Hello Everyone,
I am relatively new to the world of building and modifying electronics and have gained most of my knowledge from DIY Audio. So, after reading some forums here, I recently decided to purchase an 8x TDA1387 DAC from Cart 100. I should note that I also added the optional USB CM6631 card.
Conceptually I like the idea of a PCM, continuous calibration DAC, as apposed to R2R or even S/D, and wanted to hear one for myself. My plan was to get it and modify it according to some suggestions made by abraxalito and others. Unfortunately I have not had much success getting it to work properly. abraxalito and others have been extremely helpful on another thread, but I thought I should start one just for these issues. At this point I have opened it and tinkered around enough that the warranty is void. Plus I bought this thing to modify it anyways.
http://www.diyaudio.com/forums/digital-source/261624-tda1387-continuous-calibration-dac.html
Attempt 1: DAC arrived, I plugged it into my raspberry pi2 running Moode audio via USB. It immediately drew so much power the Ethernet stopped working on the pi. (Since then I found the option in Moode to double the USB amps, but haven't tried this yet. I also may try a powered hub.). I fiddled around with it for a while, eventually hot plugged it (not recommended), and was able to get it to work with the pi, but only got digital static unless I set the SRC in Moode to 16bit 44.1k. While music sounded somewhat audible, there were constant clicks and pops plus the USB CM6631 should be able to handle up to 24bit 192k (Again this may be something to do with the pi's issues with USB. Also, I read that the CM6631 draws its power from the USB port and not from the DAC.)
Attempt 2: Disconnected the DAC from USB, removed the CM6631 and hooked the DAC to my existing (functioning) systems optical output. I use a Focusrite Saffire Pro 24 as a stand alone DAC (ground hum when using firewire) from the optical port of my iMac running iTunes (Mac audio settings: 24bit 96k). When I replaced the Saffire with the 8x TDA1387 it functioned similarly to when I set the SRC in Moode on the pi. It was audible, but lots of clicks, pops, and dropouts. Also the 'Sync" light would turn off and on when the dropouts occurred (This did not happen with USB). When I set the computer to output 16bit 44.1k it was better and the pops were less frequent, but still bad.
Attempt 3:Connected the Saffire back to the iMac and connected the TDA1387 to the coax output of the Saffire, again similar result.
Attempt 4:Re-installed the CM6631 and connected the DAC via USB to my iMac. Same audible static issues as with the Pi except it worked right away and I didn't kill the Ethernet port when plugging it into the computer. (Probably because its not a $35 computer...) "Dumbing down" the resolution and sample rate did seem to clean it up, like with the pi, but there was still frequent clicks and pops. Also, like the pi, the sync light never went out.
At this point I decided to poke around with my multi-meter. I found that everything visually seems okay and that nothing is shorted as far as I can tell. I measured +15 and -15 on the analog side and +5v on the digital side, to the grounding plane, but nothing to the IEC's ground. The grounding planes all have near zero resistance between each other, but nothing is connected to the ground pin of the DAC's IEC except a 100R resistor that connects to a strip running along the side of the PCB. The function of this 'metal strip' appears to be how the PCB grounds to the chassis, but there is a layer of black coating on the chassis that makes it non-conductive. But again, this strip is not connected to the PCB ground planes.
Since there is no connection to safety ground, I assume that the DAC gets its reference ground from the analog RCA output jacks?.
So...Does the ground of the PCB need to be connected to the ground pin of the IEC in the DAC?
Are there any components that I should check? If so, what and how?
I don't know if it will help, but I attached a picture of the inside of my DAC. I probably should have also taken a pic of the bottom, but forgot. Ill post that later if anyone thinks it will help.
Thank you!
I am relatively new to the world of building and modifying electronics and have gained most of my knowledge from DIY Audio. So, after reading some forums here, I recently decided to purchase an 8x TDA1387 DAC from Cart 100. I should note that I also added the optional USB CM6631 card.
Conceptually I like the idea of a PCM, continuous calibration DAC, as apposed to R2R or even S/D, and wanted to hear one for myself. My plan was to get it and modify it according to some suggestions made by abraxalito and others. Unfortunately I have not had much success getting it to work properly. abraxalito and others have been extremely helpful on another thread, but I thought I should start one just for these issues. At this point I have opened it and tinkered around enough that the warranty is void. Plus I bought this thing to modify it anyways.
http://www.diyaudio.com/forums/digital-source/261624-tda1387-continuous-calibration-dac.html
Attempt 1: DAC arrived, I plugged it into my raspberry pi2 running Moode audio via USB. It immediately drew so much power the Ethernet stopped working on the pi. (Since then I found the option in Moode to double the USB amps, but haven't tried this yet. I also may try a powered hub.). I fiddled around with it for a while, eventually hot plugged it (not recommended), and was able to get it to work with the pi, but only got digital static unless I set the SRC in Moode to 16bit 44.1k. While music sounded somewhat audible, there were constant clicks and pops plus the USB CM6631 should be able to handle up to 24bit 192k (Again this may be something to do with the pi's issues with USB. Also, I read that the CM6631 draws its power from the USB port and not from the DAC.)
Attempt 2: Disconnected the DAC from USB, removed the CM6631 and hooked the DAC to my existing (functioning) systems optical output. I use a Focusrite Saffire Pro 24 as a stand alone DAC (ground hum when using firewire) from the optical port of my iMac running iTunes (Mac audio settings: 24bit 96k). When I replaced the Saffire with the 8x TDA1387 it functioned similarly to when I set the SRC in Moode on the pi. It was audible, but lots of clicks, pops, and dropouts. Also the 'Sync" light would turn off and on when the dropouts occurred (This did not happen with USB). When I set the computer to output 16bit 44.1k it was better and the pops were less frequent, but still bad.
Attempt 3:Connected the Saffire back to the iMac and connected the TDA1387 to the coax output of the Saffire, again similar result.
Attempt 4:Re-installed the CM6631 and connected the DAC via USB to my iMac. Same audible static issues as with the Pi except it worked right away and I didn't kill the Ethernet port when plugging it into the computer. (Probably because its not a $35 computer...) "Dumbing down" the resolution and sample rate did seem to clean it up, like with the pi, but there was still frequent clicks and pops. Also, like the pi, the sync light never went out.
At this point I decided to poke around with my multi-meter. I found that everything visually seems okay and that nothing is shorted as far as I can tell. I measured +15 and -15 on the analog side and +5v on the digital side, to the grounding plane, but nothing to the IEC's ground. The grounding planes all have near zero resistance between each other, but nothing is connected to the ground pin of the DAC's IEC except a 100R resistor that connects to a strip running along the side of the PCB. The function of this 'metal strip' appears to be how the PCB grounds to the chassis, but there is a layer of black coating on the chassis that makes it non-conductive. But again, this strip is not connected to the PCB ground planes.
Since there is no connection to safety ground, I assume that the DAC gets its reference ground from the analog RCA output jacks?.
So...Does the ground of the PCB need to be connected to the ground pin of the IEC in the DAC?
Are there any components that I should check? If so, what and how?
I don't know if it will help, but I attached a picture of the inside of my DAC. I probably should have also taken a pic of the bottom, but forgot. Ill post that later if anyone thinks it will help.
Thank you!
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Yeah, just those mods so far. I'm not going to try anything else until I get it stable. Thanks
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