12th April 2012 11:25 PM
pre amp help needed
Hi Guys, well i just got around to finishing my colour organ and all is now fine when i apply a line level signal, i now wish to add a pre amp at the front end so i can select either mic or line to drive the circuit, i don't know much about pre amps in terms of input/output voltages but i am assuming with a mic insert, i am dealing with a few micro volts? i need to raise this to a couple hundred millivolts using an op amp since i have one half of a dual op amp unused on my board, i can't seem to find a circuit online surprisingly, could someone point me in the right direction please?
13th April 2012 02:22 PM
A microphone has an output of about 10mV when it is about 10cm in front of your mouth and you are talking in a normal conversation level.
Then the preamp needs a gain of about 200 so that a volume control can adjust its level up or down.
Use a low noise audio opamp for the preamp.
Last edited by audioguru; 13th April 2012 at 02:46 PM.
13th April 2012 02:44 PM
13th April 2012 02:48 PM
The website does not work anymore.
Originally Posted by Mosaic
13th April 2012 02:49 PM
13th April 2012 02:51 PM
Here is the circuit image from the website....sans all the explanations about its operation.
13th April 2012 03:07 PM
I made comments on the schematic.
13th April 2012 10:58 PM
ok thanks guys, a project for the weekend me thinks.
14th April 2012 01:04 AM
An entire weekend?
2 minutes to design the circuit and maybe 5 minutes to build it.
Then 2 minutes to get the generator and 'scope warmed up.
The actual test takes a few seconds.
Drink wine or beer for the remainder of the weekend.
14th April 2012 02:09 AM
lol....your forgetting you are way more experienced than me, i try to take my time and learn something along the way.
dual op amp,
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