Electret paralleling experiment

Rapid Electronics’ 35-0190 electret mic insert is cheap enough to muck around with. Rumour has it paralleling these guys up is worth doing for extra sensitivity and noise reduction, so it seemed worth a go.

Schematic

Listen to the results, test signal provided by a bunch of gormless teens playing in the rec and some friendly sparrows. The right-hand channel is the paralleled set

Bunch of gormless teenagers and friendly sparrows 240kb mp3

Rightmark shows a 2.5dB improvement in signal level from the doubled up pair
It doesn’t pay to pull this trick directly off plug-in-power on a Sony MZ-NH700

friendly sparrows 240kb mp3

as the PIP hasn’t got enough grunt to power the paralleled pair. I measured 1.1V across the singleton and 0.24V across the pair, which isn’t enough to power the capsules, operating voltage range 1.5V to 10V. In fact the singleton wasn’t really in spec on PIP.
With the 6k8 resistors the corresponding voltages were 6.9V, 4.9V from an 8.2V onload battery voltage

Rightmark shows the corresponding drop in output

Nightjar churring over the heath

Challenging beasts to get a photo of – unusually for birds they see better in the dark than we do. I located this with a Telinga parabolic dish and then managed to line up a video cam on it set to frame-averaging night mode. They seem to be doing well on Blaxhall heath this year – there seemed to be about five individuals audible simultaneously within Telinga range.

video

Swallow sound

When one of these guys perches on the wire outside your dorm room you have to fire off a few pics – not often you get eye level with a swallow!
Nice sound too. What’s that cockerel doing going off at the end – it’s noon!