have a product / project you’re interested in? or have something to say ?
The mic preamp, although similar, differs from the original 610 in some 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 LA2A style gain control amplifier. All else-the level detection, make-up gain, and output drive circuits-are completely different.
For this project, we began by using the old green 610 console as a reference. We modified the LA610's mic preamp and EQ circuitry to be a copy of the highly regarded original, including input impedances, gain staging and bias points.
We began by adapting the LA 610's design to use a T4B instead of the T4UA, and we altered the gain control amplifier circuit to be a copy of an early Teletronix LA2A. This way, our friend could use any T4B desired-NOS originals, modern UA versions, Drip, Kenetek, homebrew, etc. Since we were given TWO LA610's to work on, a link feature seemed like a great touch, so we added that too. That meant our friend could now use his two modified LA610's in stereo compression mode.
and added a high-current output stage. Among other things, this reduced the amount of distortion we were measuring in the output signal.
Although a choke filtered supply isn't original to the 610 or LA2A, adding one gave nice results. It helped in reducing the LA610's noise floor, and seemed to alleviate some of that "fizzy" quality it had.
This way the mic pre, compressor or EQ could be used by themselves if desired, or the EQ could be routed to post-compressor. We felt this would really unlock the power of our friend's LA 610 as a studio tool.
All these changes we made lowered the distortion by a considerable amount. Our friend still wanted his LA610's to have the ability to saturate, so we added a feature we called "GROWL". It's a concept we borrowed from the old EMI TG12413 and Siemens U273 limiters. Think of it like a Level-Loc-meets-transformer type of saturation. It sounds very nice on kick or snare!
Please click here.
... we figured we'd give everyone else the same opportunity. While we don't plan on offering this for very long, it's a great way to expand the flexibility of your LA 610.