johnheath

Oscilloscope… need one.
« on: November 20, 2016, 10:49:01 AM »
Hi all…

My hobby with audio gear is turning in to more and more complex builds and repairs so I have come to the conclusion that I really need an oscilloscope to measure and test whatever I might encounter on a daily basis.

But I have no experience what so ever of using an oscilloscope so I really could use some advise on what I would need. I understand that the question itself can be a bit too wide to answer fully but surely there must be some ideas on what I could need.

My interests are within preamps, limiters, eq's and guitar amps so far… no old radios and surely no modern radios.


Any thoughts?

Best regards

/John

Nothing is impossible - It just takes some more time


Audio1Man

Re: Oscilloscope… need one.
« Reply #1 on: November 20, 2016, 12:21:23 PM »
Hi John

I would look for an ANALOG scope. DSO can fool you when making audio signals. Many of the DSO have poor converter range and looking @ a square wave it may show NOISE on top or bottom. This could be REAL or poor converter range.  Some of the NEW scopes are very good however have higher $$.  Get a local friend  that has some tools that may  help you make a good selection within your budget.

Duke :)

JohnRoberts

Re: Oscilloscope… need one.
« Reply #2 on: November 20, 2016, 12:45:59 PM »
I haven't followed the new scope market but I expect digital scopes continue getting cheaper and better values. Which means used analog scopes will be getting cheaper and cheaper.

Back in the day we used big analog scopes as room heaters to keep warm in a cold lab (sit between two scope carts), these days they are smaller and better (and cooler).

Back in the 70's I paid over $500 to build a heath kit analog scope, because that was my cheapest best option and $500 of '70s dollars is worth more now...

These days you have far better options than I (we) had. Used will be cheapest, but new are not very expensive for what you get.

JR

PS: Both analog and digital scopes will have a learning curve.
John Roberts
http://circularscience.com
Tune it, or don't play it...

johnheath

Re: Oscilloscope… need one.
« Reply #3 on: November 20, 2016, 12:51:17 PM »
Hi Duke

Thanks for your reply.

Sorry for asking but I don't know what a DSO is :-[

Analog you say? Looking around on the net it seems that analog scopes are rare and expensive… there are a few on ebay though?

Best regards

/John
Nothing is impossible - It just takes some more time

JohnRoberts

Re: Oscilloscope… need one.
« Reply #4 on: November 20, 2016, 12:53:37 PM »
Hi Duke

Thanks for your reply.

Sorry for asking but I don't know what a DSO is :-[
Digital Storage Oscilloscope....  probably too much jargon for a scope virgin...

JR
Quote
Analog you say? Looking around on the net it seems that analog scopes are rare and expensive… there are a few on ebay though?

Best regards

/John
John Roberts
http://circularscience.com
Tune it, or don't play it...

johnheath

Re: Oscilloscope… need one.
« Reply #5 on: November 20, 2016, 12:59:07 PM »
Thank you John for your answer.

Yes when I look at the leading supplier of components and electronic tools in Sweden they have a wide range of what I believe is digital scopes… prices vary from around 660USD and up… way up :) … in todays value ;)

However I guess that the rule "you get what you pay for" makes the cheapest ones less desirable?

So… for measuring noise, frequency response, gain (clipping) and all … will a "cheap scope do?


Best regards

/John
Nothing is impossible - It just takes some more time

johnheath

Re: Oscilloscope… need one.
« Reply #6 on: November 20, 2016, 01:04:42 PM »
Haha - a scope virgin I am :D
Nothing is impossible - It just takes some more time

JohnRoberts

Re: Oscilloscope… need one.
« Reply #7 on: November 20, 2016, 01:31:36 PM »
Thank you John for your answer.

Yes when I look at the leading supplier of components and electronic tools in Sweden they have a wide range of what I believe is digital scopes… prices vary from around 660USD and up… way up :) … in todays value ;)

However I guess that the rule "you get what you pay for" makes the cheapest ones less desirable?

So… for measuring noise, frequency response, gain (clipping) and all … will a "cheap scope do?


Best regards

/John
Oscilloscopes are like eyes that allow you to see voltage waveforms. Almost any scope is better than no scope (IMO), but good value depends on your budget and needs. 

Used scopes can be a bunch cheaper, but value depends on what is available in your market. Good luck

JR 
John Roberts
http://circularscience.com
Tune it, or don't play it...

johnheath

Re: Oscilloscope… need one.
« Reply #8 on: November 20, 2016, 01:36:31 PM »
Yes, thank you sir

I will look around for a decent scope


Best regards

/John
Nothing is impossible - It just takes some more time

bremusound

Re: Oscilloscope… need one.
« Reply #9 on: November 21, 2016, 02:15:12 AM »
My analog HAMEG dual trace scope, made in Germany,  is almost 40 years old and still working.
I'd go for a 203-6 or better if i would need another one.
These can be found @ebay for under 100€.


Phrazemaster

Re: Oscilloscope… need one.
« Reply #10 on: November 21, 2016, 10:56:55 PM »
I have heard it's good to look for as high a speed as possible. A 20Mhz is probably too low for what you are trying to do long term. I think you should get at least 50Mhz, and 100Mhz is better, although may be overkill. Also think about if you need 2 channels; lots of older scopes have 2 channels available and as the venerable masters have already stated the analog scopes are going down in prices as the newer digital scopes are coming up.

Bad things about used scopes: they tend to be HEAVY depending on the model. They can have problems (hey you are trying to fix problems, not buy more problems!).

I would look for Tektronix if possible, and I see quite a few on the bay at the moment. Shipping might be a bear because they are so heavy. Also some scopes have signal generators built-in - more rare - but very handy if you can get it.

I almost went for one of the newer cheapest Rigol's a couple years back, but I just wasn't doing enough testing to warrant the $500. I think they are cheaper now.

So google it up my man; ask for some specific suggestions; others will chime in here if you give it a little time.

Good luck to you!
***********************
*********************
******************
***************
************
********
*****
** * Kablooie!

Gus

Re: Oscilloscope… need one.
« Reply #11 on: November 24, 2016, 01:54:54 PM »
I would get a new DSO, something like a gw instek 2204e might be a good starter scope.
Look at the EEV blog youtube and forum for information about scopes
« Last Edit: November 24, 2016, 01:58:52 PM by Gus »

johnheath

Re: Oscilloscope… need one.
« Reply #12 on: December 02, 2016, 10:49:31 AM »
Thank you guys

A lot of valuable info here. I haven'y bought a scope yet as I am thinking of getting one with a signal generator as well… or two separate units… money is the issue here :)


Best regards

/John
Nothing is impossible - It just takes some more time

Martin Griffith

Re: Oscilloscope… need one.
« Reply #13 on: December 02, 2016, 02:39:01 PM »
Rigol seem to make nice digital scope and have a clearence site http://www.rigol.eu/clearance/  I mean to get one, but since my 30 year Tektronix is still working, I'll probably wait

johnheath

Re: Oscilloscope… need one.
« Reply #14 on: December 04, 2016, 08:06:06 AM »
I have found this… an analogue scope (and the cheapest new one)

https://www.elfa.se/Web/Downloads/l_/en/mvGOS-630FC_manual_en.pdf?mime=application%2Fpdf

Would this be a good start for me? Hard to say probably but what I mean is if it will cover the basis if I also get a function generator?

Best regards

/John
Nothing is impossible - It just takes some more time

Gus

Re: Oscilloscope… need one.
« Reply #15 on: December 04, 2016, 09:24:26 AM »
30 mHz might be to slow
Why DSOs?
Screen capture is nice
There are 50mHz DSO scopes sold in the USA with good prices. I found a 4 channel 50mhz DSO for under $400 on sale today 12/04/2016 with a search in the USA
Have you looked at the EEVblog  you tube videos about scopes? Some good information
Look for the one about scope noise and the reviews and teardowns
I watched most of the EEV blog scope videos and read a few of the forum blog threads There is good information however it can be boring
The videos and posts helped me select the DSO I bought.
You might want a 4 channel that decode serial data if you start to work on microcontrollers

Look for higher voltage probe they are an added cost
Check the cat rating

johnheath

Re: Oscilloscope… need one.
« Reply #16 on: December 04, 2016, 09:41:13 AM »
Thank you sir for your inputs

A few questions from a "scope virgin"

DSO means digital I guess but I thought this one to be analogue? Am I wrong here?
Is there a difference between digital and analogue concerning the "Mhz"?
What is the CAT rating?

And this new scope is actually 380USD (3494SEK) and shipping is free :)

Best regards

/John
Nothing is impossible - It just takes some more time

JohnRoberts

Re: Oscilloscope… need one.
« Reply #17 on: December 04, 2016, 11:36:27 AM »
Thank you sir for your inputs

A few questions from a "scope virgin"

DSO means digital I guess but I thought this one to be analogue? Am I wrong here?
Is there a difference between digital and analogue concerning the "Mhz"?
Mhz (megaHertz) is the rated HF bandwidth it is expected to work for. It may be useful to understand that they will (probably) behave dramatically differently for much faster signals. An old school analog scope will attenuate very HF signals like a gentle low pass filter.

A digital scope that samples the input signal for digital conversion will experience aliases, where higher frequency components fold back down into the passband. For example a scope sampling at 200MHz that receives a 300MHz signal will display a 100Mhz image.  Just like most test equipment you gain experience with use, but can see more confusing false images from digital than analog, while it should not be hard to get well above the audio bandwidth.  If you plan to work around digital circuitry and need to look at clocks you will need a much faster scope.
Quote

What is the CAT rating?
I didn't know but have google on my computer.
http://www.ni.com/white-paper/5019/en/
It appears to be a voltage level classification.

hope this helps

JR
Quote
And this new scope is actually 380USD (3494SEK) and shipping is free :)

Best regards

/John
John Roberts
http://circularscience.com
Tune it, or don't play it...

joaquins

Re: Oscilloscope… need one.
« Reply #18 on: December 04, 2016, 11:37:46 AM »
Thank you sir for your inputs

A few questions from a "scope virgin"

DSO means digital I guess but I thought this one to be analogue? Am I wrong here?
Is there a difference between digital and analogue concerning the "Mhz"?
What is the CAT rating?

And this new scope is actually 380USD (3494SEK) and shipping is free :)

Best regards

/John

  CAT is a rating for safety measures, as scopes usually aren't connected directly to high power sources this isn't an issue. CAT II is enough for the lab bench and is usually what you get in an scope. CAT IV is for working around high power sources, DMM for working on industrial machinery should be CAT IV

  MHz is usually about analog bandwidth, either on an analog or digital scope, meaning the max freq of the signal coming in it can work within specs. In digital scopes you also have Msps/Gsps meaning the sampling rate. Depending on the application you want your signal max freq to be a fraction of that, but in some cases is still useful over that point.

  Either instrument is meant to measure analog signals, being analog or digital is about the way it acquires the data and show it to you. Implicit over that, most digital scopes have a ton of extra features you don't have on analog ones, which makes much easier to  extract actual numbers out of it than analog ones. In an analog you can make a ton of stuff and take some numbers out, in most digital scopes you can also add measurements on a side of the screen and it will show numbers for Vpp, Vrms, freq, period, and much more.

JS
If I don't know how it works, I prefer don't turn it on.

johnheath

Re: Oscilloscope… need one.
« Reply #19 on: December 05, 2016, 05:41:33 AM »
Thank you both John and Joaquins.

You both gave me highly useful insight in some facts about scopes.

As for now I have no experience in digital circuits and basically I am focused on tube gear at the moment and I am trying and struggling to get a good grip of it all.

From what I can see now I will troubleshoot and design some tube circuitry so I guess that I could be satisfied with an analog scope, but as you say Joaquin... " numbers for Vpp, Vrms, freq, period, and much more" would probably be very good to read.


Best regards

/John
Nothing is impossible - It just takes some more time