DD/DTS 5.1 DACs & Connections

[jamison162]

I have a Denon AVR 1804 Receiver and Denon DVD 2200. Which should I use for the digital sound decoding? I'm not sure, but I believe the DVD player has the superior DAC's (Burr Brown comes to mind). Is this way definitely recommended over running all digital signals straight to the receiver? And is there any disadvantage to running analog audio from the DVD player to my receiver. If that's what I should do, I will prolly end up using the only digital coax in connection on the 1804 for my STB digital out.

Does this sound correct?

[Sir Terrence the Terrible]

I have a Denon AVR 1804 Receiver and Denon DVD 2200. Which should I use for the digital sound decoding? I'm not sure, but I believe the DVD player has the superior DAC's (Burr Brown comes to mind). Is this way definitely recommended over running all digital signals straight to the receiver? And is there any disadvantage to running analog audio from the DVD player to my receiver. If that's what I should do, I will prolly end up using the only digital coax in connection on the 1804 for my STB digital out.

Does this sound correct?

In this situation neither provide a profound audible advantage over another. Dts and DD decoding is pretty standardized. No matter which chip reproduces it, it will probably sound the same on most hometheater rigs. This is because largely the decoder is dumb by nature in both of these formats, and the encoder had the brain, and does most of the work. The decoder interprets the instructions from encoders precisely, whether its done from the receiver, or a DVD based decoder. What you should really worry about is the bass management from DVD player based decoders. Alot of players with bass management on board do not offer enough selections for bass management, or it is cumbersome to setup.

[sy_lu]

... This is because largely the decoder is dumb by nature in both of these formats, and the encoder had the brain, and does most of the work. The decoder interprets the instructions from encoders precisely, whether its done from the receiver, or a DVD based decoder....

Decoder does matter. Decoder is actually a CPU (DSP is a special CPU). Because DD and DTS are lossy compression, there are more than one way to decode or decompress. Different algorithms, speed and precision will affect the results even before it is fed to DACs.

[jamison162]

What are you telling me then?

[Sir Terrence the Terrible]

Decoder does matter. Decoder is actually a CPU (DSP is a special CPU). Because DD and DTS are lossy compression, there are more than one way to decode or decompress. Different algorithms, speed and precision will affect the results even before it is fed to DACs.

Sorry, but you are quite incorrect. Dts and DD do not use their decoder the same way as PCM does. Dts and DD come in bit packets, as opposed to bitstream like PCM. The signals contain all of the information derived from the encoder, unlike PCM which is dependent on the quality of A/D-D/A conversion. The decoder in both Dts and DD is essentially dumb, and takes ALL of its instruction from the encoder. Each process has it's own proprietory way of encoding and decoding so there is no other way to decode its signals except through their own decoding engine. Dts uses the coherent acoustic codec for its encoding/decoding scheme, and DD uses AC-3.

Dts and DD have the ability to carry extension data, PCM does not. Dts has the ability to encode more channels via that extension data, PCM cannot . PCM is not a very efficient carrier of data, both Dts and DD are. Dts can process and transparently pass 16,20 and 24bit depths at 44.1,48, 96 and 192khz, PCM data on CD cannot handle any more than 16/44.1khz on CD.
Dts can operate at both lossy and lossless modes, all of these processes are intiated by the encoder, not the decoder.

It is clear by reading the white paper of both Dts and DD that their process is quite different than decoding PCM on a CD or DVD-A.

There are special chips by both Motorola, and crystal audio that handle all the processing for both formats. These chip are quite powerful as they must decode every instruction in the data packets effectively.

[jamison162]

So what I gather is...for Dolby/DTS digital audio, the signal will be the same regarless of which component does the decoding. But...CD, DVD-A, etc., the DVD 2000 will make a difference with the better Burr Brown DAC's. Correct?

[sy_lu]

Sorry, but you are quite incorrect. .

Well, I beg differ. You are correct to the point of data unpacking. But the real decoding process starts with inverse TDAC transform. This is a DSP process can be implemented by either a fixed or floating point DSP with different speed and precisions. Just like any digital filters, the results can differ. A low speed fixed point DSP will not be as accurate compare to a high speed high bit (data wise) floating point DSP.

[Sir Terrence the Terrible]

Well, I beg differ. You are correct to the point of data unpacking. But the real decoding process starts with inverse TDAC transform. This is a DSP process can be implemented by either a fixed or floating point DSP with different speed and precisions. Just like any digital filters, the results can differ. A low speed fixed point DSP will not be as accurate compare to a high speed high bit (data wise) floating point DSP.

Dts and DD decoding is standardized, and use chips approved by both companies. Dts does NOT use TDAC, it uses ADPCM, or Adaptive Differential PCM. Dolby digital does use TDAC, but everything is completely standardized and optimized for DD decoding. The speed of the DSP processor is optimized for correct playback of each format, so it does not differ from chip to chip. Dts and DD will sound exactly the same from decoder to decoder, so there is no advantage of using an external or internal decoder.

You really need to go to Dts and Dolby's website and read up on both codecs.

[Sir Terrence the Terrible]

So what I gather is...for Dolby/DTS digital audio, the signal will be the same regarless of which component does the decoding. But...CD, DVD-A, etc., the DVD 2000 will make a difference with the better Burr Brown DAC's. Correct?

This is correct.

[sy_lu]

You really need to go to Dts and Dolby's website and read up on both codecs.


Actually, I did. Here is a quote from DD's white paper,

"The TDAC transform is basically an FFT followed by an additional ‘twiddle’ stage; it features low computational complexity with good frequency selectivity, facilitating cost- effective hardware implementation with excellent signal performance."

Any time you do a time <->frequency domain transformation by FFT, you introduce compuational error. This is because FFT is a floating point operation in nature and involves divisions. There are many ways to implement FFT and each will produce very similar but not completly identical result. The same goes with how floating point operation is implemented. You can look up any number of books or articals about FFT and its error margins.

The apporval process is means the algorithm and precision is within DD's spec but not necessay will product same result. Now as far as whether one can hear the difference that is a different story.

[Sir Terrence the Terrible]

Actually, I did. Here is a quote from DD's white paper,

"The TDAC transform is basically an FFT followed by an additional ‘twiddle’ stage; it features low computational complexity with good frequency selectivity, facilitating cost- effective hardware implementation with excellent signal performance."

Any time you do a time <->frequency domain transformation by FFT, you introduce compuational error. This is because FFT is a floating point operation in nature and involves divisions. There are many ways to implement FFT and each will produce very similar but not completly identical result. The same goes with how floating point operation is implemented. You can look up any number of books or articals about FFT and its error margins.

The apporval process is means the algorithm and precision is within DD's spec but not necessay will product same result. Now as far as whether one can hear the difference that is a different story.

When you read Dolby spec's carefully, you understand completely how they understood the strengths and weakness of their whole encoding/decoding process. The algorythm is fixed, and standardized, and the chips were designed to handle the process. Whether it is a Motorola, Analog devices, crystal audio, or any other un-named chip, the algorythm is the same, performs the same, and is implemented the same. This is to ensure quality control, and continuety accross all lines of product. The manufacturer decides the quality of any ancillary stage upstream, and downstream of the decoding chip, and how that differentiates the sound quality of their product from someone elses. It is not the chip itself that influences the quality, but the other stages within the signal chain.

Dolby digital includes quite a robust error correction system within the Dolby Digital spec So any computational errors introduced by time/frequency domain transformation are easily identified, and corrected by the system. It is not in Dolby's favor to have different levels of quality in the decoding of its data stream. That would give a manufacturer the freedom to use lost cost, poor performing chips to meet cost points. This would seriously compromise quality assurance across many lines of product.

I think what you are missing is that all of these processes occur at the encoding stage, not the decoding stage. The decoder just follows the instructions given from the encoder. So in the case of both Dts and DD, it's the quality of the encoder that makes the difference, not the decoder. I think where you are going wrong is you think the decoder actually does all of the work, and that is not so in this case.

[jamison162]

Just tell me how to hook it up - all of this is way above me. :)

[Sir Terrence the Terrible]

Just tell me how to hook it up - all of this is way above me. :)

Use whichever decoder has the best bass management. If it is the receiver, use the coaxial connection. If the player has the best bass management(doubtful) then use the 6 channel analog outputs.

If you use a ladder then this could be right even with you! LOL