A member sent me a modified version of Schiit Magni 3+ for testing. The modification is based on the fact that the power supply design violates the specification from the IC company (low drop out regulator). Here is the schematic and modifications made:
Per note from the member, specs for LM 317/337 specifically forbit using large or low ESR capacitors in the output. I have not looked at the reason but it may be that the surge current will be too high. Using an oscilloscope, member found the best, compliant solution to be removal of caps 5 and 6 and replacing C3 and C4 with 10 microfarad tantalum caps. Result was slightly improved noise on the output of the power supply:
Question is whether this improves performance any so let's measure it starting with our dashboard:
Overall SINAD is the same, dominated by the high distortion. Power supply components are more or less the same to my eye. And there are enough variations here given that the old test is 3 years old as to not be able to make precise comparisons anyway.
SNR is identical to stock unit:
Stock:
Frequency response is the same:
Lastly I ran a power sweep at 300 ohm. Results were the same in low gain but high gain produced slightly more power:
Can't imagine the power supply mod improving level of power. Maybe there was a running design change here.
Conclusions
I have not looked at the datasheet to see what it says about output loading. Trusting the member's notes, it seems to be a good change to improve long term reliability. It may have some negative impact on dynamic power but without specific testing, it is hard to say if there is any. Continuous power is at least as good as stock unit so all is well there.
I am relieved to see a mod be in service of bettering the design based on proper knowledge than vudu.
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As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Per note from the member, specs for LM 317/337 specifically forbit using large or low ESR capacitors in the output. I have not looked at the reason but it may be that the surge current will be too high. Using an oscilloscope, member found the best, compliant solution to be removal of caps 5 and 6 and replacing C3 and C4 with 10 microfarad tantalum caps. Result was slightly improved noise on the output of the power supply:
Question is whether this improves performance any so let's measure it starting with our dashboard:
Overall SINAD is the same, dominated by the high distortion. Power supply components are more or less the same to my eye. And there are enough variations here given that the old test is 3 years old as to not be able to make precise comparisons anyway.
SNR is identical to stock unit:
Stock:
Frequency response is the same:
Lastly I ran a power sweep at 300 ohm. Results were the same in low gain but high gain produced slightly more power:
Can't imagine the power supply mod improving level of power. Maybe there was a running design change here.
Conclusions
I have not looked at the datasheet to see what it says about output loading. Trusting the member's notes, it seems to be a good change to improve long term reliability. It may have some negative impact on dynamic power but without specific testing, it is hard to say if there is any. Continuous power is at least as good as stock unit so all is well there.
I am relieved to see a mod be in service of bettering the design based on proper knowledge than vudu.
--------
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/