Separate DACs for each halfwave ?

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rfbrw

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Joined 2001
Bernhard said:
The PCM61-L are doublecrowns ?

Only individual data lines.
Decoder also MN&something.
Don't want to remove the board again...
Click to expand...

I suppose the 40-pin chip could do correct 2's comp inversion but there is another possibility. If you can, look at the position of the data relative to LRCLK for each of the two dacs on a 'scope. And what is the frequency of LRCLK?
 
Bernhard

Bernhard

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Joined 2002
Wadia ?

One hour of work
 

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Bernhard

Bernhard

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Joined 2002
rfbrw said:


I suppose the 40-pin chip could do correct 2's comp inversion but there is another possibility. If you can, look at the position of the data relative to LRCLK for each of the two dacs on a 'scope. And what is the frequency of LRCLK?
Click to expand...

Pin 5 clock 2,8MHz
Pin 6 LE 176 kHz

Should I trigger from clock and put data on 2nd channel ?

Why does it say 18bit on the player's front if chips are 16 bit only ?
 
guido

guido

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Bernhard said:


Pin 5 clock 2,8MHz
Pin 6 LE 176 kHz

Should I trigger from clock and put data on 2nd channel ?

Why does it say 18bit on the player's front if chips are 16 bit only ?
Click to expand...

Some simple maths: 176kHz is 4 times 44.1kHz: player has 4 times oversampling. 16*176000=2.8Mhz: 16 bits in one frame to the DAC: 16 bit dacs at 4 times oversampling.

It's 18 bit resolution created with 16 bit 4 times oversampling.
Like philips using the 14 bit TDA1540 in CD players stating 16 bit resolution.

If you really wanna know what it is, you need to read the number and look for other chips downstream (filter,decoder). If it is not a custom chip, somebody might know what it is.
 
R

rfbrw

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Joined 2001
Bernhard said:
Wadia ?
Click to expand...

Wadia increase the effective, if not actual, resolution of their dacs by performing linear interpolation, Wadia call it Langrangian Interpolation, after the digital filter. Using this method they can add another 2x, 4x oversampling or whatever they want using only hardware. They do this, in the case of 2x, by delaying the data by half the frame time, sending ths delayed data to a second dac and summing both outputs using a single i/v converter.

Bernhard said:

Pin 5 clock 2,8MHz
Pin 6 LE 176 kHz
Should I trigger from clock and put data on 2nd channel ?
Click to expand...

There is data on the second line. If you trigger on LE , you should be able to compare the position of the data for each dac relative to LE.
 
Bernhard

Bernhard

Member
Joined 2002
rfbrw said:


Wadia increase the effective, if not actual, resolution of their dacs by performing linear interpolation, Wadia call it Langrangian Interpolation, after the digital filter. Using this method they can add another 2x, 4x oversampling or whatever they want using only hardware. They do this, in the case of 2x, by delaying the data by half the frame time, sending ths delayed data to a second dac and summing both outputs using a single i/v converter.



There is data on the second line. If you trigger on LE , you should be able to compare the position of the data for each dac relative to LE.
Click to expand...

Shouldn't the second LE also be delayed to the first ?
The LE is common for all DAC chips.
 
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