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From: "Phil Allison"
References: <email@example.com> <firstname.lastname@example.org> <3debaeec.2879341@News.xtra.co.nz> <86$6IEAG7I79EwxN@jmwa.demon.co.uk>
Subject: Re: 'Current Dumping' Amplifier Circuits ?
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Date: Wed, 4 Dec 2002 16:10:19 +1100
NNTP-Posting-Date: Wed, 04 Dec 2002 15:59:20 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"John Woodgate" wrote in message
> I read in sci.electronics.design that Phil Allison
> wrote (in ) about ''Current
> Dumping' Amplifier Circuits ?', on Wed, 4 Dec 2002:
> >** I service and test these buggers for a living, John.
> I never doubted it for a moment.
> > The THD figures I see are nearly always better than 0.1% at
> >at just below clipping into 8 ohms. Some are down to 0.005 % at that
> >( Yamaha 2200)
> > Go 0.5 dB more an the figure is 5% THD. Nothing crazy is
> Well, 0.5 dB in power terms is a 12.2% increase. In heating terms, that
> can easily take a voice coil over the magic 260 C that spells disaster.
> And amps are often driven up to 10% THD in the field. Is your experience
> of fried drivers different?
** I am not with you here, John.
The average power delivered into the speaker over some period of
time is what may overheat it - the THD of the amp is just not involved.
This average may be enhanced by amplitude compression as a result of
PA amps have had low to very low THD figures ever since they stopped
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