Which spectrum analyzer for audio application

[glias]

Hello,
I'm looking for a spectrum analyzer for audio application and to test the noise of transistor. Do you know which (maybe old one, because budget is limited) analyzer could be fine for this type of application ?

regards

 

[jcx]

PC soundcard and software are the cheapest audio analysis option today

for noise measurement you need to amplify the noise to be above that of the ADC - often done with the Q you are measuring

 

[glias]

Hello jcx,
thanks for your reply, I would prefer a true hardware solution instead of sound card+soft...
any idea ?

regards

 

[jcx]

Audio Precision : High Performance Audio Analyzer & Audio Test Instruments ? - still digital ADC/DAC + software - but in a nice box, very good front end electronics, UI, lots of canned analysis - not for limted budgets

I've not used any "old school" swept frequency oscillator analog hardware spectrum analyzer for audio - only rented some for EMI prescreening - nowhere near suitable for audio

 

[phaselag]

You should look at an FFT analyzer. HP 35670 or 35770, SRS 670/770, Advantest R9211 series.

These cover up to 100 KHz and will do a variety of analysis.

paul

 

[31697B]

There are downloadable apps for the iPOD Touch which include RTA, FFT and FREQ resp etc - just plug in your analog signal at line/headphone port/jack and you are ready to go. The FFT app is pretty basic but maybe will work for you (?). You can find more info for this iPOD Touch/ADC at Studio Six Digital LLC and at iTunes app store.

-Thx RNMarsh

 

[glias]

Hello all,
Thanks a lot for your replies... Well I'm going to look for an HP 35670 (I can't find the HP35770 ?).
For low noise test, does the HP 3560 (for example) is sufficient to measure low noise transistor (0.5nV/sqrt(Hz) for example) ...?

regards

 

[paba]

Hi get one with a tracking generator function (built in source) that you can feed into the input of your circuit under test not all of them have this. Also watch the SA inputs, some can't take much voltage some can. Finally also look at the input impedance of those inputs as it could impact the circuit your testing…

good luck
Paba

 

[mikeford]

Sounds like you are about to waste some money. Why not buy a good known transistor?

Are you sure you understand how to measure noise in a meaningful way?

 

[1audio]

Best option- buy an old Quantech. Next best probably the IOS/Android spectrum analyzer but you need to build the test system which is the lower 1/2 of the older Quantech's.

Its a test circuit that servo's the gain of the transistor in circuit at the target voltage and current and gives about 60 dB of gain which you would need for any transistor test circuit.

I can send a PDF of the manual for the Quantech so you have a better idea of the magnitude of the problem. PM me with your e-mail.