# Very Strange Frequency issue

**URL:** <https://forum.quantasylum.com/t/very-strange-frequency-issue/1874>\
**Category:** Uncategorized\
**Created:** [May 16, 2025, 3:20am UTC](https://forum.quantasylum.com/t/very-strange-frequency-issue/1874 "2025-05-16T03:20:37Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![skipburrows](https://avatars.discourse-cdn.com/v4/letter/s/8797f3/32.png) [@skipburrows](https://forum.quantasylum.com/u/skipburrows)\
**Post date:** [May 16, 2025, 3:20am UTC](https://forum.quantasylum.com/t/very-strange-frequency-issue/1874/1 "2025-05-16T03:20:37Z")

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Hi All…  
I am working on a new design that requires high frequency analytics. So I need to measure things above 80 Khz. So when I go up in frequency Im getting very weird information on the display. I am simply using a loopback XLR with Differential outs to Differential inputs. Cable checks out perfectly as far as connections go. When I go above 20 K the gain and level goes crazy. Please see Fig 1 and Fig 2. Fig 1 shows frequency at 16.7K note the gain is very close to zero dB of gain. Now in Fig 2 I simply went to 24K and the gain shows 149 dB! WTF!!! I have tried everything. Reinstalling the software and making sure Im not doing something dumb. So perhaps someone here can explain this odd occurrence.  
Thanks  
Fig 1

 ![IMG_7794.HEIC](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/2/204c23e64224937e7fd0049340349957c5036ac4.jpeg)

Fig 2

 ![IMG_7795.HEIC](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/e/ec7c6f7c313bdda6f9e8cc6d950a38ef2c93e1d8.jpeg)

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**Author:** ![restorer-john](https://avatars.discourse-cdn.com/v4/letter/r/b5a626/32.png) [@restorer-john](https://forum.quantasylum.com/u/restorer-john)\
**Post date:** [May 16, 2025, 6:47am UTC](https://forum.quantasylum.com/t/very-strange-frequency-issue/1874/2 "2025-05-16T06:47:56Z")

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If you don’t change the measurement bandwidth, that will happen.

Obviously, the sample rate is at 192k and your measurement ‘stop’ frequency needs to be also set to ~80kHz.

 ![image](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/2X/a/ac6f449eecade6785f968343bbeda43a126409cb.png)

(right click the THD button to access the options)

We all made that rookie error when first measuring- I know I did. 🙂