# "Mirror QA401 Output" option level issue **URL:** \ **Category:** QA401\ **Created:** [May 26, 2020, 7:52am UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99 "2020-05-26T07:52:44Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![zoran4afc](https://avatars.discourse-cdn.com/v4/letter/z/ba9def/32.png) [@zoran4afc](https://forum.quantasylum.com/u/zoran4afc)\ **Post date:** [May 26, 2020, 7:52am UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/1 "2020-05-26T07:52:44Z")
Hi, in the [link qa401MirrorLevelBug.wmv](https://www.hdinfo.hr/private/qa401MirrorLevelBug.wmv) is the ScreenRecorder video showing the problem with output level of a DAC when the “Mirror QA401 Output on your PC” is used. If your video player is not playing the video correctly, use Windows MediaPlayer. The generator level setting will not catch from first, i.e. DAC output goes to max level and I have to set the level again to work properly. The problem is much worse when any of the Test Plugin is used (see the attachment “v1.907 test.png”); all the measurements are made with max level, although “Gen 1” shows the level it suppose to be. The problem exists in versions 1.907 and 1.908. I didn’t test extensively, but apparently versions 1.900 up to 1.906 don’t have the problem (see the attachment “v1.904 test.png”). ![v1.904 test](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/05a7a1458c2fe606ae6966a2c1eb39149297ac01.png) ![v1.907 test](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/5cb84359accb86d18bae074441eaca54d2daac85.png) ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [May 26, 2020, 5:02pm UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/2 "2020-05-26T17:02:09Z")
Hi @zoran4afc, sorry for delay as yesterday was a holiday in the US. I will study this. One thing I note from your video is at the 1:35 mark you have -6 dB specified for the External Input Gain. If this value is anything other than zero, it will offset the measured result by the specified amount. ![image](https://canada1.discourse-cdn.com/flex032/uploads/quantasylum/original/1X/42ac6c7fd57c4a5e275da8aea151fab2fed2295d.png) ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [May 26, 2020, 8:08pm UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/3 "2020-05-26T20:08:58Z")
Looking at this more, I think there are a few things going on here: 1. When you enable Mirroring and press run for the first time, the level hasn’t yet been set. If you then increase amplitude by one step and then reduce it by one step, the correct value is written. This happens anytime you change the level using the dlg box. (eg control click on Gen1). So, the bug to be fixed here is to ensure the updated level is set for the PC in all the code paths. 2. For the automated test, the non-zero offset is one issue, but I think the issue identified in 1) is also coming into play 3. I don’t like that the frequency rounding isn’t happening for remotely generated PC tones. That is also an issue that was touched on in this thread: > [@QA401 Low Frequency Measurements](https://forum.quantasylum.com/t/qa401-low-frequency-measurements/39): > > A customer writes with an issue related to amplitude errors they are seeing on frequency sweeps below 100 Hz. These can manifest as wildly wrong gain values. These are most often related to FFT size and/or window choice in some way. But a change will be made in 1.830 to help with the issue too. The “AMP Frequency Response” plug-in was used to plot the gain of the QA401 in loopback mode, from 2 Hz to 100 Hz, log step, at 5 points per octave (this was at 48K sample rate with Hann windowing). Thes… I’ll try to get a release addressing the 3 items above turned around in the next few days. Thanks for reporting, Matt ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [June 2, 2020, 10:52pm UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/4 "2020-06-02T22:52:52Z")
Hi @zoran4afc, I think this has been hugely improved in release 1.909. Can you please try when time permits and feedback? Thanks ---
**Author:** ![zoran4afc](https://avatars.discourse-cdn.com/v4/letter/z/ba9def/32.png) [@zoran4afc](https://forum.quantasylum.com/u/zoran4afc)\ **Post date:** [June 3, 2020, 2:06pm UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/5 "2020-06-03T14:06:48Z")
Hi [@matt](https://forum.quantasylum.com/u/matt), yes, the mirror levels are now applied, thank you! Also, the Frequency Response graph is now perfect. I thought before that the problem is with my DAC, but all external DACs measured the same. Not only that Frequency Response plugin works perfectly, also the normal spectral analysis shows consistent levels at all frequencies in range 20Hz - 20kHz. This is remarkable improvement! One question: Only “Gen 1” works in the mirror mode. “Gen 2” and “Multitone” does nothing. Is that the limitation of mirror mode or bug? Best regards ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://forum.quantasylum.com/u/matt)\ **Post date:** [June 3, 2020, 2:36pm UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/6 "2020-06-03T14:36:06Z")
Yes, only Gen1 works in mirror mode. At some point in the future, you will be able to set FFT size, then generate a special chirp WAV in the analyzer app, and then loop that wav on your dac and the QA401 will capture it. But that’s a little ways off with some big items that need to be done first. ---
**Author:** ![zoran4afc](https://avatars.discourse-cdn.com/v4/letter/z/ba9def/32.png) [@zoran4afc](https://forum.quantasylum.com/u/zoran4afc)\ **Post date:** [June 4, 2020, 6:33am UTC](https://forum.quantasylum.com/t/mirror-qa401-output-option-level-issue/99/7 "2020-06-04T06:33:10Z")
I am looking forward for those future features. I hope that it will be possible to measure phase shift in mirror mode too.