I have not abandoned this project, just delayed and reorganized.
I spent two weeks in Denver for CEDIA and HAA (Home Acoustics Aliance
training. The week of training with Gerry Lemay and Adam Pelz was exceptional and invaluable. I'm definitely not
but I believe I am on the right path. After returning from Denver my health took a turn for the worse. An electronic medical device (neurostimulator) I've had implanted for 5+ years has to be removed. I'm awaiting a surgery date (within 4-6 weeks). I still need to complete my HAA HT3 practicum. Please bear with me in the meantime.
In brighter news... last week I visited the Monoprice HTP-1 design team and received a beta unit.
In regards to this project, my initial measurements with the Audiomatica Clio 12 were involved for this purpose. The noise floor of the measurements was all over the place when viewing the real-time FFT. . The measurements were also highly susceptible to EMI and probably RFI. Meanwhile, the Clio Pocket (their entry level analyzer) did not exhibit the same behavior. A few weeks ago I identified and solved the issues with the Clio. The problem was only with measuring unbalaced/RCA outputs. Why this FW-02 interface has no chassis ground terminal is beyond me.
In my frustration a started looking into the Audio Precision systems. The newer APx515 is a lower cost design very much along the lines of the Clio 12 that could meet my needs. Secondhand APs are still relatively expensive, even those EOL. I will ultimately compare the Clio measurements of the HTP-1 with those from an AP.
My prior measurements were also not well organized. I have built a template in Excel based on AES17-2015: AES standard method for digital audio engineering - Measurement of digital audio equipment
. I also had to figure out how to save and recall individual measurements for display (Clio operates nothing like Room EQ Wizars). The PC audio interfaces don't have the precision needed to use REW for most analysis.
I believe that what I observed with the noise floor and chassis ground is significant to everyone. Everyone [like me] who wants to squeeze every last drop of performance from their system, leaving nothing on the table but the money saved. Everyone who chooses science over audiophilia. Grounding the chassis of any interconnected gear with a two wire power plug to a single, common point. (Any includes equipment only interconnected via HDMI). The ground terminal of a power conditioner is a logical choice. See this article from PS Audio: How to practice best grounding
Aside from isolating issues with feeds coming from outside of the house (satellite/cable) I don't recommend lifting ground. The 3-to-2 prong cheater plugs are great for troubleshooting but not as a permanent solution. Ground loop issues need to be identified and resolved, not "floated around". The 3rd prong is called the Safety Ground for a reason.
I was able to observe the noise characteristics of the line-level with changes to the supplied AC power. The effects of the following were observed: UPS, isolation transformer, balanced power (±60 VAC), iFi's AC iPurifier, power cord guage, noisy SMPS, etc. Each had a measurable effect on the noise floor in most cases. Combinations had varying effects. However, none of these equaled the noise reduction that the simple star grounding provided. In fact, once everything was grounded the other AC filters/devices did not appear to have any significant effect on the noise floor.