TS > the largest of which I know in commercial production.
TS > Those use 3 phase power, and have a rated output Z of 0.67
 LS> Well, how well does the crown 10kw amp old up it's damping factor at 2 
 LS> ohms?. Alot of people i know run their amps at either 
I don't recall.  Note that it's rated at 2/3 of an ohm, not 8 ohms.  
Obviously they're good enough for the target customer mil contractors.  
 LS> amp's thermal lights come on.  But it does not double 
 LS> from it's 800w into 8 ohms to 1325 watts into 4 ohms 
 LS> then to 2,000 watts into 2 ohms per channel.  Bridged 
Every amp is optimized for some output impedance.  Most tube amps used to be 
actually impedance matched to their loads.  Most solid state amps are 
designed to be dynamic grounds, capable of sourcing or sinking infinite 
current.  That would make an ideal solid state amp operate almost as well 
into a 0.1 ohm load as into a 100 ohm load, though with calculable output 
ratios.  Between biasing and power supply costs, obviously that isn't true.  
The point in the range at which nominal power is spec'd, the general quality 
of construction, and the amount of degradation at either end of the range are 
what vary.  
IOW, some cheap consumer amp may be optimized at 16 ohms, rated at 8 per FTC 
standards, and usable but marginal at 4 ohms.  Many pro amps are optimized 
around 4 ohms, usable from 1 to 30.  
TS > The larger Stewart amp is about the biggest for which I see TS > a 
practical need in pro audio.  At 17 lbs. and 2 rack
 LS> 17 pound amplifier running bassbins?,  Does it have an 
 LS> external transformer or does it run directly off the 
 LS> 120AC without a toroid?
They had to be a little more creative than that.  It does rectify direct off 
the mains, though with SCRs triggered to only rectify a little more energy 
than it needs rather than run up full power supply capacity when idling.  It 
then uses a supersonic DC-DC converter which provides safety isolation from 
the mains, and can use a physically small toroid and filters due to the high 
frequency.  
10,000 W amp, 2 AWG welding cable would be TS > inadequate for speaker wire.
 LS> Depends on current gain.  I use cabling of no more 
Since when does copper wire have current gain?  
 LS> than 20 feet from the speaker of 8 AWG cable for the 
 LS> 100 sustained amperes per channel my largest amp can 
 LS> do without going into protect if a short circuit would 
 LS> happen (i've tried it, it melted the cable and dimmed 
#6 or 8 wire would likely survive.  #1 Cu would be required for that current 
under NEC if it were house wiring.  Allowable voltage drop under NEC 
translates to undesirable damping factor degredation for audio.  
I'd rather handle 5 runs of 8-2 than one run of two banded 00 rope lay 
welding cables.  Change to being a movie lighting electrician if you like 
whipping that stuff around.  
TS > Now for a really big audio amp, look at the modulator
TS > section of a high level modulated shortwave transmitter TS > sometime.  
Those can exceed 500,000 KW audio output for a 1 TS > MW TX.  (Let's just 
 LS> RF has no room in pro audio, unless you were talking about RF amps.
Do you have any concept of how a traditional shortwave transmitter is 
designed?  I did mention the modulator and audio output quite clearly.  
Facilities for broadcast are very much pro audio, to the extent that many of 
the pro audio trades have a user check off box for it on the card.  Shortwave 
is the only legal arena where it's possible to use the largest available 
tubes in an audio amplifier.  Using a single pair of non-custom catalog item 
tetrodes made by Eimac, it's possible to design a 2 megawatt audio amp 
(larger if you parallel tube pairs).  With operating headroom, that would be 
practical for a 2.5 MW transmitter emitting A3 modulation.  1 MW is the 
largest standard catalog item transmitter made without using parallel 
amplifiers.  
You could use it to drive speakers, but the 17,500 volt plates drawing 150 
amps might not be practical in the field, and the same arguments whereby 
several 1800 watt amps are more practical than singular larger ones driving 
speakers would also apply.  
BTW, in case you don't understand A3 (common AM), full modulation requires 
audio power equal to half the power of the RF carrier.  There are some newer 
solid state analog and digital designs through the 100 KW level, though most 
higher power gear still uses tubes at least for finals.  The traditional high 
level design uses an AB or B audio tube pair whose output modulates the B+ to 
one or two RF output tubes operated Class C.  
Terry
--- Maximus 2.01wb
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