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Old 27th November 2002, 09:17 PM   #1
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Lightbulb New DAC project - need some suggestions!

Hey all!

I'm new to the forum as of today. I've been reading some of the posts the last few days, and have been very pleasantly surprised

Last year, I developed an outboard Dolby Digital and DTS decoder with two other guys for our Senior Design project. We based it around the older Cirrus DSP family, using the far less complex CS4926, and the DIR portion of the CS4226 multichannel CODEC. On the output, we used Burr-Brown PCM1720 DACs and some Burr-Brown OPA134 series for the analog filtering. It was an awesome experience! I also took two DSP classes senior year. The combination really got me interested in digital audio. Up to that point, I had been a real analog junkie, hoping to design amplifiers.

I currently have a Denon DCM-370 5-disc carosel, which has HDCD decoding using the Burr-Brown DACs for those who don't know. When I bought the player... (gosh, 3 years ago now!), I was simply amazed with the sound quality. To this day, I still love the "smoothness" of the HDCD DACs.

My college roommate and I constantly tried out new CD players and DVD players, trying to find a better sound. Last year, he bought the new Outlaw 950 preamp. HOLY COW! We actually found some DACs that came near the fluidness of the HDCD DACs and yet offered additional dynamics, clarity, and punch. I'm not exactly sure which chipset is used in the Outlaw, but I'm guessing it's the CS4383 DAC. Depending on the day and the particular CD I was listening too, sometimes I like the Denon's DACs, and sometimes I liked the Crystal DACs in the Outlaw. This has spurred me on to attempt to find the best sounding DAC system (of course, this is subjective).

So... my thoughts/ideas right now cosist of the following. I obviously need a DIR, and DAC as the bare minimum. But I have decided that I want to be able to obtain more than what is offered from such a system. I'd like to recover a more stable master clock than what a standard DIR can deliver in order to reduce jitter, so I'd like to either use something like the Analog Devices Sample Rate Converter AD1890, or develop my own reliable PLL circuitry. I also have been thinking of separating the oversampling circuitry from the DACs in a configuration similar to using Burr-Brown DF1704 and some PCM1704 DACs. I would also like to try some of the more exotic stereo DACs from Cirrus/Crystal.

I had initially attempted using the CS8414 DIR in our senior design project, but we were never able to get it to even lock on a signal. I spent weeks trying to analyze the darn error outputs from it (I designed a buffer stage with some 3904's driving a series of LED's) during senior design, but we eventually just moved on to using a pre-developed uP program for accessing the CS4226 we had on hand... (time was a HUGE factor). I'm wondering if any of you have some suggestions for an easier-to-work-with DIR... there's also a very good possibility I was doing something very stupid with my prototype board (Senior Design = no sleep for 9 months )

Also, does anyone here recommend the AD1890? Anyone have any problems or good experiences with it? Recommendations for a similar, better performing device?

And... any suggestions on my selection of DACs?

In the end, I'd like to avoid having to develop a uC interface for any of the IC's I use. I'd like this design to be as simple as can be done to generate some really good sound. If a uC is absolutely necessary, what are some recommendations for some that you have had good luck with in DAC systems?

I REALLY appreciate your time if you've actually managed to make it through all this. I look forward to hearing from any of you!
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Old 27th November 2002, 09:32 PM   #2
jwb is offline jwb  United States
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I think if you search on this forum you will find that CS8420, AD189x, PCM1704, DF170x, CS43122, et. al. are the standard choices. Many people also use the Philips and Analog Devices DACs. There are many discussions, schematics, photographs, and so forth.

If I may summarize some discussions about DIRs, it would be this: CS841x have Schmitt trigger inputs which make Jocko Homo angry. CS8420 has a better receiver, but requires either dozens of pull-up resistors or a microcontroller. The AD189x is an ASRC which can be controlled without a µC, but doesn't include a receiver. The DIR1703 has a really vague datasheet but seems promising.

My preference is for the CS8420. If you don't want the sample rate conversion, that stage can be bypassed.

Good luck!
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Old 27th November 2002, 09:39 PM   #3
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I am also planning a DAC project at this time, using the CS8420 receiver/Sample rate converter, the Burr-Brown DF1704 (or 1706) upsampler/digital filter and four PCM1704 DACs for stereo balanced output. I/U converter and output stage will be from the Passlabs D1 (see service manual on www.passlabscom). I hope to have a draft drawing of the circuit finished next week. But I was also consiering the AD1896 SRC together with a different receiver.

But an open question was how to get digital data out of SACD or DVD-A, as there are no commercial products with digital outputs of this high-data rates. I am not sure if it is possible to pick up the data stream just before the integrated DACs.

peter
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Old 27th November 2002, 09:40 PM   #4
tiroth is offline tiroth  United States
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Holy god...outboard DD/DTS is the holy grail here. ^_^ Welcome.

Personally, I would recommend DIR1701/1703 for your DIR. Good jitter rejection and has 96kHz support. If needed, pass this through an AD1896--better specs than 1890.

I've already done some substantial work on a design with DIR1701 frontend and AD1896 to AD1853 DAC; this could certainly be adapted to the DAC of your choice.

You can see some info about the project here
AD1853 ASRC/DAC boards FS?

or on my website:
http://www.anidian.com/audio/construct/adac_1.shtml

If you would be interested in collaborating send me an email. (Work has been paused due to my recent marriage ^_^)
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Old 27th November 2002, 10:08 PM   #5
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Wow, responses already - you guys rule !!

Thanks a bunch now, and look forward to reading some more.

Tiroth, the DD/DTS decoder is going to be impossible for anyone without a few million $$ laying around to pay for the licensing fees. We were granted some educational licenses for our project from both Dolby and DTS... It was a lot of fun though

Tiroth, I would be interested in collaborating... my problem is that I have absolutely no experience with layout or any tecnique with respect to that.

I'll get back to you later tonight after work -

Take care all
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Old 28th November 2002, 08:50 AM   #6
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Default Re: New DAC project - need some suggestions!

Quote:
Originally posted by Tieftoener
And... any suggestions on my selection of DACs?
Have you checked here?

PCM1792 and DSD1792 with 132dB SNR
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Old 28th November 2002, 11:27 AM   #7
guido is offline guido  Netherlands
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Smile more options

Hi,

You wrote: "I'd like to recover a more stable master clock than what a standard DIR can deliver in order to reduce jitter, so I'd like to either use something like the Analog Devices Sample Rate Converter AD1890, or develop my own reliable PLL circuitry. "

Two more options:

- async reclocking
- master clock in DAC and feed it back to the transport.

Last option is the way i am going: 2*TDA1541 (one left, one right channel) and async FIFO between DAC and transport.

Greetings,

Guido B
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Old 28th November 2002, 11:41 AM   #8
skaara is offline skaara  Slovenia
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pquadrat: Im hoping to make an exactly the same dac that you Please post/email schematic/pcb when you will have it.

Tieftoener: We only need DTS decoder for ourselves not for commercial purposes
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Old 30th November 2002, 10:13 PM   #9
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>>>Holy god...outboard DD/DTS is the holy grail here. ^_^ Welcome.

I do not want to decode the DD signal, just get the already decoded I2S data stream out of the player to a different DAC. And not even for DD or any multi-channel, only for DVD-A and SA-CD.

And about licence: Don't want to sell this, and I don't care what the industry dislikes to be done. I take the right to use any bit that's on the disk, I paid for it. I don't want to copy anything. Just listen to the recording, with equipment I can trust.

skaara: will do. Just some delay because my newly build Phono preamp makes some trouble, see pass forum. And I am nut sure yet to take the CS842 or the AD1896/DIR1203.

Tieftoener:
I will do a layout for my project, maybe we can get it modular to put a DSP module as an option on it?
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Old 30th November 2002, 11:17 PM   #10
skaara is offline skaara  Slovenia
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pquadrat: You meant dir1703? I suggest you to use cs8420 or dir1703..
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