In summary, SPS80 only drops 7.7V but the linear power supply drops 23V. It is obvious that the SPS80 is far superior in loaded condition. There is some improvement in terms of 100Hz ripple and 1K Hz ripple. With additional 5400uF, there is further improvement by 0.9V.
In terms of sound, the SPS80 is so much better. The bass slam is clear, solid and transparent. It is actually more quiet than the LPS. The background is dark black. There is no need to go back to LPS anymore!
When someone tell me again that SMPS is noisy, now I have proved to myself that a good SMPS is better than LPS in all areas!!
However, I think SMPS is good for OTL as the current output is very large. In our measurement, the current at full load is 1.3A, but in theory, the peak current can reach 4A. However, SMPS may be overkill in transformer output amp!?