[sdiy] oscilloscope considerations

[Scott Evans, Gen Mgr]

I will second JH's remarks here. Unless you want the scope to work for
video as well (100-200mhz recommended here), a 20mhz scope is plenty for
audio DIY. The dual trace is very handy to explore wave forms in two
areas of a circuit at the same time. You can overlay one wave form on
top of another to check for wave form changes (desired or not). Also, a
triggered time base is useful.

I picked up a used Tek 465B on ebay for $200 and sent it out for
calibration. This is a 100mhz scope. You can find dual trace 20-40 mhz
stuff for less. I here that Leader makes some nice scopes in this range.

Good luck,

Scott Evans

jhaible at t-online.de wrote:
> 
> I'm using one of these "expensive Digital Phosphor" scopes
> at my day job, where strange trigger conditions are important,
> the frequency range goes up to 1GHz, and documentation of
> waveforms is crucial.
> 
> For the work on analogue synthesizers, however, I prefer my
> unexpensive 30MHz dual channel analogue scope.
> In fact, I have built 90% of my synthesizers using a 150-Dollar
> (new ! I've bought it used for 100 ...) 20MHz single channel
> scope. Over the years the pots became scratchy, and 2 channels
> are an improovement really. So I upgraded to a dual channel
> analogue scope for approx. 300 or 350 Dollars. It's all you
> need for analogue audio stuff, really. It does not have a
> noisy fan, and - most important - the beam is connected directly
> to the analogue input - no digital scope will give you the
> same immediate access to your signals, not even the DPO stuff.
> 
> Working with both, high end digital and unexpensive analogue
> scopes is very different. On the digital, you can catch glitches
> in their full beauty, once you have set the right trigger conditions,
> and - important - if you know there is something to look for at all!
> On the analoge, it's more likely that you see when something is
> wrong for a tiny moment. You may not see it as precisely, but it's
> less likely that it escapes your perception at all.
> 
> JH.
> 
> media at mail1.nai.net schrieb:
> >
> > I know many people on this list frequently suggest buying
> > a used
> > oscilloscope from Ebay, Nuts & Volts, and a Ham
> > flea-markets.  The Ham flea
> > market might not be a bad idea for me since Newington is
> > less than two
> > hours from here.  However, I'm considering buying a new
> > scope for two
> > reasons.  Firstly, I'm not familiar with all of the makes
> > and models, and
> > do not know which features each model has, or its fair
> > market price.
> > Secondly, I want to make sure that it is calibrated and
> > working properly,
> > as fixing an oscilloscope without an oscilloscope would
> > seem impossible.
> > So waiting for a dealer to blow out an older model might
> > be my best bet.
> >
> > Is there a FAQ or website that discusses features of
> > various scopes??  The
> > manufacturer websites haven't been all that helpful as to
> > what features are
> > actually useful.  Nor could I find descriptions of scopes
> > no longer being
> > made.
> >
> > Prices range from an Instek 5MHz analog scope for $235,
> > to digital scopes
> > costing over $16K!!  While I do not think I need a
> > digital scope, that
> > seems to be the way things are going, as a number of
> > manufacturers no
> > longer make analog scopes.  What is the real advantage of
> > an analog scope??
> > The problem with anything digital is not so much the
> > price, but that it
> > doesn't hold its value -- digital technology keeps
> > getting faster and less
> > expensive every year.
> >
> > There seem to be four types of digital scopes: digital
> > scopes with LCD
> > displays (eg. Tektronix TDS210), digital scopes with CRT
> > displays, digital
> > scopes with CRT displays that claim to have an "analog"
> > mode (eg. BK5020),
> > and expensive scopes from Tektronics called Digital
> > Phosphor Oscilloscopes
> > (DPO) that have VGA color LCD displays that supposedly
> > imitate the display
> > characteristics of analogue scopes.  I cannot afford a
> > DPO, but the digital
> > scopes with either monochrome CRT or monochrome LCD
> > screens seem
> > competitively priced.  Any ideas here??
> >
> > Another consideration is bandwidth.  I'm thinking that
> > 20MHz would be fast
> > enough for sdiy, but I have heard many people say that
> > 20MHz scopes should
> > be avoided.  Why is that??   As far as digital scopes are
> > concerned, sample
> > rates also vary.  I would think the two would be related,
> > but there doesn't
> > seem to be a correlation in any of the specifications.
> > Also, there is no
> > mention of resolution (ie. bit depth), which strikes me
> > as very odd for an
> > instrument that measures voltages against time.
> >
> > Most of the digital scopes include communications ports
> > or have them
> > available as options.  Is there any sort of standard data
> > format for
> > oscilloscopes, or are you stuck with the software
> > available for one brand
> > of scope??  Several of the digital scopes also have
> > software plug-in
> > modules that add features, such as FFT.  I think FFT
> > could be very useful.
> > However, considering that the computer hardware is
> > already there, there
> > seems to be a lack of acoustic analysis software compared
> > to what available
> > for the Techron and Goldline hardware.
> >
> > Is there anything else I should consider??  Any brands I
> > should avoid??
> >
> > Finally, is there a dealer in the U.S. that anyone would
> > recommend??  I've
> > checked out Techni-Tool and Test Equipment Depot.
> > Tektronix also sells
> > reconditioned units at a discount.
> >
> >
> > THANX!! :)
> >
> >
> >
> >
> >
> >
> >