Looks like the schematic and PCB layout are in "Diptrace", which isn't a piece of software I'd heard of before. I'd much prefer Kicad for anything claiming to be hacker-friendly or source-available. It appears this Diptrace software does have a pretty much unlimited 30-day trial, which is preferrable to Altium or Orcad, and I appreciate that they actually sell their software with a perpetual license like buying old shrink-wrapped CDs instead of some subscription hell. But Kicad is so compelling these days.

The Diptrace trial does support exporting various Altium/Orcad/Kicad/Eagle/PADS/Protel/Mentor netlists and file formats, but it would almost be easier to re-draw and re-route the design in your PCB software of choice.

I downloaded the trial and opened it up, the schematic is remarkably simple:

https://i.imgur.com/8EudXIZ.png

The un-named nets and complete lack of concern for crossing other nets is certainly one way to draw a design. On the one hand, it all fits in a single image and is pretty beginner-friendly, on the other hand, a hierarchical schematic with named nets makes it much easier to take in and reason about a single section of the design.

The PCB is simple as well, it's just a 2-layer design with all traces routed at 8 mils and generous vias at 10 mil drill/25 mil pad. Unfortunately, being a compact 2-layer design, it doesn't have good power planes, and worse yet it doesn't even try to have a ground pour at all. Here's the ground/VSS routing:

https://i.imgur.com/BcKm8vL.png

VDD/power makes a literal loop around much of the waveform output and near the scope input pins:

https://i.imgur.com/E2UK9Ot.png

I know performance isn't the primary goal of this device, but these decisions are probably leaving a lot on the table. (And here's the bottom routing for completeness: https://i.imgur.com/qxwJvpU.png)

Your eyes do not deceive you, the pin headers aren't in a straight line, they wobble up and down with every other pin 9 mils higher or lower than the previous pin. This probably makes assembly a little simpler because the pin headers will comfortably fit in the 0.0354" holes, but the insulators will flex and hold them in place even when the board is inverted to solder the bottom half, but might put some tension on the solder joints if you wanted to stack a daughterboard on it.

The main U5/U6 connectors are spaced out by 0.9" in Y and aligned in X, the -5V power connector is conveniently aligned in Y with U6 and skips two 0.1" pins in X if you wanted to include that in the design (or try to stick the whole thing in a breadboard). The J3/J4 jumpers/headers by the USB connector are on the same 0.1" grid, but inconveniently not aligned with U6 for deep integration in a breadboard or daughterboard and power isolation through a lab power supply. I do appreciate the inclusion of J10 as an extra ground pin J10 off in the corner - you weren't doing anything with that space anyways, and that's sure to come in useful for someone poking at a circuit with a meter or wiring something up!

A notable feature at this price point is the inclusion of a charge pump to generate -5V, I expected a 0-5V range with nominal rail-to-rail opamp rather than positive and negative voltages. I suppose this is persuasive when working with audio signals, which is probably a significant use case for this device. But again, the circuitous (ha) route to the opamp by the noisy VS- output signal and the decoupling and power supply to the charge pump chip U4 are not helping the performance. I doubt it would pass FCC certification, but it doesn't really have to.

All in all, a pretty neat little device at an impressive price point! Don't take my criticisms as complaining, I meant it to be constructive - well done making cool stuff and putting it on the internet!