Electret microphone question

zobsky · 16th July 2007, 04:38 PM

I should be getting my panasonic mic capsules today. Intended purpose is to measure loudspeaker response.

I need to wire up the mic capsule.

Option 1. Build a simple mic pre-amp to power the capsule (powered by battery)
Option 2. Use the 5V bias on my sound card for the same purpose

These options are described at the bottom of the page http://www.tkk.fi/Misc/Electronics/c...tretinput.html

Questions:
1. How come I never see option 2 recommended for DIY audio purposes (although I guess cheap headset mics use exactly this method)?

2. For option 2, wouldn't I still need a DC blocking capsule inline with the mic capsule ?

SY · 16th July 2007, 06:08 PM

Well, it's not like they've got a screamin' high output. Getting some voltage amplification and low source impedance locally makes the whole interfacing issue much easier. I used a single battery-powered opamp configured for 40dB of gain, and that gets the levels just right for the sound card I use.

Juergen Knoop · 16th July 2007, 06:41 PM

you could connect the capsule without any interface to the mic input
sadly the soundcards mic-input has no flat frequency response
the picture shows my onboard cmedia-card. This one of the flatter frequency responses I have seen
my older computer had a really worse mic-input
regards

zobsky · 16th July 2007, 06:57 PM

Thanks to both the posters. Those were the answers I was looking for. I'll build a pre-amp.

Juergen Knoop · 16th July 2007, 08:17 PM

this is just something to be aware of
your soundcard may be fine

zobsky · 16th July 2007, 08:44 PM

Quote:

Originally posted by juergenk
this is just something to be aware of
your soundcard may be fine

I'll try a loopback from sound card(Audigy 2) to mic input with TrueRTA. That should tell me.

Also, is there any disadvantage to the simple mic-preamp I linked to in my first post (apart from a possible issue driving long lengths of cable)? I only intend to use a meter or two for my application.

Thanks

Juergen Knoop · 16th July 2007, 09:02 PM

the circuit is for interfacing a dynamic microphone faking it into a electret one.
it won't work with a electret capsule

zobsky · 16th July 2007, 09:15 PM

Quote:

Originally posted by juergenk
the circuit is for interfacing a dynamic microphone faking it into a electret one.
it won't work with a electret capsule

That's true for for the first circuit on the page, .. not for the ones way down using a battery and a resistor & capacitor.

SY · 16th July 2007, 09:22 PM

Take a look at the Mighty Mike article that Joe d'Appolito wrote. It's a very simple circuit that works great.

Juergen Knoop · 16th July 2007, 09:25 PM

Quote:

using a battery and a resistor & capacitor.

thats not needed with a mic-input
regards

16th July 2007, 04:38 PM	#1
zobsky diyAudio Member Join Date: Mar 2002 Location: Dallas, Tx, USA	Electret microphone question I should be getting my panasonic mic capsules today. Intended purpose is to measure loudspeaker response. I need to wire up the mic capsule. Option 1. Build a simple mic pre-amp to power the capsule (powered by battery) Option 2. Use the 5V bias on my sound card for the same purpose These options are described at the bottom of the page http://www.tkk.fi/Misc/Electronics/c...tretinput.html Questions: 1. How come I never see option 2 recommended for DIY audio purposes (although I guess cheap headset mics use exactly this method)? 2. For option 2, wouldn't I still need a DC blocking capsule inline with the mic capsule ? __________________ "Any fool can know. The point is to understand" - Albert Einstein

16th July 2007, 06:08 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Well, it's not like they've got a screamin' high output. Getting some voltage amplification and low source impedance locally makes the whole interfacing issue much easier. I used a single battery-powered opamp configured for 40dB of gain, and that gets the levels just right for the sound card I use. __________________ "...we stumble and get up, we are sad, confident, insecure, feel loneliness and joy and love. There is nothing more; but I want nothing more.” - Christopher Hitchens 1949-2011

16th July 2007, 06:57 PM	#4
zobsky diyAudio Member Join Date: Mar 2002 Location: Dallas, Tx, USA	Thanks to both the posters. Those were the answers I was looking for. I'll build a pre-amp. __________________ "Any fool can know. The point is to understand" - Albert Einstein

16th July 2007, 09:22 PM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Take a look at the Mighty Mike article that Joe d'Appolito wrote. It's a very simple circuit that works great. __________________ "...we stumble and get up, we are sad, confident, insecure, feel loneliness and joy and love. There is nothing more; but I want nothing more.” - Christopher Hitchens 1949-2011

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16th July 2007, 08:17 PM	#5
Juergen Knoop diyAudio Member Join Date: Jan 2007 Blog Entries: 3	this is just something to be aware of your soundcard may be fine

16th July 2007, 09:02 PM	#7
Juergen Knoop diyAudio Member Join Date: Jan 2007 Blog Entries: 3	the circuit is for interfacing a dynamic microphone faking it into a electret one. it won't work with a electret capsule

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