Re: Microphones vs. ear sensitivity

"Pooh Bear" <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in message
news:429BBEFD.F8C0ECFB@xxxxxxxxxxxxxx
> Kryten wrote:

>> Just been playing with some cheap (ECM-66B) microphone inserts
>> The S/N ratio is quoted at 40 dB, and sensitivity at 60 dB/microbar.
>
> In short, it's rubbish.

Okay, it is pretty small so not got a great sensing area.
And for £3 I did not expect much.

I went out and bought a dynamic mic insert for £5, and this is labelled as
having 76 dB sensitivity. It is a lot bigger and heavier.
http://www.maplin.co.uk/Module.aspx?ModuleNo=29594 (type DM13)

I made up this preamplifier
http://www.zen22142.zen.co.uk/Circuits/Audio/dyn_mic/dyn_mic.htm
which is all-discrete so should have low noise.

However I didn't find it was much improvement.
There is noticeable hiss and buzz.

Hiss seems to be coming from the first transistor (BC109, common base) and
the buzz from the mic insert, because the buzz disappears when the signal
input is shorted to ground. The hiss and buzz disappears when there is no
signal to the other transistors.

Circuit constructed on a bit of veroboard - not ideal but fairly neat and
compact.

So, is this mic insert also crap, and if so how much would I expect to pay
for a good one?

Also, is this BC109 transistor just too noisy?

Or am I going to have to make a much more complex pre-amp like this one:

http://sound.westhost.com/project66.htm


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