[sdiy] Cheap audio spectrum analyzer.. finally..

[Richie Burnett]

Looks like an excellent choice, and something you should be able to trust to 
give you useful results.

A spectrum analyser just analyses a signal that you feed into it and tells 
you what it's frequency content is.  Whereas, a network analyser generates 
the drive or "excitation" signal, and then tells you what a given network of 
components has done to that signal over a given frequency range.

So, you could determine the frequency response of a filter by either:

1. Feed some white noise, an impulse, or a frequency sweep through the 
filter, and look at it's output on a spectrum analyser.  (Since the drive 
signal has a flat frequency content you can assume that any deviation from 
this flat response in the filter's output is down to the action of the 
filter you're testing.)

or...

2. Connect the input and output of the filter to the network analyser and 
let it do whatever driving and sensing it wants to produce the frequency 
response for you.  It will likely "test" the filter with a series of 
sinewaves at different frequencies and then measure the phase shift and 
amplitude change seen at the output of your filter to plot its frequency 
response.

Network analysers will often allow you to display the frequency response of 
whatever you're testing in many different ways.  Bode plot is by far the 
most common, but Nyquist, Nichols, and Smith charts might also be options 
for display.  Just use whatever is most useful and makes the most sense for 
what you are trying to do.  Have fun...

-Richie,


-----Original Message----- 
From: Jean-Pierre Desrochers
Sent: Tuesday, October 27, 2015 5:28 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Cheap audio spectrum analyzer.. finally..

I finally decided to go for this:

HP 35660A (with option 001 memory installed)
http://www.sglabs.it/public/SgLabs_HP%2035660A.pdf

It was not cheap but around one third of eBay's mean prices
for those working condition HP testers..
and the dealer was 1 hour car ride from my home.
I think it's a good investment.
Ooooff !

>>>>
>>>> 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
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at dropmix.xs4all.nl
>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2014.0.4842 / Virus Database: 4447/10892 - Release Date: 
>> 10/26/15
_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy


-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4842 / Virus Database: 4447/10899 - Release Date: 10/27/15