60-cycle hum associated with traditional single-coils, simply pull up on the bridge pickup volume knob to engage hum-cancelling mode.

Piezo Saddle Pickup System

Each string sits over a RMC Piezo saddle element that’s installed in the handmade Ebony bridge. They’re controlled by a single volume knob and emphasize the bright and acoustic nature of the instrument. When fully dialled in, they showcase that classic string clack of an upright bass.

F Bass Preamp

Our preamps are handmade right here in Hamilton using discrete components (transistors, resistors, capacitors) rather than over-engineered IC chips. This helps us achieve a more open and transparent sound that allows the instrument to translate its inherent tone without colouration. Our 3-band preamp controls Bass Boost, Mid Boost, and Treble Boost. When all are set flat at 0, there is no perceivable difference from your passive tone. This makes for an extremely predictable and shape-able tool to explore tones or to simply cater to various gigging environments. The 9V pre has a low draw allowing for approximately 500 hours of play. Now if your battery happens to die in the middle of a gig—don’t fret!— you can pop up the tone control to engage passive mode.


Through careful design and consideration of each component’s weight (down to the ounce), we ensure perfect balance whether playing in the seated position or strapped in. Our treble horns are curved outwards, set further back into the body, and carved to match the curvature of the fretting hand. This allows for easier access to the end of the fingerboard and maximizes comfort in the seated position. Our AC’s are also made with a slightly extended bass horn to bring the first position in a little closer when playing with a strap.

Cosmetic Harmony

When putting so much effort into our design, finishes, and sourcing beautiful tone woods, the last thing we want is to disrupt that aesthetic flow with plastic. So we take the time to grain match pickup shells and backplate covers from the same wood used for the body. To continue this cosmetic harmony, our headstocks are also colour matched to the body or crafted with matching wood veneers for exotic topped builds.


Our builds have been dialled in just-so over decades of refinement, however we know that all players are not made the same. We love working one-on-one to determine target feel, tone, and aesthetics. We’re happy to refer to past builds with varying combos, but are also open to new ideas that still retain the F Bass DNA. Our goal is to make your dream bass so that you can focus on your craft. We don’t want you fighting your instrument or lugging multiple basses to a single gig — so have fun jumping into our custom builder or visiting our photo gallery for inspiration. When you’re ready please don’t hesitate to give us a call or shoot us an email to get the conversation started!


4 string 5 string 6 string
Price Starting At
$6500 USD $7000 USD $7500 USD
Nut Width 38mm (1  1/2″) 45mm (1  3/4″) 52mm (2  1/8″)
Width at Last Fret 66mm (2  5/8″) 80mm (3  1/8″) 96mm (3 25/32”)
Fingerboard Radius 10″ – 16″ 10″ – 16″ 10″ – 16″
Scale Length 34″ 34.5″ 34.5″
Number of Frets 28
String Spacing at Bridge 19mm (18mm for 6 String)
Strings F Bass Steel Exposed-Core Strings
Pickups F Bass Stacked Single-Coil Bridge Pickup & RMC Piezo Saddle Pickup
Preamp F Bass 9V Preamp with Bass Boost, Mid Boost, & Treble Boost
Passive Controls Bridge Volume (single-coil or hum-cancelling push/pull), Piezo Volume, Tone (active or passive push/pull)
Neck Wood 3 Piece Quarter-Sawn Maple 
Fingerboard Wood Gabon Ebony
Body Wood Figured Maple Body (Chambered) with a Spruce Top
Tuners Gotoh tuners with 20:1 ratio
Bridge Aluminum Hipshot A Style (Handmade Ebony Optional)
Knobs Handmade Ebony Knobs
Standard Finishes: Available as Burst or Fade


+ Many Additional Finishes Available

F Bass Gig Bag Included Made with a water resistant poly-fabric with poly-leather accents, reinforced sidewalls, and a robust handle
  • Can be made LEFT-HANDED (+ 10% to the base price)
  • Can be made as a FRETTED with a Mac Ebony fingerboard and Hipshot A Style bridge (+ $350 USD list)
  • We have many additional fingerboard, exotic top, finish, and hardware options. Spec your dream “F” build in our Custom Builder!