I've drawn a schematic and have nearly finished laying out a PCB for a USB to S/PDIF converter board that includes a relay to switch between USB and S/PDIF inputs. I am holding off finishing it while I get my ezdac board built up and tested. I am still considering whether to change this to I2S output instead.
I'm using a PCM2704 for the conversion. The converter board will have an analog audio output as well.
USB interface
Glad to use your continuing input on the USB interface... this option represents for me the principal reason for adopting the ezDAC... music stored on the iMAC.
PC music storage is the way to go for "whole house music" programming.
Your response above presents interesting info. What have been some of your pre-decision thoughts. My current thoughts are:
1. Should I break the power feed to the CS8416 when switching the USB/I2S feed to the PCM1794 module? this could be simpler than preventing USB/I2S back-feed to the CS.
2. Breaking into the PCM1794' I2S lines could be the tie breaker; I am getting into my "Monk's Zen" zone needed to tackle the SMD work, and feel adding to the task with cutting into the circuit may be ill-advised.
So, the USB/SPdif conversion may be the easier approach. I still question if added signal deterioration would occur with that extra ensuing SPdif/I2S step?
3. I would want a separate audio out for local headphone listening, but maintain a good RCA out for main system out. In your case, will the audio out plans integrated to the USB/SPdif board replace/add to the ezDAC audio out section?
Thanks for your inputs,
Louis
Glad to use your continuing input on the USB interface... this option represents for me the principal reason for adopting the ezDAC... music stored on the iMAC.
PC music storage is the way to go for "whole house music" programming.
Your response above presents interesting info. What have been some of your pre-decision thoughts. My current thoughts are:
1. Should I break the power feed to the CS8416 when switching the USB/I2S feed to the PCM1794 module? this could be simpler than preventing USB/I2S back-feed to the CS.
2. Breaking into the PCM1794' I2S lines could be the tie breaker; I am getting into my "Monk's Zen" zone needed to tackle the SMD work, and feel adding to the task with cutting into the circuit may be ill-advised.
So, the USB/SPdif conversion may be the easier approach. I still question if added signal deterioration would occur with that extra ensuing SPdif/I2S step?
3. I would want a separate audio out for local headphone listening, but maintain a good RCA out for main system out. In your case, will the audio out plans integrated to the USB/SPdif board replace/add to the ezDAC audio out section?
Thanks for your inputs,
Louis
I've gone back and forth on this (I2S vs SPDIF) a few times now. My last post here said I was switching to I2S, but I haven't done anything further on the PCB design yet.
If I2S, I would run it through the ASRC AD1896, so on the ezdac I would depopulate R19, 20, and 21 and attach flywires at those points.
Yes, USB/SPDIF would be simpler in regards to having to make mods on the ezdac.
The current design brings out the audio output to make the board more useful. The local PCB shop I would use (Alberta Printed Circuits) provides 2 boards minimum, so I was thinking I may use the second board in a portable application. The direct audio output would also be useful for testing or troubleshooting without an external DAC.
The current PCB size is 2.5" x 2.8" and includes a dual opamp for the audio output and a +5 to -5 voltage converter to give me a +/-5V supply. APC will charge me $45 for 2 of these boards, no soldermask or silkscreen. If I change it to I2S it would probably be about the same size.
If I2S, I would run it through the ASRC AD1896, so on the ezdac I would depopulate R19, 20, and 21 and attach flywires at those points.
Yes, USB/SPDIF would be simpler in regards to having to make mods on the ezdac.
The current design brings out the audio output to make the board more useful. The local PCB shop I would use (Alberta Printed Circuits) provides 2 boards minimum, so I was thinking I may use the second board in a portable application. The direct audio output would also be useful for testing or troubleshooting without an external DAC.
The current PCB size is 2.5" x 2.8" and includes a dual opamp for the audio output and a +5 to -5 voltage converter to give me a +/-5V supply. APC will charge me $45 for 2 of these boards, no soldermask or silkscreen. If I change it to I2S it would probably be about the same size.
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ok, I looked at Read Research's Mains Op-amp PSU which is basically the same thing as the ezdual. They're using 10ohm 2W resistors for his R1/R2.
I've got 3x 33ohm 1/4w (in parallel) resistors that are frying. Not sure why the BOM specified 1/4w but I'll replace them with power resistors that can handle a few watts.
Maybe those are plenty enough for handling a walwart?
I've got 3x 33ohm 1/4w (in parallel) resistors that are frying. Not sure why the BOM specified 1/4w but I'll replace them with power resistors that can handle a few watts.
Maybe those are plenty enough for handling a walwart?
They shouldn't be frying, a single 33 ohm resistor can handle nearly 90mA before it dissipates 0.25W. That means a total current draw of 270mA max. for the three in parallel, and they are not even frying then. The fact that they are burning up means that there's something wrong, too much current is drawn somewhere, and a bigger resistor won't change that i'm afraid.
The ezDual is doing this on it's own, with no load? Also, the negative side seems o.k., isn't it? Post some pictures of the board if you can, maybe we can see what the problem is. See if something else gets hot, that current has to go somewhere. Are all caps' polarity in the right direction?
Regards,
Ray
The ezDual is doing this on it's own, with no load? Also, the negative side seems o.k., isn't it? Post some pictures of the board if you can, maybe we can see what the problem is. See if something else gets hot, that current has to go somewhere. Are all caps' polarity in the right direction?
Regards,
Ray
And it can handle a lot more than that before it actually fries. I think you have a direct short circuit somewhere. Try using an ohmmeter without any power applied.
So the ezDual is outputting that when it's connected to the ezDac but is okay when not connected? I still think you have a short somewhere, but it could be on the output side of one of the positive regulators.
You could depopulate all the (+) regulators on the ezDac and check resistance to ground on both the power input and all regulator outputs.
You could depopulate all the (+) regulators on the ezDac and check resistance to ground on both the power input and all regulator outputs.
My ezdual now is outputting ~ +2v/-15v without anything connected to it.
It had been working when I repaired the shorted cap. When I attached it to my ezdac I got nothing out of it, and then rechecked it again (disconnecting it from the ezdac) and got the above voltage.
I didn't keep it plugged in long ... fearing I'd blow another cap or smoke the resistors.
It had been working when I repaired the shorted cap. When I attached it to my ezdac I got nothing out of it, and then rechecked it again (disconnecting it from the ezdac) and got the above voltage.
I didn't keep it plugged in long ... fearing I'd blow another cap or smoke the resistors.
OK. Start by checking the resistance of the ezdac to ground, and then the resistance of each +ve regulator output to ground. Look for a dead short.
Meanwhile, on the ezdual, you can check the voltage input and output on the +ve regulator.
When you're ready to hook them back up, a current-limited lab power supply would be handy if you have access to one. Otherwise, use (say) 100-ohm resistors in the +ve and -ve lines running from the ezdual to ezdac. And connect/disconnect it quickly. You've had your share of smoke and broken stuff on this.
Meanwhile, on the ezdual, you can check the voltage input and output on the +ve regulator.
When you're ready to hook them back up, a current-limited lab power supply would be handy if you have access to one. Otherwise, use (say) 100-ohm resistors in the +ve and -ve lines running from the ezdual to ezdac. And connect/disconnect it quickly. You've had your share of smoke and broken stuff on this.
USB to SPDIf for ezdac
The adapter board will have USB and SPDIF input connectors, selected by a small relay and associated control signal. I'll start a separate thread once I'm ready to solicit comments on the design.
For any that are interested, I'm going back to SPDIF because it's less intrusive to the ezdac and gives more flexibility for other uses.
The adapter board will have USB and SPDIF input connectors, selected by a small relay and associated control signal. I'll start a separate thread once I'm ready to solicit comments on the design.
Question on BOM cap values
Hi All,
I'm starting to order parts for my DAC board. On the BOM posted for the 1.5 EZDAC on Evan's site C1,2,4,5,7,8,10 & 12 are shown as 10 uF, however when I go to the digitkey number shown on the BOM they are shown as 100 uF, on the digitkey site. Could anyone please let me know the right value ?
Thanks,
PJN
Hi All,
I'm starting to order parts for my DAC board. On the BOM posted for the 1.5 EZDAC on Evan's site C1,2,4,5,7,8,10 & 12 are shown as 10 uF, however when I go to the digitkey number shown on the BOM they are shown as 100 uF, on the digitkey site. Could anyone please let me know the right value ?
Thanks,
PJN
USB interface... yes.
Will be tracking your posts. I have placed this project on the back burner; had to commit to other issues; speakers and woodworking are other hobbies.
Louis
Will be tracking your posts. I have placed this project on the back burner; had to commit to other issues; speakers and woodworking are other hobbies.
Louis
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