12
Macro-T
ech Advanced
Features
The Macr
o-T
ech Series employs a number of innovative, patented
technologies. Let’
s look at them in detail.
IOC
®
(Input Output Compar
ator)
The IOC cir
cuit compar
es the output signal of the amplifi
er with
the input signal. If ther
e is any dif
fer
ence other than gain, then it
is consider
ed distor
tion and the IOC indicator fl
ashes. This LED
lights whenever ther
e is distor
tion of 0.05% or mor
e. (Note that
amplifi
er clipping is typically close to 3% THD.) An IOC condition
also is sensed by an IQ-PIP module installed in PIP-compatible
amplifi
ers.
IOC is designed to r
epor
t any for
m of distor
tion. IOC not only
checks the wavefor
m for distor
tion, but also r
epor
ts input
overload and even a pr
otective action that mutes or shuts down
an amplifi
er
. With all of these featur
es, IOC monitors the entir
e
amplifi
er
. When the IOC indicator is of
f, the amplifi
er is defi
nitely
operational and undistor
ted. IOC pr
ovides a r
eal-time pr
oof of
per
for
mance.
Output De
vice Em
ulation Protection (ODEP)
Gerald invented ODEP to solve two long-standing pr
oblems with
amplifi
er
designs:
•
Pr
eventing amplifi
er shutdown during demanding operation, and
•
Incr
easing the effi
ciency of the output transistors.
ODEP limits the signal when necessar
y to pr
event overheating
and failur
e of the amplifi
er output transistors. Cr
own engineers
established a rigor
ous pr
ogram to measur
e the safe operating
ar
ea (SOA) — r
elated to temperatur
e — of each output transistor
befor
e installing it in an amplifi
er
. Gerald also designed intelligent
cir
cuitr
y to simulate the instantaneous operating conditions of
those output transistors. Its name describes what it does: Output
Device Emulation Pr
otection or ODEP
. It not only simulates the
operation of the output transistors but it also compar
es their
operation to their known SOA. If mor
e
power is about to be asked
of the output devices than they ar
e capable of delivering under
the pr
esent conditions, ODEP immediately limits the drive level
until it falls within the SOA. Limiting is pr
opor
tional and kept to
an absolute minimum — only what is r
equir
ed to pr
event output
transistor damage.
When ODEP limiting begins, the IOC cir
cuitr
y will see that the
input wavefor
m does not match the output wavefor
m, and an err
or
signal is generated. If the compr
essors ar
e on, they will see the
err
or signal and compr
ess the input signal to corr
ect the pr
oblem.
When this happens, ther
e is no audible signal degradation.
Compr
ession is subtle, and not noticeable unless the system is
driven to extr
emely high levels.
How does ODEP limiting incr
ease the effi
ciency of the output
transistors? It keeps them at the optimum temperatur
e.
The transistors ar
e neither overheated, nor overpr
otected.
Overpr
otecting r
esults in transistors not being driven to their full
output level.
In shor
t, ODEP enables the amplifi
er to use the output transistors
mor
e effi
ciently while gr
eatly incr
easing their r
e
liability
.
Finally
, the status of ODEP is monitor
ed in two ways. First, the fr
ont
panel ODEP indicators show whether the amplifi
er is functioning
corr
ectly or if ODEP is limiting the drive level. Second, ODEP data
is fed to the PIP connector at the back of the amplifi
er so advanced
One of Ger
ald Stanle
y’
s man
y patents
.
