audio amplifier voltage

On Aug 26, 8:58 pm, snipped-for-privacy@gmail.com wrote: > Let's say I've got some 4-ohm speakers that are advertised to take up > to 400W. >

You forgot peak to peak and the RMS conversion so you need 80 Vp-p _under load_ meaning you'll need considerably more than that as the power supply droops under load. To double the power output, the power supply has to go up 1.41 (square root of 2) which means the load current also goes up 1.41. Keep in mind the power line voltage wanders around a bit too. At my house I've measured it between 108 and 122 depending if our A/C is on, how many neighbors A/C is on as 10 houses share one pole pig here. Point is, unless you use a regulated supply, your max power capability will vary quite a lot. If you design for 200 watts at 4 ohms and 108 volts, when the power line goes to 122 your power can go up to 255. Most won't consider this a problem - more power, right? But you have to be able to handle the peak voltage and currents at the higher voltages. You get the picture.

Good luck with this

GG

First off, a 200W (average power) amplifier driven with sinewaves (the normal way to rate audio amplifiers) puts out a peak of 400W.

From P = V^2/R ..... V = sqrt (P.R) = sqrt (400.4) = 40V

They weren't.

Graham

Ah, ok. I was thinking more along the lines of car audio than home audio, actually, and was wondering how big of a boost converter I'll need.

Then again, I saw a 200W car stereo amp from Wal Mart for $50. I wonder if I can build it any cheaper than that... maybe I'll just buy it and take it apart to see what toys they put in it. ;-)

Michael

That '200W' was the peak power, sum of channels, with a generous bullshit factor thrown in.

Thanks for that...! My Kenwood already is 45W x 4. Guess I don't need that amp after all...

Michael