# QA401 Right Channel Noise Problem? **URL:** \ **Category:** QA401\ **Created:** [January 27, 2021, 1:40pm UTC](https://forum.quantasylum.com/t/qa401-right-channel-noise-problem/244 "2021-01-27T13:40:49Z")\ **Posts on this page:** 2\ **Page:** 2
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [January 31, 2022, 8:41pm UTC](https://forum.quantasylum.com/t/qa401-right-channel-noise-problem/244/21 "2022-01-31T20:41:27Z")
Hi @moto and @Claudio, thanks for sharing, I’d not seen before. Yes, I think the approach in the PDF looks very solid and well reasoned. I’d note on page 3 the BNC shroud should NOT be shorted to the housing. The lower housing has a good connection to the USB ground via press-fit 3mm screw bosses. The upper housing does not (due to paint). And while all the BNC shrouds are tied together, you should measure an “open” with your DVM between a BNC shroud and the USB shell (which is USB ground, and that turns into earth ground on a PC when plugged in). ---
**Author:** ![Clayton](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@Clayton](https://forum.quantasylum.com/u/Clayton)\ **Post date:** [August 22, 2025, 3:47am UTC](https://forum.quantasylum.com/t/qa401-right-channel-noise-problem/244/22 "2025-08-22T03:47:59Z")
That’s a relief! I was having similar trouble with my brand new QA403, where the right channel noise floor measured about -86dBV while the left channel was -118dBV, even though a loopback SNR looked normal. It didn’t occur to me to check the terminators, so that was a great suggestion. After swapping the terminators, the high noise channel also swapped, proving that was the issue. After a couple of minutes of trial and error, I found that one of the inexpensive terminators was apparently bad. Thanks! [Previous page](https://forum.quantasylum.com/t/qa401-right-channel-noise-problem/244.md?page=1)