Connect spare passive HiFi speakers direct to laptop?

[pretzelz]

Hi,

My old powered computer speakers broke during a recent move. Today I went to the local TIP and found two 6 ohm Sony hifi speakers, about 30cm high and in a nice wooden casing. I tested them out on a hifi in the house and they work perfectly. (Got them for £2).

So you probably know what comes next... could I adapt the wires off the end of the two speakers so that they could plug directly into the 3.5mm audio output on the laptop? - My simple thought is, probably not, since they are passive speakers and wouldn't recieve any power from the laptop?...

Thanks.

 

[ChrisFrost]

Correct. They won't give any volume. You need an amp as well.

 

[Sam Gangee]

A few days ago I found a ghetto blaster, thrown out for the refuse collection. It was a bit battered and showed signs of corrosion but I rescued it anyway. When I connected power I found that the amplifier and radio sections worked perfectly. I haven't tested the CD player or cassette player but I really wanted it just for the amplifier anyway.

So you could probably acquire a similar item (probably in better condition) from "Freecycle" or similar and modify it to work with your laptop.

Usually, you can connect the volume control tags to a 3.5mm jack plug and it will simply work.

 

[pretzelz]

thanks, this is a good idea to go back and look for an amp. I also checked ebay and found a new mini stereo amp for £10! China of course, but I expect would do the trick nicely.

 

[dogfonos]

I also checked ebay and found a new mini stereo amp for £10! China of course, but I expect would do the trick nicely.

Just don't leave it powered up when you leave your house!

 

[braychurchmouse]

A few months ago I bought "Lepai Class T Amp TA2020" Amplifier 20WX2 from techex_online on eBay cost £8.99 plus £4.99 postage from Hong Kong. Took a couple of weeks to arrive but works a treat and VERY compact. Build quality is good, actually all seems to be on one integrated circuit and the case is actually one big heat sink.

Just looked and quite a few sellers of same or similar. (click sort on lowest price +postage and the cheapest will be at the top.)

Very small and neat but any old HiFi amp will do the same. Postage is likely to be the biggest component of cost on ebay so try and find one nearby that you can collect (click sort on nearest).

You'll probably just need a 3.5mm strereo jack to two phono plug leads. Probably a fiver in Comet, £2 on eBay and 10p at a car boot.

Having said all that you could try just connecting the speakers to the headphone output, you will probably get a small sound out of them, but don't crank it up too loud as headphone outputs are designed for higher impedance loads than loudspeakers so there is a small risk you might damage something.

 

[pretzelz]

Thanks, I looked up the amp you quoted and sure enough, its in a similar line to those I found on Ebay too. Glad to hear you were happy with it! Incredibly, I found one selling for £10 in Portsmouth, two mile away! But I'll need to get hold of a power adapter too.

 

[plugwash]

best not to by power adaptors from ebay anyway, especially from ebay sellers in hk/china.

Power adaptors are important safety devices and should only be bought from reputable suppliers.

 

[braychurchmouse]

best not to by power adaptors from ebay anyway, especially from ebay sellers in hk/china.

I don't think I've seen a power adapter in the last ten years that hasn't come from China/HK. The important thing is to get one with ample power handling, and check the polarity of the plug (positive or negative tip).

Check temperature after extended use, if at all hot, then caution is advised...warm is ok.

The newer "switchmode" adapters run much cooler.

My own Lepai off eBay came with a very nicely built switch-mode power supply that runs very cool and has the "CE" marking...and yes it was made in China.

Of course the "CE" could be counterfeit, but there again so could your car brake pads!

Its always advisable to place the power adapter where it is well ventilated and if you are ultra-cautious keep it where it won't be near anything flammable.

Also if you are ultra cautious you might do well to replace any "cheapo" power supplies that are on permanently after 5-10 years since that's when the electolytic capacitors give out (which is why Thomson Skyboxes seem to last no more than 5 years).

Hey, you could even put it in a (ventilated) fire proof box...but there again it is a building regulation that power supplies for TV loft boxes (in the loft!) are in a fire proof box and I don't know of anyone who's done that, even professional electricians.
See...
http://www.businesslink.gov.uk/bdotg/action/detail?itemId=1084696957&type=RESOURCES
http://ec.europa.eu/enterprise/policies/single-market-goods/cemarking/facts/facts-ce/index_en.htm

Sorry to ramble on.

 

[dogfonos]

plugwash wrote:
best not to by power adaptors from ebay anyway, especially from ebay sellers in hk/china.

I don't think I've seen a power adapter in the last ten years that hasn't come from China/HK. The important thing is to get one with ample power handling, and check the polarity of the plug (positive or negative tip).

This is good advice.

Whilst most electronic devices are made in China these days, the point about buying direct from a small, Chinese outlet (or more likely, an individual) is that the item isn't always what it seems and sometimes, not as described. It's not that these Chinese sellers are deliberately deceitful, I genuinely believe they don't realise they're doing anything wrong.

A brief example...
I purchased a class T amp module from an unknown seller (to me at least) on ebay direct from China. The advert had featured photos (turned out to be accurate) and a worded description (turned out to be completely inaccurate). He had simply taken the worded description from a seller of an upmarket T amp module. I only wanted a cheap T amp for experimentation so I didn’t care but other purchasers might. I explained this to the seller. He asked me to re-word the advert for him, which I did, but he never used it. I have other examples, including likely counterfeit items but I won’t bore you.

There’s nothing inherently wrong with products made in China, however, Chinese made products sourced via a reputable manufacturer undergo quality assurance so have a much higher chance of being ‘right’. I often choose to purchase cheap items from unknown Chinese sellers - sometimes I get an excellent product, a real bargain and sometimes I don’t - but I now appreciate the risk I’m taking.

 

[plugwash]

The problem with power supplies is that the only real way to find out if the transformer* has sufficient insulation between primary and secondary windings is to destructively dismantly it. Intereference suppression capacitors are likely even harder to check.

A reputable EU based vendor who buys PSUs from china by the crate load can afford to destructively dismantle a PSU as part of their quality assurance processes and it is in their interests to do so unless they like being sued (or possiblly even criminally prosecuted if someone gets killed). OTOH a small vendor in china selling direct to the european public has far less reason to care about our safety regulations and legal system.

Take a look at http://www.youtube.com/watch?feature=player_embedded&v=T88ej64aXUM note especially where he dismantles the transformer and finds that there is no fuse and that primary and secondary are only seperated by a bit of thin tape.

* Even switched mode power supplies contain transformers. They just operate at a higher frequencyso can be smaller and lighter.