MP3 player with oversampling

[wyvernone]

In the CD player days, a high quality CD player has 4x or even 8x oversampling. My beautiful Luxman CD player has 8x oversampling with S.T.A.R. filters and produced the cleanest sounds I have ever heard.

Now, does anyone know of any digital audio player, (flash or hard-drive based) that has oversampling built-in?

The reason I ask is that I have never seen any player advertised with oversampling.

I know most DAP players can play MP3 files at 44.1 kHz, or even 48 kHz frequencies, but do they have oversampling built-in? Some of the DVD players has 192 kHz DACs for DTS and 5.1 surround but none of them sound like they have oversampling for audio....

If you have never heard of oversampling in action, convert a few MP3 files to WAVs and burn them to an audio-CD and play this CD in a CD player with oversampling. For me, the output of the same song, played on the Luxman CD player with 8x oversampling is much smoother, cleaner, unlike the ragged and discrete sound coming from a standard MP3 player.

If I can find one digital audio player with oversampling that must be the first step to audiophile quality audio.

 

[infinitesymphony]

Most DACs used in CD and DVD players incorporate oversampling (usually 8x). It's so common that it's not advertised anymore. Actually, I've had a few portable CD players with 1-bit noise-shaping DACs that also had 8x oversampling.

My guess is that almost everything oversamples, unless it specifically states that it doesn't (ex. NOS DAC - non-oversampling DAC). The reason your standalone player sounds better could be attributed to other parts like the power section or the analog output section. Both are likely better than what would be included in a stock portable player.

 

[wyvernone]

Thanks....Hmmm... A quick jump to the Wolfson Microelectronics website, maker of the DAC used in the 4th generation iPOD, to check out the datasheet, and yes, the DAC has oversampling built-in!

Right. Now I 've got check out if the DACs used in Sandisk, Sony, iRiver, and Creative Zen DAPs have oversampling. Does anyone know what DACs they use off their top-of-the-head ?

 

[Febs]

The iriver H100 and H300 series use the Philips UDA 1380.

The Sansa e200 series uses a PortalPlayer 5024.

 

[craiglester]

I was under the impression that over sampling used for 2 purposes.

1. Added resolution (needs very high oversampling rates) - probably unlikely to be used in a dac.

2. Noise reduction - by taking an average of the oversapled data, mis-read data (noise) can be reduced.

I'm thinking that in a DAP the data is a lot less likely to be mis read than a CD player, and that the data isn't read multiple times. I don't know for sure of course, but if the signal is generated from a file it should be the same everytime, thus making the noise reduction oversampling rather redundant. Not sure on the added resolution bit though.

Personally I feel the better sound from your CD player is the better electronics and the filters, rather than the oversampling.

I'm sure if an Ipod had oversampling to improve the sound, apple wopuld have marketed that feature to death by now.

 

[wyvernone]

Yes the good old CD player definitely contributes to the better sound by having audiophile components, etc. But oversampling is very important when dealing with sampled data, e.g. audio

As you said oversampling basically improves the signal-to-noise ratio and reduces the quantization noise, and it does so by basically
interpolating additional samples between the 44.1 kHz samples so that the resulting analog signal is smoother, and more anti-aliased.

Imagine the standard CD audio signal, sampled at 44.1kHz, is like a stair with 44 steps, an 8x oversampling playback DAC takes this signal and plays it back at 352.8kHz effectively making the stair (still with the same height) 352 steps, the steps having smaller gaps than the original. The more steps the stair has or the higher the oversampling on playback, the more the output signal approximates the orignal smooth analog signal.

Oversampling and of course better electronic components/design in my CD player makes it have a signal-to-noise ratio (S/N) of 105 dB.

I have yet to see this number in a DAP but I am still hoping... And some DAP manufacturers don't even bother to state this number in their specifications table. Those that don't are meant for playing 128k and low-bit-rate MP3s IMO.

In this day and age of lossless FLAC/APE, 320k CBR MP3s, high-bit-rate MPEG4 files, we really need to see DAPs with better oversampling and better S/N ratio.

 

[Kabeer]

This is wayyy too technical for me, but is Dithering similar to oversampling? If so, then Rockbox has that option.

 

[infinitesymphony]

Quote:

Originally Posted by wyvernone /img/forum/go_quote.gif In this day and age of lossless FLAC/APE, 320k CBR MP3s, high-bit-rate MPEG4 files, we really need to see DAPs with better oversampling and better S/N ratio.

Well... Consider the purpose of DAPs: portability. How much will a better SNR benefit you if you're on a noisy bus or walking around town instead of sitting in your quiet listening room?

Some people have tested the SNR of iPods and from what I've seen, the average dynamic range is ~98 dB. This exceeds the maximum dynamic range of a CD (96 dB); unless you're playing back 24-bit files, it should be enough.

In the large scheme of things, oversampling only offers subtle improvement, and I'll still guess that most of the DACs in DAPs already oversample. The real improvements come in upgraded power and filtering sections, which is difficult to do at such a physically small scale.

Quote:

Originally Posted by Kabeer This is wayyy too technical for me, but is Dithering similar to oversampling? If so, then Rockbox has that option.

No, the two are totally different things... Dither is random noise applied to a signal to prevent harmonic distortion that's caused by reducing the bit-depth. For example, if you record something at 24-bit and want to put it on a CD, you'll need to change the bit-depth to 16-bit. If dither isn't used, you'll hear a lot of quantization noise, especially at low volumes. If you've ever used a really old CD-ROM drive to play an audio CD, you might have heard this noise for yourself.

Basically, dithering is mostly used in the recording process, not the playback process.

 

[Aerosushi]

A couple points:

1. Regardless of whether a DAC uses a 1X, 2X, 4X, ... 64X oversampling architecture, the final output of a digital player is always continuous (perfectly smooth) with no discrete steps (staircase). This is the role of the analog lowpass reconstruction filter at the output of the DAC.

2. The main role of oversampling, besides that of moving much of the quantization noise higher into the spectrum, is to also move the first alias of the baseband signal high enough into the spectrum to lower the order of the reconstruction filter required to reproduce the sampled signal without any aliased components. This is equivalent to increasing the number of "steps" in the "staircase" per unit time.

3. The first CD players produced did not take advantage of oversampling, requiring high order brick-wall anti-aliasing reconstruction filters. This tended to make the high end shrill and muddy due to phase issues in the filters' transition bands. To put it bluntly, older players without oversampling technology sounded atrocious.

4. I don't think any DAC produced within the last 10 years or so boasts anything less than 32x oversampling. Any DAP on the market today uses at least a single order sigma-delta oversampling / noise-shaping architecture.

5. The difference in specs between your typical DAP and CD player is largely the contribution of the headphone amp, not the DAC or reconstruction filter. Any decent DAP (designed with rudimentary engineering skill and care) with a line-out and lossless codec playback capability can be considered an audiophile-level device.

 

[wyvernone]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Well... Consider the purpose of DAPs: portability. How much will a better SNR benefit you if you're on a noisy bus or walking around town instead of sitting in your quiet listening room?

hmm... Well an wanna-be audiophiole demands the best

why else does Shure make the E500 earphones (which I have ordered) and companies such as Ultimate Ears exist?, just to hear crappy quality music?

I and I am sure lots of other people want to plug the DAP, via some sort of line-out or docking station, into the home amp/receiver. So I guess I am looking for the ultimate in audio quality.

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Some people have tested the SNR of iPods and from what I've seen, the average dynamic range is ~98 dB. This exceeds the maximum dynamic range of a CD (96 dB); unless you're playing back 24-bit files, it should be enough.

SNR and dynamic range are two different things. Dynamic range is the audio resolution and is related to the bit width of the audio sample, in this case 16 -bit.

SNR is everything to do from the DAC/filter/amp stages to the 3.5 mm jack.

 

[wyvernone]

Quote:

Originally Posted by Aerosushi /img/forum/go_quote.gif 5. The difference in specs between your typical DAP and CD player is largely the contribution of the headphone amp, not the DAC or reconstruction filter. Any decent DAP (designed with rudimentary engineering skill and care) with a line-out and lossless codec playback capability can be considered an audiophile-level device.

Your audiophile requirement is not the same as mine I guess.

Well first thing I look for is the SNR on the DAP's spec, if it's below 90dB, I don't even bother with it. I regard 100dB or more is audiophile....

Second thing: I plug the DAP's line-out and the CD-player into a home amp and let my ears do the judging. and I am disappointed with the DAP's output. This is why I am still looking.

But of course the CD- player doesn't have the abilty to store thousands of tracks

 

[Aerosushi]

Quote:

Originally Posted by wyvernone /img/forum/go_quote.gif Your audiophile requirement is not the same as mine I guess.

I'm not specifying any requirement. What I am suggesting, though, is that the line-out of a well-implemented DAP design using any decent silicon (ie. Portalplayer, Sigmatel or Samsung, for instance) will be next to indescernible from a well-implemented CD player. Both implement sigma-delta technology, which typically implies 32x or 64x oversampling.

From your perspective, oversampling is not the limiting specification, but rather the post DAC stage. That is where the terms "well-implemented" and "designed with rudimentary engineering skill and care" come into play for you. Things like proper supply decoupling, good return paths and other hidden tangibles are what make a DAP or CD player sound stellar. If I could summarize in 3 words: forget about oversampling.

One last thought - if you are selecting a DAP based on specs and buzzwords, don't. This is pure marketing...where the rubber meets the sky. Listening and judging the audio quality for yourself is where the rubber meets the road.

Best of luck.

 

[infinitesymphony]

Welcome to Head-Fi, Aerosushi! Those were two killer first posts. You have a comprehensive understanding of audio technology and will be of great help to many Head-Fiers, myself included.

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Quote:

Originally Posted by wyvernone /img/forum/go_quote.gif SNR and dynamic range are two different things. Dynamic range is the audio resolution and is related to the bit width of the audio sample, in this case 16 -bit.

Technically, they're different, but basically, they're equivalent. If you're talking about a device, then SNR and dynamic range are relative to the device (ex. iPod). If you're talking about a format, then SNR and dynamic range are relative to the format (ex. CD).

The difference is only in the way that they're measured. From Wikipedia:

Quote:

Signal-to-noise ratio is closely related to the concept of dynamic range, where dynamic range measures the ratio between noise and the greatest un-distorted signal on a channel. SNR measures the ratio between noise and an arbitrary signal on the channel, not necessarily the most powerful signal possible.

As a side note, check out the ENOB (effective number of bits) versus dynamic range/SNR table from this site... For 16-bit material, the maximum possible dynamic range/SNR is 98.1 dB. For 24-bit material, it's 146.2 dB (!). I'm not aware of any DAC that has 146.2 dB of dynamic range, so I guess the full potential of 24-bit recordings is still untapped.

 

[ILikeMusic]

Quote:

Welcome to Head-Fi, Aerosushi! Those were two killer first posts. You have a comprehensive understanding of audio technology and will be of great help to many Head-Fiers, myself included.

+1, welcome. Your posts are excellent and enlightening.

But given your comprehensive understanding of audio technology you will probably become very frustrated if you hang around here long enough...

 

[wyvernone]

Quote:

Originally Posted by Aerosushi /img/forum/go_quote.gif From your perspective, oversampling is not the limiting specification, but rather the post DAC stage. That is where the terms "well-implemented" and "designed with rudimentary engineering skill and care" come into play for you. Things like proper supply decoupling, good return paths and other hidden tangibles are what make a DAP or CD player sound stellar. If I could summarize in 3 words: forget about oversampling.

Wish I could do that. But I am thinking along the line of... if the designer of a DAP chose not to use a good DAC with oversampling - in order to save on manufacturing cost - chances are the post DAC analog stage is going to contain cheap op-amps, caps, shielding design, etc. I agree good quality sound is the whole package, but if you have a good DAC with oversampling to begin with, e.g. in the 4th gen ipod, at least some third party mod like the iMod can come in and bypass the cheap quality-sapping post DAC stage and produce the sound like it should be.

Quote:

Originally Posted by Aerosushi /img/forum/go_quote.gif One last thought - if you are selecting a DAP based on specs and buzzwords, don't. This is pure marketing...where the rubber meets the sky. Listening and judging the audio quality for yourself is where the rubber meets the road.Best of luck.

Very wise words of wisdom indeed. That 's why I don't trust all reviews and the device's market share. That's why I am trying to find out what's in the guts of the device. This plus specs help me short-list devices so I can listen to them and judge them... against the CD-player.