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Old 20th August 2013, 05:39 AM   #3511
Foxx510 is offline Foxx510  Australia
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Thanks NS. I think smd work is probably beyond me right now as I don't have my gear set up. So, first I will try a new usb-spdif board and if that doesn't fix the issue I will have to go down the minidsp route. The usb spdif board I currently have is causing all sorts of interference so there is a chance it is faulty or poorly built. It completely wipes out some tv stations.
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Old 26th August 2013, 11:09 AM   #3512
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Has anyone else have the setting change on them?
Seems some times mine goes back to default settings.
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Old 27th August 2013, 01:01 AM   #3513
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Quote:
Originally Posted by 4pyros View Post
Has anyone else have the setting change on them?
Seems some times mine goes back to default settings.
Hi,
I haven't had that happen ,Guessing,bad eprom,I have a few extra's, or a bad connection ,I would remove the eprom and reinsert it and that gray flat interconnect cable is known to give problems,oopps one more maybe a button sticking(page buttons),just push all the buttons a few times and see if any of them feel different,If the keypad has been hit hard that can damage the membrane ,calculators,Remote controls, do the same thing sometimes usually the most used key,I have found coke and coffee inside them ,lol go figure right?
Good luck!
NS
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Old 18th September 2013, 07:00 AM   #3514
Foxx510 is offline Foxx510  Australia
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Ok i'm looking at trying an improved spdif input path to the 8420 chip. Which is best - a PE 65612 pulse transformer or 2 caps and a 75 ohm resistor? I will feed either with 75 ohm mini coax and a 75 ohm connector of some kind. Cheers :-)
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Old 23rd October 2013, 07:05 AM   #3515
wxn is offline wxn  Lithuania
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I'm trying to fit a usb/spdif adapter (search ebay for "usb spdif 96khz", the small square one) and it kind of works but I have several issues:
1. The audio stream drops out every couple of minutes, especially if some electric device is being switched on nearby. I've tried all sorts of shielding schemes with no success. Sometimes these dropouts result in digital input lockout (the dull sound), but it may randomly recover with another dropout, which also indicates the DCX itself is getting contaminated with EMI.
2. DCX has trouble syncing at max volume, even more so at higher sampling frequencies. It works OK at 44kHz/half volume. If I dial anything above ~70% in software, I sudenly get raunchy and distorted sound. With 96kHz it's hard to even get it in sync, highly dependant on the cable, USB port and the music content (again, mainly level).

What I have noticed:
1. I suspect my PC PSU is far from ideal (polluted USB bus is driving the adapter crazy and possibly injecting HF noise into the DCX itself) as these problems seem to be absent when hooked up to a laptop.
2. The Tenor chip itself is not to be blamed as I have an ODAC plugged in the same system and it works flawlessly.

List of mods so far:
1. Changed the DCX digital input resistor to ~75 ohms. I have not tried to bypass the ribbon cable/relays yet.
2. Tweaked the adapter board a little by replacing caps for bigger ones and placing an RC filter on the VCC line.
3. TODO: rewire CS8420 for slave/slave operation and plug the adapter straight in through I2s. It should definitely help with the sync issue as the SPDIF stream looks somewhat "soft" on a scope, I suspect the driver circuit is not implemented very well. Not sure if it will help with the random dropouts as these may be caused by any element in the chain.
4. TODO: before doing any serious replacements or investments in UPS I decided to try the ADUMxxxx USB isolator thingy, it should arrive in a week or so.

Until then, could you guys suggest any tweaks or hacks I could try?
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Old 23rd October 2013, 07:46 PM   #3516
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Hi WXN,
Sounds like you have a bunch of noise EMI or similar on your signal,Got a scope?
The laptop runs on batteries not a switching power supply that's why it sounds better with it,
I would think,the isolator you got coming should fix it,
Their is alot on this site about cleaning up signals and computer sound sources,
sorry I can't be of better help.
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Old 24th October 2013, 03:51 AM   #3517
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laptops DO have switchers inside. the 18v is dc-dc converted many times for the various internal voltages that computers need.

no laptop is going to be rfi-quiet. it can't be.
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Old 24th October 2013, 03:55 AM   #3518
Pano is offline Pano  United States
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I've had trouble with power noise on USB soundcards. So far nothing that bad on SPDIF, unless a very long line is used. Also double check grounding, that has caused DCX SPDIF problems for me in the past.

You might try a 75/110 ohm transformer.
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Old 24th October 2013, 03:57 AM   #3519
a.wayne is offline a.wayne  United States
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Pano any experience with this unit ..? Good / Bad..?
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Old 24th October 2013, 04:00 AM   #3520
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Which? The USB to SPDIF?
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