Microphones in parallel to reduce noise

Assuming they are the bufferless version, aren't they all simply in parallel? ...Jim Thompson

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** Likely all the mics are simply wired in series and supplied with power from a DC current source and the signal taken from the top most mic. The s/n advantage comes from *correlation*.

The 10 noise signals ( from the internal JFET pre-amps) are un-correlated while the sound arriving at each co-sited mic will be heavily correlated. So the output signal will be 10 times that of one mic, while the self noise will be only 3.16 times - so a 10 dB improvement is possible.

I suspect the mics are arranged to create a directional pick up pattern too.

BTW

Dynamic mics have much less self noise than typical electrets - cos there is no internal pre-amp. Means it is easy to get a 10dB or more improvement, just by using one instead.

..... Phil

Electret mikes usually have built-in FET stage. Are you sure they are combined in parallel, not in series?

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

They are available WITHOUT the FET. I have an RFQ on my desk requesting a complex chip that will use Electrets sans FET's. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
                    Help save the environment!
              Please dispose of socialism properly!

Right. Some of ours come with FETs, some not. Some "dynamics" are really electrets in drag.

"Jim Thompson" Vladimir Vassilevsky

** So what ??

The kind with inbuilt JFET pre-amps are about a million times more common.

PLUS, to comply with the OPs post they cannot be naked condenser capsules.

.... Phil

Ok, each mic has a surface mount network around it for frequency shaping. and each one has a internal fet. Until I can dig into it in the morning I don't know the values, 805 parts that I cant see until I get a microscope. A bit of probing reveals the outer ones are tailored to low freqs, inner ones to highs, and gain increases towards the centers of the array.

Steve

So tomorrow I look at the bias string.. Ok. I didn't have time to do much probing. I did sweep the response of each one by injecting a sweep.

Steve

"krw"

** Totally stupid bullshit.

... Phil

If this is work, it should probably stay there, for the benefit of your employers and clients.

RL

BIENT ** =A0noise pickup, =A0not self noise !!

ought to

s

Mixer front ends still add thermal noise, "pal", and yes, its a conference mike.

Steve

In fact, you are. You and DimBulb; a perfect pair.

"krw"

** Totally stupid bullshit.

Why don't ya go drop dead -

you VILE LYING pile of sub human GARBAGE.

.... Phil

What sort of 'unit' ?

Why do you think it would make the unit noisy unless designed by a cretin ? Plenty of them about of course ! ;-(

You mean the inverting 'virtual earth' type ? Yes, avoiding that structure *would* avoid excess noise.

Join the AES. Or come round and look at my data library which has some excellent app notes / books on that and similar subects.

Graham

Very likely.

But dynamic capsules cost more !

Graham

Quite so.

How many Gigaohms input impedance will the complex chip have ?

Graham

Uh ? What's a 'mixer front end' ? Obviously you're not an audio professional and haven't a clue about current practice. You can make a mix stage today using inexpensive off the shelf parts that has 100dB or more dynamic range quite easily.

So what's the mix stage chip ?

Graham

Provide a link to one of these 'electret dynamics' or SHUT UP !

Graham

"Eeysore is Baaaaakk"

** But not 10 times more - you wally.

.... Phil