Rigol DS1054Z FFT for Audio Spectrum

• Rigol DS1054Z FFT for Audio Spectrum
  Posted by JayJones on 18 Feb, 2015 22:44
• Hello all
  
  First off, this forum is absolutely fantastic!
  
  I'm looking to purchase a Rigol DS1054Z for my first scope ever, and was wondering if I would be able to to use the FFT function to work in the audio spectrum?
  
  I'm hoping to start off with this scope and get away without buying a crazy expensive spectrum anaylzer.
  
  I would just be working on analog audio signals, sidechain filters, EQs, etc.
  
  If anyone has an info on the usability of the FFT for this type of purpose, it would be appreciated.
  
  Thanks!!!
• #1 Reply
  Posted by AG6QR on 18 Feb, 2015 23:16
• I don't have the 1054Z, but instead have its predecessor, the 1052E.  Some things may be slightly different, but I think the "big picture" ideas are similar.
  
  The FFT functionality built into the scope works, but it doesn't have a lot of resolution.
  
  If you're willing to wait, you can get much higher resolution results by storing a sample to long memory, uploading that to a PC, and doing a FFT operation on the uploaded sample.  Here are a couple of links describing the idea.  The 1054z should do this trick even better than the 1052e, since the '54z has longer memory.
  
  http://hackaday.com/2012/10/10/giving-the-rygol-ds1052e-scope-a-spectrum-analyzer/
  http://www.righto.com/2013/07/rigol-oscilloscope-hacks-with-python.html
• #2 Reply
  Posted by Lightages on 19 Feb, 2015 00:07
• You are likely to be happier with a program for your computer with a good sound card. There are more options, better resolution, faster update speed and the easy user interface of the computer.
  
  Try Visual Analyzer:
  http://www.sillanumsoft.org/
• #3 Reply
  Posted by Shim on 19 Feb, 2015 01:03
• You may want to have a look at the PicoScope 4262. It was designed with the audio guy in mind. I have both. While I have not played with my Rigol too much yet, so far I would say it is useless in the audio band for FFT.
  
  One thing to pay attention with it is the sampling rate. When I bought the 4262, I did not pay attention to the spec sheet, and the sales guy at the distributor did not catch it either. It is 10 MS/s. I only looked at the bandwidth which is 5 MHz, less than the 20 MHz analog scope I was replacing with the Pico. I figured if I could measure up to 5 MHz, I could look at RF filtering, etc. From my limited experience with it so far, it starts to crap out just over 1 MHz. Then I found Dave's review on the Rigol 1054z, and it seemed like a no brainer to have one of them too. For the money, you can't touch it.
  
  Look a the videos on Pico's web site. The FFT has a peak hold function which means you can use it to do a frequency response plot. You can set the frequency axis to be LOG as well as linear, which is great for audio work. It is also the only scope I know of, that anyone looking for one can afford, that is 16 bit on the vertical. The Rigol (and 98% of scopes) are 8 bit. You can get into 12 bit, but they start getting quite pricey.
• #4 Reply
  Posted by andrija on 19 Feb, 2015 06:59
• I have the 2000A series and find its FFT of little value for audio, it might be good for some basic tests such as seeing if waveform is grossly or moderately distorted, but I found it slow, clunky and quite low resolution. Might be useful if you are looking at higher voltage audio signals (maybe speaker outputs?) where a bare audio card would get overloaded. For line level signals a good audio card with good software will be able to reveal well, well beyond anything that is audible. It is really incredible what FFT and other graphs can reveal - extent of power supply PSRR, power supply oscillating, crosstalk, grounding issues, jitter, distortion...
• #5 Reply
  Posted by Solder_Junkie on 19 Feb, 2015 07:23
• Quote from: Lightages on 19 Feb, 2015 00:07

  You are likely to be happier with a program for your computer with a good sound card. There are more options, better resolution, faster update speed and the easy user interface of the computer.
  
  Try Visual Analyzer:
  http://www.sillanumsoft.org/
  

  Another one, that is free and works very well is:
  http://www.qsl.net/dl4yhf/
  
  With a sound card analyser program you can use a diode ring mixer and RF signal generator to make a narrow band RF spectrum analyser with a resolution bandwidth down to 1 Hz or so. For an easy do it yourself project see:
  http://www.qsl.net/g4aon/ssa/
• #6 Reply
  Posted by alterbaron on 19 Feb, 2015 08:37
• Can the Rigol interface with the computer via. USBTMC? If so, you could write a script to pull data from the scope and do a more accurate FFT on the computer. I've done this with one of the Siglent scopes with good results.
• #7 Reply
  Posted by Teneyes on 19 Feb, 2015 10:06
• Although a slow process, you may wish to check out
  This post
  
  But note that  most DSO only have 8bits,
  where a sound card  can have 8, 16 or 24 bits for audio frequency range.
• #8 Reply
  Posted by JayJones on 19 Feb, 2015 22:06
• Thanks for the info everyone. That Visual Analyzer software looks like it might be worth trying.
  The PicoScope is nice but out of my price range right now.
  
  Would anyone with a 1054 or similar be willing to post a quick video showing what the FFT can do in the 20-20kHz audio range, and how it is limited so I know what to look for in a "better" scope?
  
  Are there any models a small step up that might be better for audio spectrum analysis?
  
  Thank you
• #9 Reply
  Posted by Lightages on 19 Feb, 2015 22:23
• It's almost not worth the time to show you what the DS1054Z can do for audio. It is slow on FFT. Visual Analyzer is much, MUCH more useful and easy to easy. Please trust me on this as I have both. There is another piece of software you should look at if you are interested in speaker design and testing.
  http://www.speakerworkshop.com/
  
  It works very well  but unfortunately the forums and support have been shut down and what is left online is fragmented.
• #10 Reply
  Posted by JayJones on 24 Feb, 2015 12:47
• Quote from: Lightages on 19 Feb, 2015 22:23

  It's almost not worth the time to show you what the DS1054Z can do for audio. It is slow on FFT. Visual Analyzer is much, MUCH more useful and easy to easy. Please trust me on this as I have both. There is another piece of software you should look at if you are interested in speaker design and testing.
  http://www.speakerworkshop.com/
  
  It works very well  but unfortunately the forums and support have been shut down and what is left online is fragmented.
  

  
  So I was finally able to give Visual Analyzer a try last night and it works great. Even with a cheap laptop's mic input.
  
  Thanks again for the recommendation!
  
  I think I'm going to order the DS1054Z anyways, as it will be my first scope and will help in troubleshooting other areas.
  
  Thanks everyone!
• #11 Reply
  Posted by Lightages on 24 Feb, 2015 13:26
• Oh yes, the DS1054Z is a great scope, especially for the money. I wasn't trying to imply that you shouldn't get a scope, just that the DS1054Z is not any good for audio work.
• #12 Reply
  Posted by dom0 on 24 Feb, 2015 13:29
• One thing to watch out for when using sound cards for analysis work, especially cheap sound cards, is that you need to know what is caused by the sound card and what by your DUT (much less of a problem with proper gear). For example, the sound card in my laptop has usable distortion (about -90 dBc), but a perverted amount of jitter, which results in strong sidebands (first two sidebands at -50 dBc, plus minus a bit, depending on frequency). The issue is now: without secondary known-good tools, you can't really do such characterization. But a basic low-distortion sine generator can help around that, because you know that, for example, an SVO or Wien oscillator simply never shows jitter sidebands (since it's not a sampled system, obviously). With it you can characterize your ADC which you can then use to characterize the DAC. The ADC is usually better than the DAC, curiously. (You'd expect the focus would be on the DAC, but maybe it's just that a good DAC is too hard to implement in a fully integrated single chip HD audio codec.)
  (Also, this characterization is not perfect, obviously, because in most integrated codecs the ADC and DAC are driven by the same clock, which can cancel some (but not all) forms of jitter.
  
  "not any good for audio work" -> well of course it is. At least I work mostly in the time domain when working on amplifiers, "switching" to frequency domain mostly for characterization purposes. Also, a sound card won't ever see HF oscillations in any amplifier. So a scope is always worth it's weight in gold.
• #13 Reply
  Posted by Lightages on 24 Feb, 2015 13:44
• I meant the SA was not any good for audio work. Well it can show you some things, but it is very limited.
• #14 Reply
  Posted by dom0 on 24 Feb, 2015 13:49
• Absolutely.
• #15 Reply
  Posted by Shim on 26 Feb, 2015 00:25
• From what I can tell so far, I would agree that the SA in the 1054 is no good for audio. Although I have not used it for any actual testing, the pico looks like it will be. It is 16 bit too which is nice. They have 12 bit scopes for less than the 4262. You could even get one of their 8 bit models as the software is the same for the whole line, not including their automotive models.
  
  I bought my 1054 after the pico as it seemed that having knobs was easier for most day to day use of a scope than mouse clicks on some menu. I think the pico will have times where it is the better instrument to use. You would be hard pressed to touch the 1054 for the money, even in un-hacked form!
  
  Take all this with a grain of salt as I have not yet started testing of the products under development that I bought the gear for, I have only played with the gear plugging signal generator into scope type thing. 
• #16 Reply
  Posted by janaf on 26 Feb, 2015 13:23
• Good sound cards for the PC are fantastic value for the money thanks to consumer volumes. If looking for audio as in good hifi, not telephones, you want more than 16 bits, at least -100dB THD+N, 96kHz better than 48kHz while 182kHz is no real advantage.
  
  Just take care what the maximum input voltage is so you don't fry the inputs. You could build a buffer amp for some protection.
  
  Modern sound cards can run fully simultaneous input/output and a lot of the audio software can generate lots of test signals, sinusoidal, square, white / pink noise etc.
• #17 Reply
  Posted by rosbuitre on 03 Jul, 2015 17:37
• Hi
  I intend to export a file wfm to some software to do the FFT from the DS1074Z better.
  I tried to capture from the compensation signal output terminal to pendrive and many program I can't read it (WFMReader, wfm_view, WFM_viewer), I'm doing wrong or that way I can do this?
  Thanks for your help
  
  Osvaldo