I'm interested in the low frequency (1/f) performance of these VGA devices down at audio frequencies. Specs only state RTI nosie down to 100KHz. Has any one experience in in using these amps down to, say, 1KHz? The 605 has the added advantage of the input attenuator making noise perfromance independent of source impedance useful with wideband sensors that have a frequency dependent impedance such as a loop. I woudl be intersted to read opinions on the use of these devices at both audio and RF.