I suppose that depends on what you mean by "very good". The Focusrite is 0.002%. Some people may demand greater precision.
Looking for audio analyzer and have been told multiple times to go computer software route.
- Thread starter saabracer23
- Start date
trainbuftony
Electron Herder
I'm partial to dedicated hardware.
Buy nice or buy twice.
I've got an old Hp distortion analyzer which predates dos. Still works fantastic and always tells the truth. How many software updates before your computer based solution ends up as useless landfill?
I'm probably the lone voice of dissent but I like to buy a quality tool that can't go obsolete, and which is easy to service.
HP is my brand of Choice.
Buy nice or buy twice.
I've got an old Hp distortion analyzer which predates dos. Still works fantastic and always tells the truth. How many software updates before your computer based solution ends up as useless landfill?
I'm probably the lone voice of dissent but I like to buy a quality tool that can't go obsolete, and which is easy to service.
HP is my brand of Choice.
Steven Tate
CEO Flat Forehead Soc.
I'm sure there are some very good sound cards that will give good info. The main thing you want to see is a noise floor of something around -110 db plus low THD in the signal generator.
It's a question of how much you want to spend, whether or not a hardware option is available and what level of precision you're looking for. A Panasonic VP-7725 might be £1000 second hand. An Audio Precision might be £20,000.
Arta is free and an audio interface might be £200.
Only the OP knows what he needs.
Arta is free and an audio interface might be £200.
Only the OP knows what he needs.
I like HW solutions as much as the next guy but in all honesty for audio applications once you get much beyond 0.01% it's all academic anyway. Unless you want to get into a pissing contest over at ASR the difference between .01, .001, and .0001 is pretty irrelevant. Save your money.
Also, speakers are BY FAR the dominant source of distortion in an audio setup. A few percent is considered exceptional, and at the lower end of the frequency spectrum 5-10% is quite standard.
I'm certainly not saying you should accept that kind of performance from your test setup, but it helps keep things in perspective!
I'm certainly not saying you should accept that kind of performance from your test setup, but it helps keep things in perspective!
My "shoestring" solution is a Motu M-2 audio interface (~$200) paired with ARTA software (free). I cobbled together cables, nice dummy loads and built homemade attenuators along with connections for a couple of DVM's and a digital scope. I can run both channels simultaneously (only have to switch the ARTA software back and forth between channels) and I feel like I've been able to make solid frequency response and THD+N measurements on anything that I've wanted to work on.
Biggest issue has been ground loops through the USB connections, specifically when having the Motu and the DSO both connected to the laptop and trying to measure the inverting channel on an early Carver M-1.0T - that got freaky until I realized what was happening.
All that being said, I really think the QA-403 is a sweet looking piece of gear/software and will probably pull the trigger on one this year (unless I happen to run across anyone selling an older model QA-401 or QA-402 for less.) Right tool for the job, without really busting the budget.
Biggest issue has been ground loops through the USB connections, specifically when having the Motu and the DSO both connected to the laptop and trying to measure the inverting channel on an early Carver M-1.0T - that got freaky until I realized what was happening.
All that being said, I really think the QA-403 is a sweet looking piece of gear/software and will probably pull the trigger on one this year (unless I happen to run across anyone selling an older model QA-401 or QA-402 for less.) Right tool for the job, without really busting the budget.
The QA-403 is a nice looking unit. Has some cool measurement capabilities. I still like my Picoscope which can measure FR out to 1MHz using the internal sig gen which is useful for tuning the feedback of a tube amp as many times the issues are near or above 100k. The scope function will go beyond that but the sig gen maxes at 1MHz. I also use ARTA but mostly for speaker measurements. I have a woofer tester from Parts Express which has some easy to use features of its own. Can't have too many tools.
John
John
That's what I always have to tell my wife! LOL
Those Picoscopes are cool, definitely fill a niche (plus can save a lot of space if you already have a laptop or PC at the bench). The 2206B is still available, and the 2207B and 2208B look to be identical except higher bandwidths/sampling rates. I do like having my Keysight DSOX above the bench, plus it interfaces to the laptop via USB so I can capture traces and data if I need to. To each their own, right?
I've accumulated several different pieces of gear to measure distortion. I've not become an expert on any of them, but have been spending many hours on most of them to better understand them and use them properly. Here's my take on each:
Amber 3501A: Compact, easy to use, and good for quick measurements such as when testing rebuilt amps, preamps, etc. Not as accurate as some units, but still useful and usually priced pretty well.
Sound Technology 1701A: Huge, but well-built and seems pretty accurate for its age and design. Plenty of settings/features, but probably best purchased if you find a good price.
HP339A: Very accurate, good performing low-distortion oscillator. Very nice quality build and meter. Quick to use when one learns the proper operation. Much more compact than the ST. Important to get a unit in good condition - it's a lot of work to repair these, from what I've seen online.
HP8903B: Going away from analog to digital readouts, and adding some features. Still no longer current, but also very fast to use and get good, accurate readings (or accurate enough for repair/refurb purposes). Prices have risen because they are still very useful, valid instruments. Pete Millet wrote software to automate readings using GPIB. I really like mine, and recent replacement of electrolytic caps and some other maintenance increased accuracy. When I want extra accuracy I use one of my ultra-low distortion oscillators.
EIDA Cosmos ADC and APC: Purported to be extremely low distortion. If you thought the documentation on other gear was sparse, get ready for a Chinese-built unit designed and produced by a Russian engineer. You'll have to either be very familiar with this methodology or find some help online. I've taken some measurements recently and the units do seem to perform very well. They are also affordable, but you need other gear to supplement so the cost adds up. You can use the ADC with a low-distortion oscillator, or buy the APC which is quite good.
Scarlett 4i4: Higher distortion than the Cosmos, but you null out the distortion to a great extent when you create a profile in the software (I'm using REW). About as easy (or not) to use as the Cosmos.
Akitika ultra-low distortion oscillator: Really nice bit of kit for the price, easy to build and use, and very clean signal.
Finally, I have a Pete Millett sound card interface, which seems to have been designed prior to the abundance of good quality USB sound cards and seems to have been designed for internal computer sound cards. It uses a digital display that seems to be unavailable and one of the ICs has become rare and expensive, so while he still sells the face plates and circuit boards on eBay, I'm not sure it's a good choice to try to build now.
Also, I have a KA Electronics ultra low distortion oscillator (balanced or single-ended) and notch filter, and a balanced attenuator. It was easy to build but integrating it into a chassis box with the various inputs, outputs, and switches took me longer to do than building the PCB. Seems to be extremely high performance.
It you are going with sound cards, you do need some sort of attenuator. I've made PCBs for a few different attenuators for use with sound cards and have listed them for sale for cheap here in BT from time to time. I've built several into different boxes for different uses, and they are very compact.
Amber 3501A: Compact, easy to use, and good for quick measurements such as when testing rebuilt amps, preamps, etc. Not as accurate as some units, but still useful and usually priced pretty well.
Sound Technology 1701A: Huge, but well-built and seems pretty accurate for its age and design. Plenty of settings/features, but probably best purchased if you find a good price.
HP339A: Very accurate, good performing low-distortion oscillator. Very nice quality build and meter. Quick to use when one learns the proper operation. Much more compact than the ST. Important to get a unit in good condition - it's a lot of work to repair these, from what I've seen online.
HP8903B: Going away from analog to digital readouts, and adding some features. Still no longer current, but also very fast to use and get good, accurate readings (or accurate enough for repair/refurb purposes). Prices have risen because they are still very useful, valid instruments. Pete Millet wrote software to automate readings using GPIB. I really like mine, and recent replacement of electrolytic caps and some other maintenance increased accuracy. When I want extra accuracy I use one of my ultra-low distortion oscillators.
EIDA Cosmos ADC and APC: Purported to be extremely low distortion. If you thought the documentation on other gear was sparse, get ready for a Chinese-built unit designed and produced by a Russian engineer. You'll have to either be very familiar with this methodology or find some help online. I've taken some measurements recently and the units do seem to perform very well. They are also affordable, but you need other gear to supplement so the cost adds up. You can use the ADC with a low-distortion oscillator, or buy the APC which is quite good.
Scarlett 4i4: Higher distortion than the Cosmos, but you null out the distortion to a great extent when you create a profile in the software (I'm using REW). About as easy (or not) to use as the Cosmos.
Akitika ultra-low distortion oscillator: Really nice bit of kit for the price, easy to build and use, and very clean signal.
Finally, I have a Pete Millett sound card interface, which seems to have been designed prior to the abundance of good quality USB sound cards and seems to have been designed for internal computer sound cards. It uses a digital display that seems to be unavailable and one of the ICs has become rare and expensive, so while he still sells the face plates and circuit boards on eBay, I'm not sure it's a good choice to try to build now.
Also, I have a KA Electronics ultra low distortion oscillator (balanced or single-ended) and notch filter, and a balanced attenuator. It was easy to build but integrating it into a chassis box with the various inputs, outputs, and switches took me longer to do than building the PCB. Seems to be extremely high performance.
It you are going with sound cards, you do need some sort of attenuator. I've made PCBs for a few different attenuators for use with sound cards and have listed them for sale for cheap here in BT from time to time. I've built several into different boxes for different uses, and they are very compact.
Any idea where I could find that software? I've got an HP-IB adapter, and I was thinking of the Home Version of LabVIEW. If I can automate and store the results, it should be quite easy to graph them. I've done some things with L:abVIEW, but I'm sloooow when it comes to writing my own software!
ConradH
Lunatic Member
I use an 8903 with some self-written software. I drive a 2-channel dummy load and just clip-lead the analyzer to whichever channel I want to look at. For a software solution I use Visual Analyser- https://www.sillanumsoft.org/ Works great and has lots of features, including an LCR meter. The problem I have with all software is I don't trust it. There can always be some hidden setup issue that fouls the results. With real hardware you can be more sure of your answers. I also have an older HP 332A and the Bob Cordell THD analyzer I built- http://www.cordellaudio.com/papers/build_a_thd_analyzer.shtml That bottoms out at about 0.0002% midband!
FWIW, I don't measure THD looking for the lowest hardware, nor do I think it correlates to sound quality. I measure it because it gives me clues as to whether something is working correctly. IMO, the most valuable part of a THD analyzer is the residual output that you can put on a scope. That's worth way more than the THD number from a meter.
FWIW, I don't measure THD looking for the lowest hardware, nor do I think it correlates to sound quality. I measure it because it gives me clues as to whether something is working correctly. IMO, the most valuable part of a THD analyzer is the residual output that you can put on a scope. That's worth way more than the THD number from a meter.
http://www.pmillett.com/hp_8903_software.htm
Works well and it's very useful with the 8903A. Has a few little bugs, at least under Win 10, where repeated tests don't always start correctly. I use a NI HPIB/USB adapter.
Just got the laptop with software yesterday to run on my hp8903’s. Can’t wait to try it. Thanks Mr Pete if you are reading this. A hero to us techs.
This makes me wonder, does the hp 8903 have the capability to plot an riaa curve to test phono stage? I was thinking of running a test through my hegeman labs reverse riaa but not sure that would work.