Hi Olin, thank you for your answer
Do you happen to have a suggestion for the type of mic i should use in
this project ? I really don't know what should i look for. Can i use a
mic from a pair of headphones with microphone for computer use ? I
have a broken pair and i can take the mic from them.
I could only find an electret microphone at the electronics store we
have here :
ECM30B - Microphone condenser - 61db, 9.83mm
They are not listing any impedance and there is no datasheet available
for this part number on google or other sites.
Is there another preamplifier i could use ? a much better one than
opamp solution adopted by the schematic i attached in my previous
message ?

Dumitru Stama


OL> Dumitru Stama wrote:
>> I am trying to implement an aquisition system for a voice recording
>> project and i decided to go ahead using the attached schematics.
>> It is from a project found on the internet

OL> Looks like you got about what you paid for it.  This circuit only has a gain
OL> of 500 if the mic has 0 output impedence, 250 at 500ohms, and it goes down
OL> from there.  I haven't used an electret microphone before, but for most
OL> microphones that is way too little.

OL> I also don't like how the stages are DC coupled.  This will multiply the DC
OL> offset of the first stage by 100.  That may be OK in this case since the
OL> gain is so low.  If you increase gain the output offset will also increase.


OL> ******************************************************************
OL> Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
OL> consultant in 2004 program year.  http://www.embedinc.com/products

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist