Stetsom 4in1 Universal Bass Knob with Voltmeter and On/Off Switch

Our review of the Stetsom 4in1 finds it best suited for car audio enthusiasts and installers who want compact, multifunction control at the dash. The single biggest reason to buy is its combination of a tuned bass knob gain control with a built-in voltmeter and remote on/off capability, all in one unit, which removes the need for multiple separate modules and keeps installations tidy. It works equally well as a simple gain control or a mini control station for systems that require a reliable high-to-RCA input converter.

Key Features

• 4in1 design: Combines bass gain control, voltmeter, on/off amplifier switch and high-to-RCA conversion to reduce dash clutter and simplify wiring.
• Bass knob gain control: Lets the user make quick, tactile adjustments to subwoofer level without reconfiguring the main head unit or amplifier settings.
• Built-in voltmeter: Provides a continuous visual of system voltage with a blue LED display that can be toggled on or off via the level knob.
• On/off amplifier switch: Allows remote wire connection to the amplifier so the amplifier can be turned on or off with a long press of the level knob, offering convenient control from the driver seat.
• High to RCA input converter: Converts speaker-level signals from factory head units to RCA outputs for aftermarket amplifiers, avoiding the need for separate converters.

Who It's For

The Stetsom 4in1 is ideal for DIY installers, custom car builders and audiophiles who need a compact control solution that combines gain adjustment and monitoring in one module. It is particularly useful when working with factory radios that lack RCA outputs or when dash space is limited.

Those who should look elsewhere include users who require remote Bluetooth control, fully digital parametric EQs or multi-band processors-this unit focuses on core analog control and simple monitoring rather than advanced DSP features.

Pros & Cons

Pros

• Consolidates several functions into a single, neat control pod, saving installation space and wiring complexity.
• The blue LED voltmeter is useful for monitoring system health and can be turned off when not needed.
• Handy remote on/off switch means the amp can be controlled without running a separate remote circuit at the dash.
• Built-in high-to-RCA conversion removes the need for an extra line converter when using factory head units.

Cons

• Does not include advanced digital tuning features, so users seeking DSP-style control will need additional gear.
• The review sample requires proper wiring and space for neat installation, which could be a limitation for very compact dashboards.

Specifications

Product type	4in1 gain control and converter
Main functions	Bass knob gain control, voltmeter, on/off switch, high-to-RCA converter
Display	Blue LED voltmeter with one-touch on/off
Control input	Level knob with continuous touch on/off
Use case	Car audio systems, factory head unit conversion
Brand	Stetsom

Our Verdict

The Stetsom 4in1 is a practical, value-focused accessory for people who want streamlined, tactile control of their car audio without buying multiple modules. It combines gain control, a readable voltmeter and convenient remote switching with a useful high-to-RCA converter, making it a smart choice for most installs that prioritize space and simplicity.

Frequently Asked Questions

Can the voltmeter be turned off?
The blue LED voltmeter can be toggled on or off with a single click on the level knob.

Does it convert speaker-level signals?
Yes, the unit includes a high-to-RCA input converter for use with factory head units that lack RCA outputs.

How is the amplifier turned on and off?
Connect the amplifier remote wire to the control and perform a continuous hold click on the level knob to switch the amplifier on or off.