USB Oscilloscope

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I went over to a friends house today to troubleshoot a problem that was vexing me. Rather than use his Tek Oscilloscope we used his Parallax USB Oscilloscope. I was very impressed with the quality of the interface and the price. It was less than $150 shipped. Here is the LINK.

I really liked it but I have two complaints. First, it's only good for 20 volts. Nuf said. Second, it uses really basic probes. I'd like shielded 10x probes. It's far from a toy but inadequate for most tube work.

Another brand, Stingray, looks good too. And it has BNCs so you can use shielded probes but the max voltage is limited to 50V.

Are any of you using a USB Oscilloscope that you can recommend that is more appropriate for higher voltage audio work?
 
I went over to a friends house today to troubleshoot a problem that was vexing me. Rather than use his Tek Oscilloscope we used his Parallax USB Oscilloscope. I was very impressed with the quality of the interface and the price. It was less than $150 shipped. Here is the LINK.

I really liked it but I have two complaints. First, it's only good for 20 volts. Nuf said. Second, it uses really basic probes. I'd like shielded 10x probes. It's far from a toy but inadequate for most tube work.

Another brand, Stingray, looks good too. And it has BNCs so you can use shielded probes but the max voltage is limited to 50V.

Are any of you using a USB Oscilloscope that you can recommend that is more appropriate for higher voltage audio work?

Well, you can always use a 1:10 switchable probe to extend the input voltage.
Check out picoscope as well.

jan didden
 

Arnulf

Member
2009-02-02 9:41 am
I was very impressed with the quality of the interface and the price. It was less than $150 shipped.

Ouch, double that price and get 10+ times more value for your money ? OWON DSOs (standalone units which can connect to PC if needed, they also come with something that resembles real scope probes by default) start at just under $300 for the 25 MHz (100 MSPS sampling rate) model, shipped, and I distinctly remember seeing even cheaper DSO variant somewhere (possibly with monochrome LCD instead of color ?) but I forgot the brand name. It started with a 'U', I believe.

1 MSPS sampling rate might just be enough for audio though, barring experiments with square wave signals.
 
On the face of it, yes, but... especially with a lot of high speed circuits (and high gm tubes), you can get oscillations much higher than 50MHz that nonetheless affect the sound. And digital datastreams are likewise fast-moving, especially when you want to analyze risetimes and ringing. 1

100MHz is a reasonable minimum, but 300MHz or higher is often useful.
 

levelfive

Member
2008-12-02 1:36 pm
Are any of you using a USB Oscilloscope that you can recommend that is more appropriate for higher voltage audio work?

Hi, Dave

I have used Digital USB Oscilloscope (see Specifications). It's very easy to use and is not picky about the computer resources, so as not to depend on the parameters of the audio card. As advantage can also note the presence of galvanic decoupling.

This very well made device, with 15MHz bandwidth - exactly suitable for audio applications. The oscilloscope is supplied with a special software - I have used its successfully for THD measurements (you can see spectral analyzer screenshots here).
 
I have one from Velleman. It was a bit more expensive, maybe $200+ and is rated for 30V. I have a 10x and 100x probe, so should be ok to even high voltages. It has 2 channels and a function generator (which has a 2dB drop around 10kHz, but otherwise is flat). It seems to work pretty well.


Thanks everyone. Good suggestions.

Jrenkin, Do you have the Vellman model PCSGU250? I had a quick look at the specs and it would seem to be the right fit but there is no mention of isolation in the specs.

It is indeed a lot of scope for the $$.

I'll have a look at the others tonight.
 
I just spoke with a guy at Vellman. The USB products are not isolated. They have an older unit that is isolated is but it requires a parallel port and I want to use my laptop. LINK

I suppose one could use a non isolated scope safely if one was to keep the equipment under test operating off an isolation transformer (as I normally do). Does anyone want to offer up an opinion on the safety of that idea? It would seem to be a matter of when, not if, a user would forget to set the probe correctly and fry something.
 
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levelfive

Member
2008-12-02 1:36 pm
the Vellman model PCSGU250
His has a real 12MHz bandwidth - its suitable for audio, but i dont know about software - how good is it.

And I doubt that this device has no galvanic decoupling with PC :(

PS: Besides, it is made on the basis of a simple 8-bit ADC AD9288, that is too bad for device value of almost 300$.
 

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Arnulf

Member
2009-02-02 9:41 am
Does anyone want to offer up an opinion on the safety of that idea? It would seem to be a matter of when, not if, a user would forget to set the probe correctly and fry something.

Is there a particular reason why you are trying to avoid standalone units ? These are not the crates the size of an analog scope, they are few centimeters (~2") thick and fit just about anywhere. Not connecting it to your PC is the best way to ensure isolation ;)
 
Arnulf,

Do ignorance, laziness and cheapness count as particular reasons?

But seriously, your point is well taken. I looked at them last year at a store here in the US called Fry's that offers test equipment at very competitive pricing and the one I wanted was about $600. It was about 100mHz and 400V max. IIRC. So I can't say I'm unaware, but I had no opportunity to use one and didn't realize how good they are. I used my friends USB scope and I was quite impressed. My inquiry here was to find if such a thing was available at a much lower price point than the stand alone models.

After some reading and consideration of the safety issues, I think you are spot on with your recommendations. THIS scope is so much for the money that it is hard to ignore. And THIS one is very tempting too.
 

Arnulf

Member
2009-02-02 9:41 am
Do ignorance, laziness and cheapness count as particular reasons?

Well, sure :D Standalone units are easier to use than software in my opinion as you have(everything at the touch of a button, without having a cumbersome computer with accompanying keyboard, mouse and whatnot on your electronics workbench that is filled with various components and bits you're testing.

Do online sellers offer no-questions-asked returns where you live ? If they do you could order one and try it out if there are no sellers nearby that you could visit in person.
 
I have an Owon 5022DS. Its not bad for the money, but the passive LCD is a pain. Add to that the fact that you cannot tilt the instrument in any way. It either sits upright or lays on its back, which makes the narrow view angle problem of the passive display worse. But it does work quite well as an audio scope otherwise and it is supposed to withstand 300v pk on its input.

Gary
 
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