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Old 9th February 2015, 01:49 PM   #1501
Eldam is offline Eldam  France
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Quote:
Originally Posted by soekris View Post
I wouldn't remove the 330R, it's still needed as the LVDS receiver is 100R input impedance and SPDIF is 75R....
Thanks Soren
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Old 9th February 2015, 02:12 PM   #1502
Dimdim is offline Dimdim  Greece
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I'm considering making my own inputs board and I'm thinking of 2 x coax and 2 x toslink. Regarding the toslinks, I believe that I can switch between them using a 7SB3257.

Regarding the coax'es, what would be a proper switching scenario? Using two independent pulse transformers and switching (again using 7SB3257s) both of the signal lines before the +1.2V "injection"?
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Old 9th February 2015, 03:04 PM   #1503
rol is offline rol
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Having Amanero option for input board would be great.
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Old 9th February 2015, 03:24 PM   #1504
zfe is offline zfe
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Quote:
Originally Posted by normundss View Post
And lastly an observation on noise coupling through the isolated I2S connections. I was checking the DAC outputs with a scope to see if there is any high frequency noise present. There is no noise from the DAC itself, but there is some high requency noise at the outputs of the DAC when USB is powered on.

Here is output noise with USB hub powered off. It is pretty much the noise of the scope itself.
Click the image to open in full size.

And here is output noise when USB is powered on:
Click the image to open in full size.

This noise is present regardless of whether the dac itself is powered on or off. It shows that even though the isolators do break ground loops, some HF noise will get through. Don't know if it has a noticeable effect on sound quality, just something to think about.
Can anyone try to confirm this observation.

I tried to reproduce that and failed. That reason might be my, now a bit old, analog oscilloscope, a Tek 2465B.
But as the above signal looks periodic and is in a range that can be perfectly handled by it, I assumed I would see something.

First if the DAC is off, I get a next to nil signal independent is USB is attached or not.
If the DAC is running and I attach USB the level rises for about one second and then returns to the same level as before.

The USB signal came from a battery powered laptop.
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Old 9th February 2015, 03:28 PM   #1505
Dimdim is offline Dimdim  Greece
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Originally Posted by rol View Post
Having Amanero option for input board would be great.
I am considering simple u.fl pads for the Amanero (or whatever I2S source). Better yet, I'm considering a simple mux so that 2 x I2S sources are supported.
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Old 9th February 2015, 04:17 PM   #1506
Bones13 is offline Bones13  United States
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Søren,

Could you show an appropriate setup for using a balanced isolation transformer for AES/EBU SPDIF input. You showed a great one for the unbalanced SPDIF, including a bias current. Do you have something similar for balanced input?

I guess to answer my question, the side of the transformer facing the DAC stays the same as your singled ended input schematic, and the other side has the 2 windings for balanced?
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Old 9th February 2015, 04:32 PM   #1507
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Quote:
Originally Posted by zfe View Post
Can anyone try to confirm this observation.

I tried to reproduce that and failed.
I have been thinking about it myself, and it does seem unlikely that such noise would pass through the entire unpowered dac board. The period of that noise looks suspiciously similar to I2S BCLK line transition frequency, maybe that is the actual source and it got coupled into the outputs as RFI. I will reexamine the setup when I have more time to play with it.
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Old 9th February 2015, 04:39 PM   #1508
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Originally Posted by nige2000 View Post
are u saying if the source had a clean enough power supply that this unease in the sound of the dam dac will be gone?

not that I disagree upstream has a profound influence on sound quality mostly due to power supplies just not sure it would change my opinion of one dac vs another
Hey nige2000!

Based on the feedback and measurements presented so far, I think that getting the best out of this DAC will require attention in several areas in addition to the upstream source. I don't think that an optimized source will be sufficient by itself, but will play an important part. My goal with that posting was to suggest that relying only on the isolation and reclocking is likely not sufficient for ensuring the best results from a given source and offering support for normundss' measurements.

My plan for getting the best sound out of it that I can include:

1. Using an optimized computer source with a fairly low-noise I2S feed (highly-modified ESI Juli@).

2. Stout and solid power supplies for the DAM with high-grade regulation before feeding DAC, bypassing the diode bridge.

3. Taking the direct output to a off-board output stage, again with its own stout and solid power supplies.

4. Participating in the filter experimentation and hopefully that effort will develop better-sounding filter alternatives.

To me, the reports so far sound promising and worthwhile of experimentation. And I'm open to other areas to consider to get the best sound out of the device. My goal is to see how far it can go without modifying the board (not that I am above that).

And Soren, my many thanks for developing & producing this!

Greg in Mississippi
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Old 9th February 2015, 05:14 PM   #1509
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emyeuoi I'll certainly be interested in a GB for you interface PCB. Thanks

SB
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Old 9th February 2015, 05:34 PM   #1510
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Quote:
Originally Posted by Greg Stewart View Post
Hey nige2000!

Based on the feedback and measurements presented so far, I think that getting the best out of this DAC will require attention in several areas in addition to the upstream source. I don't think that an optimized source will be sufficient by itself, but will play an important part. My goal with that posting was to suggest that relying only on the isolation and reclocking is likely not sufficient for ensuring the best results from a given source and offering support for normundss' measurements.

My plan for getting the best sound out of it that I can include:

1. Using an optimized computer source with a fairly low-noise I2S feed (highly-modified ESI Juli@).
why julia@ not usb to i2s?
have you a link to the julia@ mods your thinking of?
Quote:
2. Stout and solid power supplies for the DAM with high-grade regulation before feeding DAC, bypassing the diode bridge.
no doubt
funny i got more sq out of replacing the 3.3v power than i did bypassing the bridge
Quote:

3. Taking the direct output to a off-board output stage, again with its own stout and solid power supplies.

4. Participating in the filter experimentation and hopefully that effort will develop better-sounding filter alternatives.
looking forward to the filter options
Quote:
To me, the reports so far sound promising and worthwhile of experimentation. And I'm open to other areas to consider to get the best sound out of the device. My goal is to see how far it can go without modifying the board (not that I am above that).

And Soren, my many thanks for developing & producing this!

Greg in Mississippi
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