It looks like the rising and falling edges of the TTL pulse sent via StimTracker v1 (DB25 adapter) are contaminating the signal the electrode channels of my g.USBamp v3. The artifact appears as a sharp negative deflection at T0 and sharp positive deflection at 144 ms re trigger onset (see image attached).
These artifacts are not visible in single trials but can be identified by averaging over as few as 200 trials. The artifacts occur in all electrode channels and in two different g.USBamps (tested independently). The distance between the leading and trailing artifact depends on the duration of acoustic trigger used (sample trigger corresponding to the averaged recordings is in the attached).
Have you previously encountered any such issue sending triggers to the g.USBamp hardware? Is it possible that too strong of a TTL pulse could contaminate the signal in the electrode channels as described? This issue only become a problem in the last two weeks, following 2 months of successful (i.e., artifact-free) testing with the same setup.
Any assistance is greatly appreciated.