Digmoda DSP Amplifier Line

July 1 2015, 05:00
KSC Industries, based in Chula Vista, CA, has been a leading multinational producer of high-quality audio products for more than 30 years. KSC’s Digmoda line of DSP programmable digital amplifiers and D-Pro software was originally featured in Voice Coil’s July 2008 issue.
Photo 1: Digmoda DDC Series with D-PRO GUI software

Digmoda is a series of OEM platforms consisting of digital amplifiers, DSPs, and power supplies designed specifically for audio applications. The platforms are modular in design and easy to configure to meet a wide range of requirements. In 2013, Digmoda released the Digital Power (DP) line of new price competitive subwoofer plate amplifiers. The DP line consists of two new software programmable amplifiers, the DPSW300 and DPSW1000, along with newly developed DSP software for these units.
Current Digmoda DDC Series amplifier models continue to use KSC’s proprietary DSP engine and D-Pro GUI software that programs the DDC Series amplifiers (see Photo 1). Also available for the DDC series, Digmoda developed a manufacture customizable version named D-Pro Control. D-Pro control enables end-users with access to only the specific DSP features the manufacturer determines (e.g., the adjustable compressor/limiter).
Photo 2: Digmoda DPSW300 and DPSW1000
are the same size and have the same controls and
input and output connectors. They are available in
115 or 230 V.

Similar to D-Pro Control software, the new DP Control software provides complete user programming of the DSP functions in the new DP subwoofer amplifier line. Designed to program all DSP features using fewer menu selections and less mouse clicks, it is both Mac and PC operating system compatible. As with the D-Pro GUI and D-Pro Control software, DP Control software communicates to the DSP engines via a USB cable.

The new DPSW300 and DPSW1000 models use high-efficiency, full-bandwidth, 20-Hz-to-20-kHz Abletec (i.e., the DDC series using Ice Power Class-D amps) Class-D amplifier modules (with patented technology for enhanced audio quality) and a newly developed KSC-proprietary DSP engine design (see Photo 2).

The DPSW300’s power output is 300 W, and the DPSW1000’s power output is 1,000 W with less than 1% THD driving a 4-Ω load (see Figure 1 and Figure 2). The signal-to-noise ratio is greater than 100 dB. Plate dimensions for both the DPSW300 and DPSW1000 are 12” high × 10.25” wide, mounting depth is only 3.5”, including the speaker wires. An external volume control, a power switch, an IEC cord connector, a 12-V trigger jack, and a switch for selecting the turn-on options (i.e., 12-V trigger and Auto On or On) are located on the DPSW300 and DPSW1000 amplifiers’ amp panels.

These subwoofer amplifiers accept balanced or unbalanced input connections. Stereo XLR and RCA connectors are revised to make cable connections. A pair of wires on the back of the amplifier connects the powered subwoofer output to the subwoofer driver. Line level filtered output signal connections for full-range powered speakers are made using left/right XLR and RCA connectors. The combination of a powered subwoofer with programmable left and right high-pass filtered line-level output channels makes these amplifiers with built-in user programmable DSP ideal for use as a 2.1 satellite/subwoofer system with powered satellite speakers (e.g., typically studio monitors).

The new DPSW300 and DPSW1000 subwoofer amplifiers are “cURus” and “CE” (recognized component markings by UL for North America and Europe) and electromagnetic capability (EMC) compliant for the Federal Communications Commission (FCC) and European Conformity (CE), making the task of getting system approvals much easier and with lower agency costs.
Figure 1: THD versus Power, 4-Ω load, for the DPSW300
Figure 2: THD versus Power, 4-Ω load, for the DPSW1000

The DP Control software gives the user access to a comprehensive set of controls for fine tuning the subwoofer/satellite system, while keeping things simple, organized, and easy to use. Everything needed to tune the system is accessible from the main screen, which is divided into two areas. The screen’s top half shows a plot area used to display transfer functions and import frequency-response curves.

The bottom half has several tabs that provide quick access to each channel’s EQ, level, polarity, and delay settings. In addition, there is a “system” tab that has controls for crossover and miscellaneous functions.
“Mute” controls are provided to enable simple testing and troubleshooting of individual channels. DP Control software will load frequency-response files from most analyzers that contain frequency, magnitude, and phase data (e.g., LMS, MLSSA, AP, Clio, SoundCheck, etc.). When raw driver response data is imported, the combined filter and driver response curve showing a simulated response curve of the actual measured response is displayed.

As with the DP-Pro software, DP Control software provides control of a variety of features including: crossover filters, EQ, level, delay, mute, polarity, and limiter. Crossover filter types are selected in the “system tab” and they are comprised of fourth- or eighth-order Linkwitz-Riley-type filters. “Flat” or first-, second-, fourth-, or eighth-order Butterworth-type filters for crossover design are available (see Photo 3). “Muting” of any channel or all channels is a button click away.

Settings for the “Auto” mode activation time can also be changed in the software. Selecting the “SUBWOOFER,” “LEFT,” or “RIGHT” tabs displays the filter fields for these channels. Double clicking the text field in the filter section activates that field and the data it contains or, if available, displays a drop-down filter selection list. Each of the 10 filter positions has four possible filter types.

These are “FLAT” (no filter), “Bass-shelf” (BSHLF), “Treble-shelf” (TSHLF), and “Parametric EQ” (PEQ).
Selecting the PEQ filter activates the “Q” field for additional control of the filter shape (see Photo 4).
The channel’s “Level,” “Delay,” and “Polarity” can also be adjusted by a click of the “Normal” button (see Photo 5).

Once your crossover filters and settings are complete, selecting the “File” menu enables saving settings using “Saved to Disk” in the “File” menu. Settings can be loaded later by selecting the “Load” menu. Selections that exist in the “File” menu are: “Create New Design,” “Load from Amplifier,” “Save to Disk,” “Save to Amplifier,” “Reload Factory Settings,” and “Revert to Last Saved.”
Photo 3: DP Control’s main screen shows classic filter function selections.
Photo 4: Left and right tabs contain up to 10 filter locations and seven filter types.
Photo 5: The subwoofer tab also contains up to 10 filter locations and seven filter types.

The new DP Control software and subwoofer products are impressive and easy to use. It is also interesting to note that DP Control is always running in live update real-time mode so any change in the software immediately transfers to the DSP. This feature enables you to make sonic changes in the crossover while listening to music or noise sources.

However, changes made in the DP Control software are not permanent in the DSP until you select “Save to Amplifier” in the “File” menu. This enables the DSP’s new power-up state, or you can always “Load from Disk” a saved file or “Reload Factory Settings.”

This article was originally published in Voice Coil, January 2013

An update was published here.
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