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Old 28th October 2005, 08:26 PM   #1
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Default adding Digital audio transmitter to B&O CD50

Hi

I want to build and external DAC for my old CD50, but this old player havent got a digital output. Chipset is YM3511,YM2201,PCM53JP. I have the schematics and a picture block diagram of the ym2201 and it looks like there are three unconnected pins for it.... on the board is an unmounted connector with SDSY,SDO,CLK2 and de-emph. The data streams look like this (looks od in forum copy text to notepad ).

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9_
SDSY (sYNC LEFT/RIGHT)
HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHLL LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
SDO (DATA)
HHHHHHHHLLLLHHLLLLHHHHLLLLLLLLLLLLLLLLLLLLLLLLLLHH LLLLLLLLHHHHHHLLLLHHLLLLLLLLLLLLLLLLLLLLLLLLLLLL
O2 (CLK)
HLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHL HLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHLHL

Is this left justified datastream ? when SDSY is high the CLK shifts 24 times and when SDSY is low it shifts 25 times, is this normal ?

Best regards Kim Olesen

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Old 29th October 2005, 08:42 AM   #2
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calculating...

(24+25)*44100*4 = 8643600, this is the YM2201 crystals speed to.
Will this output be accepted be a DIT4096 or CS8406 ?

Best regards Kim Olesen
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Old 29th October 2005, 06:47 PM   #3
gmarsh is offline gmarsh  Canada
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You won't be able to feed that into a DIT4xxx or CS8406 directly.

You'll need a PLL to convert 8643600 to 44.1*256 to create a clock for the transmitter, and and a bit of logic to convert that bitstream into RJ, LJ or some other format which a DIT can understand.

I don't know anything about the format, so it's hard to say what logic is needed. You might be able to do it with a bunch of 74xx, a CPLD, a FPGA, maybe even a cheap DSP chip.
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Old 29th October 2005, 10:01 PM   #4
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Hi

Thanx for !

I have looked through some yamaha datasheets today, and i your right..
Would it not be better to make a low jitter clock at 44.1khz*256 and a PLL to replace the 8.6436Mhz crystal and then convert the 24+25bit of into 32bit+32bit carrying the two 16bit for L/R only, with some logic or a microprocessor running at the 11.2896Mhz clock?


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Old 31st October 2005, 03:40 PM   #5
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Hi

CS8406 and a 11.2896Mhz oscillator might be it! CS8406 datasheet page 14
"In slave mode, the left/right clock and the serial bit clock are inputs. The left/right clock must be
synchronous to the OMCK master clock, but the serial bit clock can be asynchronous and discontinuous
if required. The left/right clock should be continuous, but the duty cycle can be less
than the specified typical value of 50% if enough serial clocks are present in each phase to clock
all the data bits."
I have 16bit data left adjusted and a left/right clock with 48.97% duty cycle... and enough serial clock cycles!

Best regards Kim Olesen

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Old 19th January 2006, 01:43 PM   #6
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Hi

At last i got time to try this out. have built a 11.2896Mhz VCO, a PLL and a low jitter 8.6436Mhz clock for the player. I have connected a CS8406 to YM2201, but the only sound i get i a loud "hiss" noise. The CS8406 is running in hardware mode and it triggers at rising clock edge and it looks like my clock is inverted. I tryed an inverter first, the same output but when hooking up a scope to the clock input i can hear some music burried in noise. tried two inverters after each other to see if the propagation delay would help. Now it plays some music burried in noise.

Ok the PLL is not in lock yet, as the original 8.6436Mhz xtal was running 2khz higher, but the Cs8406 should repeat lost frames.

any ideas on what could be the problem ?

Best regards

Kim Olesen
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Old 19th January 2006, 04:35 PM   #7
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Do you have the datasheet for the YM2201 ?
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Old 19th January 2006, 06:14 PM   #8
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Hi

No datasheet, only a block diagram, and ofcourse the cd50 service manual. The player's pcb has a lot of missing components and the 4 signals (data,clock,LRclock,deemp) ends in a 4way header so it might have been prepared for digital out. The drive is from Aiwa and the electronis is from japan, and modifyed with a b&o cpu board and some other things. I have tried to find a yamaha digital audio transmitters from 1983-85, but no luck (the player is that old ) , as these could help finding some description of he protocol.
I can take a few pictures of the data (from logicdartprobe screen) if this can help to find the right protocol.. data seems to be 16bit left adjusted.


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Old 19th January 2006, 06:40 PM   #9
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It seems odd to send serial data to a parallel input device like the PCM53.
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Old 20th January 2006, 06:03 AM   #10
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They don't ! the serial signal continues inside the chip to a digital filter/oversampling and from there to paralel output.. included a picture of the 2 chips used and a YM3015 serial DAC
is there other codes than 2' complement there have been used for cd ?
Maybe it is possible to burn a cd with sinus or square signal so that i have a repeated signal to measure at.

best regards

Kim Olesen
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File Type: zip ym_chips.zip (34.6 KB, 50 views)
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