Hello Everyone
I know enough to not be dangerous and have built point-to-point tube amp kits, but do not have a detailed knowledge of electronic components.
I have an Auralic Vega that, out of nowhere, started crazy distorting when anything but garbage came out of the balanced outs. The single ended outs would distort at high levels and were putting out a much reduced level.
I put it on an oscilloscope and it was clear most of the negative half of the signal was cut off. The Balanced showed junk at lower levels then then a cut off waveform at high levels. The single ended looked OK at lower levels but then were cut off at higher levels. For those familiar with the piece, the transition was around 80 out of 100 on the volume scale (supposedly 0.5dB per step) but does not seem stable.
The balanced outputs are supposedly class A so the lack of the negative portion of the signal on either phase of the balanced output made me think the negative power supply feeding some portion of the output circuits had failed. The single ended output is supposedly derived from the difference between the fancy class A balanced outputs, by the way. Both channels act the same.
So I opened up the unit and started carefully measuring the voltage at a few points I recognized in the power supply. Out of curiosity I measured the voltage at the aluminum seal at the top of the electrolytic caps. All were negligible (0.25 to 0.33 VDC, 0.2 to 0.3VAC) except one that was at -19.43 VDC and 0 VAC. My understanding is the seals should just float and are not tied to a terminal of the cap.
Has this cap gone to Component Heaven? Could it be the problem or a symptom of something else? Nothing I can see looks scorched or burnt or otherwise like it overheated, but most of what I think are regulators have heat sinks on them so I cannot see them.
Thoughts anyone?
I know enough to not be dangerous and have built point-to-point tube amp kits, but do not have a detailed knowledge of electronic components.
I have an Auralic Vega that, out of nowhere, started crazy distorting when anything but garbage came out of the balanced outs. The single ended outs would distort at high levels and were putting out a much reduced level.
I put it on an oscilloscope and it was clear most of the negative half of the signal was cut off. The Balanced showed junk at lower levels then then a cut off waveform at high levels. The single ended looked OK at lower levels but then were cut off at higher levels. For those familiar with the piece, the transition was around 80 out of 100 on the volume scale (supposedly 0.5dB per step) but does not seem stable.
The balanced outputs are supposedly class A so the lack of the negative portion of the signal on either phase of the balanced output made me think the negative power supply feeding some portion of the output circuits had failed. The single ended output is supposedly derived from the difference between the fancy class A balanced outputs, by the way. Both channels act the same.
So I opened up the unit and started carefully measuring the voltage at a few points I recognized in the power supply. Out of curiosity I measured the voltage at the aluminum seal at the top of the electrolytic caps. All were negligible (0.25 to 0.33 VDC, 0.2 to 0.3VAC) except one that was at -19.43 VDC and 0 VAC. My understanding is the seals should just float and are not tied to a terminal of the cap.
Has this cap gone to Component Heaven? Could it be the problem or a symptom of something else? Nothing I can see looks scorched or burnt or otherwise like it overheated, but most of what I think are regulators have heat sinks on them so I cannot see them.
Thoughts anyone?
Post the schematic. What are the power supply voltages, both before and after the regulators?
If both channels have the same fault, it appears that one of the power supplies may be down.
If both channels have the same fault, it appears that one of the power supplies may be down.
It is very-very common for the case to also be the NEG terminal. Internally, that's how it works. Any other connection would be odd.
Which makes your tenths-Volt readings on other caps suspicious.
I would not be looking at caps until I identified and measured the power supply output lines. If they make nominal-looking voltages, that's not today's trouble.
> around 80 out of 100 on the volume scale
Completely meaningless as stated. What are you putting IN? 0.1V? 10V?
Auralic Vega ? , do you mean the DAC ?
If not in any case their circuits are patented and not available to the general public , that's what it says online but maybe somebody knows differently ?
As far as I know the rules on DIY Audio wont allow patented circuits to be posted without consent of the owners .
The schematic was filed in China only .
If not in any case their circuits are patented and not available to the general public , that's what it says online but maybe somebody knows differently ?
As far as I know the rules on DIY Audio wont allow patented circuits to be posted without consent of the owners .
The schematic was filed in China only .
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Sorry - I meant to include that I was using a tone generator app on my iPhone fed to the USB input on the DAC that, as best as I can tell, should be sending 16 bit data at 0dBFS. I’m not getting output signals that match the standards, the published specs or measurements from a review, but the single ended output is closest. The balanced legs give some very strange waveforms!
I had assumed that the case would be at the negative terminal voltage if it was going to be at any, but I found some reference that indicted they should float rather than be tied to a terminal or grounded. I would think that would be best, at least in high voltage circuits, to avoid an excessive voltage difference between the cap case and its surroundings.
Unfortunately I do not currently have access to a schematic of the DAC. I might have to disassemble it to measure the voltages since the board(s) is very well masked and it’s hard to find places to measure. Perhaps it would be easier on the bottom of the board.
I had assumed that the case would be at the negative terminal voltage if it was going to be at any, but I found some reference that indicted they should float rather than be tied to a terminal or grounded. I would think that would be best, at least in high voltage circuits, to avoid an excessive voltage difference between the cap case and its surroundings.
Unfortunately I do not currently have access to a schematic of the DAC. I might have to disassemble it to measure the voltages since the board(s) is very well masked and it’s hard to find places to measure. Perhaps it would be easier on the bottom of the board.
Yes, the DAC - sorry. And I don’t expect to get the schematics and certainly wouldn’t post them without permission even if I had them.