Q5™ Upsampling

Q5 Upsampling allows digital audio signals from virtually any audio source to be resampled, resynchronized and retimed to extraordinary levels of detail. In effect, upsampling the digital data stream (up to 384kHz) allows existing “standard” CDs to have the enhanced audio clarity, richness and dynamic range that would normally be associated with SACD or DVD-A disks “upgrading” the tremendous investment that has already been made in high quality CD recordings. You may be astonished once you begin to hear what you have been missing!

With the proliferation of various digital audio formats the use of sample rate conversion in digital audio playback devices is becoming more and more common, although the arguments for doing this are not always clear. One argument often used is that upsampling improves the sound by easing the antialias filter requirements. Considering the fact that most high performance DACs have 128 times oversampling already, the relevance of this is highly questionable. So how does upsampling magically improve the signal quality, while in reality it is a lossy process. What is going on?

In the application of playback of digital audio in consumer audio devices, upsampling provides two principle benefits: good jitter suppression and format conversion. In the case of jitter suppression a well designed SRC, in this case Q5™, used together with a high-precision output clock can provide very good jitter performance, even with a jittery source. This improvement in sound quality due to the removal of jitter usually compensates for any errors introduced by the SRC. However Q5 goes that one step further with a level of THD+N being less than -144dB, meaning Q5 is the only asynchronous sample rate converter to be completely transparent for 24bit audio data. Furthermore by outputting 384kHz sampling frequencies the first stage of the cost optimized digital filters internal to high performance DACs can be bypassed, yielding a further improvement. No other software based sample rate converter on the market can match this level of performance while being implemented on low cost DSPs, hence a real improvement in sound quality is achieved.

As most modern digital audio players can play back a variety of digital sources ranging from CDs and DVD-A, the majority of the OEM-market want circuit boards that can convert the 44,1kHz CD-signal into the 96kHz of DVD or 192kHz of DVD-A. This allows the analog output stage of the Digital to Analog converter to be optimized for a single sampling frequency which is easy to achieve. On the other hand, when using a sample-rate-converter-less design, the analog output stage will be a compromise as it will have to be tuned for multiple sampling frequencies. As a result players with an ASRC and a 96 or 192kHz DAC have penetrated the audio market, and even most “pure” CD players now use this solution. Q5™ also goes one step beyond in this regard by not only supporting all standard PCM sampling frequency from CD to DVD-Audio, but also DSD 1-bit digital input from SACD. This unique feature, supplied by ANAGRAM's DSF™ Filtering technology allows Q5 to seamlessly integrate all audio formats in the system.

Finally Q5 is available on a low cost DSP, where as typical high performance sample rate converters are available only in hardware. This software based approach gives rise to systems that can be highly integrated, reducing BOM, and also that are field upgradeable that can be updated to newer sampling formats, all in all a greater level of scalability is achieved in this approach.