# QA-403 Distortion Tile **URL:** \ **Category:** QA40x\ **Created:** [September 10, 2025, 11:23pm UTC](https://forum.quantasylum.com/t/qa-403-distortion-tile/2036 "2025-09-10T23:23:41Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Buckskin](https://avatars.discourse-cdn.com/v4/letter/b/b9e5f3/32.png) [@Buckskin](https://forum.quantasylum.com/u/Buckskin)\ **Post date:** [September 10, 2025, 11:23pm UTC](https://forum.quantasylum.com/t/qa-403-distortion-tile/2036/1 "2025-09-10T23:23:41Z")
Sorry for the likely dumb question, but what is the Dist measurement tile telling me? The attached plot shows a preamp under test. As an be seen, the noise floor is in the neighborhood of -140 dBV. THD is low as well. So what, exactly are the two Dist Tiles telling me? Thanks. ![Final - C-1 Line Level - Full BillD Upgrate - Covers On](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/7/7bac4e5328bc9cb155abbbd0fccba7b781f8da04.jpeg) ---
**Author:** ![Claudio](https://avatars.discourse-cdn.com/v4/letter/c/7cd45c/32.png) [@Claudio](https://forum.quantasylum.com/u/Claudio)\ **Post date:** [September 11, 2025, 4:24am UTC](https://forum.quantasylum.com/t/qa-403-distortion-tile/2036/2 "2025-09-11T04:24:40Z")
Hi @Buckskin. “Dist” indicates the value expressed in dB of the numerator of the expression used to calculate THD. I think you will find some clarification in these posts (Dist = D): > [@QA403 feature request](https://forum.quantasylum.com/t/qa403-feature-request/1427/14): > > Yes of course, but that is a value relative to the signal S. In other words : THD= D/S and using dB expressions THD = D - S. What I was asking for was a tile of just the value of D and not its value relative to S (THD). It is a little like THD+N and N+D. THD+N is the component relative to the S signal of N+D. Of course, this is just a requirement of mine that perhaps no one cares about! smiley