Audio measurement gear

[Mivera]

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.

But with the DSIO module I will be able to right? It appears it has this capability in the manual. I'm more interested in I2S jitter than SPDIF or AES/EBU.

 

[Mivera]

Ahh here we go. I will need to make sure it's updated with this, or is brand new.

DSIO Jitter Testing

DSIO modules shipped after August 5th, 2015 are jitter-enabled. Earlier DSIO modules can be upgraded to enable jitter.

Wow it sure is daunting what this thing is capable of measuring. It may be expensive, but sure is advanced. It will take me a bit to make it through the 700 page manual

 

[Don Hills]

There will be a 4-hour written exam to pass before they'll let you out the door with it...

 

[Mivera]

There will be a 4-hour written exam to pass before they'll let you out the door with it...

I hope not! Actually they ship it right to my door. That's extra on top of the $1995. And if I don't ship fast it eats up the time I have it for. It has to come from California to B.C Canada.

 

[amirm]

That option is for design purposes and factory qualification. It is able to generate I2C streams, letting you vary jitter, etc. and see if your device can handle it. It can also be a receiving device to see if the external transmitter is working/within spec.

For the type of analysis I have been talking about it is not needed. All you need is analog input and DSP functionality which is standard on that unit (was optional on mine).

 

[amirm]

There will be a 4-hour written exam to pass before they'll let you out the door with it...

If you watch the RMAF video where they presented you can see me reaming them on usability of their devices and software. It is exceedingly simple to configure it to measure the wrong thing. And unless you use it all the time, you forget what is where.

Example of poor design is loading a programmed test and have it force an input change! Here you were testing using unbalanced BNC input and the program switches input to AES/EBU balanced. Here you are then making noise measurements and instead of measuring the noise level of the device you are testing, you are instead measuring the unused input! There is no light, indicator or anything on the device saying which input is being used for testing.

If you are a person who does this everyday you get used to it but walk away from the unit for a bit, and you forget.

Once you get past these usability challenges then it is a fine instrument.

 

[Mivera]

That option is for design purposes and factory qualification. It is able to generate I2C streams, letting you vary jitter, etc. and see if your device can handle it. It can also be a receiving device to see if the external transmitter is working/within spec.

For the type of analysis I have been talking about it is not needed. All you need is analog input and DSP functionality which is standard on that unit (was optional on mine).

Yes and it's what I want to use it for. I can test boards like the Amanero for jitter.

 

[dallasjustice]

Is the QA405 available for purchase yet?

OK I'll drop him a line on LinkedIn and we'll see. He's normally very busy though....

In the meantime, you might find this interesting. DIYA has a thread about it - http://www.quantasylum.com/content/Products/QA400.aspx

 

[amirm]

From reading their blog, it seems they built a down feature QA401 instead.

 

[c1ferrari]

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.

Amir,

How about an external monitor for the R&S? I had an AP P1DD, but traded it to my tech for work on my Studers. Currently, trying to learn how to use a calibrated, optioned Rohde & Schwartz UPV.
Help!

Sam

 

[amirm]

Does it support an external keyboard and mouse too? If so, and the interface is not horrible, it could work.

 

[c1ferrari]

Yes, one can implement an external keyboard, mouse, and monitor -- that's how mine is set up.

 

[amirm]

I don't envy the learning curve you are going through to get good info out of that . On the positive side, the performance of the unit is supposed to be excellent so please keep us posted on your progress.

 

[c1ferrari]

Thanks for the encouragement, Amir. An in-law is an EE, perhaps he can get me going.

 

[amirm]

Thanks for the encouragement, Amir. An in-law is an EE, perhaps he can get me going.

While I have never used the device, if you run into a block just post it here and I can see if I can help. Your first challenge will be getting the routing right, i.e. configuring the input and output. Start your testing with just using the instrument and feeding its output to its own input. Play a single tone and measure it to make sure that what you put out, is what is being measured. Then work on setting up a sweep in frequency. Once you get both of these tasks done, you should be comfortable with it.

 

[c1ferrari]

Thanks, Amir...eminently practical advice. I really want to measure the drivers/ribbons in the DALI MegaLine III. I've been on the lookout for a B & K or SoundFirst precision mic.
Have you ever measured loudspeakers?

 

[amirm]

I have not but I would not use an audio analyzer for either if I were measuring in rooms and not in anechoic chamber. The high resolution of these audio analyzers is only needed when the room can be ultra quiet. In a normal room your noise floor is well above even ordinary 16 bit sound cards. My weapon of choice would be an excellent mic and then REW or plain audio capture and analysis in an Audio Workstation software and/or MATLAB custom program. The former two are a joy to use compared to any audio analyzer interface. Indeed I have never tried to use the AP that I have for acoustic measurements even though it has that feature.

Are you doing this work as a hobby/interest or professional venture?

 

[c1ferrari]

My intent was to measure with the mic capsule between 5-10 cm distant from the ribbon...the idea being to ameliorate the effect of the room.

Professional venture -- hardly...I'd starve -- though I could happily enjoy the benefit of shedding a lb. or two. LOL.

Just an aspect of the hobby I find enjoyable!

 

[amirm]

Well, kudos for going that far then.

Are you renting or buying the R&S? If you have not done so yet, I would definitely start with the mic and REW software.

 

[amirm]

By the way, for driver measurements, Kippel rules the world: https://www.klippel.de/

https://www.klippel.de/our-products/controlled-sound.html

Lots and lots of good info on their site and their AES papers.

They recently released a system that measures the 3-D radiation of a driver/speaker much like Harman does but without the need for anechoic chamber! They published a paper on it at the recent AES which I will at some point do a digest on.