I want to buy an Oscilloscope

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This scope will work great, if you get it for a reasonable price. Most likely, it will be bid up past reasonable, from an audio point of view. If your projects center around audio applications, then a 20MHz unit is more than enough. You can get them new from about 300 up. You probably want to look for a dual trace, so you can monitor both the input and the output of the DUT.
 
Terry,

That scope on ebay is a beauty and way overkill for audio only work. If you are on a budget I have seen suitable dual trace scopes for as low as $20 on ebay. All you need is 10 MHz. If you are not experienced with electronics stay away from the large vintage Tektronix 500 series models like the 565. They will be difficult for you to keep running as they contain about 565 tubes. On the other hand, if what you need is a 500 watt fan forced air electric space heater for your shop, grab one!
 
I agree with Sy. I guess I would take 60MHz if you held a gun to my head and made me do it, but I'd recommend 100MHz min. Dual trace is a MUST. I also have to admit at my old age, scope measuring cursors are handy now, too.

Hitachi used to sell a decent 100MHz scope with measuring cursors some years ago that was pretty decent - easy to use, worked well and durable. I know because I still have mine. :) They show on ebay every once in a while a good prices - benefit of NOT being named Tektronix :)

On the occasions when they do, MOSFET source followers oscillate at a high frequency. Need a good scope or you might not see it or know what it is. Ask me how I know :-(

mlloyd1

Mmmmm, beg to differ. I'd look for 100MHz or better so you can spot RF oscillations. 10MHz is enough for audio, sure, but many problems in audio are the result of Bad Things happening at RF. [/QUOTE]
 
still4given said:
I'm at the point where I want to learn how to use a scope. Will something like this work for what I need?

Do I need more Mhz? I don't know anything about them. I just want to get something I can use for working on my projects and to learn on.

Thanks, Terry

Scopes are so inexpensive these days -- if you are going to remain in Audio I think you might find the Tektronix 7700s to be a great purchase -- provided you aren't limited to space -- there is an enormous number of amplifiers and time-bases available for these devices, you can use the 7L5 spectrum analyser, there's an excellent low noise differential amplifier (the 7A22N), etc., etc.

Some of the older scopes are better for testing out power supplies -- and these (like the Tektronix 535) are often given away at hamfests. The trace on these older scopes can be much sharper and brighter than a DSO --

I use both a Tek 2465 and a TDS3014. While I like the 2465 a lot if I had the space I would probably go back to one of the ancient analog models.
 
SY said:
Mmmmm, beg to differ. I'd look for 100MHz or better so you can spot RF oscillations. 10MHz is enough for audio, sure, but many problems in audio are the result of Bad Things happening at RF.


When I started out I bought a vintage (even then) scope from RCA that used a thyratron tube to develop the H. sweep. I'd be surprised if the bandwidth exceeded 500 KHz. Somehow it was useful enough to teach me more about electronics, the oscillators I was breadboarding at the time using 6SN7 tubes, and some of the tube audio amp work I was doing at age 13. Like I have done all my life, I didn't start out with a Cadillac because I needed a car, I did the best I could with the best I could obtain. Slightly later in my mid teens I built an o-scope from scratch. That project, not following any plans, just basic schematics in the RCA tube manual didn't hurt my self teaching a bit.

I don't disagree with what Sy has said about higher bandwidth being helpful in spotting birdies, but the poster Terry did not specify what projects and clearly said he wanted merely a starter scope to learn on. Man if I'd had a 10 MHz dual trace scope starting out I'd have been even more dangerous.

Yeah sure it is possible to learn how to drive on a Cadillac I guess. Rip around on yer daddy's muddy cornfield with it. :D

Me thinks a lot of you guys sure are spoiled!
 
Is 100MHz with 5V always better than 35MHz with 2mV resolution?

Just one last note that some of you may have missed. In some situations, the resolution 5mV, 2mV etc. can be as important as the frequency. I still need my Tek 442 on occasion even though it has only 35MHz bandwidth.
 
rcavictim said:



Yeah sure it is possible to learn how to drive on a Cadillac I guess. Rip around on yer daddy's muddy cornfield with it. :D

Me thinks a lot of you guys sure are spoiled!

I will readily acknowledged that I have spoiled myself. After paying for 3 undergrad educations I deserve it. What else am I going to do, buy vintage Bordeaux and watch them age?

Our tastes have just changed! I built 3 scopes when I was seriously into ham radio -- a TEK535 would have cost about $700 to $1000 back then -- there are no remnants from the first one which used (if I recall correctly) a 2BP1-11 with vacuum tube amplifiers. The second is pictured here -- now just as a carcase of a navy display -- i wonder if I have all the pieces!

An externally hosted image should be here but it was not working when we last tested it.


The third was from the article published in Radio Electronics in 1980 -- unfortunately this project stalled out because the second kid arrived and I had to take a new job!. Of course I was able to then purchase a TEK535 from Grumman's depot which made testing a lot easier.
 

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Hi Terry,

Just adding my 2 cents here...(own oppinion, use it or forget about it):

I would say that 40-60 MHz is a fine starting point. >>100 MHz isn't useful, unless you have interesting (read: odd) amp designs.
If an amp has problems, you can normally see it way below 50 MHz.

Yes, 2 channels is a must!
For audio analysis, digital storage scopes aren't always better. However, some have built-in FFT (math) functions, which can be very useful.

I agree, you don't need a Cadillac to start out with. Then again, buying the cheapest thing around might be costly in the end, when you find you really need/want features that require a new purchase.

The analog ones are usually physically bigger, but easier to get started with.

An important thing to check (which the cheaper ones don't always have) is independent/insulated inputs, meaning that input ground of channel 1 is not cvonnected to input ground of channel 2. This elliminates ground currents, and prevents accidental short-circuits if the measurement points do not have the same "nagative" potential.


If you need assistance, I'll guide you through a scope function, Terry. Maybe I should extend my guide with this stuff, too?

Jennice
 
i have the FFT modules on the TEK -- it is "somewhat" useful -- but not as good as a dedicated analyzer -- the most helpful part of the FFT is finding the exact frequency of an oscillating part and its relative magnitude. the more expensive TEK scopes can do network analysis with FFT on the fly -- which means that compensating a power supply error amplifier loop takes less time.

i wouldn't purchase an older digital scope, as one pundit has said "they don't tell the truth all the time".

a differential probe -- there have been good inexpensive designs in Elektor, Electronics World and AudioXpress -- is very worthwhile.
 
You guys are the best. I should be able to find a scope that will get me going, armed with the advice you all gave. Thanks so much.

I'm sure once I get it, I'll be back asking a bunch of silly questions.

Thanks, mercator for the link. I've printed some of that out and will be reading into it as time allows.

Thanks again,

Blessings, Terry
 
Hi guys...I've also been looking around at scopes and I've spotted something that caught my eye, its a 400MHz Philips PM 3295A. It looks way over specced but is it any good for the audio hobbyist? I might buy it regardless as it looks so damn cool.

Take a look

tonga
 

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If you have the opportunity to buy that monster for some ridiculous price, I /will/ hate you forever. ;)

A scope like that would be great for digital work. My 100MHz setup makes it hard to see some of the faster signals, like individual S/PDIF bits. The one thing that is nice about it though is the 7A22 with 10uV input range.
 
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