What basses is the STC-3A compatible with?

The harness is designed for basses with two active pickups and space for four control knobs plus a battery compartment. It arrives fully prewired and ready to drop into compatible cavities; check your bass's cavity dimensions (4.00" W × 1.50" H × 9.00" D) and control layout before ordering.

What does the Slap Switch do?

The proprietary Slap Switch allows rapid tonal switching on the fly, giving players instant access to different EQ settings during performance without reaching for individual knobs—practical for bassists working across multiple genres and playing techniques.

Can I run this on 18V for more headroom?

Yes, the circuit operates on either a single 9V battery or two 9V batteries wired in series for 18V operation, which increases headroom and dynamic range. Two 9V batteries can be housed in the control cavity if space permits.

How much EQ control does it offer?

The STC-3A provides three bands of active EQ: a stacked bass/treble control, a dedicated midrange knob, plus master volume and blend controls. Two trim pots on the circuit board allow technicians to fine-tune the frequency contour characteristics for precise sonic shaping.

Is this circuit noisy?

No, the STC-3A is designed with low-noise, low-distortion circuitry and maintains high headroom across the signal chain, delivering transparent, clean signal reproduction suitable for studio sessions and live performance.

Seymour Duncan STC-3A 3-Band Tone Circuit For Active Pickups

The STC-3A is a comprehensive prewired active tone stack that puts surgical control over pickup response directly in your hands. This harness arrives ready to drop into compatible bass cavities, delivering three independent frequency bands plus master volume and blend functions in a compact footprint. The inclusion of a proprietary Slap Switch adds practical versatility for switching tones on the fly across multiple techniques and genres.

Electronics & Signal Path

The circuit delivers three bands of active EQ via a stacked bass/treble control, dedicated midrange control, and master volume knob, all feeding into a blend circuit that manages pickup interaction seamlessly. Two trim pots on the circuit board allow fine-tuning of frequency contour characteristics, giving you and your tech precise control over the unit's sonic signature. The design maintains low noise, low distortion, and high headroom across the entire signal chain.

Power & Compatibility

The circuit operates on a single 9V battery housed in the control cavity, though two 9V batteries wired in series deliver 18V operation for increased headroom and dynamic range. The harness is prewired and ready for installation in basses with two active pickups and space for four control knobs plus battery compartment access.

Key Features

4-knob prewired harness with stacked bass/treble control
Dedicated midrange control for focused frequency shaping
Master volume control and blend circuit
Proprietary Slap Switch for rapid tonal switching
Three bands of active EQ
Two trim pots for frequency contour adjustment on circuit board
Operates at 9V or 18V (series battery configuration)
High-quality potentiometers on prewired harness
Included battery clip and stereo jack
Black anodized, knurled, dome-style control knobs
Low noise, low distortion circuitry
Dimensions: 4.00" W × 1.50" H × 9.00" D; Weight: 1.20 lbs

The STC-3A combines comprehensive tone-shaping capability with straightforward installation, making it an excellent choice for active bass systems requiring flexible EQ control and transparent signal reproduction.

Condition	New
Country of Manufacture	United States