AD1896 In slavemode how?? - diyAudio
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Old 28th August 2005, 10:04 AM   #1
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Default AD1896 In slavemode how??

I have started a new dac project with:
CS8416->AD1896->PCM1798 -> Zapfilter 2.

CD player as transport

44Khz in to AD1896->192Khz sampling out.

External clock for AD1896 24.57Mhz clock.
AD1896 must therefore be in slavemode.

What does slavemode mean in relation to mastermode?

Do someone know how to connect a divider circuit so I can get 192Khz sampling out off AD1896 in slavemode?

Best regards
Kim
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Old 28th August 2005, 11:58 AM   #2
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Here is a link for an evaluation bord for AD1896
Look page 3 to 7 to see what I am talking about:

http://www.analog.com/UploadedFiles/...EB.pdf#search='ad1896%20evaluation%20board'

Kim
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Old 28th August 2005, 01:32 PM   #3
gmarsh is offline gmarsh  Canada
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The AD1896 puts out data at 256Fs in master mode. So if you clock it's MCLK_I pin directly with a 24.576MHz clock, it will put out 96KHz.

In slave mode, the AD1896 can put out data at whatever rate you want, as long as the rate is slower than MCLK_I / 136... For 192KHz input/output, this means a MCLK_I frequency of at least 26.112MHz. You can run the AD1896 asynchronously; just tie a 27MHz crystal or oscillator to its MCLK pin(s).

The only issue here is that the PCM179x part will only run in I2S slave mode - this means you'll have to generate the I2S clock and frame sync signals yourself. But this isn't hard to do.

From the 24.576MHz clock, you'll have to generate a 12.288 (/2) I2S clock and a 192KHz (/128) I2S frame sync. You can do this by using a 74HC4040 counter, and negating the 12.288 clock with a 74HC04, 74HC86 or whatever so that its output is low when the FS changes state.

And of course, feed the PCM179x's MCLK with the 24.576 directly.
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Old 28th August 2005, 05:58 PM   #4
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Hey

Thanks gmarsh for your time and great input.

The devider circuit can I use this, at page 7 with 2 74AC161?

Letīs take your schematic

I set AD1896 in slavemode (in and out)

About the generated signals:
Do I connect the 12.288Mhz i2S to pin 25 in AD1896 and leg 6 in pcm179x?

And the 192Khz frame sync to pin 24 in AD1896 and to pin4 at PCM179X?

The 24.57Mhz clock connecting to MCLK leg 7 at PCM179X.

Or is it only Sdout and Data that connects AD1896 and PCM179X,
So the generated signals go alone to PCm179X?

Thank

Kim
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Old 28th August 2005, 10:05 PM   #5
gmarsh is offline gmarsh  Canada
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I2S clock and frame sync from the divider circuitry will go to both the AD1896 and PCM179x parts.

You can use two AC161's... but AC logic is evil (use VHC instead) and a 74VHC4040 will only require one chip to perform the division. You'll still have to invert the I2S clock to create a proper phase relationship between it and frame sync.
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Old 29th August 2005, 05:25 AM   #6
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Hey gmarsh

Thank you very much now Itīs more clear to me
I will soon start to draw a schematig

All the best

Kim
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Old 31st August 2005, 07:28 PM   #7
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Is there any performance difference between hardware and slavemode for AD1896? (technical and sound)?

Kim
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Old 31st August 2005, 09:05 PM   #8
gmarsh is offline gmarsh  Canada
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not really.

slave mode allows higher sampling rates out of the AD1896.
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Old 3rd September 2005, 10:29 AM   #9
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If i choose a 27.000Mhz clock for AD1896 /PCM179x in slavemode

AD1896 gives out 27.000Mhz / 136 = 198Khz sampling
Datasheet donīt say how to set AD1896 to /136??

And PCM1798 only has a 128 or 256FS? Forexample in PCM1798:
27Mhz clock as above will be 27Mhz /128fs = 210Khz sampling?
Pcm1798 can only do 200Khz?

With 24.576Mhz clock -> 180.7Khz out from AD1896
with PCM1798 = gives 192kHz (24.576Mhz / 128)

Can anyone clear this up for me?

I could also settle with hardware mode with 29.9Mhz osc and 116Khz samplefrekvens?

gmarsh where did you buy your X1 cb3 osc from?

Thanks
Kim
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Old 3rd September 2005, 04:25 PM   #10
gmarsh is offline gmarsh  Canada
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If you choose a 27.000MHz clock or crystal for the AD1986 and run its output in slave mode, its maximum output sampling frequency will be 198KHz. This 27MHz clock is only used internally to the AD1986 to perform calculations, it doesn't affect the input/output sampling rates in any way.

The actual output sampling frequency of the AD1986 in output slave mode is determined by the clock and frame sync you feed it - if you feed in a 12.288MHz clock and a 192KHz frame sync, it will put out audio at 192KHz.

The PCM1798, if it's anything like the 1794 or 1792, requires you to feed in data at a sampling rate of SCK/128, /256, /384, /512, and maybe other rates. It will automatically detect the rate. Check the datasheet on this one and confirm.

I've attached a 2 minute schematic of how you'll want to hook it up. I drew a 49.152MHz oscillator; you can use a 23.8MHz part instead but you'll have to use Q1,Q7 from the VHC4040 instead of Q2,Q8 to get a 192KHz sampling rate.

You can get the CB3LV oscillator from Digi-Key.


Quote:
Originally posted by kimschips
If i choose a 27.000Mhz clock for AD1896 /PCM179x in slavemode

AD1896 gives out 27.000Mhz / 136 = 198Khz sampling
Datasheet donīt say how to set AD1896 to /136??

And PCM1798 only has a 128 or 256FS? Forexample in PCM1798:
27Mhz clock as above will be 27Mhz /128fs = 210Khz sampling?
Pcm1798 can only do 200Khz?

With 24.576Mhz clock -> 180.7Khz out from AD1896
with PCM1798 = gives 192kHz (24.576Mhz / 128)

Can anyone clear this up for me?

I could also settle with hardware mode with 29.9Mhz osc and 116Khz samplefrekvens?

gmarsh where did you buy your X1 cb3 osc from?

Thanks
Kim
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