PicoScope® 2000... adequate for tube amp?

[dwinstonwood]

Hi all. I'm looking at this USB oscilloscope:
https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview

Is this unit adequate for basic tube amp testing? First I want to learn how to use an oscilloscope. Then, I'd like to check for things oscillation in amps I build, signal strength, clipping, etc. Basic audio stuff.

This unit is affordable and I have an extra laptop running Linux.

Thanks for any feedback!

[shooter]

the specs work, does accept a MAX input of 20v, so with a 10X probe you can get to 200v


if you get really geeked, the FFT feature is really handy for seeing harmonic distortions


figure out the input connectors, standard scope probes are BNC, so you'll need adaptors

[dwinstonwood]

Thanks shooter!

So, those are two things I didn't know to look for: max voltage and BNC connectors.

What max voltage do I need? I'll only be working with AC guitar signals, right?

Here's one that's less expensive and has the BNC probes and that "FFT" feature:

http://www.hantek.com/products/detail/153

Thanks!

[dwinstonwood]

And, the third candidate:
https://www.owonna.com/products_owon_vds_series_pc_oscilloscope

This one's priced in-between.

All three of these have fairly good web reviews. That is, they seem to be well known brands.

[DummyLoad]

Hi all. I'm looking at this USB oscilloscope:
https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview

Is this unit adequate for basic tube amp testing? First I want to learn how to use an oscilloscope. Then, I'd like to check for things oscillation in amps I build, signal strength, clipping, etc. Basic audio stuff.

This unit is affordable and I have an extra laptop running Linux.

Thanks for any feedback!

The third
https://www.owonna.com/products_owon_vds_series_pc_oscilloscope
would be my choice. OWON model VDS1022I

--Pete

[dwinstonwood]

Thanks DummyLoad.

The Owon VDS1022I specs say: Max Input Voltage 400V (PK - PK). I guess that's with the probe set to 10:1?

It also has "USB isolation" which they claim protects your PC.

I downloaded the software and it opens and seems to run.

[pdf64]

I’ve got a Picoscope 2205a, which is pretty good.
Whatever you get, a built in function generator is extremely helpful.
This Velleman cleverly runs its scope and gen together to produce bode plots (frequency response charts). I keep meaning to ditch the Pico and buy it. http://velleman.co.uk/contents/en-uk/p381_pcsgu250.html
It’s so annoying that Pico software doesn’t facilitate that.

[acheld]

Having used a Picotech unit for several years, I recently bought a Hantek standalone scope and much prefer it.

The Picotech unit is well constructed, high quality, and works very well, but I never really got comfortable with the software.   Whereas, the Hantek unit's software is more understandable.  At least, for me. 

So if you like Picotech software (and lots of folks do), go for it.   By the way, the main difference as you move up their product ladder is the ability to deal with very fast digital signals, none of which really applies to guitar amps.


 

[dwinstonwood]

Thanks pdf64 and acheld.

I definitely want a scope with its own signal generator. The bode plot feature is also very cool.

You save a couple of hundred dollars, or so, with the USB/PC units, but then, you're chained to the laptop & mouse instead of a knob.

I think I'll just sell a couple of antique model airplane engines (I have way too many) on eBay and buy a desktop unit with a built-in signal generator.

[pdf64]

Good point about the learning curve with the Pico software.
I’m fine with it now, but it’s taken a long time to get conversant.
For about the first 2 years of owning it, the probe cables often got removed from the Pico unit and plugged into my old analog scope, so I could move on with the task in hand. 

[Lectroid]

I've only built 3 amps, so far from an expert.  But I think a laptop would be too much in the way for me to go that route.

I'd look at a standalone scope if I were you.  Rigol and others make affordable scopes that do just fine for audio spectrum work.  Small size, fits above the bench but handy for use, and with actual knobs to adjust.  Also, one less set of cords laying around.  JMO

[dwinstonwood]

Thanks for all of the input!

Before I go any further I need to clear up some points of confusion.

1.) Is it considered a mandatory safely practice to always place an isolation transformer between the amp (unit under test) and the wall? If so, I'll need to buy one of those, too.

2.) I'm confused about the 10:1 switch on the probe. Does that actually decrease the voltage reaching the scope? In other words, if the scope is rated at 40V max can you safely connect the probe to higher voltages when set to 10:1? Of course, I do understand that I'll be measuring AC signal voltage on the grid-side of coupling caps (not plate voltage).

Thanks!

Also, Microsoft has a free signal generator app for Windows:

[shooter]

the 10X will reduce the voltage to the scope, BUT, the probe has it's own specs, IIRC a typical 10X probe will be rated at 300vdc max


the problem for "isolation" typically happen when the device being tested is at a different electrical potential from the test equipment.
an example; I needed a scope to measure and adjust the top 10% of 120,000vdc, there was a built in Vdivider but the scope still needed to measure 1200vdc compared to electrical ground.
the solution was to "float the scope", the complicated part, make sure the tech didn't get between the float and electrical ground 


for normal bech work the scope, the equipment all share the same ground, so the only worry is exceeding the scope/probe MAX operating conditions

[dwinstonwood]

the 10X will reduce the voltage to the scope, BUT, the probe has it's own specs, IIRC a typical 10X probe will be rated at 300vdc max

Thanks shooter! That all makes good sense. I didn't even think about the probe specs. 
I'll be sure to always test on the correct side of caps.

for normal bech work the scope, the equipment all share the same ground, so the only worry is exceeding the scope/probe MAX operating conditions

That's what I needed to know. I'll be testing amps that I build which will all have the power cord green/earth wire bolted to the amp's chassis.

Your help is appreciated!

[shooter]

I'll be sure to always test on the correct side of caps.

that's assuming the cap is good, not really a good troubleshooting tool 


when in doubt, sacrifice the least expensive test equipment 1st 

[dwinstonwood]

when in doubt, sacrifice the least expensive test equipment 1st 

Good point. I'll use my old Radio Shack multimeter to check caps for DC leakage.

[dwinstonwood]

More research done. Aside from the more expensive Tektronics scopes, these two brands are also well respected on places like EEVBlog, etc.

It's pretty much a toss-up. Very similar specs. The model names are even almost the same.

One difference is that the Siglent has separate controls for each channel, while the Rigol shares the two knobs for both channels. But, it's $40 cheaper.

There are used signal generators on eBay for around that much.

[acheld]

Check out Hantek DSO2D10. $245