ElectroLab AIVisual build guides
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Intermediate

Dummy Speaker Load

Build a heat-aware speaker substitute with labelled terminals, selectable impedance, and meter points across the load.

Safety first, always.

ElectroLab AI teaches theory, low-voltage electronics, and planning concepts. Mains voltage, switchboards, fixed wiring, high-current systems, and legal electrical work must only be performed by licensed electricians where required.

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Dummy Speaker LoadPower resistors form a labelled 4/8 ohm speaker substitute with voltage test points and heat-aware mounting.+-8 ohm4 ohm pairmeasurethermal mountAMPoutputPOSTS+ / -MODE4 / 8 ohm8R 50Wresistor8R 50WresistorHEAT SINKvented caseTEST POINTSAC voltsResistors become hot. Start with short low-power tests and calculate power from measured voltage.

Amplifier test tool

Build a switchable 4/8 ohm dummy load so small amplifiers can be tested without annoying speakers.

Bench time

1-2 hours

Typical parts

$25-$60 AUD

Power

Amplifier output only

You finish with

Heat-safe speaker substitute

Before the first wire

Know the build before you power it.

Dummy load resistors get hot. Mount them to a heat sink or metal plate with airflow.

Use non-inductive power resistors where possible for amplifier testing.

Start with small amplifiers and short tests until you know the heat rise.

A dummy load is silent; always watch voltage, current, and resistor temperature.

Bill of materials

7 parts groups to gather

Check every spec

QtyPartExact specWhat it doesInspect before use
4Power resistors8 ohm, 20-50 W each, non-inductive preferredAbsorb amplifier power as heat.All resistors measure close to value.
1Heat sink or metal plateLarge enough for expected heatSpreads resistor heat.No sharp edges; resistors mount firmly.
1Impedance switchHigh-current DPDT or separate terminalsSelects 4 ohm or 8 ohm mode.Contact rating exceeds test current.
2Binding postsRed and black insulated postsConnect amplifier output.Posts cannot rotate into metal case.
1Voltage test pointsBanana or pin sockets across loadLets a meter/scope measure output safely.Clearly across the load, not across switch contacts.
1EnclosureVented, heat-resistantPrevents accidental touching.Hot parts cannot touch plastic.
As neededHigh-current wireShort heavy wireCarries amp output current.No thin breadboard jumpers in the load path.

Build boundary

This is for small low-voltage audio amplifier testing. It is not a safe load bank for mains equipment, car starters, inverters, or high-power PA amplifiers.

Part modules vary. Read the markings and datasheet for the exact board in front of you before applying power.