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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Choosing the right transformer
Date: Sun, 19 Jan 2003 06:11:37 GMT
NNTP-Posting-Date: Sat, 18 Jan 2003 22:11:37 PST
Phil Allison wrote:
> "Chuck Simmons" wrote in message
> > Phil Allison wrote:
> > > ** There are several issues - the regulator must supply the peak
> > > demand though an output filter cap could reduce this figure a lot - it
> > > depends on the signal - unclipped music, clipped music or even square
> > The TI application note would seem to be based on nearly distortion free
> > reproduction of typical music programs where peak to average ratio is
> > 10:1 to 20:1.
> ** Where did you pluck those numbers from ? Your bum ?
You can find such information in the "Radiotron Designer's Handbook"
which, oddly enough, is Australian in origin.
> This makes the 8:1 for the ratio of rated power to average
> > power make sense.
> ** The peak to average voltage ratio is about 3:1 for highly compressed
> music programme or about 1/8 power on average.
I did not consider compressed program material. In my broadcast
experience, using N. A. B. practice, compression was not a factor at
all. It is not a factor in high quality recordings of traditional
instruments since loss of dynamic range is considered a serious
distortion of the program. There does exist a difficulty with recordings
of pipe organs built before the invention of the venetian swell but
these are rare.
> > > The heatsinks for the regulator may be OK at the 1/8 power, if
> > > thermal protection is provided in case this rather artificial figure is
> > > exceded.
> > Yes, whatever.
> ** Screw you shithead.
Charmed I'm sure.
> > > The AC transformer will need to supply the peak too but the long
> > > term average is way lower. If it is too small the regulation will be
> > > and make your linear regulator design very difficult and lossy.
> > Not really. It is a no brainer to size the capacitors needed after the
> > rectifier to avoid these problems.
> ** Bullshit. The caps would need to be many farads if the tranny is too
It depend on the duration of program peaks. In normal music, the
duration is short. The "Radiotron Designer's Handbook" has data but I
forget the details and I don't have my copy here. However, the caps are
largish but reasonable even in a fairly conservative design. You simply
have not calculated for cases of "average" program material.
I did assume that the OP was talking about a home system of modest power
such as many of us use to listen to music, TV and movies. The typical
operating power level is much lower than most people think. A friend of
mine has 500 watt per channel amplifier but the average listening level
in his home is about 5 watts. If his goal were industrial deafness, it
would be reasonable to use 100 watts in his house as there are no other
houses near. I have observed in the apartment complex where I live that
listening levels over 5 watts average with reasonably efficient speakers
will net noise complaints which can lead to prosecution for a
I highly recommend the "Radiotron Designer's Handbook." Even if you
learn nothing from it, it can be used as a cure for insomnia.
> You clearly know SFA about audio.
I am so glad you enjoy my posts.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
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