First, let me say that I am a hobbyist with limited electronics
knowledge.

I want to be able to record low-frequency sounds. I have a microphone
with a frequency response of 25Hz-15kHz. I need a pre-amp and have
chosen a schematic from several I downloaded.

Is there a way I can modify the pre-amp to ignore sounds over 100Hz?

On Tue, 22 Feb 2005 10:09:14 -0800, sky_diver_ wrote:

First, let me say that I am a hobbyist with limited electronics
knowledge.

I want to be able to record low-frequency sounds. I have a microphone
with a frequency response of 25Hz-15kHz. I need a pre-amp and have
chosen a schematic from several I downloaded.

Is there a way I can modify the pre-amp to ignore sounds over 100Hz?

Yeah, of course.
http://www.google.com/search?q=%22ac...=Google+Search

Good Luck!
Rich

As Rich is suggesting, a low pass filter is required. Start with a passive
type first by using only caps and coils. An active filter will take more
time to build.

Harold




wrote in message
oups.com...
First, let me say that I am a hobbyist with limited electronics
knowledge.

I want to be able to record low-frequency sounds. I have a microphone
with a frequency response of 25Hz-15kHz. I need a pre-amp and have
chosen a schematic from several I downloaded.

Is there a way I can modify the pre-amp to ignore sounds over 100Hz?

Harold Ryan top-posted:
As Rich is suggesting, a low pass filter is required.
Start with a passive type first by using only caps and coils.
An active filter will take more time to build.

Not significantly more time.
The cutoff can be made much sharper with an active filter.

....and to make a passive low-pass
he's going to need a resistor somewhere.

Resistors are not required. Just inductors and capacitors. Pi filters are
made up of an input inductor, one cap to ground and one output inductor.
Several speaker crossover filters have this circuit. Why the resistor?
Harold



"JeffM" wrote in message
oups.com...
Harold Ryan top-posted:
As Rich is suggesting, a low pass filter is required.
Start with a passive type first by using only caps and coils.
An active filter will take more time to build.

Not significantly more time.
The cutoff can be made much sharper with an active filter.

...and to make a passive low-pass
he's going to need a resistor somewhere.

Resistors are not required. Just inductors and capacitors.
Pi filters are made up of an input inductor,
one cap to ground and one output inductor.
Several speaker crossover filters have this circuit.
Harold Ryan

Aside from the fact that you described a T filter,
you are correct.

Please don't top-post.