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I don't think this is a ground loop. I've had ground loop problems in my amp and took a lot of tinkering to fix. Also I'll probably build an amp that has balanced inputs eventually so I still haven't decided if I want the Ballsie. I've been thinking about building the new Nelson design the F5 which I'm pretty sure has balanced outputs.
I would say this sound is kind of an oscillating sound though. But I'm not sure its because of the single ended use of a balanced output. Russ said he's never heard of anyone having issues with this. Honestly it's probably a problem in my setup somewhere or something.
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Quote:Current outputs can be summed directly by adding the currents (just place in parallel) but in the case of a voltage source they should be resistively summed in order to avoid problems relating to gain mismatch between the two devices - best case if they are identical they sum well, if they are not (and they aren't) you get difference currents flowing between the two output stages with each trying to make both outputs conform to what its feedback signal says it should be. This usually results in higher distortion at best, and can result in other problems. (Like fried op-amps, oscillations and frequency response errors.Note that the output of this dac is an op-amp...) This is true, and worth addressing. You can use some low value resistors (21-47R) between the output terminal blocks and your output connectors, one for each output (except grounds). They can even just replace the wires you use now.
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This is the reason for the two input resistors on the Ballsie. Yes if your going to run dual mono you should use load sharing resistors. You may be sending the output stage of the WM8740 into oscillation because of the way you have it wired. You can simply add a 22-100 ohm resistor to each output pin, or you could use either the IVY or the Ballsie. As for grounding Kevin had a good point. You really only want one ground point between boards. So if two boards share a common PS (thus a common gnd) then you don't need to use any other GND wire between them. I have not looked at your grounding scheme closely yet, but at first glance it actually does not look bad. Cheers! Russ Edited by user Tuesday, April 22, 2008 4:50:16 AM(UTC)
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Ok so your saying between the RCA and the PCB put a 22 to 100ohm resistor? Or between the 2 connections to "bridge" the PCB? Like from right channel to left channel? Also will this affect sound quality any?
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Quote:between the output terminal blocks and your output connectors, one for each output (except grounds). They can even just replace the wires you use now. Brian Donegan attached the following image(s):  OUTPUTS.gif (81kb) downloaded 445 time(s).You cannot view/download attachments. Try to login or register.
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Thanks Brian, now I don't have any 22-100 ohm resistors. I have 8.2ohms, 22kohms, 47kohms, 10kohms and some other random stuff. Figures I don't have what I need. Could I test it with any of these? Do I have to bridge the channels like that? Was another question I had because I have tons of output.
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Brian's illustration is very good, but if your doing single ended you don't need any resistors on the unused ouputs. Don't wire them at all. Leave them open. You only need the resistors on the two going to the RCA You can try using the 8.2 ohm. The rest you have are too high. Any resistor in the 10-221 ohm range should be fine. Your 8.2 is a bit below that but still may be ok. Also I have tried loading the unused side with the same impedance is the loaded side will see (for example a preamp with 47K input impedance) with a resistor of the same value. If you do this then go ahead and include the resistors even on the unused outputs. In my experience though, this does not seem to effect the performance of the DAC. So I would not bother. I would just leave them open. Cheers! Russ Edited by user Tuesday, April 22, 2008 12:59:36 PM(UTC)
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Ok I'm going to try this eventually at the moment I can't bring my self to pull it out of my system :) It sounds so wonderful. As long as I don't stop playing music of course lol.
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Well I tried the 8.2 ohm resistors and it didn't change much. Might of got a little quieter but there was also static noise all the time after that. I didn't solder the connections because I wanted to make sure it would work first so maybe that had something to do with it?
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Well if I don't bridge the connections over it still makes that noise. I don't know if that would be normal? I think I just need to get the Ballsie or build a bal to se converter.
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Do you guys think this would be a good BAL to SE converter? It's pretty simple and cheap so wasn't sure how well it would work. 
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Yes, that's the classic BAL/SE opamp circuit. It will work, but I would not use values that high(distortion will not be good with those values), and 6db gain is too much. R1 and R3 will be better at about 2.21K and R2 and R3 at 2.7K.
You can also look at the WM8740 data sheet for a goo circuit. And it has the benefit of being a filter too. Like Ballsie.
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I'll have to look at the one on the Wolfson data sheet.
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The one in the WM8740 data sheet looks a bit complicated....not sure I want to try and tackle that :) I'll think about it. Might just end up getting the Ballsie though depends on how much it would cost me to build the one wolfson recommends. Edit: Ok just looked at the dual differential one which is what I need and it doesn't look bad at all actually. I'm not sure I understand how it would connect to the Opus though. Is VOUTLN, VOUTLP, VOUTRN, VOUTRP are those the left and right outputs? Also it has a little circuit that comes off VMIDL, and VMIDR would I need to do that as well? Edited by user Wednesday, April 23, 2008 6:19:48 PM(UTC)
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Ok I took the Metronome out of the setup today and the noise was still there but just barely it was real quiet. Something I find kind of interesting. So why would the Metronome be making the sound so loud? Gotta be a setting or something I would think.... I don't know.
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Does the Ballsie need the Bipolar PSU? And then I'm guessing it needs an extra transformer as well?
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Russ or Brien
On the COD pcb's.
Are you using 2 power lines(ie Vd and Va) and one ground plane on the pcb?
Is there a way of separating digital earth and analogue earth?
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It is one solid GND plane.
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