EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: KungFuJosh on June 27, 2023, 12:23:37 pm
-
I've been interested in getting a spectrum analyzer, primarily for audio equipment testing, for a while. This seems to be a weird quest for some reason. It seems most suggestions are to lean towards basically any sound card for a computer, but I'd prefer something standalone, unless there's something 'attached' that's really nice. I'd also like the "instant gratification bode plot" feature. 😉
100Hz to 20kHz would be the absolute minimum range, but down to 10Hz or 20Hz would be better. It seems the fancier new SAs all bottom out at 9kHz for some reason.
-
I've been interested in getting a spectrum analyzer, primarily for audio equipment testing, for a while. This seems to be a weird quest for some reason. It seems most suggestions are to lean towards basically any sound card for a computer, but I'd prefer something standalone, unless there's something 'attached' that's really nice. I'd also like the "instant gratification bode plot" feature. 😉
100Hz to 20kHz would be the absolute minimum range, but down to 10Hz or 20Hz would be better. It seems the fancier new SAs all bottom out at 9kHz for some reason.
SA are primarily RF instruments.
SA for audio are called audio analysers and there are many of those.
You won't like the price.
Take a look at Quant Asylum.
Or stick with audio interfaces...
-
I've got a 35665A which is built exactly for this purpose, and in all honesty lately I keep thinking about getting rid of it and using a sound card instead.
It's nice having a standalone thing on the bench that you can just plug into and go, but it's also pretty slow/limited compared to computer based solutions.
-
If you can live with 1/3rd octave steps maybe something like the old klark teknic dn60
-
I’m using an external pro USB audio interface, 24 bit resolution with 192KHz sampling rate. REW is an excellent free app for spectrum analysis, I also have Jupyter notebook to do the same FFT Rew can do. Tons of discussions on how to do it and what interface has the lowest noise floor and distortion - see https://www.diyaudio.com/community/threads/how-to-distortion-measurements-with-rew.338511/ (https://www.diyaudio.com/community/threads/how-to-distortion-measurements-with-rew.338511/)
Back to you post - it’s attached, and REW updates the spectrum display real time on screen. Can generate signals too, however it’s not as good as a standalone precision Wien bridge. Much discussion on that too.
-
Fiiiiiiiiiiine. Software with sound card and/or audio box like the QA403 Audio Analyzer is probably the way to go. The QA403 makes me want to make something myself though.
I already have a nice Roland Studio Capture, so I guess I should look at what software is good. I'll check out REW, what else is good?
Edit: For the record, I really would prefer to avoid using my DAW for this. I would like at least the software to be standalone.
-
Two more software - free and paid:
https://sourceforge.net/projects/audmes/
https://artalabs.hr/
And again, it was not a big deal for me to roll my own 64K window size FFT in Python either.
If you like dedicated hardware, you can make a raspberry pi4 running the FFT with Jupyter notebook serving your browser to view - however you’ll not be refreshing as often as a PC or Mac does.
-
There is the HP 3561A which is nice. Old but nice.
-
https://www.virtins.com/ (https://www.virtins.com/)
They have some interesting stuff. Not free, but free to try for a while.
-
https://www.ap.com/analyzers-accessories/apx555/ (https://www.ap.com/analyzers-accessories/apx555/)
-
There is the HP 3561A which is nice. Old but nice.
Second that, they're nice, but the screens tend to fail easily because of the flyback. They do DC - 100kHz, I've had one for years.
-
I have an HP 8903B but lately have been using REW software along with a Focusrite Scarlet Solo. You can see, for the cost, the performance is good: https://www.eevblog.com/forum/testgear/question-cheap-pure-sine-wave-genertor-1khz/msg4737746/#msg4737746 (https://www.eevblog.com/forum/testgear/question-cheap-pure-sine-wave-genertor-1khz/msg4737746/#msg4737746)
-
What is the problem a wide BW SA has with low frequencies ? And why are AA so expensive then ? Measuring up into the GHz must be way harder and more expensive than audio to AM radio Frequencies.
IDK I just figured a SA could do better, even if they added another PCB for LF
-
I feel that pretty much all the audio analysers are 24bit adc's with large signal to noise ratio's of upt 120dB. Plus many different audio/Blue tooth/I2s/rub & buzz and headphone measurment applications. They all perform both digital & analogue domain measurments The APX555b offers 1.2M FFT's from dc-200Khz.
Does this justify the cost, for hobbists no it's out of the equation. Although these are mainly geared for production line testing with they ability to set up multipule tests in sequence mode
We have four audio analysers R&S UPV66 all options / AP APX555B most options / Prism sound D scope series III / Standford research SR1 (under rated in my book).
IMHO the Picoscope 4262 is also a great device for audio investigation up to 16 bits of resolution 16Mpts buffer, decent analogue genny and really good FFT's and for the cost its decent, a couple of us on here use them regularly for good reasons.
As good as all these audio anaysers are, I still use the Lecroy attached at the same time to the signle ended analogue outputs using both time & frequency domain above the usual audio BW restrictions, you can see a lot more going on further up the rev range if you like ;D
This peaked my interest although purely an analogue domain unit, its features and size make it ideal for a portable in the field unit.
https://www.virtins.com/RTX6001.shtml (https://www.virtins.com/RTX6001.shtml)
Would also agree with the HP 3561A as well if you have the spa on the bench.
-
We second the PicoScope 4262, although don't use as much as we should since it requires a laptop, and we much prefer a dedicated standalone DSO. Also does quite a respectable job as a low frequency FFT analyzer, or FRA.
Best,
-
We second the PicoScope 4262, although don't use as much as we should since it requires a laptop, and we much prefer a dedicated standalone DSO. Also does quite a respectable job as a low frequency FFT analyzer, or FRA.
Best,
1+ for Pico 4262
-
In my view it's unclear if the OP is looking for a spectrum analyser working in the audio band or a so called "audio analyser" with all the audio related measurement function.
If the request is about the second, there are some 90s R&S UPA-UPL-UPV etc. all-in-one boxes on the bay site at interesting price. As usual there are limits like FFT resolution, no more support etc. some are MS-DOS based machines.
With about 2000 USD you get a UPA that is still a good machine for not-so-demanding measures.
I personally own a AP SYS-2300, still impressive but still pricey
-
In my view it's unclear if the OP is looking for a spectrum analyser working in the audio band or a so called "audio analyser" with all the audio related measurement function.
What I really wanted was instant gratification bode plots (for things like guitar pickups, and speakers), but I'll stick with my scope for now, and eventually try out the software based stuff.
-
Focusrite 4i4 has only one linear source and about 5 in switching mode, so the sinusoidal signal is not extremely clean in generator mode. I am attaching a photo for compliance, although one of the sources is masked by cables. With REW I noticed that after 25kHz the signal drops and above 30kHz it starts to have phase noise. In loop mode, the oscilloscope seems to provide a synthetic signal because everything seems perfect. I tested with the Fluke196C, which I trust.
I also asked on this forum why most SAs start with 9Khz or a few with 5Khz. One of the answers was that there is a problem with the input capacitor. For the analog situation when the audio signal is mixed with another one, I found out that in the first Hz's nothing conclusive can be measured because the phase noise from the local oscillator extends too much. They are just findings in amateur conditions.
-
What I really wanted was instant gratification bode plots (for things like guitar pickups, and speakers), but I'll stick with my scope for now, and eventually try out the software based stuff.
Soundcard and REW provides frequency response of amplitude and phase, from 2Hz to 96kHz. Compensation is automated for 2Hz to circa 10-20Hz, and from circa 40k to 96kHz where the soundcard and probes and test rig may have a non-flat response. That is, as I understand it, your instant 'Bode' plot. For some esoteric audio applications where feedback related stability is a concern, the 96kHz upper limit can be too low, as measurement of gain and phase margins require a wider bandwidth (and hence a need to go to something like a Picoscope 2206B with FRA software to extend Bode plot bandwidth to 1MHz).
Focusrite 4i4 has only one linear source and about 5 in switching mode, so the sinusoidal signal is not extremely clean in generator mode. I am attaching a photo for compliance, although one of the sources is masked by cables. With REW I noticed that after 25kHz the signal drops and above 30kHz it starts to have phase noise. In loop mode, the oscilloscope seems to provide a synthetic signal because everything seems perfect.
I'm unsure what you are describing. You seem to infer that internal circuitry of the 4i4 is adding spurious signals to a generated sinewave, but only show a photo rather than a loopback response (!?) Your test setup may need some refinement, although it would be expected that a raw loopback would show the effects of high frequency roll-off from either the DAC side, or the ADC side, or your interconnection, which is why REW allows you to calibrate out such droop.
-
In my view it's unclear if the OP is looking for a spectrum analyser working in the audio band or a so called "audio analyser" with all the audio related measurement function.
What I really wanted was instant gratification bode plots (for things like guitar pickups, and speakers), but I'll stick with my scope for now, and eventually try out the software based stuff.
If/when you decide to try out the software-based stuff, in addition to REW you might want to look at a software package called ARTA as well. It has a number of different bode plot options to choose from, including ones that are essentially real-time using swept-sine or noise waveforms. I haven't used it, but from the documentation it is written by someone who understands signals and systems pretty well.
jason
-
I'm getting the hang of using the 35660A, 35665A, and the 3588A when fixing stereo and radio projects.
Crossovers and filters can be checked to see if channels match by using the built-in source or your frequency generator.
Set the span and the marker's location and your off and running.
The analyzers are self-calibrating and easy to use but I'd recommend that the analyzer's power supplies be rebuilt.
(https://i.imgur.com/7bNFeXd.jpg)
(https://i.imgur.com/vpv8Dww.jpg)
-
Soundcard and REW provides frequency response of amplitude and phase, from 2Hz to 96kHz.
I assume you're referring to hardware limitations depending on the sound card in use? Or does REW have frequency range limits?
-
REW has a nominal sine signal generator range from 1Hz to half the sampling rate of the soundcard used (so for nearly all soundcards that means 96kHz upper limit). The impedance measurement also uses a sinewave frequency sweep, which is from half the lower setting frequency, which afaik is 0.1Hz (I beta tested this a few years ago when I asked about lowering the low frequency limit to get a better understanding of choke impedance below the previous limit of 2Hz).
Hardware limitations mean that the soundcard and probes will likely have increasing roll-off below about 10-20Hz, and above about 40-50kHz, which is compensated for by using a calibration curve to get a net flat response for loopback, although the DUT doesn't experience a flat response signal and the compensation starts to introduce noise/artifacts depending on the level of roll-off being compensated. The low frequency response of a soundcard may be able to be modified (eg. by increasing value of any coupling caps, or removing the coupling caps and managing for a dc input). The high frequency response may be modified by adjustment of probe compensation or tweaking the compensation circuit in the probe.
-
What I really wanted was instant gratification bode plots (for things like guitar pickups, and speakers), but I'll stick with my scope for now, and eventually try out the software based stuff.
Soundcard and REW provides frequency response of amplitude and phase, from 2Hz to 96kHz. Compensation is automated for 2Hz to circa 10-20Hz, and from circa 40k to 96kHz where the soundcard and probes and test rig may have a non-flat response. That is, as I understand it, your instant 'Bode' plot. For some esoteric audio applications where feedback related stability is a concern, the 96kHz upper limit can be too low, as measurement of gain and phase margins require a wider bandwidth (and hence a need to go to something like a Picoscope 2206B with FRA software to extend Bode plot bandwidth to 1MHz).
Focusrite 4i4 has only one linear source and about 5 in switching mode, so the sinusoidal signal is not extremely clean in generator mode. I am attaching a photo for compliance, although one of the sources is masked by cables. With REW I noticed that after 25kHz the signal drops and above 30kHz it starts to have phase noise. In loop mode, the oscilloscope seems to provide a synthetic signal because everything seems perfect.
I'm unsure what you are describing. You seem to infer that internal circuitry of the 4i4 is adding spurious signals to a generated sinewave, but only show a photo rather than a loopback response (!?) Your test setup may need some refinement, although it would be expected that a raw loopback would show the effects of high frequency roll-off from either the DAC side, or the ADC side, or your interconnection, which is why REW allows you to calibrate out such droop.
I am attaching a diagram with the output from 4i4 for 20kHz sine somewhere at 1/2 FS with the specification that it is not in the loop. Everything is satisfactory, but higher in frequency we have artifacts. I am attaching two more diagrams, one up to 250kHz and the next up to 2.6MHz. The noise generated by the switching sources can be clearly observed, although it is possible that some artifacts have another origin. The noises in the last diagram do not disappear if the signal is off, but are proportional in any situation to the level of the master potentiometer. These disturbances are best seen with the oscilloscope on a rectangular signal because they have about 12-15% of the useful value. The spectral components used in the composition of the rectangle are stable over time, but the noise of the switching sources wanders continuously. I use an LC filter with fc =136Khz, N=7 at the output of Focusrite to clean all the radio frequency when I need a sine wave 20Hz-100kHz. After all, it's a 200 Euro sound card and for the hobby it's just fine.
-
I am attaching a diagram with the output from 4i4 for 20kHz sine somewhere at 1/2 FS with the specification that it is not in the loop. Everything is satisfactory, but higher in frequency we have artifacts. I am attaching two more diagrams, one up to 250kHz and the next up to 2.6MHz. The noise generated by the switching sources can be clearly observed, although it is possible that some artifacts have another origin. The noises in the last diagram do not disappear if the signal is off, but are proportional in any situation to the level of the master potentiometer. These disturbances are best seen with the oscilloscope on a rectangular signal because they have about 12-15% of the useful value. The spectral components used in the composition of the rectangle are stable over time, but the noise of the switching sources wanders continuously. I use an LC filter with fc =136Khz, N=7 at the output of Focusrite to clean all the radio frequency when I need a sine wave 20Hz-100kHz. After all, it's a 200 Euro sound card and for the hobby it's just fine.
Does '1/2 FS' mean you use a sampling frequency of 96kHz with a nominal 48kHz bandwidth?
Can you post a spectrum from say 10kHz to 2.6MHz, rather than with separate spectrum widths, to give confidence that the artifacts are shown along with the generated signal and its harmonics.
The 240kHz artifact is pretty much at the noise floor level.
The 1.1MHz to 2MHz artifacts may be just a result of your measurement system and ground/parasitic loops, given they don't disappear when the signal is off.
Can you elaborate on what you mean when talking about a 'rectangular signal'.
For use in audio measurements, I can't see what influence any soundcard artifacts in the low MHz range (or even at 250kHz if that is an actual artifact) would have on any measurement accuracy or outcome or ???
If the soundcard was in use at the same time, and in the same measurement setup along with an instrument that has wider bandwidth, then yes the other instrumentation may well be affected (eg. a DVM with 300kHz bandwidth for rms voltage, or an alternate instrument for Bode plotting like a Picoscope), but that seems to be getting into some exotic test setups where one would have to be aware of lots of potential issues.
-
I have a Panasonic VP7722A which is a very nice analyser. Being older it does not have a big graphical display that the more modern ones have, but it is simple to use and has a very low THD floor (around 1ppm or 0.00010%). Unlike some pure analog analysers like the HP 8903B (which I owned in the past) this one uses DSP to individually measure the fist 10 harmonics. The front panel can only display the first 5 but you can grab the others over GPIB. The DSP can also average out noise so that you can measure only THD in addition to THD+N. It also does IMD, SNR, and other things.
I have also used a sound card plus software (REW, Rightmark audio analyser, others), but I prefer a standalone instrument for basic measurements. There is something about cabling up a DUT to the front panel jacks, pushing a few buttons, and seeing a measurement appear on an LED display. The main benefit of the software solution is the FFT display, plus easily saving the results. The drawbacks are plenty: booting PC and software, using keyboard and mouse instead of buttons (touch screen would be nice but I don't have), and the need to roll your own interface between amplifier output and sound card input so that you don't blow up the latter.
-
I am attaching a diagram with the output from 4i4 for 20kHz sine somewhere at 1/2 FS with the specification that it is not in the loop. Everything is satisfactory, but higher in frequency we have artifacts. I am attaching two more diagrams, one up to 250kHz and the next up to 2.6MHz. The noise generated by the switching sources can be clearly observed, although it is possible that some artifacts have another origin. The noises in the last diagram do not disappear if the signal is off, but are proportional in any situation to the level of the master potentiometer. These disturbances are best seen with the oscilloscope on a rectangular signal because they have about 12-15% of the useful value. The spectral components used in the composition of the rectangle are stable over time, but the noise of the switching sources wanders continuously. I use an LC filter with fc =136Khz, N=7 at the output of Focusrite to clean all the radio frequency when I need a sine wave 20Hz-100kHz. After all, it's a 200 Euro sound card and for the hobby it's just fine.
Does '1/2 FS' mean you use a sampling frequency of 96kHz with a nominal 48kHz bandwidth?
Can you post a spectrum from say 10kHz to 2.6MHz, rather than with separate spectrum widths, to give confidence that the artifacts are shown along with the generated signal and its harmonics.
The 240kHz artifact is pretty much at the noise floor level.
The 1.1MHz to 2MHz artifacts may be just a result of your measurement system and ground/parasitic loops, given they don't disappear when the signal is off.
Can you elaborate on what you mean when talking about a 'rectangular signal'.
For use in audio measurements, I can't see what influence any soundcard artifacts in the low MHz range (or even at 250kHz if that is an actual artifact) would have on any measurement accuracy or outcome or ???
If the soundcard was in use at the same time, and in the same measurement setup along with an instrument that has wider bandwidth, then yes the other instrumentation may well be affected (eg. a DVM with 300kHz bandwidth for rms voltage, or an alternate instrument for Bode plotting like a Picoscope), but that seems to be getting into some exotic test setups where one would have to be aware of lots of potential issues.
Sorry for rectangular and FS. I had in mind square wave and Full Scale respectively. Now I have calibrated the board, I have disconnected all the unnecessary devices nearby and the LED lights. I use RG316 cables and everything is well shielded. I am attaching two diagrams with a 20kHz signal / around 55mVeff measured with the oscilloscope at the input of the analyzer and then removed. I immediately connect with the generator off and it can be seen that the switching sources are still there or somethings. You are right that devices connected together can influence each other and that radio frequency artifacts do not matter in audio. However, some high-performance amplifiers can exceed 500Khz and I heard that ten times the band limit is needed for tracking tests phase change. In short, to work correctly between 20Hz and 20kHz, it must have minimum attenuation between 2Hz and 200kHz.
-
Sorry for rectangular and FS. I had in mind square wave and Full Scale respectively. Now I have calibrated the board, I have disconnected all the unnecessary devices nearby and the LED lights. I use RG316 cables and everything is well shielded. I am attaching two diagrams with a 20kHz signal / around 55mVeff measured with the oscilloscope at the input of the analyzer and then removed. I immediately connect with the generator off and it can be seen that the switching sources are still there or somethings. You are right that devices connected together can influence each other and that radio frequency artifacts do not matter in audio. However, some high-performance amplifiers can exceed 500Khz and I heard that ten times the band limit is needed for tracking tests phase change. In short, to work correctly between 20Hz and 20kHz, it must have minimum attenuation between 2Hz and 200kHz.
Was the last plot made with the same test connections as the first two plots, but just with the soundcard not being asked to generate the 20kHz sinewave tone?
Did you do a reference plot with the same equipment and test connections in place, but the soundcard itself unpowered ?
Can you elaborate on what "ten times the band limit is needed for tracking tests phase change.", as I'm not sure what 'tracking tests phase change' means.
Do you make tests that use the 4i4 to generate signals and apply them to equipment, and have the Sigilent scope connected at the same time for measuring performance of the equipment in the frequency range beyond that of the 4i4 test signals, and is that what you are concerned about?
-
Discontinued, but definitely not a toy:
https://www.rohde-schwarz.com/us/products/test-and-measurement/audio-analyzers/rs-upv-audio-analyzer_63493-7558.html (https://www.rohde-schwarz.com/us/products/test-and-measurement/audio-analyzers/rs-upv-audio-analyzer_63493-7558.html)
Edit: looks like you can still pick up a used one from Ebay for 15-20K USD :)
-
Edit: looks like you can still pick up a used one from Ebay for 15-20K USD :)
I offered them $200. For some reason they didn't accept. 🤷🤣
-
Sorry for rectangular and FS. I had in mind square wave and Full Scale respectively. Now I have calibrated the board, I have disconnected all the unnecessary devices nearby and the LED lights. I use RG316 cables and everything is well shielded. I am attaching two diagrams with a 20kHz signal / around 55mVeff measured with the oscilloscope at the input of the analyzer and then removed. I immediately connect with the generator off and it can be seen that the switching sources are still there or somethings. You are right that devices connected together can influence each other and that radio frequency artifacts do not matter in audio. However, some high-performance amplifiers can exceed 500Khz and I heard that ten times the band limit is needed for tracking tests phase change. In short, to work correctly between 20Hz and 20kHz, it must have minimum attenuation between 2Hz and 200kHz.
Was the last plot made with the same test connections as the first two plots, but just with the soundcard not being asked to generate the 20kHz sinewave tone?
Did you do a reference plot with the same equipment and test connections in place, but the soundcard itself unpowered ?
Can you elaborate on what "ten times the band limit is needed for tracking tests phase change.", as I'm not sure what 'tracking tests phase change' means.
Do you make tests that use the 4i4 to generate signals and apply them to equipment, and have the Sigilent scope connected at the same time for measuring performance of the equipment in the frequency range beyond that of the 4i4 test signals, and is that what you are concerned about?
In fact, I did the last test with the generator connected as in the first two tests, but switched from on to off. I also did tests with the 4i4 board disconnected from the USB and indeed there are artifacts at about 100Mhz where it probably receives local FM stations and something else around 1.17Mhz but no more. I want to start a real analyzer to properly investigate. As soon as I find out, I'll let you know the result. I understand that this Siglent that I am currently using, is a teaching device and is not 100% reliable. This SA does not behave very well between 9 and 75Khz and therefore in TG mode it has the possibility of normalization for "correction". For now, I have to take out of the warehouse a 25Kg Systron Donner ultra-old mastodon, but rebuilt and tested. I don't want to use the 4i4 board at more than 20Khz because the manufacturer only guarantees up to this point, but I'm intrigued by the noise that appears at the same time as the useful signal and which is dependent on the master level and that's why I think it comes from inside.
I abandoned Focusrite and now I'm testing a white noise generator that seems to be fairly constant between 20Hz and almost 100kHz.
Regarding the 2Hz-200kHz or even 500Khz spectrum, this is the range on which the amplifier must be checked. "Such frequency extension gives the possibility to maintain the phase errors to a very low level". There are many articles on the net and the first one I found quickly is http://www.audioanalogue.com/en/maestro-monoaural/maestro-monoaural-se-power-amplifier (http://www.audioanalogue.com/en/maestro-monoaural/maestro-monoaural-se-power-amplifier)
Surely this issue is known to those who build hi-fi, but my expression was not correct because I am just an audio hobbyist.
-
My preference would also be to use a (high-end) sound card.
If you want a "stand alone" device, you can also combine it with some tablet PC. There are plenty of second hand of these,
-
nenea dani, this is all quite interesting, and I commend your efforts.
The various dc/dc on the soundcard I use (EMU 0404 USB) causes a known corruption within the 96kHz bandwidth of its measurement spectrum, and users identified a way to suppress that by re-routing a signal line away from a dc/dc internal to the soundcard. For the audio work I do, which certainly extends to 96kHz, and beyond, I know there can be some spurious signals down in the weeds on one channel of the soundcard - which can either be overlooked, or the other channel used (some users find that noise aesthetically displeasing, even though it typically doesn't detract from the measurements they are making).
When I need to extend measurements beyond 96kHz, which I certainly do for Williamson amps and typically have to go out past 500kHz to assess feedback gain and phase margins, I use a separate signal generator and a scope and some voltmeters that have enhanced bandwidth, and so there is no opportunity for the soundcard to pollute such measurements. So I'm intrigued as to what type of measurement situation could be corrupted by a soundcard emitting noise well outside its nominal measurement bandwidth. Are you envisaging that the soundcard would be in use at the same time as when measurements were being made by other equipment (which could be corrupted)?
Ciao, Tim
-
nenea dani, this is all quite interesting, and I commend your efforts.
The various dc/dc on the soundcard I use (EMU 0404 USB) causes a known corruption within the 96kHz bandwidth of its measurement spectrum, and users identified a way to suppress that by re-routing a signal line away from a dc/dc internal to the soundcard. For the audio work I do, which certainly extends to 96kHz, and beyond, I know there can be some spurious signals down in the weeds on one channel of the soundcard - which can either be overlooked, or the other channel used (some users find that noise aesthetically displeasing, even though it typically doesn't detract from the measurements they are making).
When I need to extend measurements beyond 96kHz, which I certainly do for Williamson amps and typically have to go out past 500kHz to assess feedback gain and phase margins, I use a separate signal generator and a scope and some voltmeters that have enhanced bandwidth, and so there is no opportunity for the soundcard to pollute such measurements. So I'm intrigued as to what type of measurement situation could be corrupted by a soundcard emitting noise well outside its nominal measurement bandwidth. Are you envisaging that the soundcard would be in use at the same time as when measurements were being made by other equipment (which could be corrupted)?
Ciao, Tim
It seems that we don't have to worry about what happens above 100kHz if we use the Focusrite board only up to a few tens of kHz. Indeed, the sine signal appears polluted and this makes us think, but now I understand that it does not affect the measurements. I'm trying to reach 100kHz in analog mode and that's why I built an up-mixer that moves the whole 20Hz-100kHz spectrum to 1,000,020MHz-1,100.000Mhz and thus there is no longer a problem that SA starts with 9kHz. In this way, I see everything that happens in almost 80dB. I still have to build a pure sine generator at least for 25KHz-100kHz or lower(1kHz-100KHz) and synchronize it with SA. For now I'm struggling with a white noise generator that doesn't allow a precise measurement for fc(-3dB). I still have subtle problems that don't allow me to go below 15-16Hz because I have some phase noise from the local 1MHz oscillator, but I really don't do the performance, just a hobby. I am very careful with the noise and that is why I use multiple decouplings including tantalum and only linear sources. Even if my work is in the area of switching sources here in audio, I don't even want to see it. Sometimes I use an ultra low noise LDO, but here it was not necessary. I cannot connect the SA Siglent input in parallel with the oscilloscope input because the first disturbs the second in the sweep rhythm. However, I think that the Focusrite board is not disturbed by SA Siglent.
-
I appreciate that I'm a bit late to this thread having just joined the Forum, I'm a retired noise and vibration consultant and I have one sound analysing system left that I'd be happy to sell, but I'm not prepared to ship overseas, only in the UK. The system is a Norsonic 121 that will do environmental noise and building acoustics in 1/3 octaves, I'll put a listing on the For Sale section but I'm looking for £350 for it complete. There's an intermittant issue with battery charging but it works perfectly from an external 12V source.
-
I also searched for AA options recently. I think the options are roughly:
- cheapish sound card + a free or not expensive software
- qa403 which is quite unique in this space
- expensive sound card/dac + a free or not expensive software
- quite an expensive dac (rme) + virtins mi
- virtins hardware rtx + software
- proper AAs, dscope, ap etc.
Which one to choose depends on various factors and what you want from the software and the hardware. Qa403 looks great for the price, but I never find it in stock. So I went for rme dac and virtins mi (and not only for this purpose, I use the dac for other things as well, I dont need an AA 24/7).
-
I also searched for AA options recently. I think the options are roughly:
- cheapish sound card + a free or not expensive software
- qa403 which is quite unique in this space
- expensive sound card/dac + a free or not expensive software
- quite an expensive dac (rme) + virtins mi
- virtins hardware rtx + software
- proper AAs, dscope, ap etc.
Which one to choose depends on various factors and what you want from the software and the hardware. Qa403 looks great for the price, but I never find it in stock. So I went for rme dac and virtins mi (and not only for this purpose, I use the dac for other things as well, I dont need an AA 24/7).
AFAIK, virtins hardware rtx has been discontinued long time ago.
-
I also searched for AA options recently. I think the options are roughly:
- cheapish sound card + a free or not expensive software
- qa403 which is quite unique in this space
- expensive sound card/dac + a free or not expensive software
- quite an expensive dac (rme) + virtins mi
- virtins hardware rtx + software
- proper AAs, dscope, ap etc.
Which one to choose depends on various factors and what you want from the software and the hardware. Qa403 looks great for the price, but I never find it in stock. So I went for rme dac and virtins mi (and not only for this purpose, I use the dac for other things as well, I dont need an AA 24/7).
AFAIK, virtins hardware rtx has been discontinued long time ago.
According to website, rtx6001 is still being sold.
-
I also searched for AA options recently. I think the options are roughly:
- cheapish sound card + a free or not expensive software
- qa403 which is quite unique in this space
- expensive sound card/dac + a free or not expensive software
- quite an expensive dac (rme) + virtins mi
- virtins hardware rtx + software
- proper AAs, dscope, ap etc.
Which one to choose depends on various factors and what you want from the software and the hardware. Qa403 looks great for the price, but I never find it in stock. So I went for rme dac and virtins mi (and not only for this purpose, I use the dac for other things as well, I dont need an AA 24/7).
AFAIK, virtins hardware rtx has been discontinued long time ago.
According to website, rtx6001 is still being sold.
I really don't think so. There is some possibility it might get produced again but very little as far as I'm concerned. It is on the the website but have you tried to purchase it. I don't think there's an option.
-
I also searched for AA options recently. I think the options are roughly:
- cheapish sound card + a free or not expensive software
- qa403 which is quite unique in this space
- expensive sound card/dac + a free or not expensive software
- quite an expensive dac (rme) + virtins mi
- virtins hardware rtx + software
- proper AAs, dscope, ap etc.
Which one to choose depends on various factors and what you want from the software and the hardware. Qa403 looks great for the price, but I never find it in stock. So I went for rme dac and virtins mi (and not only for this purpose, I use the dac for other things as well, I dont need an AA 24/7).
AFAIK, virtins hardware rtx has been discontinued long time ago.
According to website, rtx6001 is still being sold.
I really don't think so. There is some possibility it might get produced again but very little as far as I'm concerned. It is on the the website but have you tried to purchase it. I don't think there's an option.
You have right, I asked to virtins, they said (company) RTX (I didnt know there is another company actually producing it) discontinued it. So an option between DAC+software and proper AA is gone. So there is no option (other than a 2nd hand proper AA) from ~1.5K$ to ~5K$ or so.
-
Maybe this thread (https://www.audiosciencereview.com/forum/index.php?threads/topping-d10s-e1da-cosmos-adc-as-a-measuring-system.34723/) from Audio Science Review could be of interest.
Topping D10s + USB isolator as signal source, E1DA Cosmos ADC for measurement, and REW for processing. Total cost ~€400, and a THD+N better than -110 dB (16 Hz to 22 kHz, 1 kHz fundamental, highest harmonic 3rd at -128 dBc in this particular measurement (https://www.audiosciencereview.com/forum/index.php?threads/topping-d10s-e1da-cosmos-adc-as-a-measuring-system.34723/post-1212756)) seems pretty good to me! A downside is the low input impedance of the Cosmos ADC I guess.
If I'm not mistaken, both the DAC and the ADC have maximum sample rate 384 kHz so a pretty wide bandwidth for audio equipment.
-
Here's a measurement of my (very recently arrived) Topping D10s + Cosmos ADC (grade B), with a Hifime High-Speed USB isolator "v2" on the ADC.
With better matched levels I could apparently gain another 5-7 dB of THD+N (https://www.audiosciencereview.com/forum/index.php?threads/e1da-cosmos-adc.27038/post-1716105), but the current level of performance will be plenty for my uses anyway so I might not bother to optimize things further.
-
Finally, what is the upper frequency limit in this configuration?
-
Hi
I use the same setup-but with E1da 9038D6K as generator---just amazing performance..
Hardy
-
[attachimg=1]
RTX 6001 THD: 0,000017% = -135,391dB
-
Do you have a link to that python notebook? I'm toying around with python/jupyter controlling my chinese AWG and scope, and was looking to add some of this functionality. I'd love to peek over your shoulder....