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Old 17th December 2004, 07:29 AM   #1
ABO is offline ABO  Netherlands
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Default Is the CS8420 really that bad?

I've been reading a lot about DAC's lately. I am planning on building a DAC from Elektor boasting CS8420/8414, DF1704 and two PCM1704.
I was going to use the 8420 upsampler, but after reading this forum I am somewhat reluctant to use it.

I have following two questions:

- Is there anybody who has tried the CS8420 in this particular DAC?

I could imagine that its (subjective and objective) performance is depending on the particular implementation. For example Elektor use Goudreau's triplets for local decoupling! I would be very interested in hearing experiences from people who started with CD8414 and later upgraded to CS8420.


- Are there any other high-end DAC designs available?

NONOS DACs seem to get a lot of attention on this forum. I suspect however that the reason for their popularity is mainly induced by their simplicity and low cost.
I am looking for a available design with state of the art technology.

Thanks,

ABo
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Old 17th December 2004, 07:42 AM   #2
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Default Re: Is the CS8420 really that bad?

Quote:
Originally posted by ABO I've been reading a lot about DAC's lately. I am planning on building a DAC from Elektor boasting CS8420/8414, DF1704 and two PCM1704.
I was going to use the 8420 upsampler, but after reading this forum I am somewhat reluctant to use it.

I have following two questions:

- Is there anybody who has tried the CS8420 in this particular DAC?

I could imagine that its (subjective and objective) performance is depending on the particular implementation. For example Elektor use Goudreau's triplets for local decoupling! I would be very interested in hearing experiences from people who started with CD8414 and later upgraded to CS8420.


- Are there any other high-end DAC designs available?

NONOS DACs seem to get a lot of attention on this forum. I suspect however that the reason for their popularity is mainly induced by their simplicity and low cost.
I am looking for a available design with state of the art technology.

Thanks,

ABo

Hi ABo, I believe the reason for NON-OS is also better sound. At least for me the first NON-OS experiment was a jaw-dropping experience. Personally I do not like upsamplers. I heard two of these made by Electrocompaniet and Musical Fidelity. I was not impressed. I feel the CS8414 is worse than the CS8412 for redbook CDs.
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Old 17th December 2004, 08:00 AM   #3
Prune is offline Prune  Canada
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I've built a version of jwb's simple DAC that uses a CS8420, and I like the sound very much. However, I wouldn't recommend that chip because it has a bug (I believe in all revisions) that necessitates a workaround, meaning extra complexity (see the latest datasheet for details). I used the workaround, but if you are starting a new DAC project you should consider another asynchronous sample rate converter.

You may also look around for the few DAC projects that slave the transport to the DAC clock. That seems the best theoretical solution, though ugly in practice due to the need of an additional interconnect.

Regarding the OS/non-OS, why not add a switch so you can toggle between the two modes and be able to do listening comparisons? Using a computer to drive the switch, you can use software such as abchr to perform a blind test by yourself.
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Old 17th December 2004, 08:13 AM   #4
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Question jwb's DAC schematic

Quote:
Originally posted by Prune I've built a version of jwb's simple DAC that uses a CS8420, and I like the sound very much.
Hi Prune,
Where can I find a schematic of jwb's DAC?
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Old 17th December 2004, 08:33 AM   #5
Prune is offline Prune  Canada
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Here.
But you already know this, as I see at least one post by you in that thread.

The MOSFETs have too much input capacitance, so I replaced the analog stage with a JFET buffer, and added a step attenuator for volume control, motorizing it so it can be remote controlled. In the digital section, I added a discrete logic reset circuit to catch bug-prone states of the CS8420. Latching relays for switching I/O connections, some extra logic for control and remote control, standby supply, and it turned out a nice project.
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Old 17th December 2004, 08:49 PM   #6
JohnW is offline JohnW  Hong Kong
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"Is the CS8420 really that bad"

YES - Just Terrible! Completely destroys the audio performance / sound stage.

Also the PLL on the integral SPDIF Rx has a Bi-Modal phase noise distribution. This means instead of having a single clean narrow clock carrier (single frequency). There are two carriers (two frequencies) close together – poor PLL design.

On a spectrum analyzer sweep, the profile of this distribution depicts the wrong kind silicon……. (At least in this instants)

John
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Old 18th December 2004, 12:39 AM   #7
Prune is offline Prune  Canada
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Quote:
wrong kind silicon
What does that mean?

Also, this brings up the question of which are the best ASRC chips.
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Old 18th December 2004, 01:07 AM   #8
jwb is offline jwb  United States
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I find the CS8420 was good enough for my "cheap" DAC. The bug is annoying, but you won't run into it if you never unplug the digital cable, and if you turn off the DAC before turning off the source.

That said the AD1896 is better, and the SRC4192 is better yet, and pin-compatible with the Analog part. However with these parts you'll need a separate DIR, for example CS8416.
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Old 18th December 2004, 01:38 AM   #9
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Default Re: Is the CS8420 really that bad?

Quote:
Originally posted by ABO
I've been reading a lot about DAC's lately. I am planning on building a DAC from Elektor boasting CS8420/8414, DF1704 and two PCM1704.
I was going to use the 8420 upsampler, but after reading this forum I am somewhat reluctant to use it.

I have following two questions:

- Is there anybody who has tried the CS8420 in this particular DAC?

I could imagine that its (subjective and objective) performance is depending on the particular implementation. For example Elektor use Goudreau's triplets for local decoupling! I would be very interested in hearing experiences from people who started with CD8414 and later upgraded to CS8420.


- Are there any other high-end DAC designs available?


http://httpd.chello.nl/%7em.heijlige...tml/dactop.htm
http://www.passlabs.com/downloads/ol...t/d1_servm.pdf
http://koti.mbnet.fi/siliconf/JukkaT...-dac_no.3.html
http://www.quadesl.com/dac.shtml - Tube DAC
http://www-s.ti.com/sc/psheets/sbau013/sbau013.pdf - DEM-DAI1704: Evaluation Fixture for the PCM1704, DF1704

The designs linked to above are all conceptually similar, in digital terms, to the Elektor dac when the ASRC is functioning as a receiver and though all but the PCM1704 EVB use dacs other than the PCM 1704, they can all be adapted with relative ease to use the PCM1704. The first two options also include a PLL/VCXO retiming circuit.

Quote:


I am looking for a available design with state of the art technology.

Thanks,

ABo

A possible contender http://www.audiocraftersguild.com/XD0/XD0_index.htm
A diy PCM 1798 Dac.my PCM1798DAC!!! - See post 29.
For quite a few dacs, http://www.diyaudio.de/html/projects.html
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Old 18th December 2004, 05:05 PM   #10
gmarsh is offline gmarsh  Canada
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My rant on the CS8420...

If you disconnect the SPDIF input and reconnect the input a couple of times, it spits out garbage. The workaround (which requires a microcontroller) is to sense the lock detect output, and then reset the CS8420. Most of the time, this will make it put out good audio again, but not always - sometimes the output would be great after reconnection, but doing a reset would make the chip put out garbage.

I designed the 8420 into a board at work, then encountered this problem during reliability testing. And I had to throw out a bunch of boards because of it... The Crystal engineers were no help - they wanted me to remove a part from the board and send it to them to "evaluate"... sigh.

Nowadays I use a separate RS422 RX feeding a CS8416 (which doesn't seem to have any such problems) which feeds a separate SRC. Now that TI has tossed out their DIR170x parts, the Analog Devices RX/SRC is outdated and AKM stuff isn't easily available in North America, there's not much else to choose from...
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