I don't feel like giving the chinese more money, can I pull the pcb out of my cd-65? - diyAudio
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Old 23rd December 2012, 08:33 AM   #1
freax is offline freax  Australia
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Default Can I pull the pcb out of my Marantz cd-65 and make a DAC?

I was thinking that no matter what the chinese can throw at me I would still get a better PCB if I were to remove the Marantz CD-65 Standard Phillips tda1541 mainboard out of the player and put it into my own custom case for the purposes of a DAC.

I was thinking of just plugging an I2S bus into the TDA1541's pins and seeing if it worked or not.

The cd transport is almost completely shot mechanically so theres no point in saving that.

What does the SAA7220 do in relation to the TDA1541?

What else can I pull or chip away without affecting the DAC? Obviously the beautiful flourescent display can get the boot, a recapping of the power supply is in order, aside from that?

Is that additional floating board a reclock circuit? Should I toss that and plug the 8441P right into the mainboard?

Here are some pics so you guys can get an idea of the job at hand.

Click the image to open in full size.
Click the image to open in full size.
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Last edited by freax; 23rd December 2012 at 08:48 AM.
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Old 24th December 2012, 06:18 AM   #2
qusp is offline qusp  Australia
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no, you cannot give the SA the boot, it is everything, without it, or some custom digital filter, your dac is useless. feeding i2s to the TDA will make a raucous noise if anything at all. the SA is the digital filter.

some of the old CD players with TDA were very high quality, this does noit appear to be one of those times.... the voltage compliance and clocking will be all wrong for a dac I would think too, so this may not be as simple, or cheap as you presume.

better to just pull the DAC chip and use in one of the many designs on this forum and others
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Old 24th December 2012, 09:07 AM   #3
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1541 takes the i2s for breakfest. 7220 too, so you can choose between NOS/OS (OS for me is better) by bypassing the DF.
Clocking et cetera... cut the traces, shut everything down but the 7220, 1541, and the analog stage. Make sure you have disabled the deemphasis filter there.
Keep the PS, add some SPDIF receiver with 256mclk and you're done. Just configure it into some acceptable by 7220 i2s format.
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Old 24th December 2012, 09:16 AM   #4
josha is offline josha  United Kingdom
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Hi,

That floating board is a 'Fix' by Philips for the control circuitry, some later players had a single chip in there.

I notice that this is non A TDA1541 chip - Qusp, is this different to the A? With the A you can get rid of the filter, I need to revisit the datasheets but IIRC the non A version also needs a system clock input on pin 4.

I have done exactly what you describe but I replaced the TDA with the 'A' version, I then built a PSU for the DAC and a separate output stage, I then supplied the i2s signal from a PCM2706 USB decoder straight to the DAC - works perfectly!

If I get a bit of time I'll take some photos and sketch up the schematics from the service manual.

Cheers

Josh
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Old 24th December 2012, 09:33 AM   #5
qusp is offline qusp  Australia
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no, maybe i'm mistaken, it could be that i'm simply used to seeing a good many TDA1541A dacs that need specialized black magic clocking circuits to gain good performance out of this dac, with synchronous 4x OS DEM reclocking etc; so figured a digital filter or equivalent flip-flop/logic circuit was needed.

Secondary to this and part of the reason for my answer, is what clock speeds are available/in use on the board? I wouldnt expect good performance from just plugging in an external i2s source and using its matching MCLK if available. we can presume it accepts PCM since it worked with your PCM2706? which flavor of i2s specifically are we talking about here that is accepted natively left justified, right justified, PCM, i2s etc? did you supply a masterclock to go with the i2s? because MCLK is not part of the i2s standard. what settings are/could be hardwired into this PCB with pull-up/down resistors?

but i'll let someone who knows this dac answer more specifically, as I would need to look up its datasheet to make more reliable commentary. of course the SA7220 does take i2s, but from what I have read it tends to crap noise all over the power supply rails, so needs careful attention to decoupling

Last edited by qusp; 24th December 2012 at 09:45 AM.
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Old 24th December 2012, 09:57 AM   #6
freax is offline freax  Australia
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my I2S source is a CS8412, hardwired to a piece of perfboard:
I decided to scrap my TDA1543 DAC, I ended up not liking the sound of it and greatly preferred the sound of the TDA1541 that is in this CD player.

This board has two 7805 vregs onboard dedicated to the CS8412's digital and analog lines, but have the same copper earth bus.

What I can do is plumb the I2S out of this board into the SAA7220 or the TDA1541 chip and cut back some traces as another poster here has said.

Or failing that I can pull the TDA1541's socket and soldering it to this perfboard and going from there, I have found a few schematics which might be suitable:
http://www.fetaudio.com/wp-content/u...10/TDA1541.pdf
http://2.bp.blogspot.com/_u_EoD7hGIP...Duka+Rev+2.gif

But nothing completely certian, I don't want to end up losing this TDA1541 chip to the smoke ghosts as I'm actually very fond of its sound but I've run out of CD material to feed it with, hence the need/desire and want to keep it all on the original phillips reference board.

If I cant then Im going to pull the transformer and voltage regulators and rebuild the entire thing on a new board, I'm hunting for a scrap transformer at the moment so I don't have to do that.

Click the image to open in full size.
Click the image to open in full size.
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Last edited by freax; 24th December 2012 at 10:05 AM.
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Old 24th December 2012, 10:28 AM   #7
qusp is offline qusp  Australia
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I suggest just chucking the PCB and doing it properly. now there is of course John Brown's Epic thread on the development of his dac with TDA, very good, but very involved. you will be able to get up and going with this brief, but complete and well constructed post by Thorsten Loesch, who is a well known professional designer of the CD77. I tend to feel his approach is better anyway.

what you have above there looks like a good way to make an RF antenna, Thorstens attention to detail in grounding with solid copper foil layers is very good and accessible DIY construction, as well as excellent instruction on power supply and decoupling. if you dont have any copper foil, I could send you enough for this board in an envelope.
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Old 24th December 2012, 10:44 AM   #8
freax is offline freax  Australia
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Quote:
Originally Posted by qusp View Post
I suggest just chucking the PCB and doing it properly. now there is of course John Brown's Epic thread on the development of his dac with TDA, very good, but very involved. you will be able to get up and going with this brief, but complete and well constructed post by Thorsten Loesch, who is a well known professional designer of the CD77. I tend to feel his approach is better anyway.

what you have above there looks like a good way to make an RF antenna, Thorstens attention to detail in grounding with solid copper foil layers is very good and accessible DIY construction, as well as excellent instruction on power supply and decoupling. if you dont have any copper foil, I could send you enough for this board in an envelope.
Thanks for the help guys, and merry christmas.

I have a brand new roll of adhesive copper foil actually but thanks for the offer, the difficult part is understanding how to lay it down so it can trap that digital noise and earth it.

I have plenty of large perfboard and a solder sucker, so I can always start again. I also havent overheated the IC, been using a 30 watt iron and doing the bare minimum heating time with standard flux core solder.

I was thinking of laying down some copper tape underneath the IC, then doubling that ontop of the IC, earthing both strips at one end, the 14th pin end, then getting some copper tape and making a trap around the pcb board to surround it with copper tape, like a box with a capital I in the center, the I representing the copper that goes underneath and above the CS8412.
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Last edited by freax; 24th December 2012 at 10:53 AM.
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Old 24th December 2012, 10:49 AM   #9
josha is offline josha  United Kingdom
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These are the snips to the PCB for supplying a dedicated PSU and i2s. I didn't supply a separate clock - I have one but haven't got round to implementing it yet!

I get pretty good results just from the 2706 (this is all relative though! ie it's a big step up from the original CDP but for all I know could be miles away from a properly implemented dac). I'm a great believer in getting it working first then tweaking it!

From the datasheet you can see that with pin 27 connected to +5v (as in this case) the input format is accepted as Time MUX (2's complement).

I just took the Bit Clock, WS, Data & Ground straight from the 2706. I too have seen some very elaborate clocking schemes and will try to get round to implementing a few when I get chance.

On the diagram then;

1 - -15v Supply
2 - +5v Supply
3 - LE/WS Input
4 - BCK Input
5 - Data input
6 - -5v Supply
7 - Left Channel Output
8 - Right Channel Output

9 - On the TDA1541 datasheet it states that you need to supply a System Clock to pin 4 for NOS operation, on the A version you can leave this open. If you need to supply system clock then cut the trace indicated by the red line - however there's no easy way to attach a cable, you could solder straight onto the chip leg but be careful!

As mentioned earlier - all my work was done with the same PCB but I had replaced the DAC chip with the A version - I can't confirm that this will work with the non-A chip on your board!

I do have a non-A version so I might try it!

Cheers
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Old 24th December 2012, 11:39 AM   #10
qusp is offline qusp  Australia
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no problem, indeed take your pick

good luck with the TDA1541A, seems it turns into a loooooong journey for most but the above link cuts to the chase pretty quickly, hes got a matching tube stage posted around somewhere too, if you like Glass

honestly I dont think those 2706 are worth the effort, very high jitter by todays standards, there are many better options available here on the forum. if it accepts i2s and PCM, then just grab one of the DSD and i2s/PCM convertors like the Amanero combo384, which with the number sold in the DIYAUDIO GB means its like 39EU for our GB, which is ongoing at that price for us. you will find the latest google groups GB page linked in that thread somewhere, make sure to get the latest link because i'm not sure he fixed the first link when he moved it.

it does DSD over USB with the right dac, as well as 44.1-384kHz PCM. It is a minimal but fairly well thought out module with easy external power and isolation if you like, the onboard regs are very low noise LDOs, so not a bad start. you can tap the master clock (it has dedicated clocks for 44.1x and 48x for the audio as well as its own clock) plus there are some mods for isolated and reclocked output. which will allow tapping a proper master clock

the device is this one here

Last edited by qusp; 24th December 2012 at 11:54 AM.
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