Cheap simple audio amplifiers.

Maplin do all sorts of modules if you are able to wire these up to a PSU.

Depending upon how much you want to pay and how much you want to DIY, you could try Maplins

HTH,

Chris

"Ian Stirling" wrote | Where might I go for basic audio amplifiers? | All I want is something that has a 3.5mm input jack, | and speaker connectors. Everything else, perhaps even | a volume control, is extra. | Something around 20W.

Hmm, real watts or music power watts?

| This would be for miscellaneous household audio. | At the moment I've got various stereo units doing this, | but they are rather large, and a neater solution would | be nice.

Those amplified speakers used for computers. I don't know how many W my Altec Lansings with a subwoofer pump out, but they do the business on a Roland Virtual Guitar. Many people will have spares from buying new PC systems.

Alternatively for something a bit more gutsy than the typical maplin modules

Owain

Actual real RMS watts.

The inventor of peak music power should be burnt at the stake.

I have speakers, I am just looking for the amps. Thanks for the references, I was wondering if such a thing existed already boxed, as it's in the range of a 1 chip class D amp, which could do it lots cheaper than with linear amps, as well as using less power, and needing less heatsinking.

Most of the IC suppliers have demo boards using their amplifier chips - perhaps you could tie one of these to a big wallwart.

You'd be talking about a very weedy amp if a wall wart would power it.

You can get surprisingly powerfull SMPS wall-warts. The biggest I remember off-hand is around 30W.

The key is to run the transformer at a really high frequency, so you can fit more power through.

Easily enough to power a gigawatt of speakers (Peak Invented Music Power).

You've still got the problem of the reservoir caps though - these need to be a decent size for adequate 'music power' ;-)

I'd be inlcined to buy something off eBay. Much easier than building it.

For example;

Grrr - this is a common and seemingly self-perpetuating error. You don't mean RMS watts, you mean mean (i.e. average) watts, for a sine wave, into a resistive load. You mean the product of the RMS output voltage and current into the load. This is the average value of the power delivered - the 'heating power' in other words. That's the whole point of using RMS values for voltage and current, but it's nonsensical to talk about "RMS power".

"Dave Plowman" wrote | > Most of the IC suppliers have demo boards using their amplifier | > chips - perhaps you could tie one of these to a big wallwart. | You'd be talking about a very weedy amp if a wall wart would power it.

Amps are like computers - real ones have 3-phase hardwired in. Anything less is consumer gear :-)

Owain

The actual building of an amp can be ok - especially if a kit - but making it look good is a different matter.

Yes, strictly one should speak of RMS power into a n ohm load, which is sensiblke.

I have a 240W wallwart, well actually it's a dangly A6 size three mm thick PSU. Thinnest and smallest I've ever seen.

Its within range of a bridged single chip car stereo type chip actually.

Especially if run off 15-18v DC. And being used for audio rather than sine waves or guitars.Where avreage power is probably less tahn a watt, and smaller heastinks will work.

(i) skip. Find any old cheapo radios etc and adapt them.

(ii) as pointed out computer speakers if you want the speaker as well.

(iii) roll your own PCB including supply etc - useful if you need 10plus.

Put itin with the speaker in a veneered MDF box.

Yeah. I'd like a fairly bullet-proof device, and am not really keen on smaller heatsinks.

I was just wondering if someone had stuck a nice class D amp in a little box. The Maplin 50W 6 channel amp for 45 quid would almost suit, but i'd really like the amps seperate.

(I have signal wiring, but not speaker wiring to the speaker locations).

Oh well.

I suspect I'll watch ebay for a while, to see if anything very suitable pops up. Thanks.

No, you've missed the point completely. You should speak of mean power into a given load.