Not sure how much use this is but the company behind Leaf Audio appears to be: Shenzhen Tianzhongtian Trading Co., Ltd. https://tztwholesale.en.alibaba.com/minisiteentrance.html

Country/Region: China

Province/State: Guangdong

City: Shenzhen

Operational Address: 5H, Middle Bldg. B, Yueshang, Longhua New Dist., Shenzhen, Guangdong, China (Mainland)

Business Type:Trading Company, Distributor/Wholesaler

Year Established: 2013

Total Revenue: US$10 Million - US$50 Millio

Main Products: Business & Industry, Hobbies,CNC Products,Health Care,Toy,Comsumer&Electronics, Health&Care, Hobbies&Toys, Business&Industry, CNC&Product, ,

Address: 5H,BuildingB,Yueshang Center,Longhua

Main Markets: Central America 30.00% North America 10.00% South

About Us

Shenzhen Tianzhongtian Trading Co., Ltd. is one of the uppermost Manufacturer manufacturing Lab Instruments & Supplies and other China Business & Industry, Hobbies, CNC Products, Health care, Toys products. The warehouse of Shenzhen Tianzhongtian Trading Co., Ltd. is situated in Shenzhen China. Shenzhen Tianzhongtian Trading Co., Ltd. is a identified venture in China that is operating globally. If the PA-03 is a clone of the Audio Research LS22, here is a link to the schematics for the LS22: https://www.arcdb.ws/Database/LS22/ARC_LS22_schematic_and_parts_list.pdf

From: https://www.arcdb.ws/model/LS22