FWIW, The latest firmware update for the DR-40 now allows independent control over the two input levels. The delay setting has also been expanded, useful for live recordings when the console is far away from the band

02-21-2012 - Firmware update 1.10: Product: DR-40 | TASCAM (http://tascam.com/product/dr-40/downloads/)

But does it defeat/fix the "helicopter" noise?

With this firmware the DR-40 coud be a marvelous little recorder if it worked as advertised :( - well most won't notice, but mine sits in the drawer cause I missed that one month return policy deadline.

T

"But does it defeat/fix the "helicopter" noise?"
>> Don't know, I've never experienced it on the DR-40. But I normally only use a line level input configuration.
That said, the "helicopter" anomaly is usually the result of (inaudible) low infrasonic frequency modulations. Engaging a high-pass filter eliminated the issue when I've encountered it on other devices.