Let's Design and Build a (mostly) Digital Theremin!

Dewster, these images help a lot! Many thanks.

Finding the TOSLINK_TX part is difficoult.
post 1878: Buggins Q: "What parts are used in your design as optical (toslink) transmitter and receiver?"
post 1879: Dewster A: "https://www.goldmine-elec-products.com/prodinfo.asp?number=G16911B" with reference to Roger (pitts8rh) for the footprint.
This part is no longer available.

Just be the look of it, comparing with fotos of the main PCB, this ebay link may be it. These parts are obviously second choise with bent pins. Anyway I'd have bought them, but the parts will not be sent to Germany.
https://www.ebay.de/itm/111692790134?srsltid=AfmBOorU-U-4gMkfkj_Aws3tB-Ft9HFrAEjeiS5_0Bl4NWN_0WJSopwv

I may have to go for a different part Toslink transmitter and update the footprint.
As an alternative move the Toslink transmitter to the IO extension and connect it with a ribbon cable.
This could be the alternative: https://docs.rs-online.com/d4d9/A700000009791094.pdf

"Finding the TOSLINK_TX part is difficoult."  - gerbold

Yes, especially finding them for not outrageous prices.  Here are a couple on the US portal of eBay, doesn't say they do/don't ship to Germany:

https://www.ebay.com/itm/125935980277
https://www.ebay.com/itm/283080774405

Amazon:
https://www.amazon.com/dp/B0B1YGV918
https://www.amazon.com/dp/B09SNW3FLJ

You could just leave the TOSLINK TX off and use the electrical SPDIF connection on the expansion port.  SPDIF works just as well, though it doesn't provide the electrical isolation of TOSLINK (only a possible issue if you experience ground loop hum).

The last link was helpful. The brand is elecbee. A search revealed the companies web site. It ships worldwide and the prices are much lower than in Amazon.
https://www.elecbee.com/en-12563-toslink-socket-fiber-connector-optical-fiber-right-angle-panel-mount-with-self-tapping-hole

"The last link was helpful. The brand is elecbee. A search revealed the companies web site. It ships worldwide and the prices are much lower than in Amazon." - gerbold

~$0.50 each is a good price!  $10 shipping (to the US) is a bit steep though.  Glad you found a solution!

As I'm not a friend of flying wires, I thought about an IO-extension board for the D-Lev.
First idea how to connect it. Actually the 3pin electric connection for the Toslink are not required.

This is a first draft. All theory and untested.

Connectors from left to right:
- USB (serial connection and power supply)
- Mute button and LED
- ACAL button
- MIDI out
- Line Toslink + S/PDIF out
- Monitor Toslink + S/PDIF out

All left of the LED is a builtin USB/serial TTL (3.3V) converter. It is based on MCP2221A with max 460800 bps. One can get it as DIP14 or as SOIC14. Both are foreseen as an option.

All the USB part does not need to be assembled. It can be replaced with an AZ-Delivery HW-598USB based on the CP2102 that has an internal LDO that delivers the 3.3V for the Toslink. It is delivered with 5 pin ribbon cable that can be connected to the 5 pin header.

In order to get Toslink and S/PDIF working on the IO-extension, some changes are required when assembling the main board (but no layout changes):
- replace C3 and R8 with 0 Ohm bridges in order to get spdif_tx[0] to J2
- replace C4 and R9 with 0 Ohm bridges in order to get spdif_tx[1] to J2
- ommit R10, R11

The most problematic part is the combined Toslink + S/PDIF connector. I think there is only a single source for it.

"~$0.50 each is a good price!  $10 shipping (to the US) is a bit steep though." - dewster
When following the ordering process, there is an option (at least for Germany) to select economy shipping. It takes about two weeks but it costs only 4.30€, which is less than I have to pay for some orders within the country.

In general I'm ordering parts for 6 D-Levs. Thus the shipping cost effect is less than for a single instance.
At the moment two of my colleagues show interrest. One is a mucisian (trombone player) and the second is a DIY guy with a genral interrest in music. Hopefully I find three more interrested people.