DIY Aquarium Chiller This pre amp is a simple opamp preamp that consists of a buffer stage, a resistor ladder as volume attenuation, another buffer, then a balanced line driver. The price is paid in reduced line driving capability. Learn More. ” So it’s little wonder that her entire house was one big do-it-yourself. Should have "speaker out" on it, and a rating of ohm/watts on it. Not the one I designed, but one from a DIY kit. I added LEDs to show which output was selected, which makes it necessary to use a battery or pedal power to power the LEDs, but the switch is still passive which means you can use it either way. \$\begingroup\$ The power supply needed for an op amp may be prohibitive when this passive solution is available. It takes about 30 min to 1 hr to build.