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In Reply to: RE: What to do with an Oscilloscope posted by jedrider on March 30, 2015 at 10:35:18
"I mean, could I look at waveform distortion and really tell something about the circuit?"
Damn, that's a good question.
I can for sure and couldn't imagine being without one. BUT... transferring your question into another field, how about: "If I buy the $500 Craftsman tool set will I be able to fix the fuel injection on my car?"
The answer is the same for both: They are but tools. If you have the tools and know how to use them and understand the operational principles of what you are working on, then you can do stuff, if you lack any of the three, then probably not. That's just the way of it...
Nowadays most digital scopes also do FFT's (act like spectrum analyzers) and you will likely find that handy. As far as performance goes sample rate is the key issue. I recommend at least a GS/s which may seem over the top for audio but lot of things that matter are out-of-band. You will also need a stimulus so pick up a function generator at the same time.
IMHO an oscilloscope is absolutely the single most valuable and versatile piece of electronic test equipment extant. A DVM is number two, especially if you want to measure resistance and a spectrum analyzer usually third, except sometimes it's first...
Ultimately you really want all three, but if I could only have one, it would be a scope.
Unfortunately learning how to really effectively use them just isn't an intuitive joy for some folks, it sort-of depends on the bend of your mind whether they will seem intuitive or alien. For me it was love at first sight. On the other hand I built and fixed a lot of stuff as a kid with a 1000 ohms/volt meter, and a grid-dip meter, and a communications receiver...
I did not realize that the newer digital scopes did FFT. That could be very useful with the right auxiliary equipment. All my scopes are older CT scopes one is tube (and still works!).
I still use my boat-anchor tube scopes every day. The big knobs fit my big hands and the high resolution analog trace lets me see fuzz on waveforms that I'd miss on a digital. The high gain plug-in lets me see noise in audio circuits you couldn't see with other scopes. I enjoy using analog scopes of any flavor.
I use digital scopes at work. They increase productivity and let you see very slow phenomena. Yes, they have FFT, but IMO it's completely worthless, especially for audio. The problem is most scopes have a linear frequency scale for their FFT display. Audio requires a log display to cover any decent range and accomplish anything. An FFT scope is a poor second to a spectrum analyzer. The lower end digitals don't have as much vertical resolution as I'd really like. There are some great digital scopes out there, but the ones I'd want to own are way out of my price range.
IMO, when you say, "Damn, if I had a scope I could see this", then it's time to buy a scope. If you're wondering what to do with one, it's probably not going to help you much and you'll quickly lose interest. The above post about how you think is very important. I've worked with people who've used scopes for years but still don't know how to properly set one up to view a specific waveform or feature. It's still a matter of luck with them. You need to understand why a scope shows you what it does, and why the many triggering options exist.
But seriously, do you use an oscilloscope routinely for audio or is this one of those work related things? ;-)
"But seriously, do you use an oscilloscope routinely for audio or is this one of those work related things? ;-)"
Absolutely! I can't see what's going on otherwise. My bare eyes have a hard time directly seeing those sluggish photons. And since I'm retired what I do is usually audio related.
Yea, I've got most of the normal other stuff like THD analyzers and FFT via computer and various signal generators. The one thing I sorely would like to have is a > 1GHz spectrum analyzer but bench space and budget haven't been kind to that desire so far. (I do miss being able to drag stuff home from the office on weekends. But not much...)
Do you have an extra $1300 for a 1.5GHz entry model Spectrum Analyzer?
You're right; the price for spectrum analyzers begins around $1300 or so. However, you can get what looks like a very nice 50-MHz four channel digital storage oscilloscope for $399. I'm tempted to buy one even though I already own a Tektronix two channel digital storage oscilloscope that I paid about $1600 for twelve years ago. ;-)
"Do you have an extra $1300 for a 1.5GHz entry model Spectrum Analyzer? Rigol..."
Well, maybe not "extra" exactly but I could scrape it up. That do look interesting, have you any experience with their products and service? I'm a Tek fancier from long experience and loyalty to a local outfit but I could be bought... cheaply.
I have no direct experience but I've read reviews of Rigol gear including that Spectrum Analyzer in QST Magazine, as well as on YouTube.
I was a Tek fan for a long time too but it seems that in recent years a lot Tek instruments are just Tek spec'd but manufactured offshore. Nothing wrong with that I suppose but if you dig into the specs, like screen size and resolution, standard features, etc., other brands seem to offer more.
Agilent for example, or should I say Keysight Technologies since they changed their name last year. This used to be the old HP. Their scopes seem to offer more for less vs Tek.
With Rigol even though they're made offshore, they have good representation in the US for sales, service, and support. You might get even more for your money from brands like Owon but I wonder about US based service and support.
If you visit YouTube and search on EEVBlog you will find a long series of videos done by Engineer Dave Jones, many of them video reviews of test equipment and power supplies. If you search for EEVBlog Rigol, you'll find a bunch of Rigol gear that he's reviewed including Rigol spectrum analyzers, power supplies, and scopes.
Fun stuff, much of it I can't afford or justify as a hobbyist.
BTW, I find it interesting that Rigol's US Sales headquarters is located in Beaverton, OR. Tek used to be headquartered there, maybe they still are. I'm not sure.
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