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From: "Phil Allison"
References: <3FsT9.19037$oS1.firstname.lastname@example.org> <email@example.com> <25zT9.20644$jM5.firstname.lastname@example.org> <email@example.com> <6P2U9.21562$jM5.firstname.lastname@example.org> <email@example.com>
Subject: Re: Mosfet amp desigh sought
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Tue, 14 Jan 2003 07:23:58 +1100
NNTP-Posting-Date: Tue, 14 Jan 2003 07:13:31 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Bill Sloman" wrote in message
> "Phil Allison" wrote in message news:<6P2U9.21562
> > >
> > > Like I said, it depends how picky you are about distortion.
> > ** That remark is quite ambiguous. Do you mean audible THD or
> > it takes a spectrum analyser to identify at -130 dB ?
> The remark is entirely unambiguous - both of your examples could be
** That is the definition of ambiguous. The meaning is unclear since
several meanings can be included. See any dictionary Bill.
> > There is> no such thing as "NO crossover artifacts" in a class B or
> > > amplifier,
> > ** No equals "no audible" which equates to circa -85 dB compared
> > watt.
> This is an oversimplification.
** What ? Sub threshold sounds are audible ? Since when ?
> Bob Stuart of Meridian has presented a more nuanced view.
** More ambiguity Bill. "Nuanced" = what ? Quirky ? Hypothetical ?
BTW The people you quote have vested financial interests - best leave
them out of a sensible discussion.
> > > > though you can get them down to the level where they are
> > > difficult to detect, let alone hear - the driver stage is always going
> > > to have to slew through a few more volts than the output, so there is
> > > always a non-linearity around the zero current output, though you can
> > > smear it out quite nicely.
> > ** Lateral mosfets self bias at around 120 mA so you have class A
> > operation typically up to 200 mW or so with a 8 ohm load - this equals
> > listening level of around 80 dB SPL. Any crossover non-linearity
> > above this level and measures around -80 dB to - 90 dB compared to the
> > output. That puts it below the hearing threshold.
> I think Bob Stuart was arguing back in 1991 - in the context of
> digital audio - that the hearing threshold could and did get below
> that level in certain, rather specific circumstances.
** So what ?
There is *no way* it is audible with the masking effect of the wanted
signal at 80 dB SPL.
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