17
•
1971: Gerald Stanley invents Gr
ounded Bridge topology
.
•
1974: Gerald invents Junction T
emperatur
e Simulation (JTS).
•
1975: M-600 was the fi
rst amp to use Gr
ounded Bridge. SA-2
and PSA-2 fi
rst used JTS.
•
1984: MT
-1000 was the fi
rst combination of Gr
ounded Bridge
and JTS, and Cr
own’
s fi
rst amp intended for the MI and
Touring Sound markets.
•
1985: MT
-1200 was a higher power version of MT
-1000. MT
-
600 also was r
eleased. MT
-1200LX and MT
-600LX had a fancy
extruded fr
ont panel and mor
e displays.
•
1986: MA-10K pr
ovides 10,000 watts of power
. The fi
rst MA-
10K application is to power 465 speakers at the Indianapolis
500 Motor Speedway
.
•
1987: MA-1200 and MA-600 (with PIP panels).
•
1991: MA-3600VZ featuring V
ariable Impedance (VZ) bi-level
power supply switching. VZ technology was fi
rst pr
ototyped
in an MA-1200. The fi
rst bi-level amps wer
e MRI units custom-
made for Picker
.
•
1992: MA-5000VZ also featur
es V
ariable Impedance.
MA-3600VZ and MA-5000VZ quickly become the touring
standar
ds. MA-24x6 and MA-36x12 for bi-amping ar
e
intr
oduced.
•
1999: MA-602, 1202, 2402 and MA-5002VZ.
Crown Amplif
iers T
ime
Line
VZ theor
y f
or electr
onics-sa
vvy reader
s
VZ of
fers a simple way to apply Class-H operation to a
Gr
ounded Bridge cir
cuit. Class H changes the power
supply voltage fr
om a lower level to a higher level
when larger output swings ar
e r
equir
ed. Class H also
modulates the higher power
-supply voltage by the input
signal. This allows the power supply to track the audio
input and pr
ovide just enough voltage for optimum
operation of the output devices.
The Gr
ounded Bridge has a par
ticularly simple supply
needed for Class H in that only one supply needs to be
rail switched, wher
eas a common half-bridge (totem-
pole) output stage needs two such switched supplies
per channel. The bi-level (VZ) supply is fur
ther elegant
in that the power supply is always fully utilized in both
high- and low-voltage confi
gurations. No segments of
the power supply ar
e wasted.
Amp room at SooY
oung Ro Church in Pusan, South K
orea.
