"Is Incredible - Only In Bit Perfect -
In Resampling Mode - Is Not
Please explain this part. "
Sample rate conversion (SRC) is a process by which audio's sampling rate gets changed without affecting the pitch of the audio. Generally, SRC is best done at even multiples, such as 22.05 KHz to 44.1 KHz, or 96 KHz to 48 KHz. However a common SRC task is moving audio between sampling rates of 48 KHz and 44.1 KHz, and this is a task Creative's 10Kx audio processors had trouble with. The crux of the problem is that much audio content is sampled at 44.1 KHz (an Audio CD's standard sampling rate), and the 10K's core had a locked sample rate of 48 KHz. That meant that two SRC operations were needed to get the audio in and out of the processor, not one, which would have been the ideal case.
In other words, incoming 44.1 KHz audio got converted to 48 KHz, some processing was executed, and the audio was then converted back down to 44.1 KHz as it left the 10K audio processor. The adverse result was higher intermodulation distortion (IMD) due to band-pass ripple, and Creative has taken some deserved knocks for the 10K's shortcoming in this area. But to its credit, Creative also took the problem to heart, and dedicated about 70% of the X-Fi's MIPS budget to SRC operations. The result? Creative has stated that it's measuring THD+N on a 44.1 KHz to 48 KHz SRC operation out of the X-Fi at around –136 dB, with +/-0.00025dB pass-band ripple (using a 997Hz test tone). "
The SRC block in the X-Fi is expressly designed to make SRC an essentially lossless operation. It's a hybrid design between fixed-function and programmable hardware, where you get the execution efficiency of highly optimized hardware, plus some flexibility to those operations via programmability.
The X-Fi's core can run at two internal sampling rates, 44.1 KHz and 48 KHz, although it will only run at 44.1KHz in Creation mode, and if you specifically tell it to do so -bit perfect -
Between the beefy SRC processing horsepower and the ability to run at 44.1 KHz or 48 KHz sample rates, Creative stated that the X-Fi's audio signal quality performance will essentially be ADC/DAC (Analog-to-Digital Converter/Digital-to-Analog Converter-limited). So, high-end products will likely be outfitted with better DACs, whereas entry level offerings will have more modest DACs
Here's where it gets interesting: The X-Fi has a Creation Mode that, when activated, will let the X-Fi process dry (no effects) 96KHz/24-bit content at its native resolution. So for example, if playing a DVD-Audio disc, you could switch to this Creation Mode and have a pure 96 KHz/24-bit signal path for your playback, provided you don't apply effects. However, the X-Fi still runs its effects engines at either 44.1 KHz or 48 KHz. It cannot run them at a sampling rate of 96 KHz, but Creative has implemented what's called band-splitting to be able to apply effects to 96 KHz/24-bit content.