Re: Measuring Frequency Response of Cassette Tapes

On Sat, 9 Jun 2007 15:10:50 -0300, "Chris F."
<zappymanNOSPAM@xxxxxxxxxxx> wrote:

I've been fascinated by audio cassettes ever since early childhood, and
today thanks to Ebay I've collected many new-old-stock tapes which are now
considered collectors items. With many different tapes to compare, I'd like
to do my own frequency response tests, like those printed on the back of
many cassettes. I know that the basic idea is to compare the input signal to
output signal, and measure the difference in dB at a range of different
frequencies. But all I have for measurement is a DMM, with a range down to
about 10mVAC. Is this enough? How to I convert mVAC to dB? And is it
possible to do this with any accuracy, without spending thousands on
lab-grade test equipment?
Some of the comparisons I'd like to make are of different series of the
same tape (say, TDK SA) to see how they improved over the years, or to
compare the results of the obscure FeCr format to other formats of the day
(and yes I do have a deck with an FeCr setting). If the results are
interesting enough I may eventually post them for others to see.
Thanks for any advice.

Well, you've just typed this on a PC, and presumably, like 99.9% of
PCs around today, it has a sound card. That being so, it is your
measuring instrument. Get hold of a copy of Audacity, the freeware
audio editor. Generate a swept tone, and record it on the cassette.
PLay it back into the sound card, again using Audacity, and it will
show you the frequency response.

d

--
Pearce Consulting
http://www.pearce.uk.com
.

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