Cheap USB Oscilloscope for audio repair

bluehills5

bluehills5

Active Member
Every now and again I need a scope to analyze signals in audio gear but I do not have room for an old CRT scope so was looking at cheap PC based models (using USB port) but would like opinions on whether these would be suitable for the odd occasional repair and what options are important (eg sweep for FM alignment?). There are various models available with options so I have summarized the various models available in this chart with bandwidth, sample rate, price and any other features.

SainSmart DDS120 - 20Mhz - 50Sa/s $53
Hantek 6022BE - 20Mhz - 48Sa/s $60
OWON VDS1022I - 25Mhz - 100Sa/s $100 (USB isolation)
Sainsmart DDS140 - 40Mhz - 100Sa/s $92
Hantek 6022BL - 20Mhz - 48Sa/s $74 (Inc Logic analyzer)
Instrustar ISDS205A - 20Mhz - 48Sa/s $62
Instrustar ISDS205B - 20Mhz - 48Sa/s $80 (Inc DDS)
Instrustar ISDS210B - 20Mhz - 100Sa/s $129 (Inc DDS & Sweep)
Instrustar ISDS220B - 60Mhz - 200Sa/s $139 (Inc DDS & Sweep)
Instrustar ISDS220A - 60Mhz - 200Sa/s $ (Inc DDS)
 
1st thing: you need to make sure what freq you'll need to measure. The best scope in the world is useless if you need to measure 22MHz and the scope is 20 MHz.

For audio bandwidth, I mean up to 20KHz, or tracing signals inside an amp, you can use simply the computer with a free software like "Visual Analyzer", and a front end DIY gig you need to build to protect the sound card and have 10x and 100x attenuations. You can't measure DC voltages with the computer, just AC signals, since there will be a capacitor blocking the DC to protect the sound card.

I've used the computer based solution for a while. Very complete, very useful, but a real standalone scope is much better, (the computer has many more functions, but having a dedicate oscilloscope is easier to connect, to use, I've started to use it more and more because is always there ready to "plug and play").

I think I'm trying to tell you that an USB scope that needs a computer to work, perhaps is not very handy... I'd say, try a software based scope 1st, and see if you need more than that. If so, I'd get a standalone unit. Even a chinese handheld oscilloscope.
 
elnaldo makes good points on cpu based testing. won't get very far especially with ss equipment and rail voltages. A dim bulb tester will offer power supply testing for shorts etc. A dmm beyond that will offer component testing.. e.g. the scope is the best way to go if you need it. Digital scopes offer smaller space but not advised for tube hv.

hope it helps.
 
I'll get a free standing scope. Scope are so cheap, look into the used market like ebay also. It is not convenient to drag a laptop around. You want at least 20MHz. Like this one is cheap:https://www.amazon.com/Siglent-Tech...&qid=1495820487&sr=8-11&keywords=oscilloscope

My friend at work swear by his cheap scope that he can easily move around, it's like a big meter!!!!

I never move my QA401 signal analyzer, just the idea of I have to keep disconnect and connect the USB cable because the laptop has only one extra port that I have to use to plug in the memory stick every now and then is very inconvenient.
 
So I get what everyone says - buy a real scope. But I don't want to spend $200+ for something I use once a year (and would be one of the most expensive things I own). On occasion I borrow a friend's big ol' tektronix and it drives me mad with the slow warm up, flakey wiring and heft. I will be using it mainly for SS equipment (last time I used one was to adjust the tracking on my CD player) and my current reason for wanting one is a noisy FM tuner and I want to see if I can trace where the noise is coming from.
Looking at reviews, the really cheap (circa $20) usb scopes are nothing but sound card devices that (as elnaldo points out) can be replicated with your PC sound card and free software.
There is a decent thread at eevblog comparing the Owon 1022i to the Hantek 6022BE which concludes that the Owon is superior.
https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/
So, does anyone have any experience with any of these models (for audio repair) and whether any features are worth upgrading to?
 
If you use it once a year, keep borrowing the scope. You know FM is from about 80MHz to 110MHz, even the IF is 10Mhz. The cheap ones you listed are below 100MHz sampling rate, it's slow. If you go above $100, I would save up more money to get a real one.

For trouble shooting radio, I am not even sure the cheaper scope is good enough. Keep borrowing from your friend.
 
If you don't mind the table space, CRT scopes can be had for peanuts anymore. People want the slim sexy digital stuff. Drag it out when you need it, stuff it back in the closet when you don't.

I've been tossing around the idea of a low cost PC interface thing to do frequency response plots and the like. The way I do it now is horribly time consuming and involves way too much manual fiddling of controls and datalogging.
 
Yes, I second the good old used analog scope. If you can find a good old Tek 475, that's the only scope you need for all the audio work to FM radio.

My issue with the cheap play scope is whether it can reliably triggered. Those cheap pc scope has sampling rate of about 100MHz, it won't worth for $hit to be blunt. There is a different way of looking at wasting money, to me the total waste of money is to buy something inferior just to save a penny and end up not using it and has to buy another one in the future. But if OP insist in saving small money, it's his money.

Save the money on an expensive meter that a lot of people here suggested to buy and put the money on a decent scope. You don't want to spend $150 on a stupid meter, it's only a meter, don't make it more that just a meter to measure resistance, DC and AC line voltage. Forget about RMS and all the fancy features that pile up the cost on a meter, get a $40 meter and use the money to get a REAL scope.

Don't want to pay the money, don't get the scope.


I am eyeing on this scope:https://www.amazon.com/Hantek-DSO52...&qid=1496082379&sr=8-21&keywords=oscilloscope
https://www.amazon.com/Hantek-DSO52...&qid=1496082379&sr=8-21&keywords=oscilloscope
It is small, 200MHz, 1GSPS. At least it's good for all audio work. I have a used Tek 2465A 400MHz big scope, it's really nice, BUT it's big. Space is of premium for me. I only need the 2465A for my real contract work, I can live with this little thing for my hobby.
 
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The dungeon? 'bread and water'? get a decent scope with some resale value. Just can't run these digitals on tube circuits even with 10 x.. but diagnosing smaller related and switching.. is going to run 200 maybe less with ship but you get a 200mhz or more scope and some hacked to higher.

o'scopes don't diagnose a circuit. :D
 
Alan0354 said:
If you use it once a year, keep borrowing the scope. You know FM is from about 80MHz to 110MHz, even the IF is 10Mhz. The cheap ones you listed are below 100MHz sampling rate, it's slow. If you go above $100, I would save up more money to get a real one.

For trouble shooting radio, I am not even sure the cheaper scope is good enough. Keep borrowing from your friend.
Click to expand...
Alan's right. And I can attest to the fact that you don't need to spend much to get a good analog scope these days. I picked up a Tek 2445A 150 Mhz scope for $105. And you'll find that for troubleshooting it's better to have a stand alone scope vs a PC interface using a mouse for the controls.
 
Ray Gianelli said:
Alan's right. And I can attest to the fact that you don't need to spend much to get a good analog scope these days. I picked up a Tek 2445A 150 Mhz scope for $105. And you'll find that for troubleshooting it's better to have a stand alone scope vs a PC interface using a mouse for the controls.
Click to expand...
yep, it cost less than a fancy 4 1/2 digit Fluke meter!!!!
 
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