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Audio Precision APx516B Review

Rate this audio analyzer:

  • 1. Poor (headless panther)

    Votes: 12 8.3%
  • 2. Not terrible (postman panther)

    Votes: 26 18.1%
  • 3. Fine (happy panther)

    Votes: 75 52.1%
  • 4. Great (golfing panther)

    Votes: 31 21.5%

  • Total voters
    144
But it's probably easier if sampling frequencies are multiples and buffer size is chosen accordingly.
I am not sure I understand. Single-connection ASIO cannot use a different rate for capture and different for playback - there is no direction parameter in ASIOSetSampleRate method. Also I/O buffer sizes are equal for both directions direction - method ASIOCreateBuffers has only a scalar parameter bufferSize for all non-interleaved channel buffers (which is logical since both directions use the same samplerate and the switchBuffer callback passes data for both directions - both directions must take the same time to fill up/consume up the samples).
 
As an APX555 owner I'm curious about the performance of the "B" version.

Amir, is your 555 a "B"version? What version of software are you running?

Being retired from the industry for the past few years, I'm seeing that equipment technical performance appears to be loosing relevence.

Hi Murray,
Have you seen this link (compares oscillators for various AP models): https://www.nanovolt.ch/resources/oscillators/pdf/low_distortion_oscillator_comparison.pdf

The author (Samuel) has designed his own LDO and is highly respected in academic circles. As you will see above, his tests suggest that the ancient SYS-2722 outperforms the example (I stress Samuel's example, not necessarily your one) of 555 in many areas.

I first saw Sam's study a few years back and came to the conclusion that the 555B was released in order to reliably attain the quoted spec for the 555 oscillator. Maybe your example hits the headline spec, but Sam's one obviously didn't and for AP to have this pointed out by someone as esteemed as Samuel must have been embarrassing for them.

The problem for a lot of people now is that the 2722 will no longer be supported at the end of this year for servicing and - to my knowledge - there are no 3rd party service agents (there is a guy in the US who services older SYS-1 etc. but I do not believe he will take on a 2700). Aside from its stellar oscillator, the 2722 is generally a dog to use and lacks live FFT (R+S had this feature well before the 2700 series, so quite what AP were thinking I do not know).

I think a lot of OEMs will be looking at their 2700 machines and wondering what to do at this point... As others have pointed out, there are modern A-D / D-A options, but if you're an OEM you need hardware + software that's been designed in tandem, with calibration that clicks into place as soon as it boots (as well as floating I/O and autoranging).
 
Your 2700 machine will not stop working suddenly. They didn't got any updates for years now, the software is ancient.
When you need regular calibration you surely switched to a newer model a while ago. So they announced to not repair 20+ year old units any more.

2722 and it's brothers calculate FFTs with the internal DSP - which was VERY limited at that time. R+S has a windows computer inside, therefore has different possibilities (and which is a pain to work with nowadays). R+S are also end of live btw, not sure if they still get calibration or service but for sure not for long.

You can buy the AP software and use it with an interface ... but it get's close to the price as an entrance level test system when you need a few add ons. I really like the units and the whole system - but their software politics nowadays is a problem, the system get's unstable when you don't take all the upgrades (different versions, problems with Windows updates etc) and very expensive over time when you run with the updates.
 
not sure if they still get calibration or service

One of our UPVs was serviced back in May. They 'shotgun' replaced it, not even bothering to fault find. This involved swapping out the whole 'analogue board'. To get an idea of one, see this link: https://www.eevblog.com/forum/repair/rohde-schwarz-upv-audio-analyzer-teardown-and-repair/

If you gave me a schematic, I could fault find the analogue board. Even at the rates we were charged, I cannot see how they would've made much profit by changing out such a massive board (and they changed others as well). I think there are good reasons to think that R+S no longer have specialist audio staff and simply repair items by numbers. As you suggest, they are unlikely to be doing this for very long unless they have a lot of spares... (we found several shorted MLCC caps, and I suspect they may well have changed the entire board because of a couple of caps...).

^This is somewhat off-topic. My previous post is regarding Sam Groener's measurements. Whether the 2722 can be used in future is irrelevant. The big question in my mind is whether its oscillator is better / worse than the 555B. Sam's measurements suggest the 555 (non-B) has an inferior oscillator to the 2722. Is this the case with the B version? Is this why the B version was released?

Maybe we should have a sub-forum for test gear? This is 'Audio Science Review', right? I know of nowhere on the web that you can talk about test gear that's dedicated for audio.

NB - as someone with several AP / R+S / Prism etc analysers, I can state that 'calibration' is somewhat of a scam. The 2722 is over 20 years old and still realises factory values, on it own, or if connected to a separate machine. The same goes for the UPVs. R+S have a broad tolerance for calibration as well... Your serviced machine may well measure worse than a non-serviced one and they will simply tell you that it's normal for machines to have a variation....

The 2722 will hit -115dB THD+N @ 2VRMS @ 1KHz 20Hz to 22KHz. Once it's been on for a half an hour, it'll usually hit -116dB. This is 4dB worse than the 555B. If I get a 555 it will be for flexibility and better software. The 2722 SW was clunky even in 2002...
 
It must be said that calibration is the operation of taking measurements of standard references with the device under calibration in order to document evolution of its performance over past time intervals. Calibration is not about adjusting the device under scrutiny. Eevblog has a great video about calibration :

 
It must be said that calibration is the operation of taking measurements of standard references with the device under calibration in order to document evolution of its performance over past time intervals. Calibration is not about adjusting the device under scrutiny. Eevblog has a great video about calibration :

Depends what you specify as your process to your customers. Some customers just want a verification but some want As Found measurements and As Left measurements after adjustments. Some want a dialog if the unit fails verification before being adjusted. It all depends. A lot of calibration houses don't even have the ability to adjust the units they calibrate.
 
NB - as someone with several AP / R+S / Prism etc analysers, I can state that 'calibration' is somewhat of a scam.
I know from one of my customers they just NEED to calibrate gear which is involved into production once a year. No matter if it's needed or makes sense - it's not allowed to be switched on without the correct calibration sticker. Someone is making a lot of money with calibration there ...

Of course you need to calibrate after a repair but these units are very stable, I really don't have the need for regular calibration for my AP.
 
What components are used in modern electronics that drift to the point of needing calibration adjustment every year?

Do we still use carbon composition resistors? (clue: no)

Do we use electrolytic caps for time constant setting (clue: no)

Are we using variable resistors that drift? (clue: only if we've skimped out and bought cheap ones, or haven't augmented it with fixed resistors to minimise drift)

I don't imagine the above applies to AP in any model. Running a calibration certification company is a nice business model. You don't need to employ graduates as the staff can learn the job parrot-fashion, and the task won't fall to them if something needs adjustment (it'll go back to R+S / AP / Agilent etc, who will send you a fat invoice for turning a trimmer a couple of times). Kerching!
 
We calibrate thousands of items a year and, in turn, get hundreds of items of equipment we use calibrated by others. We even choose to internally calibrate some of our more complicated bits of equipment every 3 months to ensure the integrity of the measurements. Electronic equipment is often used as a component in a much more complicated system to derive other values (temp, humidity, pressure etc.). As a customer we can choose the calibration period of the equipment we use it has to be based on data not supposition (e.g drift over a number of years).

If I'm laying in hospital linked up to various machines I want to know they're calibrated and the equipment used to measure them was calibrated.
 
I know from one of my customers they just NEED to calibrate gear which is involved into production once a year. No matter if it's needed or makes sense - it's not allowed to be switched on without the correct calibration sticker. Someone is making a lot of money with calibration there ...

Of course you need to calibrate after a repair but these units are very stable, I really don't have the need for regular calibration for my AP.
In both the companies I put through ISO 9001 certification, calibration schedules and records were mandatory. If the interval was greater than annual, auditors wanted evidence that this was sufficient, which presented some practical difficulties. So we, like most other ISO companies, just bit the bullet and did annual which never raised the question.
 
If I'm laying in hospital linked up to various machines I want to know they're calibrated and the equipment used to measure them was calibrated.

So would I, but an audio analyser isn't a matter of life and death. Medical apparatus is a straw man argument, as unlike an audio analyser, it has electro-mechanical probes and actuators, which are likely to drift out of spec (unlike precision caps and resistors). You can easily test for yourself against another machine or an item of known calibration to see for yourself. If you know the item measured "0.0003% THD @ 10KHz" and that's what you see, then you know that your design can go to John Atkinson for review and he'll see the same figures.

If you're talking about RF gear, where you'll get fined millions by government bodies if you make a mistake, then you really need calibration certification. And if you get a stern letter from one of these bodies, you can use that certificate in your defence. Again, an audio analyser being out of cal isn't going to result in aircraft comms being affected, or someone getting the wrong oxygen level in their blood.

Unless you're working at a giant corporation and have the worry of the FCC swooping on you, then calibration simply isn't a big deal for smaller OEMs. My SYS-2722 meets every spec. My UPV meets the spec in the (very lengthy) calibration book that I got with it 10 years ago.

Calibration is highly profitable. Firms can charge large fees and they don't need to employ graduates to perform the work. Unless the FCC is on your back and you need to cover your back legally, I fail to see why an audio analyser needs regular certification. If *you know* it hits the spec, you can send it out. The RF arena is different and outside the scope of an audio website.

The discussion has been derailed by 'my firm can afford to throw money at self-adhesive labels every year', instead of anyone answering where the 555 and 555B models differ, which was my reason for bumping the thread. No one's even mentioned Samuel's PDF, which suggests that the 2722 has a better oscillator. This ought to be big news for this site. Way beyond knowing whether your machine has a sticker with the right date. Why did Samuel see these measurements? Is this a reason why the B machine came out?

NB - Samuel now works in RF. No snake oil in that field. He made the right decision.
 
So would I, but an audio analyser isn't a matter of life and death. Medical apparatus is a straw man argument, as unlike an audio analyser, it has electro-mechanical probes and actuators, which are likely to drift out of spec (unlike precision caps and resistors). You can easily test for yourself against another machine or an item of known calibration to see for yourself. If you know the item measured "0.0003% THD @ 10KHz" and that's what you see, then you know that your design can go to John Atkinson for review and he'll see the same figures.

If you're talking about RF gear, where you'll get fined millions by government bodies if you make a mistake, then you really need calibration certification. And if you get a stern letter from one of these bodies, you can use that certificate in your defence. Again, an audio analyser being out of cal isn't going to result in aircraft comms being affected, or someone getting the wrong oxygen level in their blood.

Unless you're working at a giant corporation and have the worry of the FCC swooping on you, then calibration simply isn't a big deal for smaller OEMs. My SYS-2722 meets every spec. My UPV meets the spec in the (very lengthy) calibration book that I got with it 10 years ago.

Calibration is highly profitable. Firms can charge large fees and they don't need to employ graduates to perform the work. Unless the FCC is on your back and you need to cover your back legally, I fail to see why an audio analyser needs regular certification. If *you know* it hits the spec, you can send it out. The RF arena is different and outside the scope of an audio website.

The discussion has been derailed by 'my firm can afford to throw money at self-adhesive labels every year', instead of anyone answering where the 555 and 555B models differ, which was my reason for bumping the thread. No one's even mentioned Samuel's PDF, which suggests that the 2722 has a better oscillator. This ought to be big news for this site. Way beyond knowing whether your machine has a sticker with the right date. Why did Samuel see these measurements? Is this a reason why the B machine came out?

NB - Samuel now works in RF. No snake oil in that field. He made the right decision.

As you said, the performance of an audio analyzer is certainly not a matter of life and death, but if you have been following the progression of audio development and want to be a member of an up to date and informed community, the APX555 is an easy way to to attain the status (at a 30K+ investment!) There isn't much in the marketplace that will take you further... the Groner stuff was something I experimented heavily with but didn't get me much further than the current state of the art.... without pain.

As a former 40 + year professional in the high end T&M Calibration DC to GHz arena with an additional 10 years in audio product design/development, I like to know what is going on in the present and hopefully future of SOTA products.
 
My point is you can choose any calibration frequency you want, or none at all, but if you're operating in a professional field you may have to defend that decision so it would have to be based on data, not supposition. ISO17025 lays it all out for labs that want accreditation.

We also manufacture and calibrate sound measurement equipment. That certainly does drift!
 
Calibration of an AP machine (or whatever) only makes sense if you also calibrate the operators on a regular basis ;-)
Most of the issues with credibility of measurements are operator/setup issues.
 
FYI some have bought the latest APx555 B revision and found it to underperform mine. I seem to have a unit that outperforms the spec. :)
 
That's interesting. The smaller APs I know (515, 525) all outperform their specs, my 515 is in terms of input noise better as the 525 datasheet. (1,1uV, 0,83uV(A) - spec of 525 is <1,3uV, spec of 515 <1,4uV) All of the 515/525 have input noise in this range (cause this was a discussion once with a customer cause of the "high" input noise, we tested a few).
 
That's interesting. The smaller APs I know (515, 525) all outperform their specs, my 515 is in terms of input noise better as the 525 datasheet. (1,1uV, 0,83uV(A) - spec of 525 is <1,3uV, spec of 515 <1,4uV) All of the 515/525 have input noise in this range

How does the (shorted) input noise vary across the input ranges when you manually set ranging?

The 1.1uV is a best case, yes?
 
The 1.1uV is a best case, yes?
I have an 56R at the input cause that was laying around :facepalm: and it's at it's lowest gain setting.
Unsurprisingly it rises with higher input ranges ... but I never protocoled how quickly.
 
FYI some have bought the latest APx555 B revision and found it to underperform mine. I seem to have a unit that outperforms the spec. :)
This concerns me. I have an abiding respect for Mr Groener (his chops are proven). If what he wrote is typical, but was below the 2722 - and what you are saying is also true, then that suggests the performance of the $42K machine that you buy can be somewhat of a crap shoot... Please tell me this is not the case!
 
Interesting to me that Audio Precision sees the the existing 2722 units as the competition to their new production APx555B machines. The 2722 units are now deemed to be obsolete as in no longer supported.

I still have a 2522 machine in the cage and a APx555 on the bench.

Years ago I did have a couple filter cards installed in the 2522 and the unit calibrated.
The 555 has never been off my bench or been "calibrated".

Recently I did send in a 1/4" microphone to GRAS for calibration.

All just for fun DT
 
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