Using digital out from Discman

DocLorren · 1st April 2008, 07:40 PM

I am thinking about dismantling (actually already did it ) an old Sony Discman (D-E441) so as to put it in a nice micro enclosure similar to my micro amp (Amp 6 from 41Hz see also: AMP6 in twin cases)
Now I would like to try an optical out for a future, similarly enclosed, external DAC. Even found the correct pin out on the board. However since this player works at 2.5 to 3 volt (2 AA batteries) will it be able to correctly drive an external DAC?
The internal DAC is the TC 9348FN see also this link (especially page 15) http://www.datasheetcatalog.com/data...TC9438FN.shtml

So the question is: do DACs normally require TTL voltage levels or can they function with less. If not, how can you 'boost' the digital signal to the required output?

kevinkr · 1st April 2008, 11:11 PM

Since you are planning on using toslink I think it is a matter of finding a Toshiba TOTX series toslink transmitter that operates at around 3V. Alternately you can use spdif via coax which IIRC is around 1Vpp and would only require a pair of resistors..

amc184 · 1st April 2008, 11:45 PM

Hi,

Which line were you intending to get the SPDIF data from? If there is another chip upstream of the TC9348FN that outputs a SPDIF signal, fine. However, if you were intending on tapping pin 22 on the TC9348FN, I have bad news. This pin receives I2S format data, not SPDIF.

If you intend to make a DAC yourself, this is not to bad, as I2S format is superior to SPDIF, and it is easy to make a DAC that accept I2S. If your are going to buy one, the you have a problem, as they mostly take SPDIF, very few (very expensive) models take I2S.

Anton

DocLorren · 2nd April 2008, 06:28 AM

Hi AMC184,

Thanks for the useful info. Pin 22 indeed. I did not immediately learn from the schematics that pin 22 from the DAC is receiving I2S data. Further upstream is a BA6386K processor which receives signal from the optical pick up and in between sits a RAM controller SM5902BF which function is probably just (mechanical) shock protection. Have you have any experience with DIY I2S receiving DACS?

amc184 · 2nd April 2008, 07:24 AM

Neither of the ICs you mentioned in your last post is the decoder/controller. The SM5902 is a RAM controller, the BA6386 runs the servos. What other chips are there on the board? The decoder/controller may have a SPDIF out pin. Otherwise you have two options:
- Add an I2S to SPDIF transmitter, such as the CS8406.
- Transmit the I2S directly, using something like a MAX234.

Anton

DocLorren · 2nd April 2008, 08:27 AM

Hi Anton,

You are right about the BA6386 being only the servo controller. I meant the BU 9326. It's description says servo/digital signal processor. The only other chip on the board that could apply is the MC6BHC05L15 (what a code name) which is, IMO, a more general controller of the Discman performing functions like mute/resume/battery-status and driving the LCD display.
So does the BU9326 have a SPDIF out?

DocLorren · 2nd April 2008, 08:29 AM

Pin 43 on the BU 9326 maybe?

amc184 · 2nd April 2008, 08:51 AM

Could you post a link for that BU9326 datasheet? I can't locate it online.

DocLorren · 2nd April 2008, 09:14 AM

I do not have the datasheet myself but the pic is a snapshot from the Discman service manual.

DocLorren · 2nd April 2008, 09:16 AM

Pin 69 is connected to the DAC (thus probably carrying the I2S signal) but how about pin 43?

1st April 2008, 07:40 PM	#1
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Using digital out from Discman I am thinking about dismantling (actually already did it ) an old Sony Discman (D-E441) so as to put it in a nice micro enclosure similar to my micro amp (Amp 6 from 41Hz see also: AMP6 in twin cases) Now I would like to try an optical out for a future, similarly enclosed, external DAC. Even found the correct pin out on the board. However since this player works at 2.5 to 3 volt (2 AA batteries) will it be able to correctly drive an external DAC? The internal DAC is the TC 9348FN see also this link (especially page 15) http://www.datasheetcatalog.com/data...TC9438FN.shtml So the question is: do DACs normally require TTL voltage levels or can they function with less. If not, how can you 'boost' the digital signal to the required output?

1st April 2008, 11:11 PM	#2
kevinkr Contributing diyAudio Member Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 4	Since you are planning on using toslink I think it is a matter of finding a Toshiba TOTX series toslink transmitter that operates at around 3V. Alternately you can use spdif via coax which IIRC is around 1Vpp and would only require a pair of resistors.. __________________ www.kta-hifi.net

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1st April 2008, 11:45 PM	#3
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Hi, Which line were you intending to get the SPDIF data from? If there is another chip upstream of the TC9348FN that outputs a SPDIF signal, fine. However, if you were intending on tapping pin 22 on the TC9348FN, I have bad news. This pin receives I2S format data, not SPDIF. If you intend to make a DAC yourself, this is not to bad, as I2S format is superior to SPDIF, and it is easy to make a DAC that accept I2S. If your are going to buy one, the you have a problem, as they mostly take SPDIF, very few (very expensive) models take I2S. Anton

2nd April 2008, 06:28 AM	#4
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Hi AMC184, Thanks for the useful info. Pin 22 indeed. I did not immediately learn from the schematics that pin 22 from the DAC is receiving I2S data. Further upstream is a BA6386K processor which receives signal from the optical pick up and in between sits a RAM controller SM5902BF which function is probably just (mechanical) shock protection. Have you have any experience with DIY I2S receiving DACS?

2nd April 2008, 07:24 AM	#5
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Neither of the ICs you mentioned in your last post is the decoder/controller. The SM5902 is a RAM controller, the BA6386 runs the servos. What other chips are there on the board? The decoder/controller may have a SPDIF out pin. Otherwise you have two options: - Add an I2S to SPDIF transmitter, such as the CS8406. - Transmit the I2S directly, using something like a MAX234. Anton

2nd April 2008, 08:27 AM	#6
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Hi Anton, You are right about the BA6386 being only the servo controller. I meant the BU 9326. It's description says servo/digital signal processor. The only other chip on the board that could apply is the MC6BHC05L15 (what a code name) which is, IMO, a more general controller of the Discman performing functions like mute/resume/battery-status and driving the LCD display. So does the BU9326 have a SPDIF out?

2nd April 2008, 08:29 AM	#7
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Pin 43 on the BU 9326 maybe?

2nd April 2008, 08:51 AM	#8
amc184 diyAudio Member Join Date: May 2007 Location: Christchurch	Could you post a link for that BU9326 datasheet? I can't locate it online.

2nd April 2008, 09:16 AM	#10
DocLorren diyAudio Member Join Date: Nov 2004 Location: Utrecht	Pin 69 is connected to the DAC (thus probably carrying the I2S signal) but how about pin 43?

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