DIR9001 chip

amit11

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Hi Friends,

I wanted to know what is the purpose of DIR9001 chip. This is in context of usb to spdif convertor to or dac having optical input.

In a DAC which has optical input.
I have read and experienced that the transport which is sending music data and time signals to external DAC plays an important role. The chip (dac chip) inside transport has effect on the final sound of external dac. I have some confusion here.

Who sends the data from the transport? Is it the dac chip inside the transport or dir9001 chip inside it, or both?

The actual reason and context of asking is: recently i bought NOS dac. It is being fed with apple airport express via optical and the apple airport express has pcm2705 chip inside it. The pcm2705 is a oversampling chip with filters, which will affect sound being transmitted to external dac (nos dac).
So should i buy usb to spdif convertor to get more pure data stream? I read that such a convertor has dir9001 chip (and probably also a dac chip). Will the dac chip convert to spdif data to dir9001 chip? Do both these chips have their own independent clocks? If dir9001 alone does the spdif conversion then the dac chip does not come into picture? Or both are required to do spdif conversion?

Thanks in advance.

Amit.
 
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DIR9001 is a digital audio interface receiver which is used before the DAC circuit to fed the digital signal for further processing.

The PCM2705 inside apple airport express (AAE) will be used or you can hear it only when you use the analog output of AAE.

Do not forget the Basic Function of DAC (Chip or stand alone), it is Digital to Analog Converter, not involved with DIGITAL SIGNAL transmission.

So when you are using the optical out of AAE then the internal DAC is no longer involved. You will get always Bit perfect stream in PCM through optical if only AAE is not internally programmed (intentionally) by some up-sampling circuit. And I am sure AAE will not mess with the clocks (why should they?).

You know about Cambridge Audio CXC which is just a CD Transport without any DAC. DAC chip or circuit is no longer necessary for DIGITAL Transmission. AAE will also behave like Pure Transport system without any DAC when it's optical out is being used.
 
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So it means that clock of dir9001 and pcm2705 are different and independent. Right?
So for optical out, its the dir9001 which is ONLY involved?

Sent from Note5
 
So it means that clock of dir9001 and pcm2705 are different and independent. Right?
So for optical out, its the dir9001 which is ONLY involved?

Sent from Note5

Yes, you are right.

pcm2705 is only there as the AAE have inbuilt analog output.
 
I have two models of AE. The first one has pcm2705 chip.
Second one has some other dac chip.
Both sound different. I like the first one.

But my confusion is:
The sound signature via analogue and optical of AE1 sounds same.
Similar for AE2 aswell.
Which leads me to believe that DAC chips affects optical out. (I also had read in old posts)

Sent from Note5
 
If jitter is too high, then it is possible. Jitter seems to be affecting internal DAC and external as well.
 
Jitter seems to be affecting internal DAC and external as well.

Then does it mean that the DAC of transport is equally important?

1: transport dac pcm2705 + dir9001
2: transport dac any sabre + dir9001
3: transport dac analog devices + dir9001

Will all 3 sound same via optical out of the transport?


Sent from Note5
 
Then does it mean that the DAC of transport is equally important?

1: transport dac pcm2705 + dir9001
2: transport dac any sabre + dir9001
3: transport dac analog devices + dir9001

Will all 3 sound same via optical out of the transport?


Sent from Note5

If the source hardware (whether disc pickup mechanism or network mechanism) is same and quality of signal modulator and optical transmission circuit is also same then OPTICAL OUT will sound same for all three transports provided that their down stream DAC also same. Actually Optical Out do not make any sound itself, you need a stand alone DAC down the stream. So you should had asked "Will all 3 signal quality be same via optical out of the transport?" instead what you asked for.

Now a stand alone DAC with well implemented signal (SPdif) retrieval mechanism or algorithm down the stream will make better sound than an average DAC. That DAC price with such sophisticated algorithm can try to touch sky depending on how deep research and time was spent behind the design.

So there is no place to talk about the DAC inside the Transport here, except the down stream Standalone DAC after Optical Out.
 
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