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Audio measurement gear

Mivera

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#1
Hi guys,

Discussions about measurement gear have taken place on other threads, which were off topic for the thread subjects. So I thought I would start a thread that we can dedicate to the discussion of todays latest innovative measurement gear. Amir has a very nice AP machine, so maybe when he gets a chance he can kick the thread off explaining the capabilities of his machine. In the mean time, I will be starting an intensive research project dedicated to learning everything there is about this gear, and it's capabilities.
 
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Opus111

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#2
If you'd like to talk about AP I could try inviting a contact from AP over to the discussion?
 

amirm

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#4
The Audio Precision Analyzer I have works in both analog and digital domain. The latter is FFT based which you can also do with a sound card/ADC. What it has that a sound card does not have is input auto-scaling and protection. A normal ADC will be instantly damaged if you send it signals outside of its input range with is line level/balanced. Hook it up to the output of the power amp where the voltage swings go up to nearly 100 volts and you can cook that ADC good.

The AP autoscales all the time. So I can do a test where I keep increasing the level of output signal and measure THD out of an amp as you see in magazine reviews. As the output voltage of the amp increases with increasing power it puts out, the AP automatically switches scales so that its ADC does not get damaged.

The AP is built to a very high standard. You hear precision relays clicking away and the machine is like a tank. The user interface (sans some portable machines) is all in the PC. The box only has inputs and outputs. This makes it easy to capture graphs, settings, etc. I am not a fan of the machines that have the user interface inside of the box like Rhode and Schwartz. You spend a lot of money on that and sit hunched over the little display it has to see what it is doing and setting parameters.

The AP also has a programming language based on Visual Basic so you can automatic or write new tests. Lots of factory automation is done this way for audio devices. It has I/O extenders you can get so that you can test multiple devices.

AP was the first company to focus on audio testing. They have the best brand recognition and pricing reflects that. Their "good" devices always cost $25K or thereabouts. I think their prices are too high this day and age when you can get a superb quality ADC for a fraction of the cost.
 

Mivera

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#5
If you'd like to talk about AP I could try inviting a contact from AP over to the discussion?
Yeah if you can why not?
 

amirm

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#6
I have also used the Prism Sound analyzers. They are a lot cheaper (less than $10K) but don't have the analog front-end that AP has. It is essentially a good ADC/DAC that comes with a lot of standardized tests. The user interface is very nice in that it can use the PC as the front end for all of its tests.
 

Mivera

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#7

Mivera

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The Audio Precision Analyzer I have works in both analog and digital domain. The latter is FFT based which you can also do with a sound card/ADC. What it has that a sound card does not have is input auto-scaling and protection. A normal ADC will be instantly damaged if you send it signals outside of its input range with is line level/balanced. Hook it up to the output of the power amp where the voltage swings go up to nearly 100 volts and you can cook that ADC good.

The AP autoscales all the time. So I can do a test where I keep increasing the level of output signal and measure THD out of an amp as you see in magazine reviews. As the output voltage of the amp increases with increasing power it puts out, the AP automatically switches scales so that its ADC does not get damaged.

The AP is built to a very high standard. You hear precision relays clicking away and the machine is like a tank. The user interface (sans some portable machines) is all in the PC. The box only has inputs and outputs. This makes it easy to capture graphs, settings, etc. I am not a fan of the machines that have the user interface inside of the box like Rhode and Schwartz. You spend a lot of money on that and sit hunched over the little display it has to see what it is doing and setting parameters.

The AP also has a programming language based on Visual Basic so you can automatic or write new tests. Lots of factory automation is done this way for audio devices. It has I/O extenders you can get so that you can test multiple devices.

AP was the first company to focus on audio testing. They have the best brand recognition and pricing reflects that. Their "good" devices always cost $25K or thereabouts. I think their prices are too high this day and age when you can get a superb quality ADC for a fraction of the cost.
Great info!

They definitely seem like the way to go if you have the budget for one. However I'm going to go on a mission and see if I can come up with a different solution that can approach the data acquisition accuracy/capabilities of the higher end units, for lower cost. At this point having signal generation built in isn't critical for me.
 

Mivera

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#10
I have also used the Prism Sound analyzers. They are a lot cheaper (less than $10K) but don't have the analog front-end that AP has. It is essentially a good ADC/DAC that comes with a lot of standardized tests. The user interface is very nice in that it can use the PC as the front end for all of its tests.
Cool I'll check them out as well
 

Mivera

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#11
OK I'll drop him a line on LinkedIn and we'll see. He's normally very busy though....
Right on. Hopefully he can make it.
 

Mivera

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#12
I have arranged a rental of a aPX-555 for 2 weeks. I will make sure I have a whole pile of testing plans arranged first, as well as study the manual beforehand. I can't wait to play with this precision toy!! :) :)
 

Mivera

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#14

Mivera

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#16
Yeh very expensive. My rule for rental gear is that they recoup the full price of the unit in 90 days!
I will look around and see if there's other alternatives. There's one right down the road from me at ESS, but I would rather be testing gear with ESS chips in it before asking to use it :)
 

DonH56

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#17

Mivera

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#18
I figured I would start at the top. Then I will know for sure what's lacking with lesser gear.
 

Mivera

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#19
Hi Amir,

Do you have the DSIO module on your AP unit? With that you can measure jitter direct from I2S interfaces. It would be awesome for testing USB interfaces for jitter.

http://www.ap.com/download/file/372
 
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amirm

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#20
I can measure jitter on digital serial connections (S/PDIF, Toslink and AES/EBU) but it is useless. It only gives you a number and it can't measure low levels of jitter.

The right approach is to simply digitize the input and look at the spectrum. That is what I have been showing in my posts such as this one for Regen/AQ:



All correlated jitter components show up as peaks. And noise as broadband skirts around the main tone. Now we have the spectrum and can determine audibility. A single number sum of them doesn't translate into anything useful.
 
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