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What is AU?

Sun AU is the native audio format for Sun Microsystems workstations, using simple mu-law encoding or uncompressed PCM.

What is AAX?

AAX (audio/x-aax) uses lossy compression optimized for audible audiobooks, digital spoken word. Audible Audiobook, encrypted AAC audiobook format

When Should You Use AU vs AAX?

Use AU When...

For legacy unix audio, sun workstation sound, nothing beats AU. It sets the standard for quality, trusted by professionals who cannot afford compromises.

Use AAX When...

AAX is built for audible audiobooks, digital spoken word. Think of it as the practical workhorse — small files, big compatibility, no fuss.

AU vs AAX: Key Differences

  • •AU and AAX diverge on compression: lossless compression for the source, lossy compression for the target.
  • •Converting from AU to AAX changes compression type: lossy source becomes smaller but with some quality tradeoff.
  • •How transparency is handled: AAX does not support alpha channels — transparent areas in the source will become opaque.
  • •AAX files tend to be differently sized than AU
  • •AU is optimized for legacy unix audio, sun workstation sound while AAX is designed for audible audiobooks, digital spoken word — choose based on your specific workflow needs

Advantages of AU

  • ✓AU compresses data using lossless methods, keeping file sizes manageable for Legacy Unix audio, Sun workstation sound.
  • ✓Industry-wide support means AU files open anywhere — from legacy systems to the latest devices.
  • ✓Lossless quality makes AU the gold standard for archival and master copies.
  • ✓From professional software to open-source alternatives, AU works out of the box.

Advantages of AAX

  • ✓AAX uses lossy compression tailored for Audible audiobooks, digital spoken word.
  • ✓AAX is supported natively on virtually every device, browser, and operating system.
  • ✓AAX files are compact and quick to transfer, even over slow connections.
  • ✓AAX integrates seamlessly with all major creative tools and workflows.

Common Use Cases for AU to AAX Conversion

  • Podcast distribution
  • Voice recordings
  • Streaming services
  • Audio books
  • Sound design
  • Language learning

Industry Applications

PodcastingBroadcastingAudio EngineeringLanguage LearningAccessibilityVoice-over

Best Practices for AU to AAX Conversion

  • →Converting AU to AAX: AAX preserves full audio fidelity — ideal for archiving master recordings
  • →Normalize audio levels before conversion for consistent playback volume
  • →AAX excels in professional audio workflows
  • →Always keep a backup of your original files before converting
  • →Choose the appropriate quality settings for your specific use case

Related Article

Video Compression Guide: Reduce File Size Without Losing Quality

Learn more about AU and AAX formats in our detailed guide.

Troubleshooting AU to AAX Conversion

  • !Clicks or pops in the converted AAX → sample rate conversion can introduce artifacts; use a clean multiple of the source rate
  • !AAX file has silence at the beginning or end → trim the source AU file before converting to avoid unnecessary padding
  • !Stereo image collapsed after converting AU to AAX → verify that the converter preserves channel mapping for multichannel audio
  • !The converted AAX clips or distorts at peaks → reduce the gain or apply a limiter before conversion to prevent hard clipping

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Convert AU to AAX Online - Free & Fast

Convert AU files to AAX online for free. High-quality conversion with no registration required.

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.au,.AU (max 100MB)

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About AU and AAX

AU

AU (AU audio) - Sun AU, legacy Unix audio format for Sun workstations. Best for legacy unix audio, sun workstation sound.

AAX

AAX (AAX) - Audible Audiobook, encrypted AAC audiobook format. Ideal for audible audiobooks, digital spoken word.

Format Comparison

CompressionLossless → Lossy
TransparencyN/A
Use CaseConvert from legacy unix audio, sun workstation sound to audible audiobooks, digital spoken word
File Size~Standard file sizes after conversion

FAQs

Is converting AU to AAX free?

Yes, GoConvertFile offers free conversion of AU to AAX for files up to 100MB. No registration required.

How long does it take to convert AU to AAX?

Most AU to AAX conversions complete within seconds for standard-sized files. Larger files may take longer depending on the conversion complexity.

What is AAX best used for?

AAX is ideal for audible audiobooks, digital spoken word. Audible Audiobook, encrypted AAC audiobook format

Does converting AU to AAX lose quality?

Yes, converting AU to AAX uses lossy compression, which reduces file size by discarding some visual data. Set quality to 85-95% for a good balance of quality and file size.

What file size should I expect after converting AU to AAX?

AAX files are typically 50-80% smaller than AU files because AAX uses efficient lossy compression. The exact reduction depends on quality settings.

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