High Quality DAC and Oscilloscope / XY Display

#1

Hi there!

I recently tried out the “Function” track from the new N-SPHERES album, using the FLAC file download from the pre-release. I compared what I was seeing on my oscilloscope with the video recordings and I’m impressed at how clean the recordings are, so it made me curious about some things…

Specifically, I noticed that I get some overshooting on the arrows of the axis at the beginning of the track that isn’t really visible in the recordings. I noticed that the recording has been cleaned up a fair bit, given the background is perfectly black, so maybe this post-production work on the video is the only magic that’s happening.

Regardless, the questions that I have are:

  1. What DAC setup was used? Was this just a DC coupled audio interface? Was there any signal processing used on its output?
  2. I noticed that a Leader LBO-51MA XY display was used. Is it possible that it’s easier to get a clean video from an purpose-built XY display than from a general purpose oscilloscope?

Here are the details of my setup:

  • Tektronix TAS 465 100 MHz Oscilloscope, with its 20 MHz bandwidth filter enabled and readout turned off
  • PreSonus Studio 26c, configured to 192 kHz output
  • foobar2000 on Windows, using exclusive mode output

Part of the reason I’m asking is because I’ve been working on a 3D video game rendering engine for oscilloscopes on and off for the past few years, inspired by Oscilloscope Music. This is something that I’d like to tour around with at some point, so getting the best hardware for the job is important to me. I’ve noticed other strange behaviours with this low-end PreSonus 26c, so it’s top of my suspect list, but now I’m also curious if I should look into getting a purpose-built XY display instead of an oscilloscope…

#2

don’t know about the presonus interface tbh.

i believe a modified rme fireface was used (unsoldered decoupling capacitors), but maybe it was also a motu ultralite, not 100% sure anymore. the cables introduced some noise and we changed a few times.

are you playing the wav files from the download section? the aac from youtube will introduce tons of errors.

#3

Thanks, @kritzikratzi! I originally tested with FLAC file downloads, but I can test with WAV instead. I was not using the YouTube videos. The overshooting that I was talking about is relatively minor – I’ll post a photo sometime in the next week or so when I’m back with my equipment.

Interesting point about the cables: it might be a good idea for me to use probes instead, which will allow me to adjust their compensation. Maybe even adding some high frequency filtering would be a good idea to clean up the signal?

#4

FLAC and WAV should have identical quality (lossless, 192k). generally when filming the scope it’s a good idea to use keep the intensity of the scope very low. this results in a cleaner image overall.

not sure about the filters, definitely never tried anything of that sort.

#5

Thanks again, @kritzikratzi! I think the key point is to keep the intensity low to get visuals that match the video. I see how that this is the trick to get ride of all the high frequency edges and noise that happens when moving the beam around from shape to shape.

Upon second inspection, I can see some of this high frequency noise in the video recording too, but the low trace intensity, video’s frame rate, and video’s dynamic range all help eliminate these in most cases.

Looking forward to the new release in less than two weeks!