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Sony D-E900 Player and Dual DACS? - Page 2

post #16 of 24
2/14/02 at 8:34am
Thread Starter 
Thanks Duncan! Will now proceed to do some heavy research...but hey, I'm pretty satisfied with my player (even if its possibly single DAC's great sound is all in my head).

pedxing, yup, there have been many word-of-mouth references to the D-e905 (which is the US's version of the Japanese D-E900) being dual DACs. Bear in mind many of these comments are found in head-fi/headwize archive of the past year. So, many were made out of respect of a legend/cult thing.

Web references to the D-e905/e900 having dual DACs (at least when googled) are again only found in some casual throwaway comments. www.goodstereotogo.com mentions it in passing in its CD introduction...some poll comment on stereophile again mentions "dual bitstream". Also a chinese website has profiled it against the SL-CT790 as some sort of Battle of the Great PDCPs.

But otherwise, I'm satisfied with it. I do want to find the origin/truth to this legend, so if anyone out there with past experience with the d-e900/905, know for sure, please pass it on.

Wouldn't it be just PERFECT that now that we have a source for the D-e900/e905 (out of production since 1998), we can't find out in print what made it so mythical?
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post #17 of 24
2/14/02 at 1:51pm
I wouldn't worry so much about pcdp having dual dacs or not. What it comes down to is whether or not if you like the sound of it. Its entirely possible that a single dac cd player can sound better than dual dacs. Some sales people who sell component CD player sometime say that the dual dac feature is just marketing hype and some companies stick two dacs together with some funny circuits as a cheap solution to make up for inqadequencies of a single lone dac. Other companies were more innovative and actually redesigned and fused two good dacs into one packaging (same number of chips on board then).

I have no idea what dual dacs really do, but I have read some bogus literature that certain designs make a vote which output signal is better or sometimes they use some weighed averaging based on the differences of something. Any one knows what dual dacs really do?
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post #18 of 24
2/15/02 at 7:46am
Thread Starter 
Again from another thread on here or headwize (search for dual dacs), they are basically working as single dacs for the left and right channel. So you're getting less sloppily recreated sound.

Or something...

and another web reference was in an ebay auction that someone here won. just in december.
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post #19 of 24
2/16/02 at 11:04pm

Re: Sony D-E900 Player and Dual DACS?

Quote:
Originally posted by PianoBlack
...So the question is...does anyone know if later production models of the D-e900 would NOT have dual DACs?

Note: I just want to know for bragging rights but I guess I should be satisified huh?....
I also want to brag about my E905, so I've been doing some investigating, and I think have the answer. Just received the Sony Service manual and it shows both the D-E900 & D-E905 models as identical. But it looks like the single vs. dual DAC debate may be a matter of semantics.

The E900/E905 uses a single DAC chip #TC9438FNEL. But it uses a delta-sigma modulator circuit on that chip. This circuit is also known as a "1-bit Dual D/A converter." You can see why this has been so confusing. As I understand it, this means the following:

It is a 1-bit dual digital-to-analog converter.
It does not use dual 1-bit digital-to-analog converter chips.

What may be even more interesting is this chip was not listed by Duncan as one of those in the D777. The closest chip in that model may be the #TC7089404FN. We may assume the D777 & E905 use different 1-bit DAC's.
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post #20 of 24
2/17/02 at 6:03am

Re: Re: Sony D-E900 Player and Dual DACS?

Quote:
Originally posted by saronian
The E900/E905 uses a single DAC chip #TC9438FNEL. But it uses a delta-sigma modulator circuit on that chip. This circuit is also known as a "1-bit Dual D/A converter." You can see why this has been so confusing. As I understand it, this means the following:

It is a 1-bit dual digital-to-analog converter.
It does not use dual 1-bit digital-to-analog converter chips.

What may be even more interesting is this chip was not listed by Duncan as one of those in the D777. The closest chip in that model may be the #TC7089404FN. We may assume the D777 & E905 use different 1-bit DAC's.
Saronian,

After noticing my part number was a lot different to yours, I had another look at that particular chip, and noted that the EXACT model number was TC7089404FN

the 708 was printed a lot smaller than the rest of the number... so my part number ties in a lot more with your one...

If you bear in mind that the D777 is three years the DE905s senior, then maybe, how close the model numbers of those chips are, the D777s is the same design of chip, but just an older revision?!

Also upon further investigation the 10 Second ESP Memory for the D777 is based on the CXP83416-018Q711A46E chip (largest chip on the PCB), It would be interesting to know what the equivilant part number is on the DE905?!

Also, I've just pulled this off of the 'howstuffworks.com' website... might be of some interest...

Quote:
What a 1-bit Dual D/A converter does is allow the digital-to-analog conversion to happen without the need for all those extra resistors. Essentially, this type of DAC does not use a bank of resistors operating in parallel. Instead, it creates a carefully modulated signal from the digital. The converter relies on noise shaping, a phenomenon that takes advantage of the human ear's inability to notice noise when it occurs in higher frequencies. Basically, the human ear is most sensitive to noise at 5 KHz, and is almost unable to detect it at 20 KHz.

A key part of the converter is a circuit called a delta-sigma modulator, which takes the binary signal (1s and 0s) from the CD and changes them to a steady pulse, called a pulse train. The pulse train contains an average of the change in the amount of energey represented in the sample. A low-pass filter removes all time-domain information and recovers only the average energy of the pulse train that feeds it. The key here is to understand that the pulse-train waveform is clocked at a very high frequency compared to the 44.1 KHz sample rate. The pulse train is sent through the DAC and changed into an analog signal.

The delta-sigma circuit has two main sections:

Delta receives the incoming digital signal and monitors the outgoing pulse train. It creates an error signal, which is based on the difference between the binary signal coming in and the pulse train going out.

Sigma adds up the results of the error signal created by delta and supplies this sum to the low-pass filter.

The error signal is used by the low-pass filter to average the analog signal. Basically, this means that minute adjustments are made to the analog signal to compensate for the differences between the binary signal and the pulse train. This page provides incredible detail and diagrams of the entire circuit, as well as a detailed explanation of the process.
So, if you click that link above, you will see that Dual 1bit DAC is actually a non-existant term!! - ALL 1 bit DACs use the Delta / Sigma theory!!

So, the DACs in BOTH the D777 and the D-E905, whilst maybe being of a better grade than standard DACs, are in fact based on EXACTLY the same DAC design principles as every other 1 bit DAC on the market!!
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post #21 of 24
2/17/02 at 10:38am
Thread Starter 
WAHAHAHAHA!

Thank you very much Duncan and Saronian! And that's all for this episode for 'Mysteries of the Hyped and the Obsessed'... join me next time as we explore the legend of wooden headphones...


BTW, that was amazing detective work. Good job guys!
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post #22 of 24
2/17/02 at 11:20am
lol PianoBlack, no problem

I've been puzzled myself by the hype of the Dual DACs ever since my early days on HeadWize (a year ago)... but I must confess that i'm a little bit downhearted now I know the truth.

Nevermind, on the plus side, that means that there are less things to go wrong, and it IS still a great sounding player

Oooh, only 13 days until I get my D-EJ1000... then the battle commences as to which PCDP will win my affections
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post #23 of 24
2/17/02 at 5:45pm

Re: Re: Re: Sony D-E900 Player and Dual DACS?

Quote:
Originally posted by Duncan
So, the DACs in BOTH the D777 and the D-E905, whilst maybe being of a better grade than standard DACs, are in fact based on EXACTLY the same DAC design principles as every other 1 bit DAC on the market!!
Between PianoBlack, Duncan & myself, we make a good investigative team. I like that we are getting to the truth while also acknowledging that the music and sound are most important.

I did some additional searching and found the spec sheets for both DAC chips. They are made by Toshiba and appear to be similar except for one feature. The TC9438FN, which is in the E905, incorporates the digital bass boost within the chip. You can find them as PDF files at these URLs:

Toshiba TC9404 (548K)
http://www-pr.chipbook.co.kr:8080/pd...iba/TC9404.pdf

Toshiba TC9438FN (732K)
http://www-pr.chipbook.co.kr:8080/pd...a/TC9438FN.pdf

You should check out the Mega Bass Boost frequency plot for the TC9438FN. Just as I heard, the treble gets a huge boost along with the bass.

I'm excited that Duncan is getting a D-EJ1000 and I look forward to his opinion on the sound. This is one of the best looking designs I've seen.
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post #24 of 24
2/17/02 at 6:17pm
Saronian,

Thanks for finding those PDF Datasheets... I couldn't work out who 'TC' were, so... thats good investigative work by you there

After reading the stats on those sheets, i'm really interested in an A/B comparison with the D777 and the D-E905, it looks like (on paper) the D777 is the more noise free of the two having a higher S/N Ratio... although the D-E905 might well be marginally more dynamic sounding...

And, the bass... that figures, on the D777 its normal Bass-Boost, and on the '905 its digital... obviously on-chip!

So, all in all... which ones best? well, without an A/B test i'd say its purely a matter of personal opinion, both chips have plus, and minus sides to them which probably cancel each other out at the end of the day

The EJ1000, I already know that it sounds slightly darker than the D777, but a lot quieter... but that was only a 5 minute demo... So, rest assured a proper write up will appear after some audition time

Thanks
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