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Old 6th May 2012, 04:32 AM   #661
kp93300 is offline kp93300  Malaysia
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Default unusual distortion --Still troubleshooting !

Quote:
Originally Posted by kp93300 View Post
I match it with the discrete dac from diyparadise malaysia.
It works but there is a constant low level distortion with soft music . the distortion is absent in between tracks or on pause.
I am using window 7 in a fanless ATOM based pc and Foobar .
The digital isolator is powered at 3.5 V via a salas shunt regulator that was proven to work well in another Tenor based converter.
Any idea what the cause ?
thanks

kp93300
I build a linear trans based PS for Wave io and down regulated to 4.95 V with LM 317.
Problem persisted .

The distortion noise is heard in the mid range of the speaker only and sounds a bit like tape hiss with Dolby noise reduction off.. It is not heard when music is paused , stop or between tracks. It is heard when the music is of low volume.It is heard in both channels with equal loudness and seems to be independent of loudness control. This appear constant in loudness.

The wave io isolated i2s signal has individual grounds for the data, clock and word select lines. The discrete dac i2s input has only one ground.. Could this be incompatibilty issue?

I hope to get some suggestions from other users .I have tried at the dac forum without any success.

My set up is attached for review.
Link to the discrete dac :
I Found Miss Right!

thanks

kp93300
Attached Images
File Type: jpg wave monica .JPG (136.8 KB, 528 views)
File Type: jpg monica .JPG (107.6 KB, 513 views)
File Type: jpg wave i2s gd.JPG (107.2 KB, 507 views)
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Old 6th May 2012, 04:56 AM   #662
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I wonder if you could describe the 3.5V salas shunt and its relationship to the DAC supply. Is there a possible ground loop condition between those two? Have you confirmed that the output of the salas reg is stable?
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Old 6th May 2012, 05:16 AM   #663
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@ kp93300: you have PM.
There's other thing that I want to say about your setup: I2S lines seems to be longer than expected.
m.massimo was the latest person I know that runs into the same issue: too long I2S lines. Please make them shorter if you can.
In addition to that, I notice that there's only one trafo+diode bridge+caps bundle for two PSUs: one for WaveIO (LM317) while the other is for Salas. Are the grounds between these two PSUs connected together (WaveIO & Salas)? If yes, the you do not have any isolation at all and the noise from your PC/MAC source is getting into your DAC through this common ground connection (you have bypassed the isolator this way). Not to mention the ground loop. Just make sure to keep WaveIO's supply only for WaveIO while the output side of NVE's isolator be powered from different PSU (with dedicated trafo+diode bridge+filtering) or, at least, from the digital side of your DAC board (if possible - still not recommended!).
Hope it helps,
Lucian
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Contact link for WaveIO USB-to-I2S/SPDIF board.
Daughter card GB list for WaveIO can be found here

Last edited by Lorien; 6th May 2012 at 05:30 AM.
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Old 6th May 2012, 05:29 AM   #664
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Default Yup...

The first thing I would do is to re do the I2S lines. Use tightly twisted pairs, and get them all the same length (as short as possible, with your layout it looks like you only need 3 cm of wiring or so). Use 24 or 28 awg solid core wire, and run all of the grounds. Then, at your DAC board, run an exposed wire from the ground connection along the + input points, and attatch all the ground wires right next to where the positive leads terminate: this way you keep the tightly twisted pairs together for as much of their length as possible.
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Old 6th May 2012, 06:52 AM   #665
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Is it possible the discrete dac is not fully compliant with the i2s stream off the Wave? Are there published specs for discrete dac? Not asking for measurements as they would probably be too terrifying
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Old 6th May 2012, 10:03 AM   #666
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by Wolfsin View Post
I have one built with 8740 and am trying to figure if it is worthwhile to use the 8741 on another pcb. I do not care about DSD nor do I consider a few extra dB worthwhile but the sound matters. If it cannot beat the BB1704 I will not care at all. Have you compared to Buffalo?
It cannot, and neither the ESS.
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Old 6th May 2012, 10:17 AM   #667
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by rsdio View Post
In addition to being able to withstand some noise, digital also creates a lot of noise on the supply lines due to basically passing around square waves all the time.
(...)
I'm sure you're right that clock jitter may need filtered supplies, but I still wouldn't feed a clock supply to an analog circuit, so separate is good.
Separating analog and digital supplies is obvious. But among the digital lines, how much should we separate, in a Sota setup?
Xmos for once, then the oscillators, and then the i2s output (isolated or not)

but what about the ground?
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Old 6th May 2012, 11:26 AM   #668
kp93300 is offline kp93300  Malaysia
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Quote:
Originally Posted by hochopeper View Post
I wonder if you could describe the 3.5V salas shunt and its relationship to the DAC supply. Is there a possible ground loop condition between those two? Have you confirmed that the output of the salas reg is stable?
The salas shunt is powered from a 9V smps regulated supply. The 3,6 v from the salas shunt supply the IL715 only.
The wave io board derives the supply from a 1A trans and regulated with LM 317 that provided 4.95 V . I have not confirm the stability of the shunt but it sound nice powering an Tenor usb spdif converter.
There is only 1 ground connection from the salas shunt to IL715 and one ground connection from LM 317 to wave io.
thanks

kp93300
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Old 6th May 2012, 11:28 AM   #669
kp93300 is offline kp93300  Malaysia
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Hi barrows and lorien,
Thanks for suggestion and I am redoing these lines per suggestions .
Will report back .
kp93300
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Old 6th May 2012, 02:59 PM   #670
kp93300 is offline kp93300  Malaysia
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Default Follow up

Hi All,
Please see the attached image.
I did the changes for the ground arrangement and change the i2s lines length as suggested. Hope i have interpret correctly. I use some thin solid core magnet wire.
The problem persisted .

I did a few experiment of the different types of ground arragement and none of this helps.I left the isolated ground unconnected and wire the salas power supply to the star ground ie blue terminal block. Distortion still there and there is music.

thanks to all for the input.

I am entertaining the possibility that it may be the discrete dac problem.

regards

kp93300
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