analog scope - instek gos-620, advice needed - Page 1
Forum section: electronics / testgear

author: EasyDoor
author_rank: Newbie
timestamp: May 06, 2013, 06:31:06 am
content: Hi! First of all, as my first post here, I would like to introduce myself to the community.My name is Izidor and I am 21 yo EE-to be, I had great passion towards science from young age, and last year or so I started my hobby- making/repairing guitar effects pedals, and audio amps... well basically audio electronics in general.And I think it is time to finally get some kind of analog scope. On local auction website I came across GW INSTEK GOS-620 scope.Bandwidth is really not an issue, for audio electronics, I am concerned on overall reliability and precision to money ratio.It is priced for about 350$, several months old, + 1x1 and 1x10 probes included, but nevermind the price, in Croatia things like that tend to cost a bit moreso TL;DR : have you had any experiences and what do you think about this particular scope in general, is it worth a shot?

author: flolic
author_rank: Frequent Contributor
timestamp: May 06, 2013, 07:15:46 am
content: That is waaay overpriced, but that's how it is in Croatia...I had exact that model few years ago and I sell it in 2009 for ~150$ + postage. In mint condition, with maybe 50 work hours.Instead I bought Rigol DS1102E and that's miles above that analog Instek.I would NOT recommend you that scope, maybe if you can find one for less than half that price (not gonna happen here...)Welcome to the forum btw

author: EasyDoor
author_rank: Newbie
timestamp: May 06, 2013, 12:17:55 pm
content: Well, you didn't really give me any reasons why I shouldn't get it, except that rigol is better.For my needs, that is audio electronics, I think that rigol you mentioned is a bit overkill, and beside their great performance (and god awful looks) they just ain't got the groove like old green dot on the screen O0 (also I would rather have analog scope to be something I can learn on, don't wanna get spoiled by something too fancy for my first scope)Anyway, thanks for the replay, thats why I came here in the first place I have really no experience with scopes beside the ones in my highschool and college labsAnother thing, I was convinced that analog scopes are in general better for audio electronics, am I mistaken? Also, more thoughts on GOS-620 please, I have to decide until this weekend whether buy it or not

author: Hydrawerk
author_rank: Super Contributor
timestamp: May 06, 2013, 02:44:44 pm
content: http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=6&id=75Oh, this scope is too obsolete. It's like 1975's technology... It has no readouts, cursors or automatic measurements... In 2013, there is no reason to buy a 20MHz analog scope, unless you get it very cheap...If you really want ananalogscope, buy at least a more modern one...http://www.gwinstek.com/en/product/productdetail.aspx?pid=3&mid=6&id=60Well, analog scope is like old CRT TV. Why not to use it if you own an old one and it still works, but I would never buy it today.

author: Salas
author_rank: Frequent Contributor
timestamp: May 06, 2013, 03:08:52 pm
content: I have used the 620 model enough at a friend's. Its not that great for waveform geometry. Skews enough especially beyond 2 divisions. Knobs are not too good either. Being into audio stuff myself too I would recommend you to aim at 100MHZ not 20MHZ. There will be riding oscillation bursts even in audio stuff that you can miss at 20MHZ.

author: flolic
author_rank: Frequent Contributor
timestamp: May 06, 2013, 04:38:15 pm
content: Quote from: EasyDoor on May 06, 2013, 12:17:55 pmI am not trying to pursue you to buy Rigol, but not to buy that Instek sh*t. Don't get me wrong, (usually) any scope is better than no scope, but that Instek is simply thing of a past. Others already expressed their opinions and experiences with that scope, and I can only confirm that. Not to mention ridiculous price.Quote from: EasyDoor on May 06, 2013, 12:17:55 pmFirst, there is no such thing as overkill scopeYes, now you are interested in audio electronics, but in a few months or years you will try to troubleshoot some SMPS, PWM driver or any other complex digital or analog circuit and then you will realize that scope is holding you down. 20MHz bandwidth is enough only for simplest signals, but in real world scenarios you will miss something that troubles you. There's no point to look pure 1MHz square wave on scope. But if that square wave has spikes and ringing on leading edge, you 20Mhz scope will not be able to show you that... Trust me, I'm talking from my own experience. Also on faster time bases that Instek has instable trigger, and very dark trace.If you still want analog scope, try to score some 100MHz+ model from HP/Tek/Hameg on ebay. They can be found for 100-300USD, and even when you add postage and VAT you'll have much more capable instrument for reasonable amount of money.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 06, 2013, 05:36:35 pm
content: Quote from: EasyDoor on May 06, 2013, 12:17:55 pmYou seem to think that using an analog scope is more difficult than a digital scope. It isn't. It's just different.There's no reason you have to rely on outdated technology to learn how to operate a scope, a DSO is perfectly fine as a beginner's scope. You have to know your instrument and its limitations anyways (no matter if digital or analog), so you can learn as well with something that's current technology.As to this analog Instek scope: I know that in Croatia stuff is not easy to get, but I still think you would be mad to pay $350 for such a scope. You're probably much better off even when buying some of the cheap Atten/Siglent scopes from one of the many Chinese sellers.

author: EasyDoor
author_rank: Newbie
timestamp: May 06, 2013, 05:37:09 pm
content: alright, you guys made some reasonable arguments. I guess I will drop analog scopes afterall, there are some decent rigols at ebay, not sure if I should just buy it off the bat without seeing it first tho...any other decent scopes besides mentioned?

author: Hydrawerk
author_rank: Super Contributor
timestamp: May 06, 2013, 05:45:09 pm
content: https://www.eevblog.com/forum/testgear/year-2013-oscilloscope-choices/There are many threads on scopes.

author: Kilroy
author_rank: Regular Contributor
timestamp: May 06, 2013, 07:46:19 pm
content: Quote from: EasyDoor on May 06, 2013, 12:17:55 pmTouchy issue.Depends, really. With audio circuitry, or any electrical circuit for that matter, everyone knows the *ideal* design is one which contributes zero self noise or distortions to the signal you intend to introduce to the circuit. A circuit with zero self noise is obviously not possible, nevertheless your test equipment has to be capable of at least meeting, or preferably bettering, the *best* specification of your design, or you simply won't be able to "see" what you got. Whatever that equipment is, be it digital or analog, it firstly has to be up to the task of giving you accurate feedback on what is going on with your designs.If normal run-of-the-mill audio circuits are what you have in mind, almost anything in the way of an oscilloscope will get you going. If you aspire to lash up something that delivers gobs and gobs of really clean, quiet gain, or if your circuit has complex signal summing going on, then you are going to have to examine the noise floor much more carefully because, obviously, the audio will only be as clean as the noisiest point in the signal path.Personally, I like analog scopes for audio work. But then, that's just my preference...no analog zealotry here...they're just bloody tools after all. Get something that works and start changing the world before life runs out, I say. One of my favorite scopes ever for audio work is an old analog HP 1201A storage model that was very, very good for electromyography verification and other sensitive low speed medical/bio-mechanical stuff. This is only a 500kHz scope. You really don't need much bandwidth for audio, often much less than you think. What makes this scope so wonderful for audio signal work is not stratospherically high bandwidth, but it's extremely quiet differential front end amps, outstanding CMRR, very low 100uV/DIV deflection factor and the 50k bandwidth limiting that helps clear up the range you are most concerned about examining closely. With this old "obsolete" instrument you can have a peek way, way down into a signal. Whether you care to, or are indeed able to, design an audio path that requires that degree of verification is, of course, another matter.*Sigh*...and on that issue...if nobody can hear it, then who really cares. It's all a bloody great wank fest after that. The average healthy homosapien can only be expected to hear, at most, from 20Hz to 20kHz. That's the range you want to keep clean. In reality, it's even narrower than that because our hearing is much more sensitive in the mid to high-mid ranges...artifacts are much easier to discern in that spectrum. Even if there are spurious signal anomalies out at 20MHz....10MHz....1MHz even. Other than bats, and possibly Superman, nobody is going to care, especially after steep Nyquist filtering kills it all. Unless noise/distortion artifacts fold back into the audible frequency spectrum, it's entirely irrelevant. Even a highly specified digital audio circuit, using an absolutely exceptional 192KHz DAC for conversion purposes, can be lashed up using a low speed scope for verification, providing it has the moxy to allow you to see into your signal to the depth necessary to expose any noise components that *will* mess with audible signal integrity within the spectrum of frequencies folks actually do hear. And that's all that matters.Because, if you can't hear it...well then, it never really happened in the first place, did it?

author: EasyDoor
author_rank: Newbie
timestamp: May 06, 2013, 08:50:54 pm
content: alright, I guess rigol seems the most reasonable choice here, hopefully it will survive shipping from china

author: Hydrawerk
author_rank: Super Contributor
timestamp: May 06, 2013, 10:45:58 pm
content: My DSOX2002A survived shipment from Malaysia. It came in a very huge box filled with crumpled anti-bump paper. No fear!

author: Salas
author_rank: Frequent Contributor
timestamp: May 07, 2013, 01:44:51 am
content: Quote from: Kilroy on May 06, 2013, 07:46:19 pmNo, wrong assumption.

author: EasyDoor
author_rank: Newbie
timestamp: May 07, 2013, 09:10:28 am
content: well, Salas, I must say i did not know that, much appreciated

author: Kilroy
author_rank: Regular Contributor
timestamp: May 07, 2013, 02:58:39 pm
content: Quote from: Salas on May 07, 2013, 01:44:51 amNot assuming a thing, actually.But, perhaps, I could reword that sentence a bit just to put a finer point on it. How about..."You don't really *need* a scope for audio, much less often than you think."You don't really need an ax to kill a chicken either, all you need is a bit of knowledge and your own two hands. After that, it's a straight forward procedure. In fact, I reckon a fairly compelling argument could be made that using an ax only makes things more messy and adds unnecessary complication.I'm old, Salas. I hate to imagine what I may have missed out on had I been convinced, somehow or other, that a scope was an absolute necessity and that being without one in any capacity would have prevented me from building up a good circuit. I mean, it's bloody amazing what you can accomplish in a clothes closet or children's sandbox with nothing more than a dull putty knife, a rubber mallet, and few rusty ball bearings.You don't *need* lots of bandwidth in a scope to do good audio work...really, you just don't. There are, granted, a few things you may eventually want, and bandwidth might just be one of those things. If that is the case then go to it. Nevertheless, my statement is still true. The chap in the video you posted didn't *need* a scope to show him the example circuit had sympathetic oscillations going on. He already knew what to expect and how to mitigate it. There is plenty of theory and methodology available on how to work up an audio circuit with excellent performance characteristics. Anyone can develop a wealth of solid experience and skills in this area with nothing more than patience, a pair of hands and a bit of soldering kit.Yeah, anyway...love life, live strong and start every day with a large bowl of soaked oatmeal and your sorted.

author: Salas
author_rank: Frequent Contributor
timestamp: May 07, 2013, 04:58:00 pm
content: Making do with less is a testament to ingenuity and people like Peter Walker of Quad broke ground with surely much less capable kit than a hobbyist can have today with $1K and half an hour of online shopping, but when someone is looking for an axe today and he can easily get it big and sharp, then why not? A friend scored a Tek 2445 for 250 Euro delivered recently, and about 800 Euro buys in Rigol DS2000 territory for resembling some CRO waveform fidelity plus the digital goodies. Only thing remaining to still say nowadays is "Careful with that Axe Eugene ".

author: Hydrawerk
author_rank: Super Contributor
timestamp: May 07, 2013, 05:33:57 pm
content: Even this old scope from late 1980's has readouts and cursors. But noautosetbutton.

author: Salas
author_rank: Frequent Contributor
timestamp: May 07, 2013, 10:40:42 pm
content: There was an auto trigger mode button on some Hitachis like the V-1065 and V-665 chasing the time range to catch a signal. Beyond cursors, some auto trigger, a simple storage and a delayed zoom mode there is not much more of convenience to expect finding in advanced analog of yore. Still, complex waveform fidelity and signal responsiveness are integral to analog, thus easy to get even in a basic or obscure CRO...