Eden Microphone Preamplifier. LA-610 Simple improvements. By Universal Audio Simple improvements by Fox Audio Research Updated July 5, 2012 We have been using an LA-610 in our home studio for a couple of years and although we peeked inside we had not taken the time to evaluate it in any way beyond how it sounded. Now make no mistake, the LA-610 is a good piece of gear right out of the box. Sound Skulptor - DIY Microphone Preamplifiers, Class A Mic Pre, Vintage Transformer Preamp, Professional Audio Kits. DIY Mic Preamp Kits - Seventh Circle Audio.