Suggest oscilloscope for DIY audio projects

[Ilya]

Hey guys! I'm shopping for an o'scope (cause the purchase is long overdue).

I thought that modern digital 'scopes would be ok, but they mostly have 8bit amplitude resolution (which concerns me) and their quality is somewhat suspicious. I have a feeling that they are much like digital consoles. Cheap ones are just plain crap, and good ones cost unwholy amount of $$$$.

I'm started looking at Tektronix 2445 'scopes and liked them a lot. They are somewhat expensive here but I believe I can afford that. The only thought that comes to mind is that 2445 maybe somewhat an overkill.

What do you guys think? Maybe some other suggestions? And when checking an used analog 'scope, what are common check procedures?

Thanks everybody for the input!

 

[jensenmann]

I bought two used scopes over the years and each one turned out to be more or less unreliable and defective. Since scopes are meant to be measurement tools which I want to rely on and not toys I finally came to the conclusion that I need a brandnew and reliable one. I ended up with this and couldn´t be happier: http://www.hameg.com/131.0.html It´s analog with digital control, best of both worlds.

 

[Ilya]

I bought two used scopes over the years and each one turned out to be more or less unreliable and defective. Since scopes are meant to be measurement tools which I want to rely on and not toys I finally came to the conclusion that I need a brandnew and reliable one. I ended up with this and couldn´t be happier: http://www.hameg.com/131.0.html It´s analog with digital control, best of both worlds.

Those Hamegs look cool. Although they are almost 1.5 times more expensive than I expected to spend... Need to think though.

EDIT: The model you mentioned is discontinued. Do you think the HM400 is a viable replacement?
I've checked with Farnell and they have a good price on those HM400, shipping is also cheap.

 

[Twenty Log]

I bought an analog scope...  Late 70s, out of calibration, has some issues for 1 uS scale but about $200 US for 100MHz. But with grain of salt and relative measurements it's OK.  Bought a TiePie 100 MHz; was $1300 US +/- depending on Netherlands exchange rate.  Possible things to keep in mind with USB scopes is maximum voltage probing and if there are any issues with GND connection slips etc....  I would not probe vacuum tube amps with it.  Less expensive than digital oscope but.... 

Sent from my iPun.

 

[gemini86]

I got an old BK 2560 off ebay for around 100 bucks. It said fully functioning, but I was prepared to do some work on it to get it accurate. Well, the thing came, and out of the box it was working great. It's 60mhz analog, but has a slightly lower resolution digital storage section, which is nice to have. It also has a plot function that I haven't figured out, I'm hoping i can use it to do tube curves...

 

[My3gger]

I got Tektronix 2247 from good seller in Finland for 350 eur with shipping. I'm very happy with it and it came well calibrated. Something like Hameg 205 would be good too and much cheaper.

 

[pucho812]

I got my analog hitachi duel channel  100MHz for around 50 dollars(us) would hate to buy a scope new as they are expensive.

 

[Kingston]

I thought that modern digital 'scopes would be ok, but they mostly have 8bit amplitude resolution (which concerns me) and their quality is somewhat suspicious. I have a feeling that they are much like digital consoles. Cheap ones are just plain crap, and good ones cost unwholy amount of $$$$.

8bit resolution doesn't matter. You won't see the limits of this with basic use (read: all audio use). This resolution is scaled to each input range setting. "Scale" pot is just an internal amp, no magic to it. The screen never turns into blocky digital mush because of this automation. Well, at least this is the way Rigol does it.

Resolution matters when saving data measured at certain range setting, when you zoom in the data and the scope can't change it's internal amp to match. But an analog scope wouldn't be able to do any of that anyway.

Now, sensitivity is the one spec you have to keep an eye out (mV/div) if you want to have even common multimeter voltage accuracy.

There are reviews of most modern digital scopes on youtube. The good ones no longer cost unholy amounts. That said, there are some incredible used analog scopes on ebay. Just make sure to get a calibrated one. The dealers are usually very clear about this too.

Also, here's a recent discussion on the topic of DSO's http://www.groupdiy.com/index.php?topic=49733

 

[PRR]

> 8bit resolution doesn't matter.

Agree.

8-bit is 1 in 256. The resolution is 1/2% of full screen. Most servicable analog 'scopes run the spot around 1% of full screen. Yes, when dim and obsessively Focus/Astig-ed they can do 1/2% full screen. This has never been an issue to me.

Frankly I think most post-1955 'scopes are way more than audio people really need. DC coupling and dual-trace are sometimes useful. High sensitivity and diff-input may simplify some work (I've generally adapted or cobbled boosters or diff-ins as needed).

If you work with vacuum tubes, be aware that probes have voltage limits and some modern ones may be 300V or less. (I've arced quite a few 500V trim-caps in my day.) If you probe engine ignitions (a great use for a 'scope!), the primary may kick hundreds of volts (reading the secondary is rarely done).

 

[Ilya]

> 8bit resolution doesn't matter.

Agree.

8-bit is 1 in 256. The resolution is 1/2% of full screen. Most servicable analog 'scopes run the spot around 1% of full screen. Yes, when dim and obsessively Focus/Astig-ed they can do 1/2% full screen. This has never been an issue to me.

That's an interesting observation.
There was an oppinion in the thread mentioned by Kingston that on digital scopes it'd be difficult to observe AC PSU ripple. Is that correct?

Also, PRR, can you advise any particular brands or models of digital scopes in the 500-700USD price range?

 

[Andy Peters]

There was an oppinion in the thread mentioned by Kingston that on digital scopes it'd be difficult to observe AC PSU ripple. Is that correct?

Well, the thing with PSU ripple is that it's a very small AC voltage riding on a much bigger DC voltage.

The only way to see that, with either a digital or an analog 'scope, is to AC couple the input and choose the appropriate millivolts-per-box front end gain. And you will need to futz with the triggering to get the display stable.

a

 

[Ilya]

Well, the thing with PSU ripple is that it's a very small AC voltage riding on a much bigger DC voltage.

The only way to see that, with either a digital or an analog 'scope, is to AC couple the input and choose the appropriate millivolts-per-box front end gain. And you will need to futz with the triggering to get the display stable.

Andy, am I correct supposing that it may be a common problem and is not dependent on a 'scope being analog or digital? If so, what parameters should I look for when choosing a digital 'scope? I've found a lot of cheaper chinese 'scopes, but I don't trust them...

 

[Andy Peters]

Well, the thing with PSU ripple is that it's a very small AC voltage riding on a much bigger DC voltage.

The only way to see that, with either a digital or an analog 'scope, is to AC couple the input and choose the appropriate millivolts-per-box front end gain. And you will need to futz with the triggering to get the display stable.

Andy, am I correct supposing that it may be a common problem and is not dependent on a 'scope being analog or digital?

I'm pretty sure that's exactly what I said?

If so, what parameters should I look for when choosing a digital 'scope? I've found a lot of cheaper chinese 'scopes, but I don't trust them...

Well, for starters, cost, and from that follows everything. For my use, I need a four-channel 'scope. Then choose bandwidth.

Also, are you looking forward to design which might included digital? Then a 20 MHz 'scope won't do, because it'll make all of your clocks and strobes look like sine waves.  I have one of the little Tek TDS2024s at home, 200 MHz analog bandwidth and 1 GS/s sampling. It suffices for microcontroller projects. The DPO3054 on my desk at work is a LOT better, in every respect, which it should be, given that it costs five times the little 'scope.

Fancy triggering might not be important (and why they still sell 'scopes with NTSC video triggering is beyond me); usually simple edge triggering and perhaps basic logic triggering (edge on A during high level on B) is helpful. BUT! Some 'scopes trigger better than others and without actually using the 'scope it's hard to know which models are better. Perhaps this is an area where a brand name matters.

Other fun stuff include connectivity (save traces to a USB flash drive, network interface, printer interface, etc) and if you can swing it, get something with 16 channels of simple logic analysis.

I love the idea of a USB-based oscilloscope -- why buy a display when you can use the one on your computer? -- but it's hard to justify that when it's likely that the next rev Windows won't be supported by the 'scope vendor. (And how about some Mac support?)

-a

 

[Kingston]

There was an oppinion in the thread mentioned by Kingston that on digital scopes it'd be difficult to observe AC PSU ripple.

That's why to keep an eye out for mV/div specification. PSU ripple is not actually a good example why you would need good voltage sensitivity. We already have RMS multi-meters for it.

But then sometimes you have a multimeter probing some other important spot and want to use the scope metering features...

 

[DaveP]

I bought this Tenma for £258 say $415 new.
http://cpc.farnell.com/tenma/72-6802/oscilloscope-30mhz-fq-count/dp/IN05500

Its 30Mhz, twin channel but with a nice frequency counter which is handy for setting up a frequency response test.

It's Chinese but works well enough for tube audio.

best
DaveP

 

[Ilya]

Ok, I've found several candidates so far. Here they are:

1. B&K PRECISION - BK2530B - OSCILLOSCOPE, DIGITAL, 2X25MHZ, 500MS/S507
I like that it's B&K, but it's only 25MHz and 500MS. Min. sensitivity is 2mV

2. GW INSTEK - GDS-2062 - OSCILLOSCOPE, DSO, 2 CHANNEL, 60MHZ
I've no idea how good the insteks are. But this one is 60MHz. Min. sensitivity is 2mV

3. TEKTRONIX - TDS1002C-EDU - OSCILLOSCOPE, 60MHZ, 2 CH, 1GS/S
Rather expensive, and looks like an introductory model. Min. sensitivity is 2mV

4. TEKTRONIX - TDS2001C - OSCILLOSCOPE, 50MHZ, 2-CH
Another Tek. It's actually cheaper than 1002. Min. sensitivity is 2mV

5. TENMA - 72-8710 - DSO 100MHZ 2CH, 178MM (7 IN) SCREEN
Not sure if TENMA is any good. But this one is 100MHz. Min. sensitivity is 1mV.

I'm a bit lost right now. All scopes look good, but which one is better?... Any thoughts?

 

[Kingston]

http://www.eevblog.com/ has youtube reviews on a full range of DSO's. Most of those also work as a sort of introduction to oscilloscopes and he will often point out features you didn't even know to ask. eev blog reviews have a really well done tutorial aspect to them. He doesn't assume you already know everything.

 

[alexc]

Tektronics TAS475

Not too expensive in the US, around 400usd or so - 4 channels, analog with digital control, on screen settings and best feature ever - measurement cursors for absolute voltage, relative voltage, time/freq. Has universal voltage PSU.

AC Voltage resolution varies with probe - can be down to 2mV/div

Only downside is it can make an annoying hi freq whining noise at times 


My one has been going strong for years - a good investment.

 

[bias]

I'm surprised I didn't see anyone suggest anything like this but for audio, and other applications as well, the Analog Discover Module by Digilent isn't a bad choice at all.

http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,842&Cat=17

It's only $200 USD and you get a dual channel scope, two channel function generator, 16 channels of digital logic analysis, and a 5V power supply (that honestly isn't good for too much, super low current). I have one of these and for most everything I do it's truly wonderful.

 

[Twenty Log]

I splurged for the TiePie, because it had a DLL in Windows that could automate (and collect data /  traces) plus the ARB (Arbitrary waveform generator)...

I came out of automated testing using mostly Agilent stuff (RF VNAs and Spec Analyzers over Ethernet or GPIB), so I am somewhat spoiled..

But the lower cost "analog" (digilog?) scopes look interesting for possible sacrifice to the tube power supply gods   I can keep the USB scope for the automated Excel data collection and row population for low voltage freq sweeps, FFTs or whatnot... the TiePie also has a chart recorder capability when streaming to hard drive through the DLL data collection paradigm or from their software...