سورس دیجیتال Transport & DAC

پروژه DDDAC 1794 NOS

جمعه 5 جولای 2013
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تو سایت Twogoodears مطلبی نوشته شده درباره ساخت یک DAC :

http://twogoodears.blogspot.com/2013/06/digital-skyrocketing.html

امکان ساخت پروژه تو لینک زیر هست خیلی شفاف توضیح داده و بد نیست همون DAC 1541 استفاده بشه .

http://www.dddac.com/dddac1794.html

The Digital Azimuth or DDDAC frenzy in Koln

Hi, folks… here is an essay by Reinhard, a chronicle of last weekend near Koln, with new and old friends  enjoying music in Klauscope’s Goto system glorious sound with latest Doede Douma’s and Bernd’s DACs and PSUs… Jean and Andre, James and his girlfriend and others guests from France – BUT me – were partying… I deeply missed the gathering, indeed… thanking my german pal, here is the gap filled, for posterity;-)”Dear Stefano,
first of all congratulations on your personal ameliorations in sound within your own Gotorama with “digital stream”… This is wonderful to read. And this is really awesome, isn’t it? And I know exactly how lucky you feel now… so, especially regarding this matter: welcome to the club (again)…
Let me add that we all were very sad that you missed out and that it was a pity that you were not able being part of our latest session here at “The Goto-Triangle” at Cologne just the other week, especially because of this specific theme…

This is Klaus’s system, ready for testing…
Well, right in the beginning let me thank you for allowing me to put the relevant research and listening results of this special event onto your page, so that we all are at least able to fill in this gap a little via some infos and pictures… and indeed, the results are really breathtaking, rather dramatically superior to that what you experienced on your visit last december, another really big (musically fulfilling) step forward:
1. simply because of possessing and being capable of playing the new ISO-file-format, ripped from SACD with much higher resolution than 24-192 (the amount of data is about as double as much, and you may have an idea of how small the “stairs” in digital reproduction become, building a nearly “perfect” sine-curve and how the sound gets nearly completely integrated because of that) and
2. heavy progresses within the DDDAC-areas “Quadriga” and “Octopus” in combination with Doede’s and Bernd’s corresponding power supplies for the DACs and USB… you may imagine: it’s hard to believe, but within HiFi-heaven, where we clearly are already for quite some time, there is another stairway going up (you remember: it was you, last time using the expression: “stairway to heaven” (not to quote Led Zeppelin but when entering Klaus’s “Nirvana”… and what a stairway that is…
and

Reinhard’s Quadriga, the DDDAC1794 24 Bit NOS

and picture 6, in combination with Bernd’s 18 kg power supply

What about the panel?

They were, from left to right: Triodedick, Doede Douma, Jean Hiraga, Klaus Speth and André Klein.

1. of course the whole time we held a place free for you, Stefano, but unfortunately you missed it out
2. Jean Hiraga, the “Mount-Everest” in HiFi, who meanwhile has become our long time follower and whose satisfaction, contentness, nodding with his head and grinning on his face has become more and more fulfilling… (I know that we all once started at zero, being uninformed when we were young, so if there should be somebody out there not knowing about Jean, please google… the ocean of his longtime hardcore researches and reports is way too vast to present it all here (to name just two things: class A and tube amps development…), and to make it short, Jean is the one – together with Shinichi Tanaka from Goto Society in Japan –
who have constructed, listened to, measured and reported about the most and highest end systems all around the globe for quite some forty years now…
3. Doede Douma – the “new magician” in the row… there is no longer any need for me to introduce him further, because since our last session he has established one of the most inspiring and creative sites in the net for DIYers, not only especially regarding DACs,
but as well amps, and speakers, and…
I enjoy his sites that much because I – as a non physician and non electrotechnician – understand most of what is written there, and I can clearly hear everything that what is all about… to me – it is just exactly perfect !!!
4. just the same seems to have experienced our first time guest, “Triodedick”.
Klaus supervising, w/Doede Douma and Dirk aka “Triodedick”, doing what they like most: “conjuring tricks”;-)
Triodedick is very kind and quite famous, not only among DIYers. He is a real specialist, also coming from the Netherlands (like Doede), a long time friend and colleague of Doede in studying physics and electrotechnics at Utrecht University and sharing our HiFi-hobby ever since. If you like, enjoy his sites:
and here you might find Triodedicks report – in four parts, not only for DIYers – about Doede’s “magic” DAC, the DDDAC 1794 24 Bit NOS DIY DAC (part 1 to 4)…
5. and André Klein, a very nice guy from Metz in northern France with very specific knowledge and skills, joined us again… some of you might know him from the regular European Triode Festivals in France: he is an extreme tube lover and connoisseur and the proud owner of a system based on Western Electric WE15 in combination with self-built WE amplifier model 46-B for which he won several prizes… he is an EMT-turntables-and-cartridges afficionado, as well…
5. and James, our astro-physician from Australia, with girl friend, still in the process of exploring and planning his system (having spent some 70.000€ in the past and still not content), but knowing already the very best systems in Japan and ours…
James with his girl friend, sitting and listening in the – for Hi-Fi-Fans – “center of all centers”
6. a befriended couple from Jean from France, which simply couldn’t stop getting astonished and overwhelmed… you know, how people react, when they listen to Klaus’s system for the first time. They are struck in awe. And exactly the same happened here: you couldn’t talk to them…
Jean, André, and french guest
7. and lastly, Klaus and his wife Moni,  (I do not want to produce redundant information material here, so when you google, you will find enough of what Klaus is doing for the last 40 years…)

… and this is me, Reinhard…

What was it all about last saturday ?What was the theme… the main theme?The very theme?
This meeting was some sort of fulfillment (that way, that  w e   h e r e   nod with our heads, and not anybody else) of about three till four years of research within the digital area, and here especially within the DAC-area, i.e. digital to analogue converting… and this proved to be extremely exciting!
DDDAC1794 24Bit NOS in all it’s glory, with nice display showing bits, resolution, voltage… programable…
… latest since Douglas Sax, yes, the guy from Sheffield Lab with the direct vinyl cuts… some years ago at the CES in Vegas officially claimed that vinyl is simply produced because people demand it – and  n o t  because it is better than digital – nearly everybody awoke and got curious, so did we, and especially Doede…
Suddenly everybody wanted a DAC, and everybody got a DAC, and everybody was unhappy with the results, first with the small ones, then with the big and better (?) (or at least more expensive ones) up to 7.000 €… no, I do not name them, but they are leaders on the market and very famous…
…the result was always, I repeat  a l w a y s, that way, that we were all still unhappy and more or less (mostly more) plagued by a somehow unpleasant, unprecise and muffled sound with digititis (the deficiency of getting a signal that way reproduced that the “stairs” in digital are not or hardly annoying and/or recognizable during listening – mostly caused by jitter), the results were always clearly way beneath vinyl reproduction.
We nevertheless immediately recognized the “advantages” of a DAC even if we were not happy with the implementation and realisation at the time… as is to this very day with external, i.e. not self built DACs, independent from low or high resolution (by the way the results with higher resolution are not as good in comparison to 16 Bit)…
… and exactly this was the hour of Doede, “living” in the digital world from the first moment on at university since 1976, he managed to grew up (Hi-Fi-wise) with the fulfillment of his splendid ideas, clearly and precisely, and it pregnantly shows… well, to make a long story short:
(if you should like it long, you may visit his homepage here):
Doede developed two DACs, his DDDAC1543 for 16 Bit, and later on with the upcoming of high resolution and corresponding downloads on the market his DDDAC1794 24 Bit NOS. But he not simply developed a DAC, or DACs. What makes his DACs that special is the possibility of multiplying the DAC-Chips which ameliorate the sound  a n d  reduce the jitter. As the results were really spectacular within his DDDAC 1543 he went from 12 to 24, to 60, to 120, and finally to 240 chips (maximum amount: 16 x 16 = 256)…
This is Reinhard’s DDDAC1543 16bit DAC with 120 chips, also in combination with Bernd’s power
supply – getting attested on saturday the most “punch” of all.
The sound still and still and still and still got better, dramatically better, and within the DDDAC1794 24 Bit NOS till some months ago he went from one deck to four decks (nickname “Quadriga”) and then to eight decks, nickname “Octopus”, here the sound got much better as well, but because of a 24 bit chip as a basis and an already pretty much sublime sound to start with the need of multiplying chips is not that high as with 16 bit chips… although we will test further.
During the last three years it became obvious that the results of Doede’s research were that good that the ultimate tests could only be hold at Klaus’s…why ? because Klaus’s is not only the best but the only place capable of bringing the 500 horse powers of the newly constructed DACs onto the road… I mean onto the road without squeaking… and that’s exactly the point, if it is squeaking – like on nearly every other system – you either loose music or the music is not reproduced the way you like it…
This was exactly our theme on saturday: testing these different DACs with different amounts of chips and decks without squeaking, and “with” and “against” each other, and of course with all sorts of music and resolutions, ranging from “simple” 16 bit up to 24 Bit 88, 96, 176, 192 kHz, and as the icing on the cake with for the first time ISO-files, the direct DSD.format (DSD64 and DSD128) with about the double amount of data as with 24-192…… and ooohhhh, not to forget, all this in comparison with a big lorry battery, and Bernd’s and Doede’s newly finished controlled power supplies, and a new controlled power supply from Mundorf…
Doede’s controlled power supply, to the right

Mundorf controlled power supply (for Bernd’s controlled power supply see above)
Testing results
Of course the highest amount of chips and decks were the clear winner, in combination with the superb controlled power supplies, and the Kimber USB silver cable that Klaus and I have in use..
I’ll do not enter into a description of the sound, there is not much to say, it is realistic and natural, and it is simply music, that’s what we ever wanted but never got – till now (and here ISO brings us to exactly that level in reproduction what we ever have been looking for – to me this sounds like master tape)
We can listen now to music that way that the human brain is no longer bothered by whatever things that do not belong to the music and which are simply wrong and/or artificial. Let me say: the result was: listening to music the most pleasent way out of any system I ever heard (exept mine), no matter what music and/or what loudness… (but you have to keep in mind, that I have not heard Doede’s eight deck DAC – the “Octopus” – on my system…)
USB-cables
Wow, wow, wow, that was a program… as it turned out it was nearly too much to handle… it was not of course, but after some twelve hours there was no time left to properly check out different USB-cables within this “circus”… and I have to admit, the results were so satisfying right from the beginning, that there was no real need to urge.
USB-cables… this is indeed a theme on its own… all sound different… and this within the pure digital area where only 0s and 1s reign!!!Ultimately we want to get rid of PC- or MAC-norms, i.e. USB, Firewire or whatever, in order to get completely rid of these “uncontrollable” influences. This will be our next step, to check out the PC offal and take off the digital signal directly from the motherboard, but this is still a way to go… meanwhile we have to bear with USB. And actually we use Kimber USB silver cable. Klaus and me, we both have it running (it took more than 150 hours to burn in to the point)… those of you who might want to read more about the experiences that as well others have with it, have a look here:
This cable is really good, and it has a very acceptable price, at least it may serve as a good start to compare and try out more…
Controlled power supplies
The controlled power supply (everywhere: in pre-amp, channel deviders, power amps, DAC, and later on for hard drives and within the PC) is also a chapter on its own. I remember reading Jean and others – long time ago – that there is no better power supply than batteries… and of course at that time we didn’t dare to say anything against it, neither did we try it out for ourselves… but now we really wanted to know, precisely…
Klaus got a large lorry battery, weighting some 40 kg or so, and we listened with it to music in combination with the DACs … well, it was fine, it was ok, it was quiet, and we finally presumably would have been constantly convinced if Bernd would not have constructed a new power amp, originally planned as power amp prototype for the Goto-drivers, with two trafos, one for +, and one for -, with some nine kg each, so both about 18 kg…. it was not at all constructed and intended to supply the DACs, it was just a funny idea and happened by accident to be tested out in this combination.
This testing came out as one of the greatest surprises in HiFi-history: driving some 500 g DACs (each) with an 18 kg controlled power supply!!! As it turned out it is exactly that what is needed to get the most and best music out of the DACs (the same results are valid in all other amplification areas – as indicated above)… Within the chain of the amps exactly this result is “nothing new” and known for years, but I have to admit, if I would not have heard it with the DACs, I would not have believed… and listening to these results Doede immediately began to construct a power supply for his own DAC, with really dramatic results, see picture above.
ISO
Before I start with ISO, just let me tell you that just the other day I read in “a very friendly forum”, where they are not shy to emphasize to unknown “newbies” like me, like in a canon or choir, that “friendlyness is… culture”, that ISO-files are not a “new sensation”. Well, that’s right. ISO-files per se are not a new sensation. If one is able to generate a perfect PS3-rip.Stefano, I ask you, who on earth is capable of doing that?
The “new sensation” is fortunately no longer in getting the ISO-files ripped, but in getting them properly played!Who dares to say that he is capable of reproducing ISO properly ? Knowing, hearing that what they are listening to is still not that what they are looking for? Anyway, I have biggest doubts that anybody else on the globe is able to even come close to Klaus’s results,  e s p e c i a l l y  with ISO… the Goto drivers with ISO really live up to their true potential, now they really can show what they are capable of!!!
For those who are familiar with generating ISO-files from SACD and “perfect” PS3-rips (it is indeed not that easy and not that long possible at all), and know not only how to rip but play them  p r o p e r l y, ISO-files might indeed be no “new sensation”.But I wonder if all those who are that much talking about are personally capable of at all, and I wonder of the amount of people on the globe who have these SACDs, the corresponding programs to rip them, and know how to do it properly, i.e. 100% perfect… (and not just only produce a rip like the hundreds of millions faulty ones flowing in the net containing artifical mathematical error corrections which is not music and which at least I do  n o t  want to listen to…)
Even if we take a “perfect rip”,  then we all know from tape, vinyl, CDs and SACDs how difficult – or should I say better: impossible (at least so far) it is to make ultimate and especially proper use of the corresponding infos of these specific media. We are long time researchers in trying to reproduce “that what is on CD/SACD” and not simply playing a CD/SACD. And we can assure that nobody on the globe is totally capable of – neither are we… we are struggeling to get there, and we have come closer and closer, but we are still not “there”, till this very day, but we have come closest possible now – with ISO…
Let me finish with a phrase, that I read on the “very friendly forum”, that I talked about (thanks to the one who quoted it), which really made me thoughtfully. Somebody quoted Jiddu Krishnamurti, who wrote in “Freedom from the Known”, paraphrased: “if someone says ‘this’ is ‘it’, run… “
Here I am, with that, what I have heard, and I have to say: yes, “this” is “it”. So Stefano, please, help me: Cologne Cathedral is built, and I am right in the middle… listening to the humility pipe with 16,4 cycles… I know of no better place… and I am happy… so, should I really run, go somewhere else? … and if yes, where?
Jean Hiraga, Doede Douma
Stefano, you know what it takes to bring these two guys, e s p e c i a l l y  t h e s e  t w o  g u y s, to such a deep understanding and satisfying smile –  only heavenly HiFi-delights are capable of…
Within this specific context somebody on “the very friendly tracker” asked me:
“OK “rhlauranna”, but what shall we learn from your links to Stefanos site?”
First, that I am the last one to tell “them” what “they” should learn, it’s up to them…
Let me answer the following: if someone would have told me some four or five years ago, that “my” music after 45 years in HiFi ultimately would be defined by machines and mathematical algorhithms, I would have declared him completely mad… But as as it turns out: it is exactly like that…
… and it looks like that:
PC, and MAC, and NAS, and I-Pod, and W-Lan, and cables, and… ONLY the pix is blurred, folks;-)))
Music rules…
Thanking Reinhard for his review… the links and pixes are a great support for anyone wishing to deepen the topics… and YES, sure the digital-made-right is far from being fully understood… and these guys are the daredevils who will reach the highest peak!
P.S. – some pixes are still out-of-context… will fix it soon… just wishing to share it ALL – the enthusiasm and feeling – asap.
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دو مقاله در مورد تبدیل دیجیتال به آنالوگ از Lynn Olson

پنجشنبه 20 ژوئن 2013
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http://www.positive-feedback.com/Issue65/dac.htm

http://www.positive-feedback.com/Issue66/dsd.htm

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تاثیر فیلتر دیجیتال بر پاسخ فاز خروجی آنالوگ یک سورس دیجیتال

چهار شنبه 29 دسامبر 2010
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مقاله زیر رو طراح Ayre نوشته که بنظرم خیلی خوب مطلب رو توضیح داده. قبلا هم گفتم برخی طراحان سورس دیجیتال مانند طراحان برندهای Meridian ، EMM Labs ، Spectral ، Playback Design که فیلترهای دیجیتال رو کدنویسی میکنند سعی میکنند کاری کنند پاسخ فاز بهتر بشه و سیگنال تو Time Domain وضعیت بهتری داشته باشه.

بخونید :

http://www.hifi.ir/wp-content/uploads/2010/12/Ayre_MP_White_Paper.pdf

Ayre is pleased to announce the results of an intensive research program into the audible performance of various digital filters (including “non-oversampling” filterless designs). Extensive listening tests have shown that our new custom DSP-based “Minimum Phase” filters provide a significant leap forward in both musical naturalness and ease of listening. All of our current digital products use these filters, and upgrades are also available for all Ayre disc players still in production.

The Evolution of the Digital Filter

To illustrate the performance differences between various digital filters, included are graphs of their two key parameters—their frequency response and their transient (impulse) response. These graphs allow us to trace the evolution of the digital filter,
clearly showing the changes that have led to improved sound quality.
In the beginning, there was the common linear-phase, “brickwall” digital filter. This type of digital filter is used in 99+% of all modern digital equipment, for both recording and playback, including the “Measure” position of the original Ayre disc players.
On paper, it looks nearly perfect. There is no phase shift, so it is called a “Linear Phase” filter. However, a filter can only achieve a “Linear Phase” response by introducing pre-ringing. This means that before every single musical transient, there is a “pre-echo”. In nature, there is no such thing as a “pre-echo”. All events must be “causal” in the real world—the cause must precede the effect.

A sharp, “brickwall” filter like this typically introduces about 20 cycles of pre-ringing and 20 cycles of post-ringing. It is very unnatural sounding, as the effect (pre-echo) precedes the cause (musical transient). This time-smear is interpreted by the ear-brain as both a lack of image precision in the soundstage, and also a subtle smearing of the musical sounds together.

Improving the Transient Response
The first approach to solving the problems of a conventional digital filter was to use a filter with less ringing, often known as a “slow roll-off” filter. This type of filter was used in the “Listen” position of the original Ayre disc players. By reducing the “sharpness” of the “knee” in the filter’s frequency response, the filter’s transient response is vastly improved.
Now there is only about one cycle of pre- and post-ringing. The penalty (remember, there is no such thing as a free lunch—only intelligent tradeoffs) is that there is more “leakage” (aliasing) of high frequencies above 22,050 Hz back in to the audio band. Still, this only affects very high
frequencies and the levels are low enough not to cause audible problems.
This “slow roll-off” filter reduces the time smear by a factor of ~20x compared to conventional digital filters. The net result is a much more musically natural sound, as the ear-brain is very sensitive to time-related distortions. This filter provides an outstanding compromise between frequency response and transient response, and for ten years was the mainstay of Ayre’s digital audio filters.
A natural extension to this idea is to eliminate the digital filter altogether. In theory this provides the best transient response possible from a digital playback system. There are certain audible advantages to this approach, but they are highly system-dependent and come at the expense of two separate problems.
The first is a loss of high frequencies starting at -0.75 dB at 20 kHz and reaching -3.2 dB at 20 kHz. The second is that the aliased “image” frequencies are injected into the audio signal, creating non-harmonically related distortion that increases in level as the frequency increases, reaching over 50% at 20 kHz unless additional analog filtering is employed. Careful listening tests revealed that these drawbacks outweighed the gains in improved transient response, especially given the CD format limitation with its 44.2 kHz sample rate. We therefore continued examining different approaches to digital filtering.

Eliminating the Pre-Echo
In Peter Craven’s 2004 AES paper, he proposed that the playback DAC should include a digital filter that had a corner frequency below the half-sample rate of 22,050 Hz. This would filter out any ringing (pre- and post-) that was introduced during the recording process and thereafter embedded on the disc itself. He named this an “apodizing” filter. It is a mathematical law of any filter, digital or analog, that the steeper the frequency cutoff, the more ringing it will have. In an attempt to avoid the problems of this ringing, Craven proposed using a “Minimum Phase” filter instead of the conventional “Linear Phase” filter. While this means that the phase response now varies, especially at high frequencies, there is no longer any pre-ringing. Furthermore all pre-ringing from the recording process has been filtered out, and the new playback filter only has post-ringing.
Now a giant step forward has been taken in the musical naturalness of digital audio reproduction. The unnatural pre-echoes have been completely eliminated. All of the filter’s ringing occurs after the musical transient. This is just the way that sounds occur in nature. Every sound made in the real world will have post-echoes after the original sound, so the ear-brain system more easily accepts these post-echoes from the digital filter as natural. Note that the post-ringing of a “Minimum Phase” filter is greater than that of a “Linear Phase” filter with the same
frequency response. The energy that had been contained in the pre-ringing of the “Linear Phase” filter has simply been delayed until after the transient. (Remember—there are no free lunches.) But redistributing this same total energy leads to significant gains in musical realism.
This type of digital filter is not available in off-the-shelf chips. Instead, it must be implemented in custom DSP filters. In the case of the new Ayre MP (Minimum Phase) disc players, we use sophisticated FPGAs (Field Programmable Gate Arrays) to create the desired custom filter, and the chip is easily reprogrammable should future improvements be made. This filter type is used in the “Measure” position of the new Ayre MP disc players.

The Best of Both Worlds
While the “Apodizing” filter proposed by Craven solves many of the problems with digital filters, careful listening tests conducted at Ayre showed that the multiple cycles of post-ringing still created an artificial brightness and an overall confusion to the sound. We therefore sought to combine the best aspects of Craven’s minimum-phase digital filter proposal with a slower roll-off that reduced the overall amount of ringing.
The resulting filter has no pre-echoes, and only about one cycle of post-ringing. This filter is implemented in the “Listen” position of the new Ayre MP disc players. The result is simply the most musically natural digital playback available today.
In addition to the radical improvements provided by the digital algorithms themselves, several man-months were spent conducting thorough listening tests to optimize all other aspects of the filters. The powerful customprogrammed FPGAs used in the MP series allow performance far beyond that available from off-the-shelf solutions. The mathematical calculations are conducted with 32-bit coefficients, using 64-bit accumulators to ensure the greatest degree of signal precision.
A 26x oversampling rate was determined to provide the highest level of musical realism. All of the filtering calculations are accomplished in a single pass through an FIR (Finite Impulse Response) filter. This is in contrast to conventional designs that employ a cascade of 2x FIR filters, thereby losing critical precision of the audio data as it is passed to each successive filter section. Finally, the dither algorithms for both the “Listen” and “Measure” filters were chosen on the basis of careful listening tests to provide the most realistic music reproduction possible.
The Ayre MP filter provides a significant step ahead in digital audio reproduction. The CX-7e provides this advanced technology for CDs, while the C-5xe universal disc player takes this to the limit of today’s recording technology at 292 kHz and 24 bits. In addition, this exclusive advance in digital audio reproduction is included in the Ayre QB-9 USB DAC, achieving the most natural and realistic sound available from computer-based audio systems.

http://www.stevehoffman.tv/forums/archive/index.php/t-186820.html

http://www.stereophile.com/content/meridian-8082808i2-signature-reference-cd-playerpreamplifier-measurements

http://www.stereophile.com/features/106ringing/index.html

http://hifiduino.blogspot.com/2009/05/wm8741-digital-filters.html

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سورس دیجیتال

سه شنبه 12 سپتامبر 2006
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همانطور که میدانید برای پخش یک دیسک مانند سی دی صوتی یا دی وی دی صوتی از دستگاهی بنام CD Player یا DVD Player استفاده میکنند. به این دستگاه میگیم سورس دیجیتال که به معنی دستگاهیست که اطلاعات دیجیتال را از روی دیسک خوانده و آنرا به یک شکل موج آنالوگ تبدیل میکند. این شکل موج آنالوگ در خروجی سورس دیجیتال ولتاژی بین 1.8 تا 2.5 ولت دارد که در صورت بالانس بودن خروجی این مقدار دو برابر میگردد. امروزه بیشتر کمپانی ها این دستگاه رو به دو بخش تقسیم کردند و هر یک را جداگانه میسازند. قسمت Transport یا دیسک خوان و قسمت DAC یا مبدل دیجیتال به آنالوگ. قسمت Transport دیسک را خوانده و اطلاعات آنرا رمزگشایی میکند و از طریق یک بافر به طبقه بعدی میدهد. خروجی Transport یک سیگنال دیجیتال هست که میتواند از طریق کابل نوری (Optical) یا کواکسیال منتقل شود. البته راه های انتقال فقط این دو راه نیست و بسته به طراحی Transport فرق میکند. با خروج سیگنال دیجیتال از Transport سیگنال از طریق کابل وارد بخش DAC میشود و این بخش سیگنال دیجیتال را بعد از پردازش تبدیل به آنالوگ میکند و با عبور از یک فیلتر پایین گذر به طبقه بعدی میفرستد.

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