If you are unfamiliar with audio measurements please use a search engine with the query: "audio measurements" or "audio measurement handbook" Look for publications by Richard C. Cabot and also by Bob Metzler, both from Audio Precision. There are other useful publications as well. These will provide basic knowledge. Interpretation of the following measurements is beyond the scope of this post. The data presented were acquired as follows: 1. PrismSound dScope III, picoscope 5243B 2. Garage 1217 Project Sunrise III headphone amp 3. Electro-Harmonix 12BH7 tube 4. 300 ohm load used for measurements 5. Unbalance RCA cable - Sescom with Canare L-4e6s cable 6. Balanced 4-pin XLR cable - Cable Matters 16 awg and Neutrik XLR connectors 7. Shielded 14AWG and 16AWG power cables 8. SMPS Meanwell GS40A24-P1J 24Vdc 1.67A 40W max 9. LPS 1 Jay's Audio Talema 24Vdc 1A 25W max 10. LPS 2 Keysight (HP/Agilent) U8001A 0 to 30Vdc variable 3A lab supply Presented is a comparison of 3 power supplies, their noise and respective effect on measurements using a Project Sunrise III headphone amplifier. The level chosen for this comparison, -24 dBu, highlights the effect on lower level signals as heard with an HD800 at approximately 76 dB SPL for a nominal of 85 dB SPL. Notable highlights: PS-III measurements improve with lower noise power supplies. Subjectively my ears tell me the same thing. Using an RME ADI-2 Pro and the U8001A enables an extraordinary blackground from which music appears. Setup picture: Meanwell SMPS 1mVrms 4mVpp ripple 650mA 50 KHz BW: Jay’s Audio Talema LPS 24V 815 uVrms 3mVpp ripple 650mA load 50KHz BW: U8001A 24V 110uVrms 670uVpp ripple 650mA load 50KHz BW: PS-III THD, THD+N and 1 KHz spectrum - Meanwell SMPS: PS-III THD, THD+N and 1 KHz spectrum - Jay’s Audio Talema LPS 24V: PS-III THD, THD+N and 1 KHz spectrum - U8001A 24V: A rather substantial improvement in THD, THD+N and spectrum occurs with the Talema 24V LPS over the Meanwell SMPS (provided with the PS-III.) Looking at THD and spectrum, another improvement occurs with the U8001A LPS.