The 2-ACA-Bo from ClassicAPI provides a stereo summing solution for a host of applications. The PCB consists of four amplifiers: two inverting summing amplifiers and two booster amplifiers based on the API 325 card. Each amplifier uses a 2520-style discreet opamp and API-reproduction transformer from Ed Anderson. The 2-ACA-Bo is a great way to add API-style summing to a DIY mixer project or to add headroom and punch to an existing console.

Images courtesy of ClassicAPI

Notable Features:

• Accepts any DOA in the API 2520 footprint
• Employs Ed Anderson’s 2503 and 2623-4 transformers
• Includes talkback input
• Length: 5.5” Width: 6”
• Can sum more than 40 channels!

Price: $17.50 for PCB

More information:

• ClassicAPI’s product page.
• See this thread at Group-DIY for help and ideas for using the 2-ACA-Bo.