The Velleman K8042 is a +/-15V bipolar power supply kit suitable for audio applications including the MS Matrix, Stereo Width Controller, Dual Class-A Headphone Amplifier or any application where low-noise bipolar supplies are needed. (Assembled unit shown in photo. Does not include transformer or heatsinks.)

The Hammond 1182F18 is an excellent toroid for use with the K8042: https://www.hammfg.com/part/1182F18

Low cost universal symmetric power supply
Just add a suitable transformer and a heatsink
Ideal for op-amp applications, amplifiers, and more.
Trimmers can be replaced by potentiometers to allow continuous adjustment of output voltage
LED output indicators
Compact size

Specifications

Positive and negative output adjustable between 1.2 and 24VDC (see table on datasheet, page 9 for voltage input/output options)
Output current: up to 2 x 1A continuous (with suitable heatsink)
Max. input voltage: 2 x 24VAC
Low ripple
Short circuit protection
Thermal protection
Dimensions: 3.1 x 2 x 0.9"

Data sheet and assembly instructions:

https://ka-electronics.com/images/pdf/Velleman_Power_Supply_K8042.pdf