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Comment by dofm | Hacker News Reader

Hi! Great project.

OK so I have a little J&D USB-C guitar cable thing:

https://www.amazon.co.uk/dp/B0CRR6G355

Any idea if this will work? (Notably working on my Mac but not my second generation iPad Pro, which sees it but is confused)

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From what I read you need an external interface if you want to use the board. The cable is just passing the audio signal through USB if I'm not mistaken (i.e. no Analog-to-digital conversion happening there--mac doing it for you I guess)

Not clear to me at all, but I just did a bit of a google to follow up on a thought — do you mean your hypothesis is that it's using the USB-C-specific Audio Accessory mode?

I was not aware that the Mac supported Audio Accessory mode. And the blurb for these cables talks about a sampling rate, which suggests there's a DAC in the USB-C connector end.

(Works well on the Mac, anyway — it is too much fun simply plugging my lap steel into my Mac in a way that would have been complete fantasy when I first started playing electric guitars.)

ETA: OK so it's always time to play guitar, and I plugged it into the Mac, which reports:

  Product ID: 0x126e
  Vendor ID: 0x3302
  Version: 0.01
  Serial Number: 3302126E250214
  Speed: Up to 12 Mb/s
  Manufacturer: TTGK Technology
  Location ID: 0x14400000 / 1
  Current Available (mA): 500
  Current Required (mA): 100
  Extra Operating Current (mA): 0

Which suggests it's one of these DAC-in-connector boards:

https://www.szttgk.com/en/product/conversionaudiomodule.html

It appears as an ordinary USB Audio device in the Sound panel. My likely ignorant surmise as to why it doesn't work on the iPad is that it also presents a (disconnected) output device and this is confusing the iPad. So perhaps it kind of is working but I can never hear it…

The README[1] states that you should connect a usb audio interface to the board, as it runs in host mode

[1] https://github.com/dashersw/coyopedal#everything-else

This cable presents as a USB audio interface, is the point I'm getting at.

Great finds! I'm pretty sure I'll make it work with ESP32-S3 :)

Ah, the cable arrived and I tried it. The problem is, the cable only works with USB2.0, High Speed devices, but ESP32-S3 is only USB1.1, Full Speed, so unfortunately it doesn't work.

Thank you! I am surprised it doesn't work with iPad Pro. They don't ship to Germany, otherwise I'd buy one and try. If you have an ESP32-S3 device, I can help you with it if it doesn't work.

Oh I found one on Amazon.de and ordered. Will let you know :)

Sorry — I should have added that there is a variation of this device that (allegedly) does work with the iPad Pro, so if you have time to amend your order…

https://www.amazon.de/6-35mm-Microphone-Recording-Electronic...

I don't know why this one would work and the other not, but my guess will be that this one has a chip that doesn't offer up a disconnected output device as well (which would be my totally uneducated guess as to why my iPad hates the other cable and the Mac, which has switchable output devices, doesn't)

There was an ESP32 board I wanted to try (below) but it looks like it's a 1.8" sibling of the one you are using so maybe I'll just track down the one you're using.

https://thepihut.com/products/esp32-s3-development-board-wit...

Added some info on the chip here:

https://news.ycombinator.com/item?id=49877171

Of course, what we are missing here is audio output :))) how are we going to listen to it? This S3 board has a tiny speaker, and I think for a demo it will work just fine, but :))

Yes. I just started a comment asking the same. Are there S3 boards with better audio breakouts?

There's an S3 audio board but there's no need, a real guitar interface is a much better option.

We need to get low-latency audio interfaces for this usage context down to (low) dozens of dollars rather than hundreds.

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