Topic: Zoom H4 selfnoise...

[bdasilva]

Found this on the naturerecordists group

Here's a note, reportedly written by a Zoom engineer, describing the
H4's "noise problem."

"We have figured out that the noise problem is caused by the analog
circuit board layout. So, it's not possible to solve by updating the
system software...Noise was available because battery does not apply
enough to load change. So noise is disappeared when you use a supplied
AC adaptor...Also, noise level depends on a SD memory brand, because
power consumption is different."

So far I have not seen reports listing which SD cards might be more
likely to cause noise issues due to higher power requirements.

Another web site has links to recordings that demonstrate the "noise
problem".

"There is an audible (and visible as a wave form in a DAW) periodic
tone (corresponding to the blinking of the H4 access light) on all
recordings made with battery power. (This tone may also be there at
24/96, but I cannot hear it.) There is no tone present when using the
AC adapter.

Here are links to sample recordings:
1. access light tone 44.1.wav http://www.box.net/public/xe7yvzpezb
2. access light tone 48.wav http://www.box.net/public/sobave36ct

Some people have added three 1000 mfd 4v tantal condensors over the
voltage rail.

There is also discussion of replacing the stock mic elements.