SECTION I
INTRODUCTION
The JBL Model 6230 and 6260 power amplifiers have been
designed to meet the most critical professional sound
requirements. They are rugged and road-worthy, conservatively
rated, and can handle reactive loads with ease.
The engineering design approach stresses the optimization of
each stage, allowing high slew rate and relatively low loop gain.
Overall feedback has been held to aminimum and is employed only
to stabilize the gain and the operating point. This design
approach results in amplifiers with excellent performance under
the most demanding dynamic input and load conditions. As
evidence of the stress on dynamic rather than static or steady-
state distortion mechanisms, transient intermodulation distortion
measures less than 0.03% by the DIM 100 test. (Leinonen, Otala,
and Curl, "A Method for Measuring Transient Intermodulation
Distortion (TIM)", Journal of the Audio Engineering Society ,Vol.
25, No. 4, April, 1977, pp. 170-177.)
The front panel and heat sinks of the amplifiers are made of
heavy aluminum extrusions; the chassis is fabricated of heavy
gauge steel. All internal components are easily accessible
through removal of top and bottom panels. Front panel graphic
details are incorporated on the rear side of apolycarbonate
laminate which is virtually indestructible.
JBL amplifiers use multiple 200-watt output devices in
complementary configuration for high reliability and low distor-
tion. At rated power into 8ohms, these output devices are
operated at less than 25% of their rated power dissipation. The
benefit is high reliability and long component life.
Failsafe operation of these amplifiers is ensured through
the following protection modes: Current is limited under
improper load or drive conditions. An output relay, with front
panel LED indication, protects the loudspeaker load under cond-
itions of DC offset or large low-frequency transients. The relay
also provides power-up, power-down, and "brown out" muting to
protect loudspeakers from AC power transients generated anywhere
in the signal path. LED's on the front panel indicate the onset
of clipping and standby mode.
The JBL amplifiers may be operated in the normal stereo-
phonic mode, dual monophonic mode, or bridged monophonic mode.
Rear panel switching sets these modes, obviating the need for
patch cords, level matching, etc.
Active differential input circuitry offers the benefits of
balanced operation without the use of input transformers. Input
connections may be made via 3-pin XL-type connector, three-cond-
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