Using digital out from Discman - Page 2

amc184 · 2nd April 2008, 11:14 AM

I'm not sure. It could be a SPDIF data out pin, but it could just as well be the data out line for a microcontroller interface. Do you have any more info on this chip from the service manual?

Anton

DocLorren · 2nd April 2008, 11:23 AM

Anton,

I'll send you the SM later this day to your personal email; I am afraid pin 43 is indeed the output to the interface controller. I'll check on the PCB whether the BU9326 has any other description that can lead us to the complete datasheet.

DocL

amc184 · 2nd April 2008, 11:26 AM

I just had a look at the datasheet for the very similar BU9321B, and unfortunately it is just as I thought, (43) DOUT is the serial data line for the microcontroller interface. So if you want to make the transport compatible with other consumer gear, you're going to have to use a SPDIF transmitter, such as a CS8406.

So, the DAC you want to use, will it be DIY or store bought?

Anton

DocLorren · 2nd April 2008, 11:28 AM

DIY! But preferably in kit form I am afraid.

amc184 · 2nd April 2008, 12:00 PM

Thats not so bad then. It's pointless to bother with SPDIF in a situation like this, as you'd end up with:

I2S ---> SPDIF ---> (cable) ---> SPDIF ---> I2S

besides, SPDIF is inferior to I2S anyway. There are still a couple of issues though:
- This walkman looks like it will make a poor quality transport.
- I don't think the type of I2S that the RAM controller is transmitting is standard, but I have to have a careful look.

Anyway, if you want to proceed, you're best to get a quad RS232 transmitter, such as a MAX234. You'll have to build a 5V regulated supply for it, 3V is too low. Transmit the 3 I2S lines (DATA, LRCLK, SCLK) over 50 or 75ohm with BNC connectors. You'll have to check that the type of I2S that RAM controller outputs is compatible with whatever DAC you chose.

Anton

DocLorren · 2nd April 2008, 12:04 PM

First of all, the Discman is cheap and easy to obtain! With some proper damping/suspension it may be a compact stable transport. Why do you think it is a poor choice?
Second, can't I just bypass the RAM controller? I do not need the skip-protection, that is it's function right?

Third, it is fun to try isn't it?

amc184 · 2nd April 2008, 12:14 PM

Oh, yes, definitely. I am not trying to discourage you!

It's just that it is a bit trickier than some of the other things you could chose to mod. But I guess you'll need to use a walkman to get it into a tiny case like the ones in your other post.

There is only one problem with bypassing the RAM controller (which I do think is a good idea, by the way), is that without a datasheet, who knows what kind of data to expect from the BU9326. I had a look at the BU9321B datasheet, that suggests that the I2S from the BU9326 is probably OK though.

DocLorren · 2nd April 2008, 02:09 PM

Hi Anton,

Would directly hooking up a TDA 1543 work?
See: http://www.diyparadise.com/rm20dac.html
Looks promising.

amc184 · 2nd April 2008, 09:56 PM

Yes, looks good. The output of the BU9326 looks compatible with the input of the TDA1543. If I were you, I would look at using paralleled TDA1543s, rather than just a single one. This doesn't make the design any more complex, makes it sound miles better, and I think you can get away without any active I/V conversion.

If you construct the DAC and transport in the same case, you can wire them directly to each other through 20R resistors. If you are using two different cases, I would look at using something like RS232 for the link.

DocLorren · 2nd April 2008, 10:13 PM

I would say if there is not a big choice in affordable DIY DACs that accept I2S data then there's no reason to go for an external DAC. It may be better to find a good quality I2S->DAC for internal use. I know about the parallel TDA1543 trick but feel this is a kind of silly compromise. Is it better at all than the standard Discman DAC? Has time stood still since the development of the TDA1543 (1991 right?) and sonically superior chips not been developed in the last decade? And what exactly is the reason behind using RS232 in case of two housings? Timing problems or other? More questions the deeper we go into this topic. Thanks in advance,

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2nd April 2008, 11:14 AM	#11
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	I'm not sure. It could be a SPDIF data out pin, but it could just as well be the data out line for a microcontroller interface. Do you have any more info on this chip from the service manual? Anton

2nd April 2008, 11:23 AM	#12
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Anton, I'll send you the SM later this day to your personal email; I am afraid pin 43 is indeed the output to the interface controller. I'll check on the PCB whether the BU9326 has any other description that can lead us to the complete datasheet. DocL

2nd April 2008, 11:26 AM	#13
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	I just had a look at the datasheet for the very similar BU9321B, and unfortunately it is just as I thought, (43) DOUT is the serial data line for the microcontroller interface. So if you want to make the transport compatible with other consumer gear, you're going to have to use a SPDIF transmitter, such as a CS8406. So, the DAC you want to use, will it be DIY or store bought? Anton

2nd April 2008, 11:28 AM	#14
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	DIY! But preferably in kit form I am afraid.

2nd April 2008, 12:00 PM	#15
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Thats not so bad then. It's pointless to bother with SPDIF in a situation like this, as you'd end up with: I2S ---> SPDIF ---> (cable) ---> SPDIF ---> I2S besides, SPDIF is inferior to I2S anyway. There are still a couple of issues though: - This walkman looks like it will make a poor quality transport. - I don't think the type of I2S that the RAM controller is transmitting is standard, but I have to have a careful look. Anyway, if you want to proceed, you're best to get a quad RS232 transmitter, such as a MAX234. You'll have to build a 5V regulated supply for it, 3V is too low. Transmit the 3 I2S lines (DATA, LRCLK, SCLK) over 50 or 75ohm with BNC connectors. You'll have to check that the type of I2S that RAM controller outputs is compatible with whatever DAC you chose. Anton

2nd April 2008, 12:04 PM	#16
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	First of all, the Discman is cheap and easy to obtain! With some proper damping/suspension it may be a compact stable transport. Why do you think it is a poor choice? Second, can't I just bypass the RAM controller? I do not need the skip-protection, that is it's function right? Third, it is fun to try isn't it?

2nd April 2008, 12:14 PM	#17
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Oh, yes, definitely. I am not trying to discourage you! It's just that it is a bit trickier than some of the other things you could chose to mod. But I guess you'll need to use a walkman to get it into a tiny case like the ones in your other post. There is only one problem with bypassing the RAM controller (which I do think is a good idea, by the way), is that without a datasheet, who knows what kind of data to expect from the BU9326. I had a look at the BU9321B datasheet, that suggests that the I2S from the BU9326 is probably OK though.

2nd April 2008, 02:09 PM	#18
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Hi Anton, Would directly hooking up a TDA 1543 work? See: http://www.diyparadise.com/rm20dac.html Looks promising.

2nd April 2008, 09:56 PM	#19
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Yes, looks good. The output of the BU9326 looks compatible with the input of the TDA1543. If I were you, I would look at using paralleled TDA1543s, rather than just a single one. This doesn't make the design any more complex, makes it sound miles better, and I think you can get away without any active I/V conversion. If you construct the DAC and transport in the same case, you can wire them directly to each other through 20R resistors. If you are using two different cases, I would look at using something like RS232 for the link.

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2nd April 2008, 10:13 PM	#20
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	I would say if there is not a big choice in affordable DIY DACs that accept I2S data then there's no reason to go for an external DAC. It may be better to find a good quality I2S->DAC for internal use. I know about the parallel TDA1543 trick but feel this is a kind of silly compromise. Is it better at all than the standard Discman DAC? Has time stood still since the development of the TDA1543 (1991 right?) and sonically superior chips not been developed in the last decade? And what exactly is the reason behind using RS232 in case of two housings? Timing problems or other? More questions the deeper we go into this topic. Thanks in advance,