Javier
Administrator
Digital bytes
Posts: 987
|
Post by Javier on Jan 4, 2015 12:25:57 GMT
DSD as "Direct Stream Digital" is a marketing term invented at the time when SACD was launched. DSD as Direct Sigma-Delta (aka PDM) is a different thing and was there way before. When CD patent was close to expiring and the stream of royalties Sony and Philips were enjoying would cease, the former tried to come up with a new source of revenue from patents and hardware with a very simple idea. PDM ADCs were common at the time and their raw output format (IE non decimated/converted to PCM) was used for archive purposes so why not make it available in a new hardware and software platform? thus SACD was launched with tons of hype. PDM or Sigma Delta DACs were introduced in the late 80s/early 90s to overcome two problems with (by then) mainstream ladder (aka R2R) DACs, notably cost, need for complex oversampling and filtering, glitching and lack of linearity. Ladder DACs need extremely highly accurate matched resistors and going beyond 18bit resolution means very difficult to make chips which means pricey. For example a single 24bit channel part like the TI PCM1704 costs $50 and a minimum of two are needed (2 x $50 = $100) whereas the most expensive Sigma-Delta chip currently available, the ESS ES9018 costs $65 as outperforms it in very single measurable way by a rather big margin. . Early Sigma-Delta chips were single bit somewhat crude (BTW, just like their R2R counterparts) and got a bad reputation. With time they got much better and those early designs were replaced by "low bit" (5-6bits) parts using multilevel PDM with greatly improved performance to the point they kicked R2R chips out of production. Almost every digital device purchased in the last 20-25 years uses a Sigma Delta chip so in effect every time you listen to your CD Player, MP3, DAP, Smartphone, TV, etc. you are actually are listening to a variation of "DSD" as this chips internally need to convert like PCM to their internal PDM format. The current new wave of interest on "DSD" is derived from the idea that as we all have SD chips in our digital stuff, instead of letting the PCM to PDM lossy conversion take place inside a cheap and resource limited chip, it is technically better to A) get something already in its native format to avoid less than optimal conversions or B) do the conversion in a much powerful platform like a modern computer using software. Whether all the above makes any sense is, of course, open to debate. Technically new variants of DSD like DSD256 or DSD512 are better than any PCM format and allow for extremely simple DAC designs with amazing performance but.... is it audible? is it worth the extra expense in storage and gear? well, lets say 99.99% (or more?) of the world's population is perfectly happy with 128Kps MP3, so most likely not, however I'm all in for technical perfection and extreme engineering if I can afford it (not ATM ). For me it is not about "good enough" but rather about "Excellence".
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 13:59:29 GMT
Many report dsd as sounding more analogue. I find that though with hi res FLAC. It's smoother with deeper bass and smoother treble. Mind you, that may not be just the format but the mastering!! No bidding on the x3 today, Simon!!! You may have got it at a good price.
|
|
Javier
Administrator
Digital bytes
Posts: 987
|
Post by Javier on Jan 4, 2015 18:41:51 GMT
HiRes PCM has the theoretical advantage of higher dynamic range of up to 144dB for 24 bits Vs 96dB of standard resolution of 16 bit found in CD or DVD and also extended frequency range equal to half the sampling rate (fs/2) so, for example, 192KHZ sampling rate would translate to a 0-96.000 Hz range. Provided most people don't listen at real 96dB and cannot hear above 16-17 KHz the "theoretical" advantage can be moot. But then, there are other technical advantages of higher than 16 bit and 44.1KHz (CD) or 48KHz (DVD) (moot for most people as well). Playing straight 44.1 or 48KHz would require a "brick wall" filter, that is an extremely steep low pass filter at the Nyquist frequency (44100/2= 22.050Hz) that would remove all content above that point. In practice this is too difficult to implement and also impacts phase response very badly so designers and manufacturers came up with a solution: oversampling. This means digitally processing the incoming signal to increase the sampling rate to a higher one, for CD 8x is typical, and then use a much easier to design and gentler on the signal 2Nd or 3rd order reconstruction filter. This is mostly done by using a technique called linear interpolation which inserts a number of "invented" samples which were not present in the recorded event between real ones. In most chips this is not done in a single pass but rather in three consecutive 2x iterations due to lack of computing resources. In this case, the higher the incoming signal (IE higher res) the less it will be oversampled so a 192KHz file would only need a 2x pass Vs the required 3 passes for a CD file or if you have a DXD (aka 352.8KHz) file it will bypass oversampling altogether. So potentially HighRez "can" be technically superior to standard resolution in that they are capable of producing sound much closer to the original within the audio band. Then there is the problem of digital filtering...
Higher than 16 bit has the advantage of providing more headroom and higher accuracy when processing signals, very important when mixing or mastering but in a DAC it basically allows for digital volume with little to no loss. In the real world the best DACs archive a maximum dynamic range of barely 21bits ENOB (Equivalent Number of Bits) or 129-130dB, anything over 120dB is merely academical as that is the pain threshold.
DSD is very different to PCM as it is basically a digital image of an analogue signal so far less processing is required, to convert it back to analogue a simple analogue filter is required. DSD found in SACDs is called DSD84 (1bit at 64 x 44.100 = 2.8GHz) but not it is possible to find recordings made in DSD128 or even DSD256. The higher the DSD rate the less steep the required analogue filter, DSD512 would require such a gentle filter that it would almost cause no measurable phase errors. Generally speaking, DSD has better time domain characteristics than PCM and same or better frequency response but cannot be processed as such, it needs to be be at least converted to multi level PDM from 1bit PDM or minimal processing. Until quite recent times there were no native PDM tools for the studios and mixing and mastering had to be done either by converting to PCM (thus negating all potential benefits) or in done in analogue and the digitized at the end. Gear for DSD in the studio used to be made only by Sony and was both limited in functionality and very expensive which made it rather uninteresting for most studios and engineers but in the last years new affordable recording systems capable of even 4x DSD (aka DSD256) are becoming available and also software tools capable of mixing and (up to a point) mastering in native PDM (multi bit) at much more reasonable prices. There are quite a few specialized labels offering pure DSD files but like HighRes PCM it will, without a doubt, remain always a niche market.
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 18:51:07 GMT
Great. Just using the X1 has slowed down my cd listening tbh. It's just so much more convenient and good files sound fantastic. Getting hold of them is another story though!! Some companies demand very high prices for hi res stuff which imo isn't really justified. It's such a pity that a company like Amazon don't offer albums as CD, hi res and low res. I'm sure the high res might do very well and maybe outstrip CD's. The 24 bit 192 FLACS I'm listening to at the moment are just full and delicious sounding!! I'm becoming more and more converted to these formats if I'm honest. Does anyone know of a good supplier of mainstream stuff? A few places listed here: www.cnet.com/uk/news/top-6-sites-for-buying-flac-music/www.digitaltrends.com/music/best-sites-downloading-hd-music/I've been listening to all 4 of Brahms symphonies today on 24 bit FLAC and its like Radio 3 on steroids. Very large dynamic range, although the recorded volume is low since there really isn't much compression. Way more natural sounding even on DT770. The recordings aren't as harsh in the top end; whether that's a side effect of the resolution or eq'd, but it s extremely good, even from a cheap Fiio dap. I'm not certain if the X1 down converts or whether it plays at proper resolution, but they are damned good. Makes you very aware of testing headphones - so much depends on the quality of recordings used and the source. Even the DT770 sounds pretty sophisticated from FLAC to Polaris. Brahms takes on this enormous sense of power. I see that there are a few x3's on EBay Simon. I reckon £150 which is quite tempting. The worst thing is the prices asked for hi res albums in many cases. just read the "admin note", thought i was going mad
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 18:53:10 GMT
Many report dsd as sounding more analogue. I find that though with hi res FLAC. It's smoother with deeper bass and smoother treble. Mind you, that may not be just the format but the mastering!! No bidding on the x3 today, Simon!!! You may have got it at a good price. yeah, but ironically , i think i would prefer the x1 then thats £50 towards a pair of closed phones.
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 19:05:22 GMT
Oh sorry Simon. I was trying to cheer you up!! I've also seen a new one being sold at £135. So you may be 'stuck' with it!!
In all these formats Javier, it is going to encourage more 'Herbert's' recording at home and producing their own digital downloads. I've seen a few peddling their wares on HF and frankly, the music was .........
Lovely and hi res, but .......
The idea of hi res being available cheaply for home users is going to produce a lot of home made products. No longer need the labels ... Then what?
Frightening.
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 19:19:32 GMT
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 19:24:53 GMT
Don't buy them Simon. They don't look right. What do you want to pay? Around £100 was it? Not sure if you'd get them at that price.
I'm waiting for the 7100 to drop. They're not accurate, but fun.
The d600 really hammers out Peter Gabriel. Listening to Sledgehammer' is just ........ Bloody great!!! The bass just drives it hard!!!
I must admit, I'd be tempted to mix it this way, but hi fi people would moan about reggae bass levels!!
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 19:33:03 GMT
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 19:36:46 GMT
The problem is that I'd pay £149 for a new one rather than £130 or so for a second hand one. Also, the people who bought them may have paid a lot more for them so would be unwilling to go too low.
Your only £20 higher for a new one there.
Oh .... Sorry. They're ex-display not new!!!
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 19:53:06 GMT
The problem is that I'd pay £149 for a new one rather than £130 or so for a second hand one. Also, the people who bought them may have paid a lot more for them so would be unwilling to go too low. Your only £20 higher for a new one there. Oh .... Sorry. They're ex-display not new!!! not exactly new no, but can be returned as they come from a store outlet. almost a "no brainer", i am only dithering because funds are tight at the moment. (my kids are 18 in march!!!)
|
|
oldson
extremely active
Posts: 1,678
|
Post by oldson on Jan 4, 2015 20:57:49 GMT
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 21:18:29 GMT
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 4, 2015 21:19:20 GMT
Come to think of it, we could have an area to plant cheap hi fi offers. That might be useful for people searching for things!!!!
I'm thinking of shortening the lead on my k550 so that I can use it more easily outside in the garden in the Summer!!
|
|
Rabbit
Administrator
Posts: 7,087
|
Post by Rabbit on Jan 5, 2015 18:11:57 GMT
Shit. ....... Simon, one hour to go and it looks like you might get it!!!!
|
|