This summer a friend approached us about a mod for his pair of LA610′s. The LA610 has become an almost iconic channel strip in today’s recording world.

The LA610 takes its name from the UA610 mic pre/EQ and LA2A optical compressor. Ironically, the LA610 seems to be neither. I reverse-engineered the circuit, and found that the mic preamp is similar, but differs from the original 610 in significant ways. And the compressor section is only loosely based on the LA2/LA2A. It uses a T4-like opto element (called the T4UA) and an early LA2A style gain control amplifier. But all else-the level detection, make-up gain, and output drive circuits-are completely different.

It will be interesting to construct some mods for these LA610′s. A short list of what I’d like to do is:

• Perform some tests to see what the THD+N, IMD, and frequency response look like
• Map out an overview of circuit changes for the compressor section based on the LA2A, including a conversion to T4B
• Map out an overview of circuit changes based on the classic “green” UA610 console
• Figure out some potential signal routing changes, and look into creating a method of bypass for each section
• Add a “link” feature so our friend can use his LA610′s in stereo.

I’ll be tackling each section step by step, and posting a blog about each one. Stay tuned for updates!