[sdiy] Cheap audio spectrum analyzer

[Jean-Pierre Desrochers]

Richie,
Thanks for your kind yet easy suggestion.
I was aware of that way to do spectrum analysis.
Unfortunately I do not have a sweepable signal gen on hand.
And doing so I would not have any way to know
at what freq the sweep is at on the screen..



Le 2015-10-26 13:22, Richie Burnett a écrit :
> An interesting bit of kit Rick!
> 
> JP have you thought of just using an analogue scope and a sweep
> generator to automatically measure the frequency response?  You
> probably already have these two items.  You set your function
> generator to produce a sinewave sweep between 20Hz and 20kHz with a
> pulse at the start of each sweep.  Then set your oscilloscope's
> timebase to trigger off the pulse at the beginning of each sweep, and
> display the output of whatever your testing on the Y-channel of your
> scope.  It's a cheap and dirty way to plot a magnitude frequency
> response.
> 
> Not the best video but hopefully you get the idea...
> 
> https://www.youtube.com/watch?v=xb3cLtAtE1s
> 
> -Richie,
> 
> 
> 
> -----Original Message----- From: Jean-Pierre Desrochers
> Sent: Monday, October 26, 2015 5:01 PM
> To: Rick Jansen
> Cc: synth-diy
> Subject: Re: [sdiy] Cheap audio spectrum analyzer
> 
> Le 2015-10-26 11:51, Rick Jansen a écrit :
>> http://www.cnx-software.com/2013/07/24/359-red-pitaya-board-combines-an-oscilloscope-a-spectrum-analyser-a-waveform-generator-and-more/
>> 
>> ~360 US$
>> 
>> rick
>> 
> 
> Thanks Rick but,
> This still needs a PC to run...
> 
> 
> 
> 
>>> On 26 Oct 2015, at 16:25, Jean-Pierre Desrochers <jpdesroc at oricom.ca> 
>>> wrote:
>>> 
>>> 
>>>> Again, what do you mean by "cheap"...? What is your budget, and what
>>>> level of performance do you want to measure?
>>> 
>>> Lower than $500.
>>> 
>>> 
>>> 
>>> Le 2015-10-26 11:18, Neil Johnson a écrit :
>>> 
>>>> Jean-Pierre Desrochers wrote:
>>>>> Do you know of a cheap audio spectrum analyzer I could buy to check 
>>>>> 20-20khz frequency response on audio stuff ?
>>>> Define "cheap".
>>>>> That would includes sinus generator + analyzer in the same box.
>>>> Ok.
>>>>> I checked on eBay and most analyzers are RF band based and are so 
>>>>> $$$$$ expensives. But 2 things:
>>>> You're looking for the wrong kind of thing.
>>>>> - I don't want to use analysis software on a separate PC - Any DIY 
>>>>> projects with micro/graphic LCD would do.. I want a standalone 
>>>>> analyzer.
>>>> Well, for a complete standalone box I would recommend an HP Dynamic
>>>> Signal Analyser, such as the venerable 3561A, or something a little
>>>> more modern such as a 35660A. Pros: all-in-one, built-in screen, 
>>>> will
>>>> do amplitude and phase response. Cons: dynamic range ok but won't 
>>>> get
>>>> down to the very low levels of noise and distortion.
>>>> The next step up would be audio analysers, such as the HP 8903 or
>>>> something from Audio Precision. While the 8903 does have a built-in
>>>> computer and can do sweeps, the display is 7-seg LED so you'll need 
>>>> a
>>>> pencil and some graph paper. The Audio Precision kit needs an
>>>> external control computer, but can measure the very lowest noise and
>>>> distortion.
>>>> Again, what do you mean by "cheap"...? What is your budget, and what
>>>> level of performance do you want to measure?
>>>> Neil
>>>> --
>>>> http://www.njohnson.co.uk [1]
>>> 
>>> 
>>> 
>>> Links:
>>> ------
>>> [1] http://www.njohnson.co.uk
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