Buffalo III I2s problem - diyAudio
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Old 10th December 2013, 05:53 PM   #1
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Default Buffalo III I2s problem

Hi all

I have connected the Buffalo III to the Airport Express N version by the i2s interface from the AEN.
The problem is that the lock is unstable no matter what bandwidth I choose for the filter.
I have tried different grounding including twisting the ground wire around the serial clock wire.
The cables are very short and I have tried to isolate the clock from other wires.

At it best the lock LED blinks a couple of times during the beginning and then it becomes stable for 5 minutes then it starts to loose lock a couple of times.

I have tried to leave it play all night long but no changes, it still loosing lock in the morning.

The internal DAC (CS4344) in the AEN does not have any problems at all, it just plays while the BIII drops out. (Runs on the same i2s bus at the same time)

Then I was thinking of noise from the switch mode supply of the AEN so off it went and I supplied the AEN from a lab supply.

No change at all.

The I was looking at the serial clock and there was some overshoot ringing so I applied a variable resistor to find the best value for a clean square.

About 68 Ohm seems to be a pretty good value so I went for a fixed resistor and this did help on the locking problem but it did not eliminate it totally, so i am asking you guys what is wrong with the clock signal showed in the pictures.

One picture is without resistor on the serial clock.
The two others is with 68 and 87 Ohm on the serial clock.

I am out of ideas and need some input for other tests.

Thanks and best regards

Chris
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Old 10th December 2013, 11:48 PM   #2
4est is offline 4est  United States
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Maybe try a MC resistor in series to slow the rise time? I have seen 100 ohm used for that.

Last edited by 4est; 10th December 2013 at 11:51 PM.
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Old 11th December 2013, 02:03 PM   #3
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Can you post a picture of your wiring?

Also, what are you using to power the Buffalo (and settings etc)?
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Old 11th December 2013, 04:26 PM   #4
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Hi

Thank you for the replies.

Today I have tried with this :

MPZ1608D101B TDK | Mouser

Instead of the 68 Ohm resistor and in serial with the resistor and it did not make any difference.

However the result was the same without the 68 Ohm resistor, so the TDK did help compare to no damping at all.

It seems like the locking problems in the beginning is better with the TDK but it loose lock several times over a minute test.

The first picture is the TDK and the 68 Ohm in serial.
The other picture is the TDK alone.

Any thoughts ?

Best regards
Chris
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Old 11th December 2013, 04:31 PM   #5
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I have also tried to connect a signal generator and with this, the DAC was not loosing lock at all.

Please see attached pictures.

Chris
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Old 11th December 2013, 04:46 PM   #6
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Regarding the wiring then here is some pictures.

I have tried to remove the other wires so only GND and SCLK was connected.

The white power supply is for the AE and the black is for the DAC.

All the dip switches is set to ON and it make no difference how I set the filter bandwidth.

The SW2-5 S/pdif auto detect dip does not do any difference.

I have been reading that the best sound is with the SW1-5,6,7 set to default so the goal is to get it to work with this settings.

I have some 2mm coax cable will it make any difference do you think ?

I really appreciate all you help.

Thanks
Chris
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Last edited by cringvig; 11th December 2013 at 05:08 PM.
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Old 11th December 2013, 09:44 PM   #7
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Sounds like a cool project.

Often this sort of problem is because of an intermittent clock or one with extreme phase noise. Such a problem can be hard to spot with a scope. I have seen this situation occur when a bit clock is generated by PLL or other other such clock multiplier or divider.

Most synchronous type DACs like the CS4344 won't lose lock on such a clock, but instead will pass along the error as noise.

You know the DAC itself is fine because it locks well from the signal generator.
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Old 11th December 2013, 09:47 PM   #8
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Which firmware version are you using? If its the old firmware you may need to reverse the switches (on = 1 vs on = 0)
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Old 13th December 2013, 05:55 AM   #9
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Hi Russ

Thanks for your feedback.

The board is brand new, Brian did send it a couple of weeks ago.

I would like to achieve my goal with the Buffalo being a intergrated part of my iMac / Itunes setup and the problem is that my iMac is located far away from the stereo.

So a Buffalo DAC with its own IP address would be kind of cool

If these problems is created in the processor of the AE then I am not sure how to solve the problem.

What about Ianīs FIFO reclocker, would this be a solution ?

As I understand then it remove the original clock and then send the I2S signal to the DAC with itīs own new clock.


Thanks

Chris
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Old 13th December 2013, 08:35 PM   #10
glt is offline glt  United States
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Does it work with the spdif output of the AE?
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Last edited by glt; 13th December 2013 at 08:38 PM.
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