Hey Wim,

Glad to hear that the grounding solution was in fact the easiest fix, for now. 
Yeah, extra wiring is ugly, but sometimes it’s necessary to make things work 

Chris T-H

On Sep 20, 2018, at 1:40 PM, Wim van Dam 
<wim.van....@gmail.com<mailto:wim.van....@gmail.com>> wrote:

Thanks everyone for your suggestions. Chris was right: I needed to ground my 
recorder. The buzz stopped as soon as I wired the headphone jack to a gas pipe 
in my house. While my Marantz PMD661 is a nice recorder, it apparently is not 
designed to be powered by AC while getting its signal from another AC powered 
microphone. In the long run I will probably get myself a proper external 
battery for the recorder, but for the moment I'll fix this with some ugly 

Thanks again.

Wim van Dam
Solvang, CA, USA

On Thu, Sep 20, 2018 at 1:08 AM, Magnus Robb 
<magnus.r...@me.com<mailto:magnus.r...@me.com>> wrote:
Wim, I don’t know if your Marantz accepts external USB power. If it does you 
could buy a high capacity powerbank (say, 20000mAh or more), connecting it with 
a USB cable, and that would probably solve both problems: autonomy and noise.

all the best,

Magnus Robb

On 20 Sep 2018, at 00:13:39, Wim van Dam 
<wim.van....@gmail.com<mailto:wim.van....@gmail.com>> wrote:

[I'm not sure if this newsgroup is still alive, but here goes.]

This week I finally installed my OldBird 21c microphone and I'm having some 
noise issues. In my setting I use a Marantz solid state recorder for my 
recordings. When I power this recorder with its standard AA batteries, things 
are fine but it does not allow me to record for more than a few hours. When I 
use AC power for the recorder instead, a lot of noise shows up at 1500Hz, 
1620Hz, 1740Hz, 1860Hz, etc. Likely this has to do with the fact that the 
recorder and the OB21c microphone use the same AC outlet.

What is the best solution to this problem?

Wim van Dam
Solvang, CA, USA

Christopher T. Tessaglia-Hymes
Field Applications Engineer
Bioacoustics Research Program, Cornell Lab of Ornithology
159 Sapsucker Woods Road, Ithaca, New York 14850
W: 607-254-2418<tel:607-254-2418>   M: 607-351-5740<tel:607-351-5740>   F: 

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