ECP T4 technical measurements Standard Prologue 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 technical measurements posts. The data presented were collected as follows: 1. PrismSound dScope III, picoscope 5243B, Keysight 34465A, Cal Test CT2593-2 balanced probe 2. Balanced XLR cables Belden 1800F with Neutrik 110R AES connectors (if used) 3. Single Ended cables Audioblast HQ-1 1.5 ft with Rean RCA connectors 4. 32 and 300 ohm loads used for measurements 5. dScope analyzer sample rate 48 KHz unless otherwise noted 6. 0dBu level used for testing unless otherwise noted 7. Amplifier input to output gain set for 0 dB unless otherwise noted 8. Audioquest Forest and Schiit Pyst USB cables used with measurement equipment 9. Vaunix Lab Brick USB hub 10. Shielded 14AWG and 16AWG power cables 11. ESD, EMI/RFI controlled lab bench and workspace Measurements are made in accordance with AES17:2015 Sensitivity data for two headphones to keep in mind while viewing these measurements: HD 650 impedance 300R, sensitivity 98 dB/mW HE-500 impedance 38R, sensitivity 89 dB/mW SPL levels for above headphones for reference: 0 dBu 300R 2.00 mW - 101 dBSPL @ 98dB/mW 0 dBu 30R 20.00 mW - 102 dBSPL @ 89dB/mW All testing performed at 0 dBu unless otherwise noted. This level is consistent with listening to headphones (referenced above) at 90 dBSPL average with peaks to 100 dBSPL, if the music has 10 dB Peak to Avg ratio. That is LOUD for long listening sessions. ECP T4 Measurements commenced after 168 hours of burn-in. Measurements each session began after 2 hrs warm-up. Measurements were performed over a period of several days. Index Post 1 - measurement setup description, highlights Post 2 - 300 ohm load SE input SE output part A JJ ECC81 tubes Post 3 - 32 ohm load SE input SE output part B JJ ECC81 tubes Post 4 - 300 ohm load SE input SE output part A Mullard CV4024 tubes Post 5 - 32 ohm load SE input SE output part B Mullard CV4024 tubes Post 6 - corrections or additional data if necessary Post 7 - backstory Notable highlights: Noise floor and residual mains noise are lower than -100 dBu which provides excellent blackground. Dynamic Range is approximately 108 dB. Bandwidth is > 300 KHz for 300R headphones which will result in excellent transient response. Distortion is 2nd harmonic dominant, with 3rd harmonic 20 dB lower and higher order harmonics lower than residual mains noise. This tends towards a very clean yet euphonic sounding presentation. Measurements of the T4 in my lab are long and storied, which will appear in another post. The greatest difficulty measuring the T4 was caused by my tendency to listen to amps while they warm up. In the case of the T4, good intentions ran afoul of lengthy listening periods. Total time allotted per session was spent listening to whole albums rather than measuring. Setup picture (measurements): Typical setup picture (listening): Output Impedance HiZ 26Ω LoZ 6.3Ω LoZ was used for both 300Ω and 32Ω measurements posted. 300Ω on HiZ is substantially similar to 32Ω on LoZ.