X-Fi and the Elite Pro: SoundBlaster's Return to Greatness
by Derek Wilson on August 30, 2005 11:59 AM EST- Posted in
- Smartphones
- Mobile
The X-Fi Audio Ring: Powerful and Flexible
Putting aside marketing buzz words and the slightly tacky Xtreme Fidelity moniker, the new generation of sound cards from Creative Labs is quite impressive. The technological advancements come from the inclusion of four key new features: the ring based architecture, a high quality sample rate converter, a powerful DSP, and on-board RAM. First on the chopping block is the Audio Ring.
Another reason why Creative may have chosen to support so many internal channels is so that it can handle algorithms that call for splitting or duplicating an audio stream for multiple different types of processing and analysis. This could range from using CMSS-3D (Creative's new surround upmixing feature) to efficient implementations of complicated high order N-tap and feedback filters. Creative doesn't talk much about the uses of these internal channels, but many of their new features include detecting aspects of the audio being played in order to enhance the sound. It seems likely to us that the algorithms that implement their new features would rely on the high number of channels and the flexibility of the ring architecture to get as much done at one time as possible in order to keep from introducing an unacceptable amount of latency.
Now that we know how the ring works, here's what each node on the ring does:
Transport: This handles moving audio streams in and out of local RAM as well as over the PCI bus to system RAM. The Transport engine manages over 1000 DMA channels to both the PCI bus and local SDRAM. Being able to manage so many DMA requests at a time is important for dealing with the latency of PCI and effectively managing the volume of data with which the new solution is capable of working.
Tank: Its name is based on the tanks that held mercury used to create high quality analog delay lines. The tank engine is capable of fractional and modulated delay lines (delays that don't line up with the sample pattern and delays that change over time). The tank engine supports up to 1024 accesses per sample. This means that the tank engine can assist in many types of effects including: chorus, reverb, reflections, and interaural time delays (for positional audio effects). These effects are employed quite a bit in many of the audio processing features of the X-Fi, so avoiding the use of a DSP for the creation of a delay line is very helpful in spreading out processing power.
SRC: The Sample Rate Converter seamlessly transforms any audio stream or channel to any other supported sample rate with very low ripple and THD+N. We will cover this node in detail as it is one of the key features of the new architecture, allowing Creative to convert the sample rate of all audio multiple times independently of any other audio with little to no discernable loss in quality.
Filter: The filter engine implements 512 floating point 2nd order IIR filters. This is the fundamental building block of sound synthesis, 3D spatialization, equalizers, speaker calibration, and a host of other features. There are 13 filter types implemented in hardware from direct and parametric 5 parameter EQs to notch and peak filters. Complex (higher order) filtering and synthesis can be achieved by looping through the filter engine multiple times until the desire result is achieved.
Mixer: Consisting of 256 audio summers, 1024 parameter combiners, and 4096 single segment parameter rampers, the mixer is where internal audio channels come together. Parameter mixing and ramping are used to control effects combining for things like 3D audio effects in game. Instead of single segment, the parameter rampers can also support either 1536 multi segment rampers or 4 multi segment shapes (possible shapes are linear, pseudo exponential, and pseudo logarithmic).
DSP: The X-Fi Quartet DSP is so named because it supports 4 hardware threads. Each thread has access to two SIMD (single instruction, multiple data) units for easy stereo and complex math processing. NVIDIA has called a multiple SIMD processing unit MIMD (multiple instruction multiple data), but Creative has dubbed the overall architecture TIMD (Thread Interleaved Multiple Data) due to the hardware threading support alongside traditional methods. The Quartet DSP is central to many of the X-Fi features and we will cover this hardware at length as with the SRC engine.
Audio I/O: This node handles moving the final processed audio streams to output either digitally or through a DAC, and can also acquire input from each of the source options on the hardware. Audio sources in memory do not enter the path through this node, and likewise for audio written to memory (or a file). This block manages all the physical I/O ports on the X-Fi card.
Having easy access to any of these structures at any time during audio processing will greatly simplify the process and increase the complexity of operations possible on X-Fi hardware. In order to further optimize the architecture, Creative has introduced three distinct modes in X-Fi. These modes outline the basic type of path that audio streams will take through the ring. For instance, professional audio programs require very low latency audio from the sound card when recording. In order to accommodate this, the Creation mode limits the types of processing done to less complex (and faster) algorithms. Creation mode also allows synchronized audio streams for proper integration into a studio setting. These features aren't necessary when in Gaming or Entertainment modes, as the focus of these modes is on generating or heavily processing audio before input or output.
Architecting the card like this isn't useful unless the nodes on the ring are powerful enough to exploit the potential. Creative has spent quite a bit of time in making sure that this is the case. Their components are high quality and introduce as little distortion and noise as possible in order to make heavy processing of audio on a consumer sound card a reality. (Whether this is really a good thing or not is still up to the end user.) Over the next couple of sections, we will cover the most important components of the audio ring, as well as explore what is possible when all of this hardware sings in unison.
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SDA - Wednesday, August 31, 2005 - link
>>For listening, I generally stick with my Sony MDR-7509 headset. I also have the Sennheiser HD580 that I use to audition sound hardware. The reason I stick with the Sony gear for general listening is due to my environment. I can turn everything off when I need to do a noise test or listen closely to something, but the lab with all the computers and workstations running is not a quiet environment. I realize that open air headests will reproduce (especially) the low end in a more appropraite manner, so I do listen with them, but I know the sound a little better on the MDR-7509s as I've been using them for a long time. >>Are either of those headphones being amplified? If not, you are probably putting unfair stress on the sound card's line out, and should at least compare with and without an amp (lots of sound devices sound great if not under undue stress). Also, consider getting monitor speakers to test surround sound output.. old Minimus-7s will do if you're on that tight of a budget (no bass whatsoever, but surprisingly neutral midrange and treble for small bucks and a small room), otherwise look around.
>>I am planning on picking up the HD650 as I've heard great things about them. >>
Enh, they're not different enough from the HD580 to warrant buying if you're looking for sound test gear. Get something with a different flavor first (Grado SR-225 or Alessandro MS-2 for high-current low-impedance rock phones, AKG K501 for analytical ridiculously inefficient mid-impedance phones), and get a reasonably good amplifier (no need for audiophile BS, just something with enough balls to run a K501).
>>Doing something like a double blind subjective study on audio is difficult. People that don't know how to listen won't be any help because even if they hear a difference they won't know how to describe it very well. People who do know what they are talking about are hard to come by in volume. Don't get me wrong, we'd love to do something like this. But we just don't have any idea how to work out the logistics. Suggestions are welcome. >>
Find three different people who know what they're talking about and aren't slaves to the placebo effect. Have them test the gear in a double-blind setting.
More specific advice... look for musicians. Especially look for musicians for testing songs heavy on specific instruments: someone who plays, say, the violin will know exactly what a violin will sound.
>>Also, I appreciate the suggestion to avoid general statements about the goodness of something. It is a good suggestion even in cases where we know everything about everything in detail. There are always surprises and erring on the side of caution is the best way to go. We will be more careful in the future. >>
And, fwiw, I appreciate the maturity and responsibility one gets from AT editors. (Yes, I can give compliments too!)
DerekWilson - Wednesday, August 31, 2005 - link
I am not sure if I want to go with active amplification. I understand that stressing the opamps on the card towards the top end of their range could adversly affect their linearity. But my impression is that spending this much money on an audio card means a listener should not have to invest in an amp to get the best quality sound. We want talk about the audio as it will be heard by our readers.Do you have a different opinion on the subject?
And thanks for the suggestions on speakers and other headsets.
SDA - Wednesday, August 31, 2005 - link
>>I am not sure if I want to go with active amplification. I understand that stressing the opamps on the card towards the top end of their range could adversly affect their linearity. But my impression is that spending this much money on an audio card means a listener should not have to invest in an amp to get the best quality sound. We want talk about the audio as it will be heard by our readers.Do you have a different opinion on the subject? >>
The amplifiers on sound card line-outs are rarely equipped to drive headphones, especially not extremely power-hungry one. While I agree there is value in an ampless test, I also feel that an amplifier would be a good idea for pure line-out performance. A lot of us don't put any real strain on the line-outs, after all, and I'd like to see how evening the playing field a little helps various cards.
At any rate, spending this much money on (insert piece of equipment here) never entitles a listener to avoiding another link in the chain entirely. Not that headphone amps are a necessity, but hooking a $200 headphone to a line-out of a $400 sound card is a little silly and probably wouldn't yield sound as good as a lower-tier sound card and a cheap headphone amp (the things don't need to be pricey, just gutsy enough to power any normal dynamic headphone with ease).
Xentropy - Wednesday, August 31, 2005 - link
Sorry this is a bit off-topic, but you seem to know what you're talking about, and everywhere else I've asked I've gotten audiophile answers (e.g. buy this or that $2000 piece of equipment), so......What reasonably priced headphone amp(s) can you recommend for use between a soundcard and a set of HD570's?
SDA - Thursday, September 1, 2005 - link
The PPA and M^3 are reasonably priced, at least from a DIY perspective. At a lower price point, PIMETAs are fine.If I were you, though, I would upgrade that HD570 first-- driver upgrade (meaning speakers or headphones) is generally much more noticeable than amp or source upgrade. If you like a bass-n-treble signature, try the HD590; if you like something bassy and trebley but with midrange in the bargain, try a Grado or Alessandro. A very simple amp / 'CMoy' (buy on Head-Fi or somewhere, they're overpriced on eBay) with a decent op-amp (OPA2134PA is fine) covers a surprisingly large amount of the gap between no amp and top-end amp-- the biggest thing is taking undue stress off of the sound card's line out.
Or, you know, buy a $3000 amplifier, and line it with sound-improving rainbow foil (hur hur hur).
mindless1 - Friday, September 2, 2005 - link
Personally I found an unbuffered design like a CMOY to be a more similar to a soundcard's line-out than to a Pimeta, PPA or M3... they're all fairly harsh with terrible channel separation.SDA - Friday, September 2, 2005 - link
What op-amp? An unbuffered design is bound to be heavily opamp-dependent.. I've heard some that I'd prefer a Sony D-33's headphone out to, and I've heard others that are 80% of a META42. A great op-amp might be terrible in an unbuffered design for current output reasons.mindless1 - Friday, September 2, 2005 - link
Just about any mid-grade or better? I find some of my favorites, like AD8610, AD843, and OPA637, all sound far better unbuffered than jellybeans like TL072 or old standards like JRC4556/8, BUT *almost* anything buffered beats them. Higher current chps like LM6171 give more current but still lack quality sound. I "almost" find completely dreadful, entirely unmusical general purpose opamps sound as good buffered as the average "good" opamps in an unbuffered configuration... and it doesn't even take much of a buffer to make that difference.This is of course keeping in mind the current limitations, they don't even sound very good at low output. IMO, a CMOY type design is only useful for higher Z cans that need a bit of a volume boost. Then again, vast difference in price too, some people have enough spare parts to crank out a CMOY on protoboard plus $10. CMOY is like a gateway drug, it only teased me onto harder habits.
SDA - Friday, September 2, 2005 - link
Wow... well, I guess our ears just disagree there, especially since the AD8610 is my favorite for unbuffered. I still prefer buffered, of course, I've just always felt that an unbuffered AD8610/20 or similar CMoy-type amp covers a good chunk of the gap. Well, each to their own, I suppose, and AT editors should be looking for something higher-end anyway.mindless1 - Thursday, September 1, 2005 - link
Well, LOL."Audiophile" <> reasonably priced... never has and never will.
However, a ballpark $200 headamp might be a "PPA v2" custom-built with AD843 opamps rolled in. Thee are a few lists of trade builders for PPA2 or other customizable amps that you can DIY, actually tailor to your cans, or to your tastes, there is a vast gulf between gamer pseudo-audiophiles that buy Creative Labs cards with digital tricks and those who simply want cleanest analog possible and bit-perfect digi out. Wheverver you fit into the grand scheme, may dictate the optimal amp for you.
Then you'll want another amp, and more cans, and another sound card, and a DAC, and... Sorry about your wallet. ;-)