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Dell’s USFF Internal Amplified Speaker

DellMiniSpeaker.jpgI bought a Dell Optiplex GX620 USFF (Ultra-Small Form Factor) machine last week, and it came without an internal speaker. I didn’t know the speaker was optional until a machine turned up without one, but a look at my three SX280 USFF machines (built in exactly the same case) showed a very small plastic unit that pulls easily out of the chassis when you lift a plastic tab. It’s wired to the mobo through a conventional 4-pin header. And most interesting of all, it has circuitry on its back.

A look through a loupe showed four solder pads (on the left in the photo above) labeled P5V IN, SPK DET, GND and AUD MONO. These correspond to the red, white, black, and green leads respectively. It took me ten minutes to lash up a test on my Heath ET-3200 breadboard. With 5V on the red lead, common on the black lead, and some sine wave from my audio generator on the green lead, that one tiny little doodad filled the shop with an 800 Hz tone.

I’m pretty sure the SPK DET lead allows the computer to know if there’s a speaker in place; my VOM shows it tied to ground. The IC is almost certainly an LM4871 1.1W audio amp. The National Semi logo is on the chip, and the printed number is RA4871. The Dell part number for the assembly as a whole is Y2298.

I needed to order one for the GX620, so I ordered two, and if I need a subminiature speaker amp for a project, it’ll be in the drawer with my other small speakers, ready to go. $2.69 at the CompuFlea eBay store.

10 Comments

  1. Great information! I ripped one of these out of a dead Optiplex at work and was thinking of breadboarding it to see it work. Found this page googling “SPK DET” in an attempt to see if anyone knew what it was. Thanks for the info and wire colors!

  2. K. Kerd. says:

    So, for common usage with other audio source. i must discard the white cable and use P5V In for 5 volts DC and AUD MONO for line in and share the GND with ground for 5V and ground of the line in. Am i correct ?

    1. As best I know, yes. Keep in mind I did the lashup five years ago, and haven’t messed with the device since. (I’ve been working on other projects, primarily SF novels.) You can leave the white lead open; some VOM probing showed it tied to ground on the speaker PC board. I think what happens with it is that the machine looks at the mobo header pin it connects to, and if the pin is open (probably pulled to rail by a resistor on the mobo) there is no speaker installed, but if the pin is held at ground, a speaker is plugged into the header. That’s speculation on my part, but it’s a reasonable thing for a mobo designer to do.

      The ground line is a common ground. Audio ground and power ground both. AUD MONO is line in, that just means “mono audio.” Works like a champ! Good luck with it. Feel free to let us know how you do.

  3. K. Kerd. says:

    Hi,
    It works like we mentioned. Now i use it with my under-desk PC project. It is an ordinary itx motherboard. i use 5V from front USB header and line in + ground from front HD audio header. This small speaker is loud enough for YouTube clip and music. I have tried with another SFF Dell speaker in rectangular shape but this round speaker is more clearer in sound quality. Thanks a lot for you information.

    This it the speaker at work !
    goo.gl/KeQ0na

    1. The little rectangular speakers were designed for the SX260/SX270 line from 2000 to about 2004, but they were lousy speakers and I rarely saw one installed in an actual machine. The round ones like this are actually pretty good, and I have four or five in a drawer somewhere, awaiting projects that need audio.

      That’s a very cool project, BTW. Good luck and thanks for posting the link!

  4. Will l. says:

    Awesome I to was trying to figure spkr set. Thanks great information. It good to feel the geek! Yah

  5. CHOPPERGIRL says:

    Leave it to Dell to fuck every god damn thing up, and I mean everything, even something as simple and standard as a PC speaker.

    There is a 4 pin standard speaker pinout as old as time everybody knows, and it is this one, and Dell has to make everything they make completely incompatible with everything else:

    https://en.wikipedia.org/wiki/PC_speaker

    Thanks for your article and link to fleabay, I would of never figured this stupid shit out otherwise. I’d never buy a Dell myself, but find I have to support other people’s crap that weren’t as smart as me to never buy name brand PC crap. Stick to whitebox, if there is even anything as Whitebox left, if there is even a PC market left…

    1. CHOPPERGIRL says:

      Your ebay link no longer works. Is there any way to wire up an non-amplified speaker to these pinouts and have them work. I already have hotglued in 3 mini-small speakers from old Magitronic 486’s, and they fit perfect, however, the pinout doesn’t match Dell’s at all. I assume maybe you could wire up one speaker lead to Audio Mono lead as your signal line, and the other speaker lead to GND as the reference?

      1. Audio Mono may well drive a speaker, at low volume–I’ve never tried it–but I don’t think the experiment would hurt anything. Yes, the other line should go to ground. So give it a shot. I’m not in a position to try it myself right now.

      2. Dell likes to create its own standards, heh. This has been their way since the dawn of Dell time.

        The eBay link is from 2011, and eBay storefronts don’t always last six years. Dell spares are abundant, and if you want the speakers I’m sure they’re out there somewhere, cheap. Just search for “Dell internal speaker”. Here’s one of the rascals for sale right now, for $7:

        http://www.ebay.com/itm/Y2298-Dell-Inc-Optiplex-SX280-Internal-Speaker-0Y2298-/252918515503

        The white-box market is now a black-box market, and driven by gamers. I use the BlacX case from Thermaltake and I love it. SATA slots on the top for quick backup direct to drives. There are still box shops around who can put them together if you don’t want to. I had a shop in Colorado Springs do it for me because I was busy with other projects, and it’s a fine machine.

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