API 2510 and 2520 opamp upgrades

Scott Liebers is a recording engineer, Luthier and former and broadcast engineer at KNOW, the Public Radio affiliate here in the Twin Cities. (His responsibilities included maintaining the recording equipment as well as mixing live bands for their all-music channel, The Current.) Reliability is a major issue in an on-air facility, so when Scott started having issues with a six-year-old API Legacy, he went outside the box for a solution.

His problems started with the 2510 opamps used in the 550L EQ's, three per module. (In most applications, the 2510 is used as a buffer amp running on ± 28 volt rails.) Op amps that die within the five-year warranty period are replaced free, but after that they're $75 each plus the old one sent in as proof of ownership. Initially he planned to repair the opamps, which are potted and not easily disassembled without further damage, so he eventually sought out a local design and packaging guru to design a replacement.

Scott felt that the potting compound did not dissipate heat causing the transistors to eventually cook themselves to death. (The console is on 24/7.) The new design uses two boards instead of one, has chemical fuses on larger heat-sink- mounted output transistors, and while still using surface mount parts, it's now serviceable. See FIGURE-1.

Replacement opamps are $65 each in lots of 5, $75 each for single purchase.
Contact Scott and Eddie
FIGURE-1: Replacement for API 2510 opamp by Scott Liebers. This is the output transistor side. The lighter green areas are copper (protected by a conformal coating) the surface area under the transistors help to dissipate heat.