Oscilloscopes - what specs to look for?

eyrepm

Just get this 100MHz dual trace Tektronix, it’s calibrated with probes, and it’s got a digital "frequency counter", and "volt meter" in it as well, you can download the instruction book on line. I had one for years, very reliable, wish I still had it, as I really don’t like the new digital Chinese produced crap.
The seller has 100% good feedback.
All you need is then is a audio frequency generator and you’ve got the works for a cheap test bench. That you won’t have to update.
https://www.ebay.com/itm/Tektronix-2236-100MHz-Oscilloscope-w-counter-timer-DMM-Calibrated-Two-Probes/153883356962?epid=2253449959&hash=item23d429af22:g:754AAOSwpnpeg4MD#viTabs_0

Cheers George

Here’s a link to a Tektronix CFG250 audio frequency generator, a great little unit I also used to have.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR1.TRC0.A0.H0.XTektronix+CFG250.TRS0&_nkw=Tektronix+CFG250&_sacat=0
  
For $400 you've got the lot then DMM, Frequency Counter, 100MHz dual trace scope and a frequency generator.  
All quality Tektronix gear.
 
Cheers George

Actually the same guy with the Tek scope also has a couple of good frequency generators, including a Tek CFG250, the B&K one in nice.
https://www.ebay.com/sch/m.html?_odkw=&epid=2253449959&_ssn=shorewa8&hash=item23d429af22%3Ag%3A754AAOSwpnpeg4MD&item=153883356962&_osacat=0&_from=R40&_trksid=p2046732.m570.l1313.TR12.TRC2.A0.H0.TRS0&_nkw=Generator&_sacat=0

Cheers George

Noise and bandwidth are directly linked in most modern scopes. The higher bandwidth ADCs will also have more dynamic range when used at lower sample rates. This is probably the biggest price differentiator as well, as the cost of the ADC is usually the most significant parts cost of the scope. 

I was recently in the market for a scope to use for DIY audio purposes and decided to go for the Siglent SDS1204X-E. This is a 4-channel 200Mhz scope and cost about $750. This might be a little overkill, but offers a lot of nice features including FFT functions for distortion analysis. 

I started my career doing electronics design 40+ years ago, but it's been quite a while since I did any hands-on work, or bought a scope for that matter. The capability of the sub $1K scopes is mind-boggling compared to what I used to spend 10X+ that amount on a few decades ago. 

100 Mhz should be the minimum, it will be beneficial for viewing parasitic oscillations. FFT analysis is a plus, especially high resolution. Most budget scopes have a math function to do this but the Rhode & Schwarz models have the highest resolution for the dollar. The 100 Mhz RTC1000 model is around $1,200, but you also get a waveform generator, digital volt meter, and component tester. The stuff packed in there would have cost you tens of thousands of dollars not too long ago. The $2,000 RTC2000 model has 10 bit A/D converters for even sharper FFT and waveform viewing.

It's a lot of overkill for what you are trying to do -- and a lot of money for the occasional DIYer -- but if you are interested in diving in to amplifier design or repair, then you'll never outgrow those scopes.