Amplify from Microphone level to line level?
Andy Isaacson
I don't know what voltage the microphone is at; i do know that i need
the line output to be around 200mv. (I think; i'm not much of an
electronics
person :-)
Apologies if this is a FAQ.
Andy Isaacson
isa...@sebeka.polaristel.net
Chris Ford
<isa...@sebeka.polaristel.net> writes:
>
> How can i amplify from a microphone-level signal to a line-level signal?
> I don't know what voltage the microphone is at; i do know that i need
> the line output to be around 200mv. (I think; i'm not much of an
> electronics
> person :-)
>
You can use a simple OP-AMP based amplifier in non-inverting mode. You need
a gain of about 10-20 to amplify a mic to line level. Ask in your local
Radio Shack store if they sell a microphone preamplifier kit - That should
do the job. Good Luck.
Chris Ford
Innovision Concepts Ltd.
Tom Loredo
The best method depends on the mic signal type. If it's an unbalanced
signal (just 2 conductors, ground and signal), then just use an
op amp. Whether you configure it to invert or not is immaterial,
unless you need a special phase relationship with some other signal.
If it's balanced (3 conductors, +, -, and shield), you can still
use an op amp, but you should configure it as a differential
amplifier to get the benefit of the balanced topology (less hum
and noise). If good sound quality is a concern, use the
Analog Devices/PMI mic preamp chip, the SSM-2017. It is very
easy to use (just requires a couple passive external components),
and is used in a number of pro, studio-quality mic preamps. It
is more expensive than an op-amp, however, at about $6 per chip.
Allied and Newark carry them.
Electronic Musician magazine or Recording magazine had a phantom-powered
mic preamp DIY project a year or two ago; I can provide the reference
if you need it. PAIA provide it as a kit; they are on the web at:
If ease of availability is a concern, just base your project on the
TL082 op amp that you can get from Radio Shack. I just built a
simple unbalanced mic preamp with it for my mom for use at the
elementary school she works at (for a school play).
Good luck!
-Tom Loredo
Richard Steven Walz
Andy Isaacson <isa...@sebeka.polaristel.net> wrote:
>How can i amplify from a microphone-level signal to a line-level signal?
>I don't know what voltage the microphone is at; i do know that i need
>the line output to be around 200mv. (I think; i'm not much of an
And therein lies your problem. When *I* want to make sure of such an
interface, I measure the microphone output, and the required input AC
to activate the VU meters to where they saturate at 0 dB. Then I simply
produce a simple amplifier to crank the mike up to the level of the input.
There is no "sure" way to do this, which is why people who always post this
damned question never get a straight answer! There are a number of
standards for "line level" and a number of VERT different kinds of mikes!!
(P.S., I always use my voice and sing ooooooooooh, [a sine wave], as loud
as I can produce comfortably. Once I used my scope to make sure my mouth
wasn't saturating and clipping the sound!!) My method always yields gains
that are quite close to the acceptable range!
-Steve Walz rst...@armory.com