random_number<0
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- May 2, 2020
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My 851D kicked the bucket recently and it's out of warranty, so I opened it up to see if re-seating connections might fix the channel/static issue, whether there were any terribly obvious issues with caps, solder joints, etc., and, of course, to take some photos.
First look: Nice toroidal transformer, dedicated headphone amp at the bottom. There are two PCB's at the top of the photo. From left to right, the lower PCB has analog outputs (balanced XLR and stacked unbalanced single ended) with dual Analog Devices 1955 directly below the analog outputs, moving to the right: 2 optical and coax inputs/outputs, DAC/DSP section in the middle, some control circuitry (triggers and RS232), and then power on a separate PCB to the far right.
Daughter board has, from left to right: AES/EBU input, BNC input, 2 more optical inputs, USB B, and USB A for Bluetooth, and a trigger.
There's also a vertical PCB at the very bottom for LCD, physical buttons, and volume.
Close up of the lower board analog, DAC, and DSP sections, with the daughter board removed. Wires were in the way here, but I moved them for the next photos:
Rows of nice caps:
Analog and DAC section again, without wires in the way:
Close up of DSP, giant IC:
Dedicated headphone amp PCB:
Power section, dedicated hard switch above the IEC plug:
Daughter board:
Was a little surprised to see this on the bottom of the daughter board. Looking closely, the PCB's are nowhere near as clean as I would expect (dust aside):
Requests, comments, corrections welcomed in replies. Suggestions too. I tested the headphone amp and it has dropped one channel and has static in the other, which is the same as the balanced and unbalanced outputs. Doesn't matter which input is selected. Digital passthrough doesn't have any issue. So I think power is clean and there's a component that gave up the ghost in analog stage... but it could be in the DAC / DSP stage... I haven't seen any schematics for this unit.
First look: Nice toroidal transformer, dedicated headphone amp at the bottom. There are two PCB's at the top of the photo. From left to right, the lower PCB has analog outputs (balanced XLR and stacked unbalanced single ended) with dual Analog Devices 1955 directly below the analog outputs, moving to the right: 2 optical and coax inputs/outputs, DAC/DSP section in the middle, some control circuitry (triggers and RS232), and then power on a separate PCB to the far right.
Daughter board has, from left to right: AES/EBU input, BNC input, 2 more optical inputs, USB B, and USB A for Bluetooth, and a trigger.
There's also a vertical PCB at the very bottom for LCD, physical buttons, and volume.
Close up of the lower board analog, DAC, and DSP sections, with the daughter board removed. Wires were in the way here, but I moved them for the next photos:
Rows of nice caps:
Analog and DAC section again, without wires in the way:
Close up of DSP, giant IC:
Dedicated headphone amp PCB:
Power section, dedicated hard switch above the IEC plug:
Daughter board:
Was a little surprised to see this on the bottom of the daughter board. Looking closely, the PCB's are nowhere near as clean as I would expect (dust aside):
Requests, comments, corrections welcomed in replies. Suggestions too. I tested the headphone amp and it has dropped one channel and has static in the other, which is the same as the balanced and unbalanced outputs. Doesn't matter which input is selected. Digital passthrough doesn't have any issue. So I think power is clean and there's a component that gave up the ghost in analog stage... but it could be in the DAC / DSP stage... I haven't seen any schematics for this unit.
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