DAC for CD-ROM?

Zero One · 3rd May 2007, 03:22 AM

I have got an old sony CD-ROM up and working in my home hifi, currently using a remote SMPS and it sounds surprisingly good, much better than I expected, and way better than the other CD and DVD players I have here, not as good as my TT but at least I can listen to it without wanting to put an LP on.

So now I turn to the concept of the external DAC and I need some help.

I assume the digital output from the back of the ROM would would need some sort of convertor to make it work with an external DAC.

DIY paradise have a USB to SPDIF module, I assume this would be fine, but how would it need to be hooked up considering there is no usb to start with.

DIY Paradise also have the monica DAC which looks cheap enough and should be OK I think.

Does anyone have any ideas on external DACs for CD-ROMs and what works best, any help would be appreciated

An additional issue I would like to address is noise, my whole system is Battery powered so noise levels are zero, but of course ROM drives make a fair mechanical racket so it distrubs the peace, any ideas on silencing the drive?

Thanks in advance
Zero One

analog_sa · 3rd May 2007, 09:12 AM

If you must use spdif you only need to get the TTL level out of the cdrom to match the spdif specs. A buffer+resistor divider+transformer would be my preferred solution. Most DACs would probably work with a TTL signal anyway.
Forget about the usb converter. It's completely irrelevant.

Btw, if the cdrom sounds better than your other cd players, they suck big time. And so does your tt.

Zero One · 3rd May 2007, 09:56 AM

Thanks Analog, that helps, any idea where I can get a circuit diagram for that.
No doubt a couple of the CD players I have more than suck, but at least 2 of them are supposed to be not bad at all, so I am rather surprised by the ROM.......but its no Turntable, maybe one day I will hear a digital front end that really rocks, but I won't hold my breath.

analog_sa · 3rd May 2007, 11:45 AM

Hi Zero One

This has been covered here many times if you only have the patience to search.

What is your dac? You may wish to examine the existing DAC in the cdrom and consider using the input signals already present instead of spdif.

The TTL levels are not really a problem with most receivers. If anything the CS8412/14 are happier with TTL input. The lack of 75ohm output seems more detrimental. The attached circuit will do the job and will work better with an isolated output. Spencer is still selling extremely cheap Midcom transformers suitable for the job.

Leolabs · 5th May 2007, 02:10 AM

Hi Zero One!Nice to know some1 is using a CDROM as source too.

dangus · 6th May 2007, 02:56 AM

About the DAC... some possibilities:

use an AV receiver that accepts digital inputs and let the internal DACs do the job.

salvage the digital filter and DAC section from a dead CD player, add a digital receiver chip to turn the S/PDIF into what the filter expects.

buy a bare-boards DAC kit from eBay or someone

some people say good things about the Behringer SRC-2496 as a DAC. It also operates as an ADC, which makes it a good companion to a PC that has S/PDIF I/O.

josiphal · 6th May 2007, 08:22 AM

Quote:

Originally posted by Zero One
I have got an old sony CD-ROM up and working in my home hifi...
So now I turn to the concept of the external DAC and I need some help.

If the cd-rom is old enought (not one chip solution), then EIAJ lines can be found on decoder chip (CXDxxx), and contected to TDA1543A without receiver (CS8412/4). Better than SPDIF, pure and simple.

Zero One · 6th May 2007, 08:43 AM

Thanks for that josiphal, about how old is old, this one is a Sony CDU 4811 and has no indication of speed, most do so I guess it is an early one?

As said it sounds surprisingly good, I had a quick look inside a couple of nights ago, it seems well made, lots of shielding on important chips, heavy, thick circuit board, very solid metal mechanism. Actually quite a bit better built than other drives I have looked under the covers on.

I compared it to the sound from a windows multi media computer I have, and my i-Mac it eats both and especially the PC....frankly the PC is virtually unlistenable, hooking it to the hi-fi just makes the whole thing sound even more horrible!

It is not a single chip job so I guess things are looking good. I will have a look for that chip during the week.

josiphal · 6th May 2007, 09:27 AM

Quote:

Originally posted by Zero One
Thanks for that josiphal, about how old is old, this one is a Sony CDU 4811 and has no indication of speed, most do so I guess it is an early one?

On internet CDU4811 is "Sony CDU 4811 Internal 48x CD-ROM Drive". So if it is true, direct CXD TDA connection is not possible, also device is not so good because the audio cd plays at higher then 1x speed.

If this info is false, and the cd is very old, then everything is possible, and you can check this thread for begining.

TBKK · 26th June 2010, 08:50 PM

Dear Analog_sa

I have an CAL dac and i have try the TTL to Coax converter
and have try to lock the CAL dac but no succes.
I have an normal cd playetr with digital output and it works with the DAC
do you please have any suggestion
Thanks
TBKK

3rd May 2007, 03:22 AM	#1
Zero One diyAudio Member Join Date: Apr 2006 Location: Goulburn NSW	DAC for CD-ROM? I have got an old sony CD-ROM up and working in my home hifi, currently using a remote SMPS and it sounds surprisingly good, much better than I expected, and way better than the other CD and DVD players I have here, not as good as my TT but at least I can listen to it without wanting to put an LP on. So now I turn to the concept of the external DAC and I need some help. I assume the digital output from the back of the ROM would would need some sort of convertor to make it work with an external DAC. DIY paradise have a USB to SPDIF module, I assume this would be fine, but how would it need to be hooked up considering there is no usb to start with. DIY Paradise also have the monica DAC which looks cheap enough and should be OK I think. Does anyone have any ideas on external DACs for CD-ROMs and what works best, any help would be appreciated An additional issue I would like to address is noise, my whole system is Battery powered so noise levels are zero, but of course ROM drives make a fair mechanical racket so it distrubs the peace, any ideas on silencing the drive? Thanks in advance Zero One

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3rd May 2007, 09:12 AM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	If you must use spdif you only need to get the TTL level out of the cdrom to match the spdif specs. A buffer+resistor divider+transformer would be my preferred solution. Most DACs would probably work with a TTL signal anyway. Forget about the usb converter. It's completely irrelevant. Btw, if the cdrom sounds better than your other cd players, they suck big time. And so does your tt.

3rd May 2007, 09:56 AM	#3
Zero One diyAudio Member Join Date: Apr 2006 Location: Goulburn NSW	Thanks Analog, that helps, any idea where I can get a circuit diagram for that. No doubt a couple of the CD players I have more than suck, but at least 2 of them are supposed to be not bad at all, so I am rather surprised by the ROM.......but its no Turntable, maybe one day I will hear a digital front end that really rocks, but I won't hold my breath.

5th May 2007, 02:10 AM	#5
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Hi Zero One!Nice to know some1 is using a CDROM as source too.

6th May 2007, 02:56 AM	#6
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	About the DAC... some possibilities: use an AV receiver that accepts digital inputs and let the internal DACs do the job. salvage the digital filter and DAC section from a dead CD player, add a digital receiver chip to turn the S/PDIF into what the filter expects. buy a bare-boards DAC kit from eBay or someone some people say good things about the Behringer SRC-2496 as a DAC. It also operates as an ADC, which makes it a good companion to a PC that has S/PDIF I/O.

6th May 2007, 08:43 AM	#8
Zero One diyAudio Member Join Date: Apr 2006 Location: Goulburn NSW	Thanks for that josiphal, about how old is old, this one is a Sony CDU 4811 and has no indication of speed, most do so I guess it is an early one? As said it sounds surprisingly good, I had a quick look inside a couple of nights ago, it seems well made, lots of shielding on important chips, heavy, thick circuit board, very solid metal mechanism. Actually quite a bit better built than other drives I have looked under the covers on. I compared it to the sound from a windows multi media computer I have, and my i-Mac it eats both and especially the PC....frankly the PC is virtually unlistenable, hooking it to the hi-fi just makes the whole thing sound even more horrible! It is not a single chip job so I guess things are looking good. I will have a look for that chip during the week.

26th June 2010, 08:50 PM	#10
TBKK diyAudio Member Join Date: Jun 2010	Dear Analog_sa I have an CAL dac and i have try the TTL to Coax converter and have try to lock the CAL dac but no succes. I have an normal cd playetr with digital output and it works with the DAC do you please have any suggestion Thanks TBKK

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