Software dbx-II|Disc Compatible Compander

  DxII Codec is a modern digital equivalent of the traditional dbx-II/Disc system which was one of the outstanding analog audio tape/LP noise reduction systems. The software is capable of decoding/encoding dbx-II/Disc formatted audio in digital domain with ease, quality and efficiency. Benefiting from the proprietary DSP engine and the GUI (graphic user interface), the process can be accomplished in realtime with intuitive user interaction.
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Deeper optimal result can be achieved by using the advanced tools coming with this software which was not available elsewhere with the traditional analog hardware, as specified below:

  • The dual-meter display visualizes potential risks of dynamic-range overload or underload, with adjustable means for instant correction.

  • The Azimuth and Gap-Loss tools can compensate minor imperfection of analog tape player used for digitizing audio tapes.

  • The Play Trim is another tool for compensating weakened signal on aged pre-recorded tapes.

  • The EQ Converter offers digital translation between 120μs and 70μs IEC tape equalization standards — if such a flexibility is not found on a given tape player/recorder.

  • The RMS timing slider offers optional flexibility to adjust the compander's tracking speed.

  • The built-in tone generator offers 1kHz 0 dB Reference Level signal for easy calibration.
Most of the fine-tuning tools can work independently of the dbx-II/Disc codec, which can also be applied for refining non-dbx formatted audio.

DxII Codec is a stand-alone GUI app without relying on any other DAW host. It allows the computer to serve as an external(outboard) dbx-II/Disc unit in one of the following four modes:

Input Output Comment
Audio In File a digitizer/recorder, with dbx-II/Disc codec
File Audio Out an audio file player, with dbx-II/Disc codec
File File an off-line dbx-II/Disc processor, with batch capability
Audio In Audio Out an on-line dbx-II/Disc processor, with slight delay

Currently supported audio file formats are:
WAV, FLAC, AIFF: up to 96k/24bit.
MP3, AAC, M4A: up to 48k/VBR.
* Excluding some proprietary variants having the common file extensions, or additional format-normalization may be required.

The software comes with embedded user manual on each major functions.

A VST plugin is also available as an optional software component of the application. However, it is currently in experimantal stage and requires the full application being installed on the same computer.

Please note that this software is suited for the consumer grade dbx type-II or type-Disc, which is not compatible with the professional grade dbx type-I.

  Audio Demo #1 (Jazz)
Audio Demo #2 (Symphony)
Audio Demo #3 (Drum & Beat)

Software vs. Hardware?


It depends on which domain the audio is to be processed — analog(A) or digital(D)? Basically, traditional hardware is good for A2A, the new software is better for D2D, and either are ok for A2D or D2A. But there are always more details...

The outstanding noise reduction performance of dbx-II/Disc system is based on so-called "linear-decibel companding", which was a rather high challenge for analog hardware to precisely implement because "linear-decibel" is essentially logarithm/exponent in the practical form. Transistors have to operate in nonlinear region to obtain the desirable logarithmic-/exponential-like behavior, which is a rather narrow, unstable and individually different region. The same challenge also extended to the dedicated dbx IC chips which integrate many transistors on a wafer. Therefore, an analog dbx-II/Disc hardware unit normally requires fine compensations, adjustments and maintenance with pro equipments and experiences. The factory calibration may drift over long time and the original design spec (100dB dynamic range with < 0.5% THD) may not always be guaranteed.

In contrast, DSP (Digital Signal Processor, including computer) is particularly good at implementing "linear-decibel" type of audio companders including dbx NR. The numeric algorithm can achieve higher precision and lower distortion than analog hardware without needing compensations, adjustments and regular maintenance, but with gifted digital advantages such as zero new noise, mathematical accuracy, wider dynamic range and much lower cost. It will consistently stay in known working condition. Unlike typical analog dbx-II/Disc hardware which had fixed tolerance in co-working with tape/player/recorder, this software is able to collaborate with imperfect partners by providing additional compensations in azimuth/gap-loss/play-trim/EQ for better overall performance.

However, the software is not made as an upgrade of the original analog dbx-II/Disc system,instead,being as closer as it is. The digital engine is designed with full respect to the original system's topology with the same 2:1 pre-emphasized compression and the same 1:2 de-emphasized expansion and controlled by the true RMS level detector with the same capacitive timing characteristics, even not attempted to "fix" the inherent side-effects such as "breathing" and intermodulation. It is just a new digital alternative that can accomplish the same traditional work with modern technology, without unnecessary improvements or compromises. For those who are transferring audio contents across the analog(A)/digital(D) border, the software is suitable for digitizing legacy tapes (A2D) or recording new tapes from bitstream (D2A). In case a dbx-II/Disc analog hardware unit is temporarily unacquirable or degraded, the software can serve as a similar role if double D/A A/D conversions are acceptable. And finally in dealing with pure digital archive (D2D), the software will make impossible possible.


Audio Demo #1 (Jazz)
Audio Demo #2 (Symphony)
Audio Demo #3 (Drum & Beat)

dbx-II and dbx-Disc are the tape noise reduction systems developed by dbx Inc..

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Frequently Asked Questions (FAQ) Contact:

See also:
DDi Codec (for Dolby-B/C)
DxI Codec (for dbx-I/Disc)
NAK T-100 (Audio Analyzer)