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Neumann U87 Ai Noise problem

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Neumann U87 Ai Noise problem

Postby maxmatthewsmusic » Tue Aug 04, 2020 1:55 pm

Have been recording with a Neumann U87 Ai for months.
Just this morning I started getting this noise:

https://soundcloud.com/max-m-818183176/ ... 7-ai-noise

Any advice would be much appreciated

Max
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Re: Neumann U87 Ai Noise problem

Postby Hugh Robjohns » Tue Aug 04, 2020 2:58 pm

There are two possibilities:

1. The diaphragm(s) is/are contaminated causing the bias voltage to leak away resulting in noise.

2. One or more capacitors or transistors in the mic is dying and needs replacement.

Option 1 is the more likely. Contaminants on the diaphragm cause moisture to be retained which, in turn, creates a conductive path between diaphragm bias voltage and ground. Contaminants can come from smoke or, more often these days, from the microscopic spittle of close singers. Significant changes in humidity can make the problem appear and disappear seemingly at random. You can sometimes make the noises go away if you gently dry the mic out by sealing it in a bag with fresh silica gel packets for a couple of days, or place it in an open bag (to keep the dust at bay, but let the moisture out) in a warm airing cupboard for a few days.

But either way, if the problem persists it will require a professional clean or repair.

H
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Re: Neumann U87 Ai Noise problem

Postby maxmatthewsmusic » Thu Aug 06, 2020 3:02 pm

Hey Hugh thank you very much for the detailed feedback.

I think the diaphragm is contaminated. I placed the mic in its case with some silica and this partially alleviated the problem however it seems to have gotten worse again. I'll get in touch with Neumann and see what can be done.

All the best

Max
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Re: Neumann U87 Ai Noise problem

Postby John Willett » Wed Aug 12, 2020 4:01 pm

Hugh Robjohns wrote:....or, more often these days, from the microscopic spittle of close singers.

The way to protect from this is to use a pop filter.

Although almost any pop filter will protect from spittle - the foam based ones can be washed easily to remove any contaminants / spittle. EG: Håkan and Rycote both make this type (there waas someone else, but they seem to have gone away).
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