Re: Audio distortion measurement

From: john jardine (john_at_jjdesigns.fsnet.co.uk)
Date: 10/07/04 

Date: Thu, 7 Oct 2004 00:54:22 -0700

"Rob" <seegoon99NSpam@yahoo.com> wrote in message
news:Xns9579CF99EE304robd00hotmailcom@196.25.240.158...
> Hi all.
> Is there a simple way to measure distortion in a audio amp.
> I am looking to measure over a frequency range of say 200 - 2Khz.
> It will be a low power amp (intercom) , and obviously not hi-fi quality.
> I would just like to get a basic distortion measurement. Does
> not have to be anything fancy.Looking for a simple analog design.
> ie No computer / capture card / software.
> A notch filter method is fine but only works for one frequency , I am
> looking to have continuous coverage from 200 - 2000Hz.
> I get the feeling that what I need may not be "Simple" , but maybe someone
> out there has some ideas.
> Thanks
> Rob

Maybe simplest is to build a tunable '2 opamp bandpass filter' set with a
sharp 'Q' of maybe 10 or more. Audio tuning over 20:1 range by means of a
radio style 2 gang variable capacitor. 200Hz-20kHz frequency range would be
easily available.
Essentially it would function as a manually tuned, audio wave/spectrum
analyser as each audio distortion component could be measured/examined in
turn.
It's very easy to design using barely any bits and pieces. Jim Thompson has
the 'DAPB' circuit etc on his web site.
regards
john

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