I think the cable routing looks fine. If you tilt the boards a bit so you can run it without the usb input touching the chassis then you will know if that is the problem.
So, it worked fine, then developed a whine? Did anything change? Anything get moved?
Regarding io's earlier post I deleted them because they are not relevant to Luke's problem.
Lukes DAC was working fine previously. This is a new issue not related to the DAC PCB.
As far as the scope shots io posted go, it looks like an apples oranges comparison. If you take a scope shot of one half Opus output without any BAL/SE stage such as IVY III or Ballsie Lite, it will look very much like what io posted. Also certain filter settings can make it look like that too. because of pre-post ringing. Not GND.
If you run the opus DC coupled through a proper output stage as recommended it will not look anything like what io posted.
Cheers!
Russ
Lukes DAC was working fine previously. This is a new issue not related to the DAC PCB.
As far as the scope shots io posted go, it looks like an apples oranges comparison. If you take a scope shot of one half Opus output without any BAL/SE stage such as IVY III or Ballsie Lite, it will look very much like what io posted. Also certain filter settings can make it look like that too. because of pre-post ringing. Not GND.
If you run the opus DC coupled through a proper output stage as recommended it will not look anything like what io posted.
Cheers!
Russ
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io really having a hard time following you. I am happy to consider your input but perhaps private email would be better. Then you can give me a more accurate description of what you are doing. I would love to be educated if you have something truly useful to show me.
I look forward to hearing from you.
I look forward to hearing from you.
thanks for staying peaceful guys 
io, I gotta admit, I'm also not sure what it is you're seeing an issue with. I'll let you work that out with Russ. Let us know whatthe results are if you have a good discussion.
Luke, I guess you say this was working well at some point, so that is strange.
- you're listening to SE outputs direct from the DAC? (hot & GND) or Diff? Same noise either way?
- have you checked all the settings? (I don't have time to review them now, but no loose connections on the receiver board or DAC?) Changed Fs, etc...
- FWIW, on my board I connected mute to the signal valid flag from the receiver so I don't hear junk when the DAC is not locked to a valid signal...
-CK
io, I gotta admit, I'm also not sure what it is you're seeing an issue with. I'll let you work that out with Russ. Let us know whatthe results are if you have a good discussion.
Luke, I guess you say this was working well at some point, so that is strange.
- you're listening to SE outputs direct from the DAC? (hot & GND) or Diff? Same noise either way?
- have you checked all the settings? (I don't have time to review them now, but no loose connections on the receiver board or DAC?) Changed Fs, etc...
- FWIW, on my board I connected mute to the signal valid flag from the receiver so I don't hear junk when the DAC is not locked to a valid signal...
-CK
Nothing has changed, but its ok with music playing, its when you turn the volume down low, or stop the music. Its likely that I didn't acknowledge something was wrong from the start.
thanks for staying peaceful guys
io, I gotta admit, I'm also not sure what it is you're seeing an issue with. I'll let you work that out with Russ. Let us know whatthe results are if you have a good discussion.
Luke, I guess you say this was working well at some point, so that is strange.
- you're listening to SE outputs direct from the DAC? (hot & GND) or Diff? Same noise either way?
- have you checked all the settings? (I don't have time to review them now, but no loose connections on the receiver board or DAC?) Changed Fs, etc...
- FWIW, on my board I connected mute to the signal valid flag from the receiver so I don't hear junk when the DAC is not locked to a valid signal...
-CK
yep SE, hot to ground I use. Have not tried any other mode, but it really sounds digital?
The WM8741 is a differential DAC, not SE, so using just half of its output will never sound really good. You need a BAL/SE stage like IVY-III or Ballsie Lite to cancel out common mode noise/distortion. Since there is more than one way to do this we don't do it on the DAC board, that way the builder can use a transformer, tube stage, or one of our modules. Whatever they choose.
But honestly I am not thinking your problem is with the output, but it is very hard to say. If you use it balanced out and it goes away, then that most likely is your issue, or at least you know the path to a solution.
reviewed your setup. Can't see anything wrong. I forgot you're using the USB input.
I use the spdif receiver and a Balsie for SE output. No issues.
USB could be part of the noise issue, but you tried with a laptop, and that should eliminate any major ground loop noise issues. And most likely also eliminate any software dependent issues...
good luck. sorry can't be of more help...
Hi Russ, I have a balanced tube pre and the problem is still there. I cant help but think the usb reciever shield is touching the grounded chassis, is it not possible that i have a ground loop in my usb cable from pc to dac? I guess its dumb to remove earth from the chassis so maybe I disasemble it see what happens. Then again I could just listen to really loud music
Ah ok well that actually is a very helpful bit of info, because what it means is that the noise is not common mode (unless your tube amp has very very poor CMR).
Is the noise sill there when you disconnect the USB cable?
A couple things to try.
1) Alternate power supply. Even 4 AA batteries in series should work fine.
2) Alternate source, perhaps it is the USB module that is damaged. Do you have access to a SPDIF module? Or some other I2S source?
Is the noise sill there when you disconnect the USB cable?
A couple things to try.
1) Alternate power supply. Even 4 AA batteries in series should work fine.
2) Alternate source, perhaps it is the USB module that is damaged. Do you have access to a SPDIF module? Or some other I2S source?
doesn't seem like ground loop (though I don't know how the USB receiver would respond to such noise) But if you tried from a laptop, that should have isolated any ground loop. (I assume you ran laptop from battery, and not connected to anything else)
as a complete guess, I'd suspect that USB rcvr...
Volumite settings and measurements
There was a deleted picture posted by IO because of his post seemed out of ongoing topic. I repeated some of his experiment, using 1Khz/0 Db square pulses. My results confirm Russ's interpretation, there are remarkable effect of filters of Opus (in case of squre pulses). The first picture corresponds to Filter 4 and the figure on the bottom is shows Filter 1. Clearly seen why some of us would better prefer the later one. The balanced outputs of Opus + Volumite were used (+ default Elna Silmic II caps). There was no difference in between filter settings using sinus waves. Cheers, János
There was a deleted picture posted by IO because of his post seemed out of ongoing topic. I repeated some of his experiment, using 1Khz/0 Db square pulses. My results confirm Russ's interpretation, there are remarkable effect of filters of Opus (in case of squre pulses). The first picture corresponds to Filter 4 and the figure on the bottom is shows Filter 1. Clearly seen why some of us would better prefer the later one. The balanced outputs of Opus + Volumite were used (+ default Elna Silmic II caps). There was no difference in between filter settings using sinus waves. Cheers, János
Attachments
Make sense. And thanks for the pictures.
(Not sure what you label as filter 1 and filter 4)
According to the volumite code published by Russ and the latest WM8741 data sheet,
The volumite setting setting for photo 1 is for OSR low and filter 2: "minimum phase soft knee". Minimum phase reduces pre ringing and increases post ringing as you can see in the photo. "a lot of people" think this is "better" because it has less pre-ringing
The volumite setting for photo 2 is OSR low and filter 4: "linear phase apodizing". Linear phase has preringing and post ringing (as you can see in the photo). Apodizing means it rolls earlier than 20K, so you may loose some of the HF information.
(Not sure what you label as filter 1 and filter 4)
According to the volumite code published by Russ and the latest WM8741 data sheet,
The volumite setting setting for photo 1 is for OSR low and filter 2: "minimum phase soft knee". Minimum phase reduces pre ringing and increases post ringing as you can see in the photo. "a lot of people" think this is "better" because it has less pre-ringing
The volumite setting for photo 2 is OSR low and filter 4: "linear phase apodizing". Linear phase has preringing and post ringing (as you can see in the photo). Apodizing means it rolls earlier than 20K, so you may loose some of the HF information.
How is it possible to change between the filters ?
I use Silk Volumen trafos and no analog filtering at all.
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