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| Looking for an audio analyzer |
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| 1audio:
For what its worth I use regularly a Boonton 1120, a modified Shibasoku 725, a QA401 and 4 different soundcards. Its not the tools but knowing what to look for. Any of these can show you pretty much any aberration if you know what to look for. The QA401 + a handful of BNC-RCA or BNC-Banana adapters makes it compatible with 90% of anything you may want to do. There was a possible promise of a standard audio driver for the QA401 but not yet. And there is an API if you want to create specific tests or test suites. I think its the best value simple because it will just work. A sound card + HPw works or Arta or REW or RMAA or . . . will work fine after you sort it out which could take some time even if you have done it before. Even RMAA which is simple can lead you astray if you don't have the right interfaces selected etc. Jen's analyzer will be at least 2X a QA401. And its slightly better than an Emu 1616M or 1212M on the ADC (better analog) but the EMU DAC is not as good. (I mostly use the EMU in XP for stability but Win 10 is OK with a clean install). The QA401 has an automatic input attenuator but is still limited on its peak input. Same for most audio stuff. Very few won't smoke when measuring AC line distortion for example. However I need to measure everything from headphones and speakers to SOTA DAC's so many options are needed. Some which can't be done with an APx555 without an additional $10K of addons. The RME babyface would be a great starting point with software (RMAA?) and some interface cable/adapters. Learn how to make some measurements and how to see when its all lying to you. When you need more look at the options. |
| DaJMasta:
Thanks for all the input so far, the discussion of the differences between the frontends of an audio analyzer vs. that of a soundcard have been helpful too. I think part of the appeal of a purpose-built analyzer, at least initially, was that it was so well characterized. If I make a mistake in taking a measurement and realize it, then the finger can almost never be pointed at an analyzer because all the specs are laid out and built to be stable. It's been amazing to me how many high-end interfaces there are available which don't even have a manufacturer-specified noise floor or THD rating, but every dedicated analyzer will have data on that, evenness of frequency response, and many other aspects. Looking around, there has been some helpful info in the form of consumer run tests of some of these itnerfaces, but the "guarantee" of reputable test equipment has it's appeal. That said, most of the cheaper, but still well performing, dedicated analyzers aren't as well suited for my FFT tasks as a soundcard is. All-in-one units like the UPL make extended data capture a pain, and computer-attached units like the ATS-2 have options, but without ASIO or other sound drivers, don't have easy ways of getting that data into other software, some of which seems ideal for the kinds of recording and visualization I want to do. Not being in an industrial environment or testing totally unknown systems means the input protection and attenuation options are less important, and if I really wanted absolutely quantifiable numbers for signal strength and whatnot.... I can just use my multimeter or scope to get the voltage of a sine at X output level and do a little math to convert the axes to volts or what have you. I've also been sort of insisting on the THD+N figure specifically for the +N, something I've run into issues with before. I've had pretty significant hum on supposedly good internal PC sound cards, and have only been satisfied with the noise floor for normal recording levels with my latest refresh of equipment - both the mics and the interfaces I've been using before have been audible. While I don't expect to be hearing noise under -100dB or something, I have heard some in the -90s, so I wanted to aim as low as possible to avoid issues with it, even if the parts of the signal I probably care about are still well above even the audible noise floors. The EMU cards sound like great choices, and they're pretty cheap on ebay right now, but they're internal and I don't want to be hauling around a desktop to take measurements... plus my previous issues with in-case emi or power conditioning related hum. Looking at lots of external interfaces, the newer Motu 624 looks like a good contender. Notably lower advertised noise floor than the babyface pro at only slightly more price, a compact size, and the signal paths seem to be the same hardware as the Motu 1248, which has been characterized by some end users and seems to meet its spec and have very flat frequency response. A Prism dScope III ticks all the boxes across the board and seems like a great unit for the $6000 or so price tag..... but that's still quite a price tag, and I think a lot of its capability would be lost on my applications. I agree the QA401 seems like a clear winner for general audio testing in terms of value for performance, but if I can get a good preamp with phantom, the right connectors, standard sound drivers to use whatever software I want, and a lower noise floor out of an interface, I think it's a better choice for me. So that's the plan for now, a good interface coupled with rightmark and spectrum lab because they're free. Once I get a better feel for the software side and the measurements/data recording I want to do, I can invest as needed in a software suite. |
| amirm:
--- Quote from: DaJMasta on January 10, 2017, 07:47:52 am ---I think part of the appeal of a purpose-built analyzer, at least initially, was that it was so well characterized. If I make a mistake in taking a measurement and realize it, then the finger can almost never be pointed at an analyzer because all the specs are laid out and built to be stable. --- End quote --- This is by far the reason I use my Audio Precision. I bought a TI EVM with their nice ADCs and AES capture but I had no idea what it was supposed to have spec-wise. I publish my results so I need others to be able to trust and/or repeat them. With sound card you just can't do that. There are also potential issues around ground loops and such with PC cards which are reduced if not avoided by using an external analyzer. Still, the cost is just way too high for satisfying one's curiosity and or casual measurements. So going with the PC solution as you mention is the right path for you for sure for now. |
| ci11:
--- Quote from: DaJMasta on January 10, 2017, 07:47:52 am --- Not being in an industrial environment or testing totally unknown systems means the input protection and attenuation options are less important, and if I really wanted absolutely quantifiable numbers for signal strength and whatnot.... I can just use my multimeter or scope to get the voltage of a sine at X output level and do a little math to convert the axes to volts or what have you. --- End quote --- Probably a workable idea but the linearity and flatness of frequency response of the DMM and especially a scope you intend to use should be checked since accuracy at audio frequency bandwidth is not what the designers of these devices usually have in mind. Many DMMs can only measure Vrms out several hundred Hz and not beyond. --- Quote --- The EMU cards sound like great choices, and they're pretty cheap on ebay right now, but they're internal and I don't want to be hauling around a desktop to take measurements... plus my previous issues with in-case emi or power conditioning related hum. --- End quote --- The E-MU 1616m was made with 3 different interfaces: PCI, PCIe for desktop and a Cardbus interface for use with laptops. All function equally well. And the E-MU 1616m "Microdock", the breakout box where all connections are made to analog and digital I/O, supplies 48V Phantom on both mic input channels. Also attached is a plot from the noise floor plot of my 1616m using ARTA. Input was shorted but plot used the Hanning window but not averaged. Averaged noise floor would be around -150dB for this setup. The 1616m was plugged into wall AC and there does not appear to be an issue with EMI or hum, even at 60/120Hz here. |
| DaJMasta:
Very impressive! I think all I had seen on ebay was the internal card versions, and PCMCIA would need an adapter for modern laptops (I've had a couple laptops since I had one with a PCMCIA slot!), but adapters certainly do exist. I remember a little after when Creative bought them, I was looking at sound cards including a couple of E-MU options. I remember them not actually being too expensive, it's neat to think they were well enough designed to stand up so well for so long. Given that they were priced to compete with high end consumer options, I wouldn't have expected the longevity. |
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