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Old 9th February 2007, 12:17 AM   #11
rossl is offline rossl  United States
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But I ran the player with the cover off and it still loses lock. Maybe it is my soldering job and a pin came loose when the board heated up?

Since I built up two boards, I wire up the second board to see if it does the same thing, and yes I still lose lock occasionally. I have some RAM heatsinks on hand and some thermal epoxy, so I used a hacksaw to cut down a RAM heatsink to fit on a 3x5mm chip and glued it on just in case it is a heat problem.

The RAM heatsink on the resampler chip and another one on the Crystec oscillator don't seem to help. Both boards lose lock, so it is likely a digital problem. I'm thinking that I also may have a problem with the drive to my optical Toslink output. I am also playing around with my reset circuit. Using an RC reset and disconnecting the reset from the DVD player makes no difference at all.

Now I suspect something that Dr. Oehlrich has discovered and has published in his thread. The DVD player doesn't use left-justified for 192K. It reconfigures the DAC chip and switches to I2S data format.

The Oppo971 doesn't have SACD capability anyway so I give up on the Oppo971 and attack the Oppo981.
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Old 9th February 2007, 12:18 AM   #12
rossl is offline rossl  United States
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The Oppo981 with SACD capability has arrived and the fine folks at Oppo have made it much easier to modify. No more trying to tack wires onto 0.5mm IC pins. They have put in a nice connector location right next to the DAC.

I have decided to output the SPDIF on 75 ohm coax this time, so I drill a hole in the back of the Oppo981 and attach a new coax connector.

It would be much easier to just rewire the existing coax connector, but I have left it intact so I can do quick comparisons.

http://home.columbus.rr.com/rossl/im...od/981coax.jpg

In a few minutes I solder on the wires and hot glue the board on top of some capacitors. I turn on the unit and I have sound. Beautiful sound from CD, SACD and 96K DVD-A. 192K still does not work. I listen to several discs and run the player for 30 hours straight. Still sounding good. Silky smooth SACD sound.

http://home.columbus.rr.com/rossl/images/mod/981mod.jpg

Well, now I still don't know what was wrong with the install in the Oppo971. It wasn't a heat problem because the 981 gets very warm, and the board is working fine in the Oppo981. It may have been my soldering job or the optical Toslink circuit.
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Old 9th February 2007, 12:19 AM   #13
rossl is offline rossl  United States
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The problem with 192K DVD-A discs is an inconvenience, but it is not that bad. Out of the 30 DVD-A discs that I own, only two have 192K data anyway. The Alan Parsons HDAD disc has both 192K and 96K stereo data tracks. The "Best of REM" DVD-A has stereo 192K and 96K multichannel mix, so if I choose the 5.1 mix and let the Oppo downconvert to stereo 96K, it plays OK. 192K sampling is not widely used.

http://home.columbus.rr.com/rossl/im...1mod_side1.jpg

I can live without 192K sampling. To detect and convert would require a programmable IC like Herr Oehlrich has done. I could do it in a small Altera, but the CS8421 would also require an analog switch IC because it detects resistors at reset to choose its configuration.

The nice little connector on the Oppo981 also presents another opportunity if we revisit the simple but incomplete adapter solution. If I were to give up sample rate conversion and 192K capability, a very small board could be built with just a connector, a CS8406, and a few resistors and caps. This could be done at a low cost. The output could be wired to the existing coax jack and would be a very simple mod that would provide SACD at 24/88 and DVD, DVD-A, and HDCD all at their natural sample rate and full bit depth. It would be a mod that a lot of DIYers could do easily.

The connector pattern on the Oppo981 appears to be .075" spacing in an offset pattern that I haven't seen before. If anyone knows who makes that connector please post. It's not metric spacing unless someone makes a connector with pins on 1.9mm centers. I measured it twice to make sure.

http://home.columbus.rr.com/rossl/im...d/981conn2.jpg
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Old 9th February 2007, 12:20 AM   #14
rossl is offline rossl  United States
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Some simple analysis testing. I have an Audigy2 sound card in my PC that will accept 96K SPDIF. However the Creative drivers route the data through the onboard DSP and perform volume control and sound effects on the incoming data.

I uninstall all Creative drivers and software from my PC and install the free KX drivers. KX has a direct input for SPDIF that bypasses all processing.

http://kxproject.lugosoft.com/index.php?skip=1

The 96K data is routed directly into Adobe Audition so that I can analyze. I am getting bandwidth out past 40K with no clipped samples.

http://home.columbus.rr.com/rossl/images/mod/bott.gif
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Old 9th February 2007, 07:54 AM   #15
hwb is offline hwb  Germany
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Hi rossl,

I've done exactly this kind of mod for the DV575 and 585. I've just skimmed through your posts and got one quick remark:

Quote:
Originally posted by rossl
Playing a DVD-A with 192K sampling had horrible noise.
Quote:
Originally posted by rossl
The CS8421 resampler chip uses slave mode on the input and master mode on the output.
This won't work with a 24.576MHz crystal. When the output of the 8421 is set to master, it needs at least 130xFSI as clock, so the frequency of your crystal is too low for 192k input. That was my mistake at first, too.

More comments and perhaps some measurments on DVD and SACD playback once I got more time.

Holger
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Old 9th February 2007, 05:59 PM   #16
rossl is offline rossl  United States
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Quote:
Originally posted by hwb
This won't work with a 24.576MHz crystal. When the output of the 8421 is set to master, it needs at least 130xFSI as clock, so the frequency of your crystal is too low for 192k input. That was my mistake at first, too.
Thank you very much for your help. Unfortunately it is not possible to reconfigure or fix the 192K problem with my circuit board the way it is.

I will have to design another circuit board with the CS8421 configured as slave mode on both sides. A 27MHz low jitter oscillator will clock the CS8421. I will remove the cheap crystal on the Oppo main board and clock the MediaTek MT1389 with the precision 27MHz timebase also.

Then I will need the 24.576MHz low jitter oscillator to operate the CS8406 transmitter in master mode to clock samples out of the CS8421 at 96KHz.

That should fix the problem

I also want to devise a scheme to use the standby power to operate the oscillators at all times. Then they can operate, stay warm and stable 24/7, as long as the unit is plugged in.
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Old 5th March 2007, 01:55 AM   #17
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rossi & hwb ...

I didn't want you guys to think you were just spinning away on this thread without any feed back from some of us ... You are not alone in the quest for a better DVD-A / SACD player.

Q & A for rossi: You mentioned he was waiting for an Oppo 891. I got mine about three months ago and love it so far ... I just added some extra tantlum caps to the power supply and plastic MKT to the power input on the DAC board = no noticable improvements (and no degradation either .... ). I suppose you already know the magic trick to get it to play PAL Zone 2 / Euro DVDs ...

Anyway I was wondering if you plan on any serious mods to this inepensive player??
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Old 7th March 2007, 12:57 AM   #18
rossl is offline rossl  United States
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I have ordered the second version of my mod board for the Oppo981. The first board sounds fantastic but has a few small issues. The sound gets better after the low-jitter clock has been running nonstop for a week.

I have improved the clocking by adding a low-jitter clock, a 27MHz oscillator, to clock the Main Oppo DVD board and the Cirrus Logic resampler chip. I am still using the low jitter Crystec 24.576MHz for the audio clock.

Also improving on the power supply to keep the low-jitter oscillators running 24/7 on the standby power.

An improved reset circuit. I was able to lock up the first board with a power transient by pulling the power cord for a couple seconds and plugging it back in. Now with some extra tantalum caps and some logic to keep things going on power glitches.

Added transformer output coupling and option for 110 ohm AES/EBU or coax output.

I should have the boards in one week and running when I have time.
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Old 7th March 2007, 03:45 AM   #19
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rossi: I am very interested in any improvements to the '981. If you need a small financial boost to follow through on any replacement boards, parts, etc. say so. I am prepared to buy a copy of your (hopefull stuffed) board if possible.

" ... Also improving on the power supply to keep the low-jitter oscillators running 24/7 on the standby power. ..." The Oppo folks seem to be quite proud of their PS as per the friendly notice on the cardboard /metal shield. Other than extra tantlums on the PS +/- 9 VDC outputs, I couldn't see how to improve on it without a complete referb or replace = your descriptive methodology would be appreciated here ... step one: get the iron hot, step two: put down the coffee, step three: find the reading glasses, ...

(I have a neat trick for switching supplies that really knocks the noise floor down, but it only works under load and had not considered the pesky standby circuit as being a problem ... why don't these guys just let the pilot light go out at shut off? = it would save us all a boatload of greenhouse gasses )

Anyway, please let me know as I have taken the Oppo koolaid ...
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Old 10th March 2007, 01:03 AM   #20
rossl is offline rossl  United States
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Hi FastEddy,

What kind of external DAC do you use for listening?

On the Oppo switching power supply, absolute low power supply noise is not essential in my implementation of the Oppo. I am using it as a digital transport with HDMI digital video and my digital audio output. So, I am leaving the Oppo cheapo switcher alone. Making the switchers a little more quiet will probably not be noticable unless you use the analog outputs.

The stock Oppo power supply caps are too small and probably cannot keep the supplies stable during any kind of glitch. That is why my new board monitors the Oppo 3.3V supply and reset line in the new reset circuit.

I need 3.3V and 2.5V for the Cirrus Logic resampler chip and the Cirrus Logic digital audio transmitter. The Oppo sends the data from the MediaTek chip to the onboard DAC as 3.3V logic, so I used 3.3V as the VL on the Cirrus Logic resampler chip.

My board's power supply solution is to take the standby ( always on ) 5V and drop it through a diode to about 4.3V. Then I use multiple tantalum caps as charge storage that will keep the oscillators running through power glitches. The linear LDOs that I am using just need a few hundred millivolts of headroom. I also took some precautions to keep the the 27MHz and 24.5MHz oscillators from beating or interacting. We need clean power to keep the jitter low.

I ordered 5 boards because that was the minimum order at the prototype PCB house that I use. I should have 3 extra for anyone who is interested in experimenting and testing this. The boards end up costing about $15 each because of the low volume.

I didn't buy parts to stuff all 5 boards. Especially the the two Cirrus Logic chips CS8421 ( $9.10 at Digikey 598-1126-5-ND ) and CS8406 ( $5.04 at Digikey 598-1121-5-ND ) I only bought two each of those chips. The rest of the parts are not that expensive. I did buy enough of the low-jitter oscillators for all 5 boards.

New PCBs should be here next week!
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