Software dbx-II|Disc Compatible Compander

Deeper optimal result can be achieved by using the fine-tuning tools that come with the software, as specified below:

• Dual-meter: visualizes potential risks of dynamic-range overload or underload, with adjustable means for instant correction


• Play Trim: compensates for signal degradation with aged pre-recorded tapes.


• Azimuth Correction: a limited-effect tool for remedying slight phase displacement and high-frequency loss caused by the azimuth error of the playback head.


• Gap-Loss Compensation: a limited-effect tool for counteracting slight playback head wear.


• EQ Converter: a utility for converting between IEC 120μs and 70μs EQ schemes, offering flexibility when the tape player/recorder lacks this option.


• Ref. Tone Generator: offers 400Hz 0dB signal at Dolby Reference Level for easy calibration.


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

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:

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. 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.

Minimum System Requirements:
Mac: macOS 10.10 (Yosemte) or later
PC:  Windows 10 v1703 (build 15063) or later

How to Install:
The software is being distributed via App Store or Microsoft Store.
The best way to download and install the app is to use the OS built-in "Store" app (such as "App Store" on macOS or "Microsoft Store" on Windows 10+). A registered user account with Apple or Microsoft will be required to start. Although a transaction can be finished outside of the Store, e.g.: via a Web browser, the actuall download/install should be completed by using the OS built-in "Store" app. So, it is recommanded to do all the procedures by using the "Store" app.

How is the software compared to analog hardware?

It depends on which direction the audio is going to be transferred between analog(A) and digital(D). Basically, analog hardware is good for A to A, digital software is good for D to D, and both are ok for A to D or D to A. But there are always more details...

Analog hardware was the native form of the dbx-II/Disc system. However, analog circuits were not very good at implementing this so-called "linear-decibel" compander. Transistors have to operate in the nonlinear region to achieve the desired logarithmic/exponential behaviors, which is a rather narrow, unstable and individually different operating region. So, an analog dbx-II/Disc hardware device usually requires maintenance on a regular basis. Or otherwise, 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.

Contrastingly, DSP (Digital Signal Processor, including computer) is particularly good at logarithmic/exponential operations. The numeric algorithm can achieve superior precision and lower distortion than analog hardware without needing compensations, adjustments and periodic maintenance, but with the gifted digital advantages such as zero new noise, mathematical accuracy, wider dynamic range at much lower cost. It will consistently stay in the known working condition.

On the other hand, DSP may never "upgrade" the dbx-II/Disc system beyond its established standard. Instead, a successful DSP emulator will be the one that best imitates the analog prototype by specifications. Therefore, the DSP engine in this app is designed with full respect to the original analog system's topology, with the same frequency weighted 2:1 commanding ratio, and with a true RMS level detector with the same capacitive timing characteristic, even not attempted to "fix" the inherent side-effects such as "breathing" and intermodulation.

The software app can be used for digitizing dbx-II encoded audio tapes or LP records, or recording dbx-II encoded audio tapes from digital audio files, as well as used as an external (outboard) dbx-II/Disc unit in realtime, or an offline dbx-II/Disc post-processor for file-to-file decoding/encoding.

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..

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