DxI Codec is a modern digital equivalent of the traditional dbx-I noise reduction system for RtR (reel-to-reel) analog audio tape. The software is capable of decoding/encoding dbx-I formatted audio in digital domain without needing a dedicated analog hardware decoder/encoder. Benefiting from the proprietary DSP engine and the concise GUI, the task can be accomplished in realtime with intuitive user interaction, or more swifty with the batch processor.

The software is able to adapt to different tape EQ standards. The built-in dedicated converter can easily translate audio material between CCIR/IEC1 and NAB/IEC2 specifications at different tape speeds. Aided by this converter, EQ mismatch is no longer a problem. It also allows a single-standard RtR machine being virtually used as a dual-standard one.

Dynamic range (DR) mismatch is another caveat in using high-ratio companders like dbx NR, which includes potential DR underload in compressing process and the potential DR overload in expanding process. The concern is addressed by the app with a novel dual-meter display that visualizes the potential DR mismatch, along with a threshold slider for instant correction.

As a new digital re-implementation of dbx-I NR, the software allows the traditional dbx NR encoding/decoding tasks to be able to benefit from the gifted digital advantages, such as: zero new noise, mathematical accuracy, maintenance-free and very low cost. The digital codec's tracking speed is also adjustable for some special needs, such as decoding an audio material that was pre-encoded by a drifted hardware dbx encoder. However, the software is not made as an upgrade of the original analog dbx-I system,instead,being as closer as it is. The digital engine is designed with full respect to the original analog system's topology with the same 2:1 pre-emphasized compression and the same 1:2 de-emphasized expansion which are 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-I 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 archives (D2D), the software will make impossible possible.

DxI 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-I/Disc compatible unit in one of the following four modes:

- from Audio-In to File (a digitizer/recorder).
- from File to Audio-Out (a player).
- from File to File (an off-line processor, with batch capability).
- from Audio-In to Audio-Out (a through 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.

A VST plugin is also available as an optional software component of the application.

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

Please note that this software is suited for the Pro grade dbx type-I on reel-to-reel tape, which is not compatible with the consumer grade dbx type-II on cassette tape. However, it does come with an additional dbx type-Disc codec, which is suited for LP records.

What’s New

Version 2.3.0

Updated the embedded user's manual.
Added instruction about VST plugin.


Chen Wang
1.5 MB

OS X 10.10 or later, 64-bit processor



Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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