DAC: Frequently Asked Questions

1 Generic Questions

1.1 What is a DAC?
1.2 Why use a DAC?
1.3 What is 24/96, 24/192?
1.8 I purchased a 24/96 player and it doesn't work at 96k with an external DAC, why?
1.9 I purchased a Pioneer which is supposed to output 96KHz but only get 48KHz. Why?

2 Technical Questions

2.1 What is a Local VCO?
2.2 How does it help to eliminate jitter?
2.3 Why do you have a high-stability reclocker for the Odéon-Ag ?
2.4 What is your take on out-of-the-box power supplies? Why haven't you done that yet?
2.4 What is so great about your Solid-Tube output stage?
2.5 How does the 220 digital filter in the Platinum work?
2.6 How does it compare to the latest 4 second filter out there?

3 Product Specific questions

3.1 Can the Odéon 24 bits DAC convert regular 16bit CDs?
3.2 Is the Odéon compatible with HDCD?
3.3 What about 192KHz, Do you support 192KHz?
3.4 Is the Odéon compatible with SACD?
3.5 Isn't a plastic case without shielding prone to receive EMI noise?
3.6 Why did you use such a cheap looking power cord on the Odéon-lite ?


Q: 1.1 What is a DAC?

A: A DAC or Digital to Analog Converter is a component that takes a suite of numeric numbers and to be stored in digital format such as CDs. Since music is stored as numbers in a CD, a DAC is required to convert that stream of numbers back into an analog signal suitable for amplification.

Q: 1.2 Why use an external DAC?

A: An external DAC can be desirable to upgrade the quality of a system. Because an external DAC concentrates on doing just the conversion from digital to analog, its quality is usually superior to that of a DAC inside a player. And because it is a separate component, the user can swap it as any other unit to seek the best quality possible. We pride ourselves in the analog qualities of our DACs. Our Odéon-Ag surpasses all of the DACs we've put it against.

Q: 1.3 What is 24/96, 24/192?

A: 24/96 stands for 24-bits/96KHz. It means that the digital signal that represents the analog audio is composed of 96000 samples per second per channel and that each sample has a resolution of 24 bits. It is also called 96/24 sometimes. Compared to regular audio CD (16-bits/44.1KHz) a 24 bits sample is 65536 times more precise than that of a CD and there are more than twice as many samples. Put differently, a 16 bits CD sample can only represent a analog signal with 65536 different levels while 24 bits allow to represent that signal with over 16 Million levels. Compared to 24/96 high-resolution digital audio, a 16-bits/44.1K CD represents only 30% of the resolution. It's like the definition of the signal was cut by 2/3 leaving only 1/3 of it. Compared to 24/192, a CD holds just about 15% of that resolution. The result of 24/96 and 24/192 is a high-definition format which can represent an analog signal much more acurately that legacy CD formats. The availability of DVD format which allows to store higher amounts of data than a CD (close to 8 times more) brought 24/96 and 24/192 formats to consumer homes.

Q: 1.8 I purchased a 24/96 player and it doesn't work at 96k with an external DAC, why?

A: When the 24/96 format first came out, there were some questions about copyright violations by allowing the AES/EBU interface to export the new high resolution PCM streams outside the players. Most vendors decided to down sample 24/96 to 20/48 and convert the high resolution stream internally. Unfortunately, due to the low cost of these DVD players, the internal DACs are not all that good. If you do want to experience 24/96 with an external DAC such as our Odéon-Ag, you will need a DVD player that actually outputs 24/96. We wanted to compile a list of players that do export 96kHz out of the box but the list keeps changing. Pioneer, Theta Digital, Meridian, and some other brands do output 96KHz but we can not name them all here. Before you purchase your DVD player, make sure that it actually outputs 96KHz.

Q: 1.9 I purchased a Pioneer which is supposed to output 96KHz but only get 48KHz. Why ?

A: By default, Pioneer players are programmed to output 48KHz only, even thought they are capable of exporting 96KHz. This decision was made by most DVD manufacturers to be compatible with older legacy DACs. It is necessary to go into the setup menus to enable the player to output 96KHz. If once you have done this, you are still getting 48KHz out, that is because you are probably listening to a regular movie. Make sure that the disk you have in the player is a 24/96 (or 96/24). All standard DVD movies typically output 48KHz.

2 Technical Questions

Q: 2.1 What is a Local VCO?

A: VCO strands for Voltage Controlled Oscillator. It is an oscillator that mimics a frequency based on a reference. It basically averages the time distance between the reference frequency edges and recreates a stable frequency equal (or multiple) to that reference. Because a VCO averages the timing of the reference frequency, high frequency jitter is removed from that refence. Also, VCO are usually used to multiply that reference frequency. In the case of our Odéon-Ag DAC, the VCO uses a frequency up to 512 times the reference. This further reduces any possible residual jitter when the frequency is finaly divided.

Q: 2.2 How does it help to eliminate jitter?

A: One needs to remember that jitter manifests itself by slight early or late delays in the edges of a frequency signal. However these delays are not cumulative, this means that the sum of the delays is null in average, in other words, the sum of the errors cancels itself out. Because a VCO averages the time distance between the edges of the reference frequency over mutliple edges, it does elliminate high frequency jitter present in the source signal.

Q: 2.3 Why do you have a high-stability reclocker for the Odéon-Ag ?

A: Theoretically, a local VCO can eliminate high-frequency jitter but practically, such a VCO would take too long to lock on to the input signal and have a tendancy to wow or flutter. Also, when running at sampling frequencies such as 96KHz, it is common to run the local VCO at 256 times the input frequency, instead of 512 times as we usually do for 44.1KHz CDs. This does not reduce the jitter as efficiently as a 512x overclock. The conclusion is that VCO can only reduce jitter but not eliminate it. Our high-stability reclocker does resample the input frequency to an internal 20ppm high-stability crystal and great caution is taken to carry that clock over an impedance matched trace directly to the DAC chip. With this design, we can safely say that the conversion is done over a virtually jitter free local clock reference.

Q: 2.4 What is your take on out-of-the-box power supplies? Why haven't you done that yet?

A: There are two ways to work a power supply; IN and OUT of the box. Both have advantages and inconvenients. Manufacturers who decide to export it only tell you about the advantages. We will tell you the advantages and inconvenients of our method. There is a major inconvenient in exporting the power supply out of the box in which is that a serious DAC design should have two power supplies, one for the digital domain (AES3 receiver, digital filter) and one for the analog domain (DAC and Audio section). Some DAC manufacturers will make you think that you are getting a good deal because the power supply is out of the box when in fact, they are only providing one single power supply for the entire DAC. But for those who do it right (use large connectors with multiple power sources) there is still another large inconvenient which is that the digital power supply is carried in a cable extremely close to the analog supply cable (usually both in the same braid). Over the distance of that out-of-the-box power supply, the capacitance between the wires actually couples the noise from the digital power supplies into the analog supply. What you are not told is that digital power supplies are quite noisy (not to say Very noisy) and carry very high frequencies. The capacitive coupling of cables (no matter how small) is just as good as a conductor at those frequencies and the digital noise ends up in the analog power supply which defeats the purpose of having a separate cable for both - much less power supplies out of the box.

I believe there are a lot more advantages in using power supplies in the same box and do it right, mainly because one can keep the distances that the power supply has to travel short and thus, highly reduce emmited noise (let's not forget that a conductor is an antena too). If you opened one of our DACs you will see TWO toroidal transformers; one for the digital and one for the analog. Also they are physically positioned close to the components they power which means that the power supply is not transported over long distances. This really does lower the level of noise and the result of cleaner power supplies is inevitably a cleaner sound.

The one inconvenience mentioned everywhere is that the magnetic noise of transformers resides in the same box as the electronics. But before throwing such statements out it helps putting things in perspective. The amount of magnetic leakage is proportional to the size of the power supply (and quickly decreases with distance at the frequency handled). In the case of a DAC such as ours which power's consumption is less that 4 Watts, there is not much power being transformed and we use toroidal transformer which are the best for they have virtually no leakage. We place no analog components closer that 1.5 inches from any transformers which is a very safe distance to guarantee no magnetic induced noise.

We guarantee you that you are getting the BEST design in our opinion but we only have one more thing to say, just try it out against any DAC of any price with or without a separate power source and make your own opinion for yourself.

Q: 2.5 What is so great about your Solid-Tube output stage?

A: Solid-Tubetm is our signature technology. Although we invented it in 1997 while designing our next generation of amplifiers, its design is excellent when used in low power analog stages. It is a new and clever combination of jfet, mosfet and bipolar transistors where each technology works at hiding the shortcomings of the others while extracting only the most desirable linear characteristics of each. Such an assembly creates a building block similar to a tube yet yields excellent linear characteristics remindings of the sound of tube components. Solid-Tube is experienced as a very natural and extremely open sound stage where the system disappears to leave only the music. Yet this transparent sound comes with a touch of warmth otherwise found in tube electronics, we call it Solid-Tube technology.

Q: 2.6 How does the 220 digital filter in the Platinum work?

A: That is our latest two to the power of twenty re-clocker technology included in the Odéon-Platinum. Thanks to the ever shrinking silicon, our new reclocker technology is capable of interpolating the input signal to 220; that is, between every two digital audio samples entering the DAC, our reclocker re-creates over one million data points allowing us the resample the signal with an incredible acuracy to a new local precision clock of 210KHz for a virtually jitter-free performance. Combined with our award winning digital filter which can virtually recreate 24 bits of detail out of 16 bit CDs, the Odéon-Pt will not only deliver the finest performance from high-resolution audio sources but it will also bring your current CD collection to a new and incredible level of detail and sound stage as it upgrades them to 24 bits at 210KHz.

Q: 2.7 How does it compare to the latest 4 second filter out there?

A: There is nothing extraordinary about an insanely huge amount of cacaded gates to delay the signal by 4 seconds. It is one thing to queue up enough samples to analyse the input signal, while it is another to waste silicon real-estate to simply delay it. We believe our 2 to the power of 20 digital filter is the state of the art in digital filtering and up-sampling technology. Not just because it is the result of over 7 years of research on the subject, but it is capable of accurately recreating over 1 million samples between two of the of the input signal. And it olny delays the signal by about 23milli seconds. This allows us to observe the signal with at least one thousand samples while we keep gathering signal history past the first 23ms of audio to further push the depth of the filtering analysis. In a way, the audio signal improves ever so slightly past the first 23ms of an audio track but in practice, it is un-noticeable. Once you think about it, notbody can judge audio performance based on the first 23ms only of an audio track!. The big advantage of our filter is that the delay is small enough that it becomes possible to use the resulting DAC in practical applications such as cascading more than one for multi-channel configuration or better yet, use it in a audio/video configuration where the picture needs to be in sync. with the audio. Remember that our Odéon-Ag and Odéon-PT DAVs will be upgradable through the use of DSP add-on boards to extend your high-end 2 channel audio system to a high-end multi channel audio/video system.

Product Specific Questions

Q: 3.1 Can the Odéon 24 bits DAC convert regular 16bit CDs?

A: Yes of course. All our DAC products are 16, 20 and 24bits compatible and they will actually upgrade the quality of the input signal by up-sampling the data to 24 bits before conversion. Our DACs also oversample the input sampling frequency by up to 4x for the Silver and Platinum. The original Odéon-lite will upsample up to 2x. This means that when converting regular 16bits/44.1KHz CDs, the Silver and Platinum series are actually upsampling to 24bits/176.4KHz while the Odéon-lite upsamples to 24bits/88.2KHz. All our Odéon DACs detect the format on the input and will convert anything from 8 to 24 bits at sampling frequencies from 32kHz to 192kHz (Silver and Platinum) or 96KHz (Odéon-lite).

Q: 3.2 Are the Odéon products compatible with HDCD?

A: Absolutely, all our DACs products are HDCD compatible. We beleive our proprietary digital filters are better than all 3rd party filters we have tried. For this reason we are not adopting 3rd party filters such as HDCD. Even though our digital filter does not decode HDCD, it will play such recordings reverently. We invite you to stack our DAC against any HDCD specific DAC out there and compare for yourself.

Q: 3.3 What about 192KHz, Do you support 192KHz

A: Both the Odéon-Ag and Odéon-Pt (Silver and Platinum) DACs supports 192KHz over SPD-IF. When the Odéon-Ag first came out, the 192K interface was experimental but it is now supported over optical link and compatible with both our higher-end DACs. The only caveat is that there are almost no modern DVD players that do output 192KHz over optical. It is actually rare to find DVD players that even output 96KHz, although those are more readily available. (We at Birdland, use computer IO cards to test and play 192KHz sources).

Q: 3.4 Is the Odéon compatible with SACD?

A: Both the Odéon-Ag and Odéon-Platinum were designed with SACD in mind. When the Odéon-Ag first hit the market, there as no published standard by Philips or Sony of an interface between the transport/player and external DACs. We left the door open by adding internal slots for hardware upgrades while we waited to see which interface would support the format. There were drafts for Firewire IEEE-1394 with DTCP encryption along with a few other proprietary interfaces. As of January 2010, no interfaces widely available on players have seen the day except maybe HDMI but it also seems as SACDs didn't penetrate the market as well as Sony hoped (probably because the 24/96 and 24/192 formats are widely supported over legacy interfaces such as optical Toslink). Either way, the lack of availability for a standard helped us decide not to manufacture an upgrade card for the Silver or Platinum series. You may want to check our up-coming Platinum-71 multi-channel DAC with HDMI inputs though. Both DTS and Dolby have the equivalent of lossless uncompressed multi-channel master audio which we believe killed the need for SACD which was only two channels.

Q: 3.5 Isn't a plastic case without shielding prone to receive EMI noise?

A: Actually, aluminum cases only shield electronics from the electrical vector of high frequency noises. If you were to open one of our DACs you will notice that our Printed Circuit Board (PCB) is double sided (which means there are traces both sides of it) and that half the bottom side is practically a SOLID COPPER plane connected to the analog ground (the other half is also a solid copper plane connected to the digital ground). These planes act as an electrical shield like an aluminum box would. Of course, for such a unit dealing with line signal levels, aluminum or not shielded case, we strongly recommend you DO NOT place it on top of a TV set, Video projector or very close to your power amplifier, It simply is not a good idea regardless of the case.

Q: 3.6 Why did you use such a cheap looking power cord on the Odéon-lite?

A: At the time of design, we believed that a fixed cord would be preferred as it would offer better direct connection. And because our box is not metallic, there was no real advantage in using a 3 prong plug (besides the limitation in back-pannel real-estate). The AC wire in the Odéon-lite is literally the same as the one found in larger round power cables with three conductors except for it has no ground. We do understand now that, most our customers want IEC so they can trade power cords for higher-end cables or for the convenience of not having a permanently attached cord. All our newer units use IEC or some otherwise detachable cord.
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