| Safe_Cracker |
I am new to electronic diagnosis but very willing to learn. I want to buy an Oscilloscope but I know nothing about them. I wan to be able to set my amplifier gain settings, and also help aid in amplifier repair. I was peaking on E-bay and there are thousands of choices, literally! What should I look for and what does it mean like 4 channel, 60hz, 200hz, etc on the listings?http://cgi.ebay.com/Tektronix-2465-...1QQcmdZViewItem
Also would a handheld work? Like this one?http://cgi.ebay.com/Velleman-10-Mhz...bayphotohosting
Thanls for any help, Polo..:) |
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| Safe_Cracker |
| THANKYOU! Polo..:) |
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| mastertech |
well my professor Barry once told me any osciloscope is better
than no osciloscope if you are newbie dont invest big just yet
ask a friend service tech for affordable but good ones
cheers |
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| lineup |
| quote: | Originally posted by mastertech
well my professor Barry once told me any osciloscope is better
than no osciloscope if you are newbie dont invest big just yet
ask a friend service tech for affordable but good ones
cheers |
That is right, mastertech
Most any old oscilloscope with 2 channels will do for audio.
If they can show good below 1 MHz.
It is not at all as those expensive HF scopes.
Myself have an old and very heavy english all tubes scope
I got for free by a nice engineer working in an electronics repair
:) |
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| jacco vermeulen |
Polo,
you live in the States, plenty of really cheap Tektronix's to buy.
Don't buy a handheld if you are new to this.
I would look for something like a 2465 once you've done some time on an average scope. Spending $200 on something you have no idea on knowing if it is sound may be blowing cash away.
The $50 you spend on a starters scope you will probably receive again when you sell your scope later.
Lots of information on scopes has been posted in a couple of threads, Mark Gulbrandsen and Jackinnj are knowledgeable on Teks, to name two. |
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| eapavant |
| It might be best to determine your needs a little better. A fast sample rate and high bandwidth can really help trying to solve problems. 10 Mhz is no good if your amp is oscillating much higher. |
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| Dryseals |
I've used scopes for a 30 years, believe me they have come along way in this time period. For a beginner and for what you are doing, I would recommend an older model analog scope and not worry about the MHZ too much at this point. I just picked up a Tektronix 2 channel 15MHZ analog for $61 to the door on Ebay. The sysc is off a tad but thats repairable (I worked in a cal lab repairing these things many years ago), service manual was $4.
Anyway, bigger is better, digital storage various outputs, nice options, but expensive. Some folks tend to pick up well with scopes more than others, before I would dive off into an expensive model, I would get an el cheapo and learn from there. The thing you'll need to know about the scope is if it works correctly or not. If you are just getting into trouble shooting, the first thing you do not want to trouble shoot is a scope, because you have to use a scope to fix a scope.
So my reccomendation to you is to look for a two channel analog in the less than 25MHZ range that works. Plenty of Tektronix T921s and 22s on Ebay and many other brands. |
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| jackinnj |
the 2465 is the mercedes of the last edition of analog scopes from Tektronix -- and they can be fixed -- buy one from a seller with a lot of positives
the older lab type scopes from Tek take up a lot of space but have myriad plug-ins -- the 7700, 7100 and 7900 series.
it isn't that you should just consider TEK -- HP, B&K, LeCroy, etc. all made excellent analog scopes as well
here's one suggestion for a complete test set up -- tek made a great modular power supply -- the TM500 series -- there is a scope plug (SC502, 503, 504) in for this as well as digital multimeters, signal generators, pulse generators -- if you see a Tek SG505 signal generator snatch it up |
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| Safe_Cracker |
| Thanks again for all your help! Polo..;) |
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| Apex Jr |
I would concur with a lot of the comments given.
I've sold scopes for quite awile, but at present have
no stock. I would say for you to look for Tektronix
1st with the 465 B and not just the plain version.
Has all the revisions and the problems worked out.
Also the 2465 also. I wouldn't buy the Tek T921's
0r 22's you'll have problems with the knobs breaking off.
The shafts are made of plastic.
Steve @ Apex Jr. |
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| kevinkr |
I have a TEK 2245A at work and one at home as well.. Works great, available on eBay for well under $400 typically. (Got mine for $300)
100MHz, 4 channel (2 are limited sensitivity) delayed timebase, many trigger options, (trigger actually works unlike some earlier ss models) auto setup, time, frequency and voltage measurement by cursor, microprocessor controlled. Reliable. |
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| jackinnj |
| quote: | Originally posted by Apex Jr
I would concur with a lot of the comments given.
I've sold scopes for quite awile, but at present have
no stock. I would say for you to look for Tektronix
1st with the 465 B and not just the plain version.
Has all the revisions and the problems worked out.
Also the 2465 also. I wouldn't buy the Tek T921's
0r 22's you'll have problems with the knobs breaking off.
The shafts are made of plastic.
Steve @ Apex Jr. |
Further to your comment -- the mesh grid inside the CRT of the 2215 is prone to deformation if the scope is "manhandled" -- I had one of these and was able to install a new CRT, but wouldn't recommend it to anyone for second hand purchase. |
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| Safe_Cracker |
Ok, I know you guys may not be big fans of these but I need prtability also, reason for looking at handhelds. I noticed some decently priced items like the Fluke scopemeter 99B V 2, nice looking piece and has a 100mhz bandwidth. I will mainly be using it to test/ adjust car stereo amplifier, gain settings, etc. Will this do the job? I am not worried about the cost approaching $1000, nor am I rich but I have a couple of costly hobbies I am getting out of like R/C helis and boats (some may know what I mean?). Thanks again for your help! Polo...:)
http://cgi.ebay.com/ws/eBayISAPI.dl...ADME:L:RTQ:US:1 |
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| eapavant |
| Ya that scope might work. The things you really need to look at are, ANALOG, at least 100 Mhz bandwidth, sensitivity of 1 or 2 mV.cm, and not digital. That is what is important for audio amp trouble shooting. Also a 1x/10x probe. Auto pulse-parameter measurements, waveform plots and pre triggering event storage are not really a big deal. The thing with digital is they are sampled data tools. A good analog scope is a much more versatile tool. If setting gain is you main goal get a good dmm. A Tek. 465 is a good start, or get one of the smaller ones in the 24 series. Just my two cents. |
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| Safe_Cracker |
| How would a dmm show a clipping signal? Polo.. |
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| eapavant |
| quote: | Originally posted by Safe_Cracker
I am new to electronic diagnosis but very willing to learn. I want to buy an Oscilloscope but I know nothing about them. I wan to be able to set my amplifier gain settings, and also help aid in amplifier repair.
Thanls for any help, Polo..:) |
I guess just take our advise or not. Good luck getting a scope, it will open up a lot of new doors. I know it did for me. |
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| Safe_Cracker |
| quote: | | If setting gain is you main goal get a good dmm |
I am very greatfull for any and all info listed here, but looking at what you said I am interested on how to set the amplifier gains using a DMM. I had no idea this could be done without seeing the wave form? I am very interested in learning so don't hold back. I am listening to what you guys are saying, don't think I am not I just don't know the difference between a digital/analog scope and/or why one will work and the other won't. I am very greatfull for you guys taking your time to point things out for me. I am not new to Car audio and use to be an auto tech until I had to have pins put in my back, now I deliver refrigerators, lol. Thanks...Polo.. |
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| mobyd |
I bought a Tek 2465A on EBAY, and liked it so much that I bought a second one (2445) for my soak test trolley. Lovely scopes - even though they cost me about a tenth as much as my fancy pants THS720 digital....you live and learn!
M |
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| jackinnj |
| one worthwhile thing to purchase is a decent of scope test probes -- if you can't afford TEK consider B&K. |
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| lgreen |
I would recommend this guy for a scope- his prices are about the same as EBay but his stuff is actually working.
Used Test Equipment
I bought my Tek 265 M from him, with probes and such...
And then I bought a signal generator, DMM, etc.... |
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| TerryC |
| quote: | Originally posted by eapavant
It might be best to determine your needs a little better. A fast sample rate and high bandwidth can really help trying to solve problems. 10 Mhz is no good if your amp is oscillating much higher. |
What is a reasonable bandwidth for troubleshooting an amp? |
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| Nigel Goodwin |
| quote: | Originally posted by TerryC
What is a reasonable bandwidth for troubleshooting an amp? |
A 20MHz is plenty, a 10MHz would be as well - fears about an audio amplifier oscillating at greater than 10MHz are unfounded!. |
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| Safe_Cracker |
| So I could a 10Mhz scope and troubleshoot anything that I may need be on an amplifier? Polo |
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| Nigel Goodwin |
| quote: | Originally posted by Safe_Cracker
So I could a 10Mhz scope and troubleshoot anything that I may need be on an amplifier? Polo |
Yes, it would do almost anything you ever need! - higher bandwidth is nice, but only very rarely needed!. |
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| Safe_Cracker |
Thanks Nigel, so what is wrong with the handhelds? I am always on the run and a clunky tube unit is ok for the work bench but I need something batter powered but yet functional for the road or away from home, would a Fluke scopemeter work in this instance? Polo..
PS- Thanks again.. |
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| EC8010 |
The problem with the handheld 'scopes is that they are digital. Digital 'scope have all sorts of lovely bells and whistles like automated measurements and cursors, but they inevitably come with aliasing problems due to limited sample rate and record length. That's not a problem if you're an experienced user and know how to spot when the oscilloscope isn't telling the truth, but it's not ideal for a beginner. For analogue audio, a 20MHz two-channel oscilloscope will do.
If you want it to have decent triggering (and you do) you're probably going to want a Tek. If you want to look at digital audio, you need something faster, and 100MHz is more like it. The Tek 465B is a nice 100MHz two channel scope with delayed timebase, but it's getting a bit long in the tooth, so reliability might be an issue. The next generation on is the Tek 2445B or 2465B. As has previously been mentioned, the 2465B is a lovely 400MHz 'scope, but it's not cheap. And if the "Y" amplifier hybrid fails, you're stuffed (they're not made any more).
I would echo the advice of others here; buy a cheap 20MHz 'scope to learn on, then buy a nice Tek when you know enough to be able to check it out throughly for faults in the warehouse (or wherever you buy it). The most important test for a Tek is to apply a sine wave and shift it up and down the screen to check that it doesn't change its amplitude;if it does, the "Y" amplifier hybrid has failed and they're not available (if anyone knows of a source for a 2465B, I'd love to be corrected).
Finally, there are other oscilloscope manufacturers, but Tek made the best analogue 'scopes. I have a Tek analogue and a Tek digital. With hindsight, if I could have afforded a LeCroy digital, I would have done so, but it would have almost doubled the cost and I dithered enough as it was before splashing out the money for a new oscilloscope. |
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| Safe_Cracker |
| So is a digital that has a sample rate of say 5GSa/s - 9.9GSa/s and a bandwidth of 100MHz - 349MHz considered good? I am glad to see everyones point of view, it will make me a better shopper for sure, lol .. Polo. :D |
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| Nigel Goodwin |
| quote: | Originally posted by EC8010
Finally, there are other oscilloscope manufacturers, but Tek made the best analogue 'scopes. |
As with anything, this is purely a personal opinion!.
When I upgraded my scope at work a number of years ago, I had a Tek on trial, I was VERY disappointed with it. We sent it back and had a Grundig scope on trial, and it absolutely wiped the floor with the Tek!. I'm still using the same Grundig scope, it's been great!.
However, I'd love one of the Tek LCD digital scopes! :D |
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| EC8010 |
| quote: | Originally posted by Nigel Goodwin
However, I'd love one of the Tek LCD digital scopes! :D |
My TDS3032 has 300MHz analogue bandwidth and a maximum of 5GS/s, which is quite good. What limits it is the record length of only 30k points. That means that at slower sweep speeds, the sample rate has to fall, leaving it open to aliasing. Nevertheless, it was the first digital 'scope I'd seen to be able to display a line of colour bars that looked credible. What I'd like is a LeCroy 300MHz 2.5GS/s scope with 1M point record length...
Another thing about oscilloscopes is that people do have strong personal opinions and preferences. |
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| kmj |
Does anyone have a Link or a recommendation for a signal generator (PC-program)? Preferably freeware.
Ok, that some can be a bit noicy but I will probably work quite nice to start with. |
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| jackinnj |
www.trueaudio.com has a nice synthesizer and it's free --
here's a new scope from Tektronix if anyone cares to drool on their computer:
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| EC8010 |
| quote: | Originally posted by jackinnj
Here's a new scope from Tektronix if anyone cares to drool on their computer: |
I think my keyboard's about to stop working. Please Santa, can I have one for Christmas? (Even the base model would do.) |
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| Nigel Goodwin |
| I think, as a suitable penalty, 'jackinnj' should be made to buy every poster in this thread one of those! :bawling: |
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| jacco vermeulen |
Jack,
why the modesty ? The DPO7254 is just € 23K overhere, only needs the
€ 13.5K samples accessory. |
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| freakyone |
Would a 1 channel 10Mhz oscilloscope come in handy working with amplifiers?
Whats the point having two channels??
cheers! |
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| dfdye |
| quote: | Originally posted by freakyone
Would a 1 channel 10Mhz oscilloscope come in handy working with amplifiers?
Whats the point having two channels??
cheers! |
You bet it would!
The two channel models are good if you want to compare signals, or if you are triggering off of an external source. Though I find it helpful to compare input and output signals on the same screen, a single channel scope would at least allow you to see what is going on with the output of your amp. This would definitely be a nice tool
The next question is always how much? I have seen Tektronix 475's on ebay for ~$300 before, which is a great deal IMO even for a used one if it is working properly. Those guys are tanks!!!
If you are buying a cheap one, remember that with test equipment you often get what you pay for. The failure rate for a new, cheap scope is sometimes greater than for an older, quality scope.
If, however, the price is right, then the scope will definitely help out.
The next question is what will you be using for a test source? Do you have a function generator? |
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| Mark A. Gulbrandsen |
Two things... Only buy a dual trace scope since it allows alot more flexibility. Once you get into using your scope a single trace unit quickly becomes outmoded and you'll be wishing you had bought the dual trace. Affordable new digital scopes are still in the dark ages so don't go that route and older digital scopes that might be usable to look at complex waveforms that inexpensive digital scopes can't display are many times not repairable!! Also there is only one analog scope to buy and that is Tektronix. Nothing else out there can even come close to the build quality, performance, and reliability of a Tektronix 465B or 475B scope. They have been the industry standard for several decades now. When looking for a Tektronix only go for the B models as they have several advantages over the first models such as LED indicators instead of incandescent and many other features to make them even more reliable and consistant in performance than their predecessors...... A "B model" will generally cost about 100.00 higher than the older model Teks but the extra expenditure is well spent. Stay away from the seemingly good deals on the 465M scopes as they are not even a close resemblance to the much better 465 or 465B scopes!!
E-Bay is a good place to look but try to avoid buying from the large test equipment dealers.... but do purchase from someone that will guarantee it to function properly on arrival or someone that has had it recently calibrated. Sphere up in Canada is a very good place to buy from, Walter will stand behind any item he sells.... he also has one of the largest stock of Tektronix parts and crts around. There is also still an advantage to the Canadian dollar conversion too.
Keep in mind that the last price for a new 465B was just over $4,000.00 US in 1980 dollars so if you have to pay $300.00 to $500.00 for a nice clean one you're getting a bargain. I wonder what $4,000.00 1980 dollars is in todays dollars?????
Sphere Test Equipment
Mark |
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| wrenchone |
I would second the recommendation of an analog scope for the beginner - they don't alias. However, I would also advise getting as high a bandwidth as possible, especially if you're going to do things like cascoding. I had an oscillation problem with a cascoded emitter follower that looked like no big deal with a 30MHz scope, but turned out to be 0.5V p-p at 80MHz with a proper 100MHz scope. (Any more amplitude, and I could have started my own FM station). Teks are good, but the Kikusui 100MHz scopes also look good in terms of features and affordability. Can someone comment that has had some direct experience with the Kikusui scopes?
As for digital, I would stick with someone like Yokogawa or LeCroy that got convinced earlier on about the importance of memory depth. Most of the cheaper/older digital scopes have pitiful memory size.The older HP digital scopes also have a pretty hideous user interface to boot. |
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| SY |
| I use a Kikusui 100MHz scope and have only good things to say about it. |
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| Mark A. Gulbrandsen |
Sy,
With all due respect lets throw it in the back of my service van for 5 years and see what happens to it....:bawling: . Lets also place them side by side and see which one has the better build quality. Having been on and off the road doing service work for in excess of 25 years I would only ever place my bet on the TEK.
Mark |
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| jackinnj |
| quote: | Originally posted by Mark A. Gulbrandsen
Keep in mind that the last price for a new 465B was just over $4,000.00 US in 1980 dollars so if you have to pay $300.00 to $500.00 for a nice clean one you're getting a bargain. I wonder what $4,000.00 1980 dollars is in todays dollars?????Mark |
A little over $8,000 for consumer items, not quite so for electronics, however, which for the most part have experienced declining real prices.
FWIW, the Tek 2465 can be had for around $300- $400 -- this thing will lock onto virtually any signal. There are a number of folks who deal in this range of scopes -- and you can check them out by their feedback notes.
A number of the ancient Tektronix scopes like the 545,547, 535 are very, very low noise and still in service. |
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| SY |
| quote: | Originally posted by Mark A. Gulbrandsen
Sy,
With all due respect lets throw it in the back of my service van for 5 years and see what happens to it....:bawling: . |
For that sort of service, I'd indeed look elsewhere.
For use on a diyer's test bench, well, I've been using mine pretty heavily for close to 15 years with no problems. I check calibration periodically and that's about it. |
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| Brian Beck |
I use a pair of Tek 475s, one with the DMM option, but lately I can't brag about their reliability. Those damned tantalum bead caps keep expiring, and they leave this world as a charred and stinking short circuit that seems to take out transistors. Recently, I replaced 3 bad tantalums in one 475 and two transistors that died as a result. My only other complaint about the 475 series is that the display spot is large due to the high accelerating voltage needed for fast sweeps. This results in slightly blurry waveform traces, at least compared to my HP 1710 or my older Tek 453 (with a nuvistor front end and solid state elsewhere). With all Tek scopes from the last few decades, proprietary hybrid circuits are used for gain. The 475s have been reliable in this area, but my buddy’s two 2465s have a penchant for expiring hybrids. And these are made from unobtainium. Still, I recommend Tek 400 series or the 7000 series plug-in models. But they all used a lot of tantalum beads – look out!
I’ve seen SY’s Kikusui model (or a similar model) before and it looked very nice, but I don’t know anything about its reliability or parts availability. It looked as rugged externally as a 475. SY, does it use hybrid circuits? |
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| Mark A. Gulbrandsen |
When TEK crt's get old they typically do begin to go soft and can't display a very sharp trace... this is incidentally common to just about all CRT's in other scopes and especially CRT's in projection television sets. Best thing to do is replace the CRT with another one andrecalibrate. My 7904 has that problem to some extent and I'm getting a new CRT for it...(ok it came from Texas Instruments and probably ran 24/7 for its entire life!) it has a 15kv accelerating potential which is a hell of alot of voltage on that small of bottle but accelerating potential aside declining emission from the electron gun is normally the main cause of not having a sharp trace. My 465B crt has a trace thats as sharp as the point of a needle. It gets a few hours use just about every week and I have never had a tantalum cap go but I don't have any of the older plain 465/475 models around any longer, I'm not sure that the B models use those same tantlum caps and I'd bet that this is one of the things that was taken care of in the B model scopes. I agree that the 2400 series of scopes are definately ones to stay away from. Some were good performers but when they die thats pretty much it unless you locate a scrapper unit to get parts from.
It is general knowledge that the later produced TEK analog scopes had inferior CRT's in them that typically could not produce sharp traces.... Thus the delcine of the analog scope began and several years later the TEK CRT plant ceased operations completely.
Aside from the 465B I also own:
7904A 500 mhz Lab scope
7603 Storage scope
214 Dual Trace Mini Storage Scope (Hand Held)
SC501 Monitor scope- TM-500 series
SC-504 Dual trace 80 mhz scope-TM-500 series
310A All Tube Scope
All of them work perfectly with the exception of the 7904's crt.
Mark
Inside the 214 after installing new Ni-Cads. I paid 35.00 for it on E-Bay. Failed batteries will not allow the scope to function at all as they are an integral part of the power supply. This is the most common problem with the TEK Mini Scopes. Many of these like mine are practucally given away because most are not aware of the battery issue. |
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| bulgin |
Hi Cracker
I use an Isotech ISR 635 35MHz, bought from RS a long time ago.
I can't really fault it and remember I got a very nice Gerber combi knife tool chucked into the deal.
Cheers
bulgin |
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| SY |
| quote: | | does it use hybrid circuits? |
I don't know. I'm embarrassed to say that I've never opened it up.
Maybe that says something for the scope. |
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| jackinnj |
| quote: | Originally posted by Mark A. Gulbrandsen
7904A 500 mhz Lab scope
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The 7904 and 7104 were used at Oak Ridge for various timing purposes. |
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| Mark A. Gulbrandsen |
| quote: | | The 7904 and 7104 were used at Oak Ridge for various timing purposes. |
I can't say that I use my 7904A for timing purposes...... I generally use it because its just plain fun to use and really accurate too.
| quote: | | I don't know. I'm embarrassed to say that I've never opened it up. |
The inside of a scope can be a thing of beauty..... or a rats nest that shouldn't be allowed to exist! In the photo below the bottom side of a TEK 315D tube scope that is nothing less than a work of art!
Mark |
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| Brian Beck |
| Just as a general comment - IMO, the pinnacle of analog design can be seen in test equipment from Tektronix and HP (especially) from the era of 1955 through 1985 (roughly). Schematics, both tube and solid state, from these items would make good case studies for electronics students. The designers met challenges of extreme performance requirements, stability and reliability with some very clever designs. A lot can be learned just by studying the schematics. I expect that the same can be said of European equipment from this era, but I have less experience with it. |
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| wrenchone |
I've picked up a small menangerie of scopes over the years - here are my comments:
HP 54520 500MHz 2 channel scope - Very fast, memory is acceptable (32k/channel). It has a floppy for waveform storage (a plus if you want to easily document your work). Lots of features, but user interface is terrible, so it takes the manual and some digging to get at them. I got this one for high speed pulse and laser work, knowing full well what sort of user interface it had.
Yokogawa DL1200A - great user interface, 4 channels, 100 MHz, 100k memory/channel. No floppy, uses expensive and outdated memory card requiring an equally expensive and outdated reader for waveform storage. Scope has a printer, so could print and scan images in a pinch. Later Yokogawa scopes have a floppy for image storage. The latest ones have a USB port (memory stick, anyone?).
Hitachi V302B - 2 Channels, 30MHz BW, basic features. This is an excellent beginner scope and goes for a song these days. I paid ~850 for mine in 1982, and it was a bargain then. This was my workhorse scope for years until I got the 465B.
Tektronix 465B Rack mount version. Classic workhorse scope, 100MHz bandwidth, good panel layout, all the features you need, including delayed sweep. Mine has a somewhat soft trace, but is still very usable.
Tektronix 2246A - This is also an excellent scope, with 100MHz BW, 4 channels, trace readout, and a load of measurement functions. I also have one of these and a late model Yokogawa digital scope at work. I use the analog scope when I want to do really low noise measurements.
Tektronix SC504 - 80MHz, dual trace, fits in TM500 series rack, takes two spaces. This scope is very compact, but the small screen and control size make it difficult to use for old codgers like me. The same is true for the whole series of modules for the TM500 racks. Maybe It'll be ok now that I have my bifocals.... The advantage of these modules is that you can fit a whole lab's worth of functionality in a little rack that doesn't take up much bench space. Power supplies, function and pulse generators, multimeters, counters, distortion analyzers, etc. are available.
One suggestion - for those who want to document their work and only have an analog scope, Sony sells a scope hood that fits the old floppy-based Mavica cameras. It works very well, and beats the heck out of using the old Polaroid scope cameras. No doubt a clever person could gin up a hood out of some cardboard and tape that would work just as well. |
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| dfdye |
After all of this discussion of ultra-high end scopes, I think an appropriate question is "What do you NEED for audio?" This latest round of discussion was kicked off with questions about a 1 channel 10Mhz oscilloscope. Though I agree with pretty much everyone's assertion that two channels are definitely more desirable, if you are willing to switch probes back and forth then a single channel scope can indeed give you a great deal of information about how an amp is behaving.
All things being equal, I am betting that one could find a reasonably priced, high quality used scope for a decent price that would be accptable to Freakyone, but this was not the question! freakyone wanted to know if one particular scope would be useful, and I think the answer is "yes."
Quite honeslty, after playing around with the trueaudio.com scope for a while, I think this would potentially be pretty useful too if somebody is really in a monetary pinch and can't afford a decent used scope. I especially like the included waveform generator, though if you don't have a good sound card I could see potential problems using both the function generator and the scope at the same time. I have only played with this on my laptop and though the signals are indeed ugly at time (especially when considering that the sampling rate of the scope is 48kHz), it is a nifty piece of software.
So, after this rambling, what specifications do you all think are necessiary for a scope for testing audio equipment? How fast do you need to go? How many channels? (I say 2. Input and output, but I can see 4 for stereo as being useful too) How durable? (I say moderate at best, since most of us will put it on our bench and leave it there--no back of vans for us) What accessories? (I think a 10X probe + standard clips and cables should be fine)
Feel free to add to this list or elaborate on what limits you have run into with your gear so that someone seeking a scope can know what to avoid.
As a disclaimer, I personally use a TDS380 in my lab at work and a 475A at home, so I have never had any problems with audio signals or testing and am a little spoiled. I would recommend either of these for general use. (obviously the TDS380 is a little overkill! :D) |
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| Mark A. Gulbrandsen |
I would not get a scope that has less than 60 mhz bandwidth for audio use. It also HAS to be dual trace but a delayed trace feature is not really all that necessary. Condsidering that I bought my 465B in near mint condition for just $75.00 plis shipping I don't think price is really all that much of an issue here because juat a couple of hundred bucks gets you a clean high end scope if you are a careful shopper and get one where the seller warrants its functionality and will take it back if its not up to snuff.
Indeed...these days VERY CAREFUL SHOPPING will reward a scope hunter to no end and getting a very high end name brand unit is quite easy.
Mark |
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| wrenchone |
I would advise anyone starting out to buy the best scope they can afford. Start out with analog, as there is better bang for the buck. Get 2 channels - all of the scopes I've seen these days have at least 2 channels anyway, unless you unearth some old monster from the dinosaur era. When all is said and done, the working (albeit imperfect) scope sitting on your bench, no matter what brand, is tons better than the perfect scope that is forever out of reach. Even if the calibration is off, you at least get an idea of what's going on in your circuit, and that's better than running blind with no scope at all.
The Hitachi and Kikusui scopes appear to be real bargains (<$100). They go for very low prices on the auction sites because they don't have the recognition factor of the Teks and HPs. I've been tempted by the Kikusui 100MHz scope (routinely listed for below $100), but I already have too many scopes as it is. The Hitachi V-302B was $850 20 years ago, but they go for far less than $100 these days, and that's a nice bit of scope for the money. |
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| john65b |
Kinda dumb question, but is WINSCOPE (free) worth using on basic Amp spec'ing like watts/channel, distortion, etc?
I have three laptops and six desktop computers and I wouldn't mind putting one to use... |
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| dfdye |
| quote: | Originally posted by Mark A. Gulbrandsen
I would not get a scope that has less than 60 mhz bandwidth for audio use. |
Mark, I'm just not sure that is necessary. I'm not saying it isn't useful for testing other stuff, but I was trying to isolate what is needed for AUDIO testing. I think we can all agree that Nyquist frequency is not a good baseline for minimum specification for a scope, but assuming one would want to test from DC to ~25 kHz, would you really need to get a 60 MHz scope to do this? I'll go out on a limb and say 10X Nyquest should be good to produce an acceptable waveform. It may not be pretty, but it will be diagnostic. If I use that baseline, then a 0.5 MHz scope should be able to produce an "acceptable" waveform for a 25 kHz wave. The 10MHz scope specification in question is 20 times this!!! I may be missing something here (or may have goofed up my unit conversion), but I really think 60MHz is past the baseline. I would say MINIMUM specification should be 1MHz, and 10 MHz should be more than plenty.
Just to be clear, I too would recommend getting as nice of a scope as you can afford (within reason, of course), but I’m just not convinced yet that you need a 60 MHz scope. If we weren’t limiting usage to audio, I would be right there with you (though I would have said 40MHz off the top of my head, if for no other reason than it is the spec of the TDS 1000, which is one of my favorites.)
Mark, I’m not necessarily saying that I think you are wrong, but I don’t follow the logic. Is there a specific reason you picked 60MHz?
BTW, that was a great find on your 465. I haven't seen a working unit for under $250! |
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| Mark A. Gulbrandsen |
These days when I think audio that also includes digital audio equipment...CD players , PCM power amps, etc., and thats about the minimum bandwidth one can get away with for working on digital audio. More bandwidth is even better with upcomming Blue ray and other HD stuff into the future. When working on analog power amps and checking for or looking for oscillation problems that extra bandwidth is also necessary. At work I repair and adjust a lot of Dolby Digital cinema readers and this requires at least a 60 mhz scope bandwidth with superb triggering to look at the video signal that comes off the film scanner CCD camera... ditto for Sony SDDS ccd cameras and these are even touchier to set up and require more bandwidth because of the higher data rate over Dolby Digital. CD players also have similar requirements.
Mark |
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| dfdye |
Well, that just makes too darn much sense. Consider me sold.
Thanks for the follow up,
David |
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| jleaman |
| quote: | Originally posted by Mark A. Gulbrandsen
These days when I think audio that also includes digital audio equipment...CD players , PCM power amps, etc., and thats about the minimum bandwidth one can get away with for working on digital audio. More bandwidth is even better with upcomming Blue ray and other HD stuff into the future. When working on analog power amps and checking for or looking for oscillation problems that extra bandwidth is also necessary. At work I repair and adjust a lot of Dolby Digital cinema readers and this requires at least a 60 mhz scope bandwidth with superb triggering to look at the video signal that comes off the film scanner CCD camera... ditto for Sony SDDS ccd cameras and these are even touchier to set up and require more bandwidth because of the higher data rate over Dolby Digital. CD players also have similar requirements.
Mark |
Mark if you had 250$ us what scop would you buy *FOR* working on small amps such as chip amps testing cables working on aleph amps etc etc nothing hi end that would require a fast scope? Im in the market to buy one. but not sure if i need a 100mhz or not. The next piece to buy is a dul psu but regulated.. they are cheap on ebay too. 1004 ish. |
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| dfdye |
| quote: | Originally posted by john65b
Kinda dumb question, but is WINSCOPE (free) worth using on basic Amp spec'ing like watts/channel, distortion, etc? |
After trying it out for a few minutes, I think it is a nice little piece of software. I must say that TrueRTA seems to be a little more geared toward audio testing, but WINSCOPE seems like it has more "real" oscilloscope functionality. Either of these will get you some help in a pinch, but like Mark and I have just been discussing, they are both limited to the speed of your sound card (which is ~44kHz) which doesn't really do a good job of telling you what is going on in the higher frequencies. As such, distortion measurements in this range will be pretty difficult IMO. Plus, I am going to bet that the noise/distortion of your sound card will be greater than the amp you will be testing, making a difficult situation to deal with. Hope this answers your question.
David |
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| Mark A. Gulbrandsen |
Jason,
There are two really good scope dealers in Canada. One is Sphere Test Equipment
The other is a guy on E-Bay and his On-Line Store is called The Oscilloscope Store
Check with both of these places and see what 250.00 will buy. I've dealt with Walter at Sphere many times and he gives first rate service and delivers quality equipment and parts. The Scope Store guy on E-bay has excellent feedback and some really really great old tube scopes(and solid state) for sale albiet at pretty high prices but they also come with a 1 year/90 day CRT guarantee! I love his motto...."We Only Do Tektronix"
Happy shopping!
Mark |
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| poobah |
| A 60 mHz scope is already limping a little at 6 mHz. When things go wrong... sometimes the details are in the "edges". Audio could involve digital stuff. 60 mHz is about bottom of the barrel these days anyway. |
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| dfdye |
| quote: | Originally posted by jleaman
Mark if you had 250$ us what scop would you buy *FOR* working on small amps such as chip amps testing cables working on aleph amps etc etc nothing hi end that would require a fast scope? Im in the market to buy one. but not sure if i need a 100mhz or not. The next piece to buy is a dul psu but regulated.. they are cheap on ebay too. 1004 ish. |
I hope you don't mind me offering a suggestion, but I found this Tektronix 475 on eBay that looks like it is in pretty good condition. There is a chance it could stay under the $250 since the bidding might be light tomorrow in light of the holiday. This scope is one of my favorites.
David |
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| dfdye |
| quote: | Originally posted by poobah
Audio could involve digital stuff. 60 mHz is about bottom of the barrel these days anyway. |
Yea, the digital argument convinced me. I guess my head is still stuck in analog land. :snail: |
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| poobah |
| That deal looks good... |
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| Mark A. Gulbrandsen |
I agree with you completely Poobah. Remember with an H-P, or Tektronix they typically go out alot further than the spec says. My 465 for instance does close to 130 mhz, my SC-504 does about 110 mhz before rolling off to any great extent, not bad for both a 100 mhz and 80 mhz scope! This is typical of high end scopes and one other good reason to do careful shopping and get yourself one of the higher end scopes. It can be your first scope and the last one you will need.
Mark |
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| jleaman |
| quote: | Originally posted by dfdye
I hope you don't mind me offering a suggestion, but I found this Tektronix 475 on eBay that looks like it is in pretty good condition. There is a chance it could stay under the $250 since the bidding might be light tomorrow in light of the holiday. This scope is one of my favorites.
David |
Available to United States only :( |
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| dfdye |
Woopsie! I forgot you were in Canada. My bad! Though Mark's comments about the Canadian dealers make a lot more sense now. :D
Speaking of which, the places that Mark listed seem to have some good scopes, but the prices are indeed more steep. The Tektronix 2215 that Sphere has especially cought my eye, but is $450. I have used one of these before, and had no major complaints during the time I used it.
Good luck hunting one down within your price range!
David |
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| poobah |
2215 is newer... my first scope... brand new! in '83.
Some of this stuff is getting pretty old. Caps are caps, If you find a working jewel... the same logic applies, recap it before you start smoking **** you can't replace.
;) |
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| 1audio |
For audio work the Tek 5000 series are a fantastic bargain. This has 2 super hi-gain differential amps in the box and the current price is very low ($20.00) http://cgi.ebay.com/Tektronix-5110-...1QQcmdZViewItem
Because the 7000 series is faster these are usually ignored. I have 2 I use for monitoring the outputs of distortion analyzers and they are simply workhorses. And if they really break they are cheap to replace. The 5440 series is good to 50 MHz I think with the right plug-in.
I have lots of 7000 frames and plugins, and a THS720 for portable use but I spend as much time looking at the display on the 5000s. An they are big CRTs (6 1/2") so they are easy to see.
-Demian |
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| jackinnj |
| quote: | Originally posted by 1audio
For audio work the Tek 5000 series are a fantastic bargain. This has 2 super hi-gain differential amps in the box and the current price is very low ($20.00) http://cgi.ebay.com/Tektronix-5110-...1QQcmdZViewItem
Because the 7000 series is faster these are usually ignored. I have 2 I use for monitoring the outputs of distortion analyzers and they are simply workhorses. And if they really break they are cheap to replace. The 5440 series is good to 50 MHz I think with the right plug-in.
I have lots of 7000 frames and plugins, and a THS720 for portable use but I spend as much time looking at the display on the 5000s. An they are big CRTs (6 1/2") so they are easy to see.
-Demian |
I have a pair of 5103's -- in the same family to which Demian refers -- I use this one with a 5a22n Differential Amplifier -- the 5000 series saw many applications in the medical and manufacturing industries where low noise was (is) important. I think that this particular scope cost me about $10 -- but the 5L4N spectrum analyzer was ~$100. (I now use an HP3577a spectrum analyzer.)
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| Mark A. Gulbrandsen |
Hey, I'd be interested in that 5L4N spectrum analyzer!
Mark |
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| john65b |
Well, I won that Textronix 5110 osciliscope for $20 that Demian referred to (Thanks!).
Now, can anyone direct me to a good tutorial on how to use it for spec'ing audio gear? Power/Distortion/clipping?
I appreciate it! |
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| Mark A. Gulbrandsen |
A scope is just the beginning! You will need to buy a distortion analyzer to read the distortion content and to look at it. Also most distortion analyzers double as an AC RMS meter and that works for calculating power outout. You will also need a sine wave audio oscillator of very low distortion... some distortion analyzers also have this built in. Look on E-Bay for a clean Sound Technology 1700 series distortion analyzer. They are one of the best units built for this purpose and can be had for just a couple of hundred dollars in excellent shape. The ST is capable of reading ultra low distortion levels, it has a built in ultra low distortion sine wave oscillator. You will also need various load resistors, I reccomend all 4 oohm since you can make what ever you need out of stacking or paralleling them.
1700B For Sale
Mark |
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| dfdye |
As for clipping, I think you can pretty easily see that by waveform shape going through your scope. If it doesn't look right at the +/- peaks, it is clipping! :D
Seriously, I think somebody will be a little more detailed, but that is what I have been looking for as to limits. I usually back off a good percentage past that to ensure these limits aren't reached, but again, I am sure somebody has a better method than this. |
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| dfdye |
| quote: | Originally posted by john65b
Well, I won that Textronix 5110 osciliscope for $20 that Demian referred to (Thanks!). |
I just saw a lot of 4 of these go for $20.50 with 11 modules! I can't believe I couldn't talk myself into gettin in on that one!!!
David |
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| jackinnj |
| quote: | Originally posted by Mark A. Gulbrandsen
A scope is just the beginning! You will need to buy a distortion analyzer to read the distortion content and to look at it. Also most distortion analyzers double as an AC RMS meter and that works for calculating power outout. |
i think that I am going to have to design a very low-noise, non-FFT DA which folks can plug into a Tek 5000 or 7000 series, perhaps with a little USB jack on the front ...
if you want a great AC RMS meter consider the HP3400 series meters, the HP3581 wave analyzer , HP3586 selective level meter etc.
the Krohn-Hite 6900 distortion analyzer is a real buy if you see one -- it has a quite good oscillator (THD% is 0.001 to 0.002%) with 5.1V output, and automatically sets the notch for the distortion analysis. You will need an outboard attenuator to use the oscillator. |
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| john65b |
Holy ****, what the hell did I get myself into?
I was hoping I could just throw a dummy load across my amp speaker outs, play a 1khz sine wave CD, connect the osciliscope before and after the dummy load and be able to read clipping/power output, and maybe distortion levels...
Hmmm, I work with a lot of EE's (I am an ME), so maybe i can "Borrow" a spectrum analyzer from work should I need one... |
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| dfdye |
| quote: | Originally posted by john65b
Holy ****, what the hell did I get myself into? |
Well, if you really want distortion measurements. . . .
But don't let Mark scare you too badly. You don't need all of that for basic amp diagnosis, but they are needed for noise measurements. You can get a bunch of information and do a lot of diagnosis just off of your scope. |
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| john65b |
Cool. Had a quick case of buyers remorse there...
I was trying to think of other things I could use the scope for beside amp diagnostics ...computer hardware, maybe speaker building?
Any other ideas? It would make me feel better about te purchase. |
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| dfdye |
Sure. I like the square wave test to get an idea of frequency response. The front edge of a square wave is composed of high frequencies while the tail is composed of low frequencies. A rounded edges on the front of the square wave indicate high frequency attenuation while rounded edges on the back end show low frequency attenuation.
You can measure clipping by looking at sine waves and looking at the peaks to make sure the waveform is still in tact.
You can measure/adjust gain by comparing the intensity of input and output signals.
The list keeps going, but distortion is a little harder to do with just a scope (meaning I don't know how :))
Besides, for $20 you can't really have too much remorse anyway! :D |
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| Mark A. Gulbrandsen |
| quote: | | I was trying to think of other things I could use the scope for beside amp diagnostics ...computer hardware, maybe speaker building? |
Thats easy! Open it up.... have it framed... and then hang that work of art on the wal for all to see!
Mark |
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| 1audio |
John:
Congradulations! You have a scope that can handle most audio needs. The differential amps on that go down to 50 uV per div. No hum or noise can escape that. (And you can get other plugins for that scope with wider bandwidth and other functions cheap.)
I have many distortion analyzers and its a wonderful pursuit, but it may be no more relevant than "angels on the head of a pin". Finding noise, oscillation etc. are much more important to good sound. And with opamps the distortions are usually infinitely small or gross enough to see on the scope.
An AC voltmeter is useful for checking gain and power output etc. I would get one of these http://cgi.ebay.com/FLUKE-8920A-Tru...1QQcmdZViewItem
that I think is overpriced or http://cgi.ebay.com/FLUKE-8921A-TRU...1QQcmdZViewItem
better price or a Fluke 8800 ac-dc-ohm meter (which are great bargains for 5 1/2 digit meters).
A good function generator will also be more useful, since it can supply multiple waveforms and a good one will be extremely flat response. One like this http://cgi.ebay.com/KROHN-HITE-1200...1QQcmdZViewItem
that should be $50 not $250.
And then the probes and cable to hook this stuff up that will cost more than the hardware.
Good probing!
-Demian |
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| blumenco |
I found an old tube unit. a heathkit push pull oscilloscope for 3 dollars the other day. it only goes up to 100k hz. maybe that is all I need for tube amps though...
Clark |
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| 1audio |
| quote: | Originally posted by dfdye
The list keeps going, but distortion is a little harder to do with just a scope (meaning I don't know how :))
:D [/B] |
You can use the X/Y function to check for distortion. X for the input and Y for the output and look for a wiggle in the line. Its not too sensitive but you may see something. And with two diff plugins you can see things that would be hard to see other ways. You could also look at the difference between the + and - inputs of an op-amp and see what distortion the amp is trying to remove directly.
-Demian |
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| dfdye |
| quote: | Originally posted by 1audio
You can use the X/Y function to check for distortion. X for the input and Y for the output and look for a wiggle in the line. |
I'm assuming you are actuallying using the amp as an amplification device! :D:D:D
If you amplify the input, then the scaling between the input and output will be off, even if you have perfect reproduction. X-Y would still be non-zero and probabaly quite large assuming you have any decent level of gain. The only way you could get a null would be if you had a unity gain device. |
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| 1audio |
The 5A22 is pretty linear and has a huge dynamic range. One is connected across the input in the first slot. The second is moved to the last (timebase) slot and connected across the output. The gains are adjusted to match. Big nonlinearities jump right out- clipping is flat lines appended to the ends of the trace- big harmonics will show in waves in the trace.
However comparing across the +/- inputs of the opamp will show exactly the differences between the input and output. The feedback circuit will scale precisely.
-Demian |
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| EC8010 |
| quote: | Originally posted by john65b
Cool. Had a quick case of buyers remorse there...
I was trying to think of other things I could use the scope for beside amp diagnostics ...computer hardware, maybe speaker building?
Any other ideas? It would make me feel better about te purchase. |
An oscilloscope is just about the most massively useful instrument a serious electronics engineer can purchase. It isn't precise, but it's great for pointing the direction in which to look, and that's vital. |
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| anatech |
I'll second what EC8010 said!
Well put sir.
-Chris |
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| ezkcdude |
| I got a Tek 465B off eBay for $142.50 (+shipping) a couple of weeks ago. It's my first scope, and is absolutely fantastic! It even came with 2 10X probes. I'm prototyping a DAC now, which will use a 24.576 MHz XO. Will I be able to see that signal clearly on this scope? |
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| anatech |
Hi ezkcdude,
I don't think you will have any trouble with that scope to see your signal.
-Chris |
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| EC8010 |
| Not quite. Bear in mind that you're hoping to look at 24.576MHz square wave, so that means it's composed of the fundamental plus 1/3 H3, 1/5 H5, 1/7 H7 etc. To get a reasonable approximation, you really need to see the ninth harmonic unattenuated, but the 465B is -3dB at 100MHz, so you're not going to see an accurate representation. That doesn't mean the 465B isn't a good 'scope - far from it, just that if you need to see that sort of thing accurately, you need a 300MHz 'scope (lots more dosh). Negatives aside, you will be able to see whether you've got a master clock and you will be able to probe for noise on supply rails etc. And at the price you paid for it, that 465B (with probes) was a bargain. |
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| anatech |
Hi EC8010,
True, I have analog signals on the mind. To see the edges accurately you are quite right!
Thanks for setting the record straight.
-Chris |
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| ezkcdude |
| quote: | Originally posted by EC8010
Not quite. Bear in mind that you're hoping to look at 24.576MHz square wave, so that means it's composed of the fundamental plus 1/3 H3, 1/5 H5, 1/7 H7 etc. To get a reasonable approximation, you really need to see the ninth harmonic unattenuated, but the 465B is -3dB at 100MHz, so you're not going to see an accurate representation. That doesn't mean the 465B isn't a good 'scope - far from it, just that if you need to see that sort of thing accurately, you need a 300MHz 'scope (lots more dosh). Negatives aside, you will be able to see whether you've got a master clock and you will be able to probe for noise on supply rails etc. And at the price you paid for it, that 465B (with probes) was a bargain. |
Thanks, that makes sense. As you suggested, for now I just want to make sure I have the clock set up correctly. |
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| poobah |
You'll see your clock just fine... it will just have some wigglies on the corners. Doesn't mean the wiggling is in the circuit, OR the scope... just that the higher harmonics are missing.
:) |
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| anatech |
Hi poobah,
Could be Wookie hair ........ :xeye:
-Chris |
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| ezkcdude |
| Actually, I was thinking about this some more. Specifically, I'm wondering about the shape of the waveform. Isn't the output of an XO a sin wave? It's not a digital signal, strictly speaking, is it? |
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| poobah |
The outputs of the oscillator circuit are squared-up... to prevent the dreaded jitter.
;) |
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| anatech |
Hi ezkcdude,
I am pretty sure the oscillator modules output a square wave. You want a fast rising and falling edge for a clock signal.
-Chris |
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| poobah |
| Ha ha... got there first! |
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