John, thanks, neat circuit just ordered the opto couplers I think I will try using my cheap eBay Chinese DC-DC regulators. They seem to be OK. You know I have had an idea running around the back of my head of burning mp3 files on micro sd boards. I chased steam excursions out of Birmingham for years and took a lot of svhs video with some really good audio. I have sounds from N&W 611 and 1218, Sou. 4501, S&A 750 pacific, Nickle Plate 2716 Berk. The CP Royal Hudson, T&P 610 and a few more. My big problem is my old svhs camera bit the dust years ago and my last svhs vcr occasionally eats tapes. Have not pulled the cover to check out the problem. Also have many still images shot on medium format film.
I plan to make/play with your circuit but I think I need to order at least one ERR sound converter and see if they play well with the L2RU boards. I think I could let the coupler pulse start a timer and get some whistle function but might as well spend the money on the sound converter. Thanks again, John
