# Timing jitter between audio stimulus and eeg maker using parallel ports

**URL:** <https://discourse.psychopy.org/t/timing-jitter-between-audio-stimulus-and-eeg-maker-using-parallel-ports/44387>\
**Category:** Builder\
**Tags:** timing\
**Created:** [March 26, 2025, 5:52pm UTC](https://discourse.psychopy.org/t/timing-jitter-between-audio-stimulus-and-eeg-maker-using-parallel-ports/44387 "2025-03-26T17:52:43Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Tim\_Dressler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/tim_dressler/32/44724_2.png) [@Tim\_Dressler](https://discourse.psychopy.org/u/Tim_Dressler)\
**Post date:** [March 26, 2025, 5:52pm UTC](https://discourse.psychopy.org/t/timing-jitter-between-audio-stimulus-and-eeg-maker-using-parallel-ports/44387/1 "2025-03-26T17:52:43Z")

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**OS** (e.g. Win10): Win10  
**PsychoPy version** (e.g. 2024.2.4 Py 3.8): 2024.2.4  
**Standard Standalone Installation? (y/n)** If not then what?: y  
**Do you want it to also run online? (y/n)** n  
**What are you trying to achieve?:** Send a parallel port marker for an audio stimulus

**What did you try to make it work?:** After having massiv jitter (+/-15ms and more) in my main experiment I created a ‘bearbone’ experiment in the builder with only a parallel port and a audio stimulus. I also created similar set ups with code components and ‘pure’ code. I also used different settings (e.g. sync to screen, samplerate, …). I use th ptb backend as all other backend fail to work (altough being explicitly installed)

**Link to the most relevant existing thread you have found:** [Inability to have precise timing for auditory stimuli](https://discourse.psychopy.org/t/inability-to-have-precise-timing-for-auditory-stimuli/34031)

**What specifically went wrong when you tried that?:**  
The experiment runs without problems however, when comparing the true onset of the sound and the marker there is a lag of ~5ms (as promised by PsychoPy’s website) BUT also a massiv jitter of about ~10ms or more (depending on settings).

I am really under time pressure and would appreciate a speedy response!

Thank you!

Tim