Id say generate a square wave to the input.

If you get a square wave out its pretty good response
you need like 100 third order (ODD) harmonica to get a good square wave.
If the top of the wave slopes one way you need better high response.
if it slopes the other you need better low response.

It is how you calibrate a scope probe for the best response.

It should test any wide BW responses you want to.

Download and install the program called Audacity and you can play with
WAVE files of your own making.

Build an amplitude demodulator out of a diode and a capacitor
and build your own low freq demodulator.
Play the sound through a portable MP3 player into the demodulator
into your amplifier ???

I set my 1000Hz tone decoder this way for WWV.
But for WWV 1000 HZ you need no demodulator.
The player handles 1000Hz just fine.



Just an idea.



-----Original Message----- 
From: Richard Schneider
Sent: Sunday, December 05, 2010 8:06 PM
To: PSNLIST@..............
Subject: Testing Amplifier Frequency Response



Hello PSN,



I would like to run a frequency response test of my amplifier/filter but I only have test equipment in the 50 Hz to 50 KHz range.



Do any of you have a recommendation for constructing a generator that would output DC to 5 Hz with a uniform (flat response) 
voltage?



There was a CD disc someone was selling (RefCD) at the URL below that modulates a 1 KHz sine wave with a 1 Hz since wave. I believe 
the idea is to filter out the 1 KHz signal at the output of a PC sound card. What are left are pure VLF signals that could be used 
to sweep the amplifier/filter.



http://www.science-project.com/_members/science-projects/sponsorads/refcd/seis.html



I know there are several freeware tone generators you can download, but I don’t think a PC sound card can reproduce DC to 1 Hz. Am I 
correct?



Thank you,



Rich



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