FAQ
TL;DR: Typical car radios draw 10–20 W in normal listening, and “The standard situation is 10–20W.” Use a 12 V, ~10 A desktop supply and wire +12 V to both red and yellow, ground to black. [Elektroda, bestboy21, post #16979236]
Why it matters:** This FAQ helps you choose and wire a safe, quiet power source to run a car head unit at home, especially if you’re unsure about amps, wiring, or speaker count.
Quick Facts
- Recommended bench supply: 12 V DC, about 10 A, rated ~120 W. [Elektroda, Pedros050, post #16979163]
- Wire +12 V to ISO red and yellow; ground to ISO black. [Elektroda, Pedros050, post #16979195]
- Normal listening power: approx. 10–20 W total output. [Elektroda, bestboy21, post #16979236]
- Four 4 Ω speakers can sometimes exceed 100 W at high volume. [Elektroda, bestboy21, post #16979236]
What power supply should I use to run a car radio at home?
Use a 12 V DC desktop supply around 10 A (≈120 W). It suits typical head-unit loads and casual listening. If you plan four speakers and loud sessions, the 10 A headroom helps. This matches the suggested “Desktop 10A 12V, 120W” adapter. [Elektroda, Pedros050, post #16979163]
Can I use an old ATX computer power supply instead of buying a new one?
Yes, a working ATX PC power supply can power a car radio. It offers a solid 12 V rail and ample current. Many hobbyists repurpose ATX units for bench audio tests. Ensure it is functional before use. [Elektroda, Pedros050, post #16979113]
How do I wire the radio’s ISO power leads on the bench?
Join the radio’s red and yellow leads to +12 V from your supply. Connect the radio’s black lead to ground. This mirrors standard in-car wiring and ensures memory and ignition lines receive power. [Elektroda, Pedros050, post #16979195]
Do I need to connect all four speakers for testing?
No. Two speakers are enough for bench tests, and even one will work. This reduces load and current demand while you verify power and functions. [Elektroda, raficool, post #16979184]
How many amps do I need if I’m only using two speakers?
A 12 V, 10 A desktop supply is a practical choice even with two speakers. It provides margin for peaks and avoids shutdowns during louder passages. “Model: Desktop 10A 12V … 120W” was recommended. [Elektroda, Pedros050, post #16979163]
Will a laptop or decoder power adapter work for a car head unit?
Similar 12 V adapters can work, but many decoder or small brick supplies provide fewer amps. They may fall short if you turn it up or use more speakers. Choose higher current if possible. [Elektroda, Pedros050, post #16979195]
Does a 120 W label mean the supply always consumes 120 W?
No. 120 W indicates maximum load capability, not constant draw. The radio only pulls what it needs at a given volume. “This is the maximum load power of this power supply.” [Elektroda, Pedros050, post #16979234]
How loud can a head unit get with four 4 Ω speakers?
At high volume with four 4 Ω speakers, a head unit can sometimes exceed 100 W total output. Normal listening is far lower. “The standard situation is 10–20W.” [Elektroda, bestboy21, post #16979236]
What is the “ISO plug” on car radios?
The ISO plug is the radio’s standard power/speaker connector discussed here. Power pins feed red (ACC) and yellow (BATT), and black is ground. Speakers connect on the second plug. [Elektroda, Pedros050, post #16979195]
Quick how-to: How do I power a car radio safely on a bench?
- Set a 12 V desktop supply and confirm polarity with a meter.
- Connect +12 V to the radio’s red and yellow leads; ground to black.
- Attach one or two speakers, then power on and test functions. [Elektroda, Pedros050, post #16979195]
What if I only have one speaker handy?
That’s fine for setup and testing. One speaker is acceptable and reduces the current requirement while you verify power and audio. “Two is enough and even one.” [Elektroda, raficool, post #16979184]
Why does amperage matter when choosing a supply?
Available current must match your speaker count and volume. Lower-amp supplies may be insufficient, especially with four speakers. Check your plan before connecting. [Elektroda, Pedros050, post #16979182]
4x50 or 4x45 probably has something like that
