The Standard DCX2496
The Good:
The
DCX is a highly flexible digital crossover for loudspeaker builders or
live sound systems. It can accept stereo analog or digital inputs and
split the signal for tweeter, mid and woofer (or other configurations),
sending the signals to 6 analog outputs. Parametric EQ and adjustable
time delays are also possible, allowing correction of the speakers and
room. The adjustable crossover slopes allow more flexibility than
typical analog crossovers.
A Problem:
The features of DCX mentioned above are superb,
however there is an achilles heel; the analog inputs
and outputs have relatively high distortion compared
to the best alternatives.
The type of distortion that is poor on these units is
Intermodulation Distortion (IMD) which is not
specified in the Behringer manual. IMD can cause a
tiring and hard sound.
The solution - Modification
In
fact, the DAC and ADC chips inside the DCX are high-end items from AKM and
Cirrus Logic. Much of the music you listen to will
have been recorded using these same converters, as
they have been used inside audio interfaces from
industry leader ProTools.
The distortion of the
DCX is created by the analog signal conditioning circuits, not the
converters themselves. Unfortunately, simply replacing the op-amp chips in the
existing circuit does not correct the distortion issues.
To avoid replacing almost every
part in the existing circuits, the solution is simply to replace the analog
circuits in their entirety with something better.
Upgrade circuits
available from BehringerMods are offered as a self-install kit
and include a 'link PCB' that connects between the existing
ribbon cable to minimize install effort. Note that removal
of some parts and soldering is still required.
These new upgrade
circuits allow the signal converters in the DCX to
reach their full potential with low
distortion and noise of all types.
Upgrade Circuit -
The BehringerMods upgrade PCB conveniently handles
both analog input and output conditioning on a single
board for Inputs A,B and Outputs 1-6. Input C is not
modified.
The signal levels are changed to 2V rms full-scale,
matching well with domestic hi-fi equipment.
The input section is implemented using a fully
differential op-amp from Texas Instruments (OPA1632),
purpose made for driving audio ADC chips. The circuit
can be fed from either a single-ended or balanced
input. A dedicated voltage reference is used to
provide bias for the ADC, allowing for the lowest
possible noise level.
The output section is a 'floating balanced' design. It
can perform 'active ground cancelling' even when used
in single-ended systems.
The output circuit is
built around Texas Instruments 'SoundPlus' OPA1652
op-amps allowing the full performance of the DAC chip
to shine.
The circuit comes with DC
blocking and power smoothing capacitors from respected brand Panasonic.
The Behringer DCX when
modified with this new circuit is capable of less than
0.001% THD and IMD from analog input to output.
When used single-ended, Pin 3 must be
grounded, either to Pin 1 or the connected equipment.
Learn more about
the distortion types of the DEQ and DCX here:
Proof of Upgrade Performance
Short FAQ here.
Online Shop
|