Products > Test Equipment
Looking for an audio analyzer
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jackenhack:
I'm currently finishing up a headphone amplifier build and I got the QuantAsylum QA401 when I started developing the amp. With todays extremely low noise and distortion figures on op amps, You'll hit the bottom of what the analyser can measure very quickly. I had to build a twin-T notch filter and get hold of a extremely low THD signal generator to be able to measure below -108dB THD. Getting a industry standard Audio Precision is the dream, but they are way to expensive for me...
_Wim_:

--- Quote from: jackenhack on January 04, 2017, 07:43:29 pm ---I'm currently finishing up a headphone amplifier build and I got the QuantAsylum QA401 when I started developing the amp. With todays extremely low noise and distortion figures on op amps, You'll hit the bottom of what the analyser can measure very quickly. I had to build a twin-T notch filter and get hold of a extremely low THD signal generator to be able to measure below -108dB THD. Getting a industry standard Audio Precision is the dream, but they are way to expensive for me...

--- End quote ---

But the question is, why would we need to see lower than that? It can be fun as a technical exercise, but it will not improve the sound quality we hear any more…
DaJMasta:
I mentioned the QA401 in the original post and I just don't have any experience with the software, which would probably be the big component of it.  A 32 bit DAC and ADC sound fancy, but it doesn't look like the specs are any better than the 24 bit competitors, and I think it just comes down to physical restrictions of the design and parasitics at that point.  Since that is very software dependent too, I'm not sure how much performance would actually differ from just using my existing equipment.

The CLIO pocket seems like a similar little device, but the big drawback is that it's only a single channel.  Sure you could get two, but it seems like there's several options for this sort of USB box with some converters so it may be easier just to pick another if I go that route.  I think the measurement mic pack is probably not worth it for me - just the mic itself isn't that expensive and I've got interfaces that are probably better than a built in USB thing, so then it comes down to the software and it does seem like there are affordable options.  I've also got an older dedicated SPL meter, a CEL-231 with a calibrator box.  Sure, the cal seal on the inside is from 1992, but the spec is down to +-1dB , which isn't really common with most inexpensive meters :)


I think in the short term, getting rightmark and experimenting with my current interfaces is basically a no-brainer, but I agree with the liking a hardware solution sentiment.  It also seems to afford you some more input protection, better filtering, more EMI rejection, and a cleaner power supply without having to put everything on an external power conditioner.  Maybe a good interface can give you performance good enough that you can't really hear a difference, higher performance will still get you more fidelity in the visualization and the same amount of accuracy with a shorter sample time, and since I do want close to real time FFT visualization, the extra dynamic range will help keep the visualization from getting too noisy when turning up the responsiveness.  Another concern is that I'm trying to be as scientific as possible with my main use - the measurement of instrument sounds - mostly because I don't know what results I'll find.  Having better equipment will let you see more detail in the minor differences and reduce the chances of running into hardware artifacts or limitations in the measurements that are difficult to identify.  I'm looking for an instrument that can beat the specs on my current hardware because my current hardware seems to edge out my own ear across the board (I've been honing my listening skills for a while now as part of my trade), and I don't want to run into a situation where my measurements can't match that level or my ears can match it with another couple decades of experience.  I want measurements that are good enough that no one can hear beyond them, because some of the people who may eventually be interested in my data may literally be the most discerning listeners in the world.


Couple new questions from reading through datasheets and such:
Are there audio analyzers that provide phantom power?  Are commercial phantom injectors also noise sources?  I assume it's a concern with ultra low noise gear, but is that a common issue?
Do you think it's valuable for the generator side of the instrument to produce more than sine waves?  It seems like some of the lowest distortion generators are pure sine only, but I've already been using some AM and added harmonics in signals on my existing function generator... is that something that's likely to be useful?  I assume all the normal audio rating specs are done with sine only, but it's definitely not a "realistic" test signal.
Loboscope:
Although human ears and human hearing are fantastic and amazing in respect of its construction and function, there will be no doubt that any reasonably decent technical solution will be far better in terms of precision, reliability and reproducibility of its results.
The frequency response of any decent high-quality (omni-)microphone will be easily outplay any adult ear and there are for example some new Sennheiser Studio-Microphones which will reach up to 50 KHz. Also the dynamic range of a really good microphone/amplifier will exceed the total amount of our ears because there are microphones which will deliver a low distortion output up to 140 dB and a decent amplifying circuit will also let pass the signal unspoiled.
And the great amount of the dynamic range of our ears from 0 to nearly 120 dB (normally the maximum pain threshold) will only be achieved by an time-consuming adaptive process. If your ear has been exposed some time to a strepitous environement you will afterwards not be able for some time to hear really quite sound for some time. This is due to the internal protective mechanism of our ear.
And all the functionality will only be completely there, if our ears are sane and undamaged.

But the most erratic part will be our brain itself which must interpret all the signals coming from our ears. And the brain will interpret continuous - because this is the task of our brain. And there will be expectations, mistakes, misconceptions and so on.
Mostly the expectations will colour our perceptions.

So I will underline that any (half-)decent microphone, amplifier, interface and software will give you the all the reliable results you want to have measuring audio sources like musical instruments, voices and so on. And today it is not necessary to pay a fortune for having professional results.
Even a simple and dirt cheap app like "Speedy spectrum analyser" will show astonishing results.
amirm:

--- Quote from: DaJMasta on January 04, 2017, 09:59:17 pm ---Couple new questions from reading through datasheets and such:
Are there audio analyzers that provide phantom power?  Are commercial phantom injectors also noise sources?  I assume it's a concern with ultra low noise gear, but is that a common issue?
--- End quote ---
XLR inputs are for line level capture and not microphone.  So they neither provide phantom power no mic amplification.


--- Quote ---Do you think it's valuable for the generator side of the instrument to produce more than sine waves?  It seems like some of the lowest distortion generators are pure sine only, but I've already been using some AM and added harmonics in signals on my existing function generator... is that something that's likely to be useful?  I assume all the normal audio rating specs are done with sine only, but it's definitely not a "realistic" test signal.

--- End quote ---
The common way to do this testing is to use a synthetically created test file and using that through a DAC for the source.  These are mathematically produced and with dither can go down to any depth you want.  No need to use any analog generator.  And for testing things like DACs, you just feed them the digital stream eliminating.

You can even create the files using your DAW.  Just make sure you add dither (TPDF) so that you don't see the distortions caused there in your analysis.  YOu can create single frequency and sweeps as needed.
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