I recently bought an Aquarian Audio H2-XLR hydrophone and found a problem
that I don't understand.
The H2-XLR requires phantom power. When I supplied the 48V power from my
Marantz PMD670, the noise level was so high the hydrophone was absolutely
unusable, and I thought I'd have to send it back. However, when I
supplied 48V power with a Sennheiser MZA14 the noise level was amazingly
reduced. Does anyone have any idea why this should happen? I have had
no trouble powering MKH20s, an MKH30 or MKH60 from the PMD670.
Because the local ponds have been frozen up until now (no frogs calling
around here) I tried the hydrophone in a fast moving stream nearby. Along=
each shore was a 4-foot wide ice shelf undercut by the rushing water. The
open water was roughly 10 ft wide. The hydrophone was in a relatively calm=
area about 10 feet upstream from a small drop in the stream bed. Water
depth was less than 1.5 ft. The following is a sample of the
recording. There is some obvious low frequency buffeting due to the fast
flowing water, some pops that I suppose are due to the mic being struck by=
small bits of solids carried along by the stream, and also some musical
plinks that may be related to the ice melting. The recording was made with=
the PMD670 using the MZA14. Not too bad given the less than ideal
conditions.
http://mysite.verizon.net/vze78my5/sitebuildercontent/sitebuilderfiles/vlyc=
reekduringthaw01a.mp3
Still I am puzzled by the phantom power/noise problem with the PMD670.
David Martin
________________________________________________________________________
________________________________________________________________________
|