# Despite what people say, my JDS Labs Atom CAN power a pair of passive speakers (???)

#### SorenTheOutcast

##### New Member
I'm not sure if i should be concerned about it, but everywhere i looked i only found people saying that the JDS Labs Atom cannot power passive speakers because the RCA outputs are only for data.
Well, i doesn't seem to be the case for me. I just tried plugging into my Atom (yes, only through the rca ports) 2 small passive speakers that i have in my livingroom (they came with my stereo; i'm pretty sure they are fairly cheap) and they worked. I managed to get them to a decent volume as well, but the audio was slightly distorted (probably because of the poor quality of the cabled that would make noise when i moved them)
Is there anything wrong with this? Have i even broken something?

I can see two issues.

Problem 1:
The output device used in the Atom is the TI LME49600. It has a output current rating of 0.25 A. As power is I^2 * R, with an 8 ohm load, the max power you will get is only be 0.5 W. If the load is 4 ohm, max power will be reduced to 0.25 W.

Problem 2:
The amount of heat the LME49600 generates increases as the output load resistance decreases. Going to page 14 of the data sheet equation 2, the max heat the LME49600 dissipates is (I_s * V_s) + V_s^2 / (2 * pi^2 * R). With V_s at nominal 30 V (difference between positive and negative rails), I_s = 0.015 A, R = 8 ohm, heat = 0.45 + 5.70 = 6.15 W. Without a real heat sink, 6.15 W is way too much heat to dissipate with only the PC board, and the LME49600 will probably go into thermal shutdown pretty easily.

LME49600 data sheet:

The RCA port is connected to the headphone output essentially. You will get sound that's for sure. But there's not enough power. The device is not designed to be dissipating that much heat for long periods of time. But it depends on the sensitivity of your speakers. You may be able to use it relatively safely at night. But it's never recommended.

The other posters are right. Its possible you have bad cables but that is not the main problem. You need a speaker amp. If you are on an extreme budget, a lot of amps are available for less than \$40 from companies like Douk Audio, Nobsound, and Lepai that will give you great results on cheap speakers and work great with your Atom.

I'm not sure if i should be concerned about it, but everywhere i looked i only found people saying that the JDS Labs Atom cannot power passive speakers because the RCA outputs are only for data.

Cannot and 'is not recommended' are 2 different things.
0.25W (8 Ohm) is enough for medium to high efficiency speakers to produce background music.
(250mA peak = 177mA rms) = 0.25W in 8 Ohm and the IC's inside will be dissipating a LOT of heat as there is 2V across the speaker with 0.18A (both so that leaves 9V with 0.18A (= 1.62W) in heat dissipation for the IC and it has no sufficient cooling for this.
That means that while your speaker is getting 0.25W your amp is dissipating 6x that much and is not designed for this (but can reach it)

If that is enough for you ... O.K. but is no proof that it can be used to drive speakers to decent levels nor is it recommended.

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You can use a beerglass to hammer a nail in a wall. But nobody with some brain would say it's the recommended tool.

what is up with the strange run of threads from people wanting to use headphone amps to drive speakers the past couple weeks??

what is up with the strange run of threads from people wanting to use headphone amps to drive speakers the past couple weeks??
i have no idea. i posted this same thread 3 times on 3 different forums yesterday if that's any relevant

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