> My explanation of the phenomenon goes like this: each amp has its
> own random noise, so summed together they add 3 dB of noise. But the
> two-amp configuration increases the signal by 6 dB, so there's a 3
> dB improvement in signal-to-noise.
Dan,
The alternative connections I envisaged are two inputs at -6dB into a
balanced input or the whole signal going into an unbalanced input, not
half of what is available.
I've spent some time with the INA163 data sheet, and it is basically
very good. However, the EIN figures at low gain are poor due to a high
output stage noise level, and the quote appears to be at 60dB gain
setting which is high for general field recording. A studio mixer
could easily have the gain resistor on a preset, but it can't be
easily incorporated into a fader in a portable mixer. Switched
preset perhaps.
What may be a problem for battery use is the twin rail power supply.
The minimum rail to rail voltage is 9V - the end point of a 12V
battery. At 10ma current per stereo stage, the battery requirement for
a standby device is getting a bit high. I may have a play with one -
with a transformer. :-)
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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