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Old 1st April 2008, 07:40 PM   #1
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Default 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?
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Old 1st April 2008, 11:11 PM   #2
kevinkr is offline kevinkr  United States
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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..
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Old 1st April 2008, 11:45 PM   #3
amc184 is offline amc184  New Zealand
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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
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Old 2nd April 2008, 06:28 AM   #4
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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?
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Old 2nd April 2008, 07:24 AM   #5
amc184 is offline amc184  New Zealand
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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
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Old 2nd April 2008, 08:27 AM   #6
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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?
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Old 2nd April 2008, 08:29 AM   #7
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Pin 43 on the BU 9326 maybe?
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Old 2nd April 2008, 08:51 AM   #8
amc184 is offline amc184  New Zealand
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Could you post a link for that BU9326 datasheet? I can't locate it online.
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Old 2nd April 2008, 09:14 AM   #9
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I do not have the datasheet myself but the pic is a snapshot from the Discman service manual.
Attached Images
File Type: jpg bu9326.jpg (56.9 KB, 218 views)
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Old 2nd April 2008, 09:16 AM   #10
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Pin 69 is connected to the DAC (thus probably carrying the I2S signal) but how about pin 43?
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