Hi Tom,
Yes it's the interface board designed by Piet for the eTap2hw project. IIRC the main difference between it and the recommended circuit is that it uses a JFET input stage to emulate a triode valve (the 'Fetzer valve' circuit).
Piet has just started a new blog and I believe he has archived all the old Echotapper stuff so you'll likely find the schematic https://vividinteract.com/.
Best wishes,
Phil.
SKRM-C8-eTap2: For Piets echotapper
Re: SKRM-C8-eTap2: For Piets echotapper
Philip Hawthorne
Blue Nebula Development Team
Blue Nebula Development Team