TIP: Click on subject to list as thread! ANSI
echo: pro_audio
to: TERRY SMITH
from: LASZLO SOKOLAI
date: 1996-02-15 20:43:00
subject: Re: big, big, big sound!

TS > TS > LS> As you know, or should know, the impedance of a
TS > TS > LS> speaker is a reactive load, never stays at one
TS > TS > LS> impedance.  I could visually see that happen over the
TS > TS > Unless you defeated normal AC line protective devices, how TS > did
TS > you sustain 100 amperes?
TS > LS> Simple, plugged the amp into a 25 ampere 120 volt plug, 120 volts
TS > dipped
TS > LS> to 90 volts, and that's what i measured using an
TS > LS> ammeter in parallel with a 8 ohm speaker.  The
TS > Sounds like you need better building wiring.  Ammeters are
TS > series devices BTW, unless they're AC current transformers
TS > (amprobes) or DC hall effect transducer instruments.  If
TS > you connect an ammeter in parallel with a driver, you
TS > likely have a near short load from an ammeter shunt with
TS > little current to the driver.
I meant amp in parallel with 8 ohm speaker, and the ammeter in between the 
two.
The building's wiring is ok, except for line losses from the 6 guage wire 
they feed the house on AFTER i installed the proper 0/3 cabling on my 200 
ampere meter feed.  Still hydro insists on using 6 guage from the pole to the 
house.
TS > LS> speaker did not like it, i measured 167 volts at 100
TS > LS> ampers into the speaker.  I noticed amps are getting
TS > If you mean 100 amps at a fractional ohm shunt impedance,
TS > and 167 volts with no load or an 8 ohm speaker, those are
TS > NOT numbers which can be simply multiplied to calculate
TS > real power.  Still, 100 amps sustained long enough so that
TS > an ordinary ammeter could read it represents a LOT of power
TS > for an audio amp.  167 volts RMS into 8 ohms would yield
TS > nearly 3500 watts, or 435 watts if peak to peak.  100 amps
TS > into a 0.05 ohm shunt would yield 500 watts, but represent
TS > healthy reserves to deal with driver reactance.
Well, i used the ammeter in series with the drivers.  The current went up 
when i dropped the impedance to 4 ohms, but the voltage from the amp stayed 
steady and slow even when the line cord voltage took a nosedive.
TS > LS> very efficient, 75 percent efficiency rating is on
TS > LS> all my amplifiers with this class AB dual rail system.
TS > It would be hard to spec meaningful efficiency on such a
TS > design without the context of the measurement conditions,
TS > as it would be highly variable.
Yes, i figured that much out talking to an amplifier company named Mark 
Levinson and Krell.  Class A/B has distortion which i did not know about 
until now.  The distortion between the puch pull rails known as crossover 
distortion when the transistors are not working to their linear maximum.
Laszlo Sokolai
Team ANTI-Windows95/PRO-OS2/PRO-UNIX/PRO-XENIX/PRO-DOS
lsokolai@bbs42.com
lsokolai@albedo.net
lsokolai@roxanne.bbs42.com
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