Version: Firmware 13.1.3 + DOS 2.2.4 Date: 2019-02-12

[David A]

I did before and after measurements today, I could measure no difference that was bigger than run to run variance. I did all the tests with Sam off.

But what did you measure?

The thing you need to remember about measurements is that they tell you a lot about what you measure and they tell you nothing about what you don't measure. You can measure frequency response and with the same digital data going to the Devialet you shouldn't see a difference in frequency response because RAAT and AIR should both deliver identical digital data for the music or test signal You can do waterfall plots and RT60 measurements but those tests tell you about speaker behaviour and your room's acoustic behaviour and shouldn't change with Roon vs AIR.

If there is an audible difference it should show up on testing but it won't show up if you don't do tests for the thing which is causing the difference. For years the only measurement done for distortion by one magazine was a simple measurement of the overall percentage of THD and the reviewer used to say that there couldn't be an audible difference between 2 amps with identical THD measurements . He wasn't measuring the harmonic structure of the THD and he wasn't measuring IMD. Differences in those measurements explain why 2 amps with the same percentage of THD can sound different. People didn't start measuring jitter until a year or two after the first CD players hit the market and people used to look at reviews and see distortion measurements which didn't include jitter, see no difference in the measurements, say there was no difference between player A and player B so there couldn't be an audible difference. Jitter measurements proved there was a difference and it was audible.

If there is a difference between RAAT and AIR, it should show in measurements but you are going to have to measure something where the difference shows. If you don't measure the right thing, then you won't get a difference in measurements. 2 different CD players can measure identically for THD and IMD and sound different because of jitter. If you don't measure jitter you won't see a difference between those players but if you measure jitter you will. Two amps may both show 1% THD and sound different but if you don't measure the level of each harmonic in the THD signature you won't see differences in THD that make an audible difference. As I said at the start, measurements tell you a lot about what you measure but nothing about what you don't measure. Just because some measurements don't show a difference doesn't mean anything if you're not measuring the parameter that is different.