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From: "Phil Allison"
References: <3E2A306E.64A1B96F@webaccess.net> <3E2A4186.BF5DE7BC@webaccess.net>
Subject: Re: Choosing the right transformer
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sun, 19 Jan 2003 17:30:41 +1100
NNTP-Posting-Date: Sun, 19 Jan 2003 17:19:44 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Chuck Simmons" wrote in message
> > > Phil Allison wrote:
> > > > ** There are several issues - the regulator must supply the peak
> > curent > > demand though an output filter cap could reduce this figure a
lot - it
> > > > depends on the signal - unclipped music, clipped music or even
> > waves.
> > >
> > > The TI application note would seem to be based on nearly distortion
> > > 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.
** The numbers are what ? Power ratios ? Voltage ratios? It matters a
It looks to me like the voltage ratios of uncompressed speech - which
gives massive and unrealistic power ratios.
> > 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
> > music programme or about 1/8 power on average.
> I did not consider compressed program material.
** Silly boy - the idea is to establish some sort of "worst case" use of
a power amp.
> > > > The heatsinks for the regulator may be OK at the 1/8 power,
> > > > thermal protection is provided in case this rather artificial figure
> > ever> > > > exceded.
> > >
> > > Yes, whatever.
> > ** Screw you shithead.
> Charmed I'm sure.
** That was a stupid and offensive remark.
I have had a fucking gutfull of them here !!!!!
> > > > The AC transformer will need to supply the peak too but the
> > > > term average is way lower. If it is too small the regulation will
> > poor> > 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
> > small.
> 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.
** And I have no bloody intention of doing anything so damn stupid either.
A proper design MUST be based on a predictable worst case - not stupid
There may easily be requirements with recorded music for full output
lasting 10 -20 seconds or more - takes a damn big cap to hold up that long
> 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.
** He might want to put his Yamaha keyboard through it too. What does
that do to your nice comfy peak to average ratios ???
> I highly recommend the "Radiotron Designer's Handbook." Even if you
> learn nothing from it, it can be used as a cure for insomnia.
** May I suggest it is NOT suitable for bashing people over the head
with - esp me.
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