Tech Stuff

Connections and amps

This is a legacy page covering connector types, impedance, and amplifier power — useful background even though most of it isn't DJ-specific.

The original diagrams for this page (connector drawings, wiring illustrations, screenshots) haven't been carried over in this rebuild — the explanations below stand on their own, but redrawing the diagrams is on the list.

Connectors

The three you'll run into most as a DJ: XLR, phono/RCA, and 1/4-inch jack.

XLR connectors are the professional standard for microphones — they lock in place rather than pulling loose like a jack plug, and come in balanced and unbalanced forms. Unbalanced connectors carry one or two conductors plus a shield; balanced ones add a third conductor and offer much better noise immunity over longer cable runs (12ft/4m or more), which is why they're standard in studios and broadcast. Many modern DJ mixers use a combo XLR/jack input, which is why the mic input often has that oddly shaped, slightly oversized socket.

The 1/4-inch jack is what's on the end of most headphones (aside from ones using a smaller 1/8-inch jack). Two bands near the tip means stereo; one band means mono.

Phono/RCA connectors are the most common input/output on a DJ mixer, always in a left/right pair. The red plug is right, the white (or yellow) plug is left — "R is R" (red is right) is the easy way to remember it.

Turntables also carry a separate ground wire, usually ending in a small metal loop. Look for a thumbscrew on the mixer marked GROUND, loosen it, hook the wire's loop around the post, and tighten it back down. Skipping this causes a persistent hum along with static pops and crackles.

Impedance

A mismatch in impedance (measured in ohms) between equipment can noticeably affect sound quality:

• High-impedance output into a low-impedance input: distortion from the higher voltage, and a thinner, tinnier tone from the mismatch.
• Low-impedance output into a high-impedance input: weak signal, muffled tone, and exaggerated bass.

As a rule, the following circuit's input impedance should be lower than the impedance of whatever's feeding it — low-into-high generally works, high-into-low can cause damage. Speakers are more forgiving of a mild mismatch, but check your amp's rated power at the impedance figure it quotes, and make sure your speakers can handle the worst case — exceeding it is a fast way to blow a speaker. The same logic applies to headphones: check your mixer's quoted impedance and try to match it.

Worked example: combining speakers of different impedance

As an example: an 8-ohm speaker, a 6-ohm speaker, and two 4-ohm speakers, all wired into the same amp.

Wired entirely in parallel, total impedance works out to roughly 1.26 ohms. Wired entirely in series, it comes to 22 ohms — series impedances simply add together, while parallel impedances need the reciprocal method (flip each value to a fraction, add them over a common denominator, then flip the result back).

In practice, a mix of both got closer to a usable value: the two 4-ohm speakers wired together in series, the 8-ohm and 6-ohm wired together in series, and those two resulting pairs wired to each other in parallel — landing on roughly 5.1 ohms overall, close enough to the amp's rating to be safe.

To wire speakers in parallel: connect all the positive terminals together, and all the negative terminals together, then connect that combined pair to the amp. To wire in series: the positive wire of the first speaker goes to the amp's positive terminal, its negative wire goes to the second speaker's positive terminal, and the second speaker's negative wire goes to the amp's negative terminal. The downside of series wiring is that if one speaker fails, the rest of the chain goes silent with it.

Amps

A quick disclaimer: everything here comes from general research and conversations with a college audio technician, not formal training — treat it as a starting point, not gospel.

Amplifiers are rated for maximum sustained output. Speakers carry two ratings: average (RMS — the maximum sustained output they can handle) and peak (the maximum they can handle momentarily, always higher than the average, which is why manufacturers tend to lead with the peak figure). As a rule of thumb, a speaker's average rating should sit above the amp's rated output, and its peak rating must always exceed the amp's output.

If you need, say, 200W of total output, running three 100W amps at roughly two-thirds power each is generally more resilient than one 200W amp or two 100W amps at full tilt — if one amp fails, you lose a third of your power rather than half or all of it. Worth noting: doubling perceived loudness takes roughly a tenfold increase in amp power, not simply double the wattage.

Rough amp power by room size

Room size	Amp power per channel (watts) for full-on dance music
Empty-ish bedroom	20–40
Full-ish bedroom	40–60
Big room / small hall, half full	80–150
Large hall, half full	150–300
Large hall, packed	500–800

Room decor matters too: hard, reflective surfaces (wood floors and walls) carry sound further, so you need less power; soft furnishings, carpet and a packed crowd all absorb sound, so you may need a bit more.