3
The Charge-Coupled Topology
The “charge
-
coupling” technique was first employed on JBL’s K2 S5500 loudspeaker system by
Chief Engineer Greg Timbers and was used subsequently on all high
-
end JBL Synthesis models,
including the top
-
of
-
the
-
line Everest DD66000. The technique involves replacing a given capacitor
in a crossover topology with two series capacitors of twice that value (this series combination is
equivalent to the original value), with a DC bias injected between the two capacitors through a
large value resistor. This DC
-
biased topology mitigates the effects of dielectric absorption and
the distortion associated with a change in the direction of current as the input signal transitions
from positive to negative (i.e., zero crossing). The theory of operation is explained in detail in the
following excerpts from the K2 S5500 product overview:
http://www.lansingheritage.org/images/jbl/specs/home
-
speakers/1993
-
k2
-
s5500/page10.jpg
http://www.lansingheritage.org/images/jbl/specs/home
-
speakers/1993
-
k2
-
s5500/page11.jpg
http://www.lansingheritage.org/images/jbl/specs/home
-
speakers/1993
-
k2
-
s5500/page12.jpg
What You’ll Need
To complete the project build, you’ll need the items listed below. Links for each item are
provided to the recommended items/brands we’ve used in our own builds, but feel free to use
what works best for you.
•
(2)
Echo Mountain Audio Model 4425 Crossover boards
•
4425 Charge
-
Coupled parts kit for Model 4425 from Solen
(see Parts Information
section and Appendix A for more details)
•
(2)
9V batteries
•
(2)
9V battery holder clips
•
(2)
9V battery connectors with flying leads
•
Zip ties
•
Soldering iron – The
PACE ADS200
is excellent, made in the USA, and what we use
•
Small, smooth
-
jaw (non
-
marring) pliers
•
Wire cutters
•
Wire strippers
•
Eutectic (Sn63/Pb37) flux
-
core solder – not lead
-
free! We use
Cardas solder.
•
De
-
soldering pump
•
Adhesive for staking large components (capacitors and inductors) to the PCB – we
highly recommend
Eclectic Products E6000 Clear adhesive
•
Heavy duty double
-
sided tape
