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From: firstname.lastname@example.org (carltons)
Subject: Re: Output Impedence
References: <3DB97CF0.1682A5C0@gv.net> <3DBACD20.9BD49213@rica.net>
User-Agent: NewsWatcher-X 2.2.3b2
NNTP-Posting-Date: Sun, 27 Oct 2002 00:03:42 GMT
Date: Sun, 27 Oct 2002 00:03:42 GMT
In article <3DBACD20.9BD49213@rica.net>, John Popelish
> carltons wrote:
> > A good, modern audio amp is designed as a voltage source. Its output
> > impedance is extremely low and is exactly where it should be. This is
> > achieved through very high gain in the amp with no feedback and a
> > controlled gain with feedback. Conjugate matching of the output is
> > downright silly in most applications. Modern amps drive their speakers in
> > complete sync with the incoming signal, that is, the output SPL out of the
> > speaker matches the incoming signal level. There is no "boinga boinga"
> > under-damping like you get with a tube amp. If you want under-damping to
> > colour your music, don't use a good amplifier, get a 6L6 and pay through
> > the nose for something that you can do with a DSP. BTW, I was designing
> > circuits using 12AX7's and 6L6's in 1962, so don't give me the flame for
> > being anti-firebottle.
> Of course, you can load the output till the signal drops 2% and take
> the output impedance as 1/49 of the load resistance that caused that
> droop and not risk much.
Just out of curiousity, I wonder if the circuit designer considers if the
customer will try to match his output impedance? I would say under most
circumstances that the finals would probally explode due to the current
demand at the mid rail bias level. Anyone not seen secondary breakdown
first hand? How about a Rds on of zero ohms due to metal to metal
migration? Life is no fun without expensive solid state devices lying
around dead due to burn out.
Oh yeah! It's fun to watch a 6L6 arc over at a KV of B+ :-)
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