Drawing on Analog osciloscope

[PorażonyMati49]

Hi!
Recently i got this old 80s analog osciloscope and wanted to try drawing some images. I used some speaker PCB with Beken 3254 bluetooth module. and amplified signal by 10x because it was to low. Results where pretty nice but only with symmetrical shapes like circle or flower. Asymmetrical shapes where deformed, heart looks more like half circle... I am wondering is this because my osciloscope is too cheap or because of noise from LM358.

Thanks!

[Alex Eisenhut]

With the focus that bad something's wrong somewhere.

[David Hess]

Audio outputs almost always suffer from phase distortion which will cause distortion in the drawing when more than one frequency is present, which will be the case if drawing anything more complicated than circles.

[Renate]

Your audio adapter has no DC or low frequency response.
Try drawing a square. Then look at the two channels by normal XT and not XY.

[David Hess]

Your audio adapter has no DC or low frequency response.
Try drawing a square. Then look at the two channels by normal XT and not XY.

My usual test is to generate a square wave to check the transient response.  Some audio power amplifiers will produce a clean response, but the DAC or CODEC will not.  Tape recordings are especially bad, but none of this matters for audio fidelity.

If you know your stuff and have the right oscilloscope, then the square wave can be transformed into a Bode plot showing amplitude and phase response.

[oz2cpu]

please see this

https://blog.dzl.dk/2026/06/03/more-scope-vector-shenanigans/

all files for the Tektronix logo can be found here
webx.dk/teklogo.zip
including a simple how to make your own graphics intro