Cheap simple audio amplifiers.

"Ian Stirling" wrote in message

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".
--
Andy



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Yes, strictly one should speak of RMS power into a n ohm load, which is sensiblke.
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No, you've missed the point completely. You should speak of mean power into a given load.
--
Andy



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Ian Stirling wrote:

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.
3 suggestins
(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.
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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.
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wrote:

W my

on a

PC
could
power, and

actually.
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suitable
If you're handy witha soldering iron you could try this site:-
http://sound.westhost.com/pcb/pricelist.html
Neil
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Ian Stirling wrote:

Believe me, it doesn't matter. Those all in one chips have thermal shutdown anyway.
I spent a large part of my life designing audio power stuff. For disco or gutauisr/keyboarsd use, yes, the bugers run em at full power contnsuoly. For PA or music uses below the level of gross distortion, teh peak to mean levels are something like 3-10:1.
I actually think that 'music power' is indeed a meaningful thing. Its possible to design an amp that may have an RMS rating of 20W, that sounds as loud for teh same distortion as a 100W true RMS amp.
It depends on what you want it for. For HiFi use I'd rather have peak power than RMS power, tho both togther are nice.

Class D sucks by and large. Not very hifi - even today.

Someone was selling a mixed bag of car radio chips on there. These are really incredibly easy to get working - just follow the manufactureres design notes. Fed from a 12v AC transformer/rectifier/capacitor (about 4700uF) to give about 16-18v DC, (could use nice LV lamp toroids etc) you get either 5W stereo into 4ohms, or 20W mono in bridge format. Perrt clean power - usually around the 0.2% distortion at sensible power level...couple that up to a decent car speaker in a box, and you have a nice localised sound source. Anyway 5W to 20W is only 6dB, and you can get 6dB by buying a better than average loudspeaker... Not sure what the final application is - I asume some way to spread Jazz FM throughout the house?
Second hand car radioscan be pirated as well.
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