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Old 7th August 2011, 03:11 AM   #1501
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On the other end, I missed the batch of available Trident. (Never wait!!) When will a new batch be available ?

Thanks,

Davide
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Old 17th August 2011, 06:22 AM   #1502
glt is offline glt  United States
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Default BII 80Mhz still going strong...

Was able to play 352.8K tracks without any noise. Critical parameters seem good I2S wiring arrangement, FIR filter set to slow, Quantizer at 8bit true differential.

The only issue is during silence (pause, gap or stop) where instead of silence, I get a loud hiss with very peculiar characteristics:

The level and tone of this hissing sound changes with the volume setting with some settings giving more volume than other settings but not related to the amount of volume attenuation. In addition, FIR sharp filter results in a louder noise than the slow filter. The quantizer bit depth also changes the amount of noise coming from the DAC. The IIR filter and the notch delay don't seem to have any effect.

Any hints as to what is going? I know the upgrade to 100Mhz clock was to resolve some of these issues, but when playing music the 80MHz clock doesn't seem to cause any problems.

Are there any secret register I can use? :-)
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Old 17th August 2011, 10:14 AM   #1503
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Quote:
Originally Posted by glt View Post
The only issue is during silence (pause, gap or stop) where instead of silence, I get a loud hiss with very peculiar characteristics:

Any hints as to what is going? I know the upgrade to 100Mhz clock was to resolve some of these issues, but when playing music the 80MHz clock doesn't seem to cause any problems.

Are there any secret register I can use? :-)
I had met same probrem when I was trying to play 352.8k files
on my 80mhz Buffalo II. I couldn't solve this and felt clock upgrading makes it far easier...
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Old 17th August 2011, 12:06 PM   #1504
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I noticed the same thing with the SDTrans using 80mhz clock.

Interestingly - I never had any such issue with my XMOS board. 80mhz or 100mhz made no difference running at 352 or 384khz.

You might also try 9bit Pseudo diff.
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Old 17th August 2011, 03:03 PM   #1505
glt is offline glt  United States
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Thanks for the replies.
(The following only relates to NOT playing music with 352.8Khz material: during stop, pause or gap between songs, and only to the 80MHz part)

Russ: 9 bit Pseudo differential gives a higher pitch hiss
wktk_smile: yes, upgrade will solve the problem, but for now I don't want to touch the board; it is so well made :-)

I did further experiments:

If I turn the volume digitally (at the application, OS or driver) to zero, then the noise appears. So somehow it can't handle continuous zero data.
If I turn the volume digitally near zero, then clicks/crackling will appear...
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Last edited by glt; 17th August 2011 at 03:15 PM. Reason: Update...
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Old 17th August 2011, 03:09 PM   #1506
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I can't think of a good reason to not run the LRCK all the time. I do on my XMOS firmware.
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Old 17th August 2011, 03:19 PM   #1507
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glt

One thing you could do is remove the ferrite that powers the on-board clock and try passing in the master clock from your source. Running a synchronous clock makes it easier to lock on to really high sample rates, but it come at the cost of moving the clock reference to one that may not be as low jitter.

But since you are experimenting it might be fun to try.
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Old 17th August 2011, 04:18 PM   #1508
glt is offline glt  United States
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Thanks Russ.
Since one of the innovations of the ESS DAC is its asrc engine/jitter reducer, I always thought synchronous operation was like turning the engine off your Ferrari and having a horse pull it :-)
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Old 17th August 2011, 04:58 PM   #1509
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I always thought synchronous was the best way to go provided you have good low jitter clock(s) close to the DAC. As good as the ESS ASRC and jitter reduction circuit may be, it's debatable whether it completely eliminates jitter.
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Old 17th August 2011, 05:17 PM   #1510
glt is offline glt  United States
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I absolutely agree.

But considering that considerable amount of effort has been invested in the ASRC:
- Patented technology
- Use of an ultra low phase noise Crystek clock next to the DAC. The clock is an integral part of Buffalo probably laid out for minimal perturbation
- Dedicated power supply for the Clock

Bypassing it just doesn't feel right :-)
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Last edited by glt; 17th August 2011 at 05:20 PM.
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