What Oscilloscope specs for audio work, diagnosis and repair?
in [Repair]
|
Prev: Anna Thoms is hot
Next: Dog fixes phone...
From: Jim Yanik on 3 Apr 2010 11:44 K Fodder <abc(a)123.com> wrote in news:4bb75ca6$0$14752$c3e8da3(a)news.astraweb.com: >>You should also get a potential divider for when working on the o/p >>area as you are bound to have the attenuator set on the wrong scale >>,some time, and at least blow the first transistor. He means blow the scope's input transistor/FET. > > You mean like a varible resistive dummy load for the output? > > > get a 10x probe; it divides the signal by 10 and givs a higher input-Z,for less circuit loading. it turns the scopes nominal 1 Megohm input Z into a 10 Meg input. Less capacitive loading,too. you can also get switchable 1X/10X probes,but they cost more and are more trouble,IMO. -- Jim Yanik jyanik at localnet dot com
From: Jim Yanik on 3 Apr 2010 11:52 K Fodder <abc(a)123.com> wrote in news:4bb741a5$0$7727$c3e8da3(a)news.astraweb.com: > Hi can someone please help me with what scope I should get for > Audio equipment repair? I need to have flexibility so I wont > have to buy another for a while. A benchtop model is fine. > > I want something specifically to cover tube/valve amps. > I need to be able to check the performance of amp and see if > my input signal is distorting, deteriorating, has interference > or other types of problems that plague audio. > > What the max MHZ range would I need to aim for? > What other features would it need or be handy? > Do you know a specific brand and model? > Do you think I need any other equipment? > Whats a good brand/model function generator? > > Lastly I have read suggestions that I should get an older analog > scope for this work. And then read the digital ones "can" do the job. > It is a bit of conflicting information what do you think? > > What would be best for audio and offer the most flexibility? > Or has there been a scope that covers both digital and analog well? > > Detailed answers are fine. Learning... :) > A nice,simple,inexpensive used TEK scope would be the T922/T932/T935 or 442 scopes;15MHz or 35Mhz. They don't use any custom ICs,have simple attenuators,have a decent size CRT graticule,and aren't too old. Negatives are the plastic case that allows chassis flex,easy to break knobs that are no longer available. I'd avoid the T912 storage scope. Next inexpensive TEK scope I'd recommend would be the 2213/2215/2235 series (60 Mhz to 100 Mhz),but those do use a few TEK-made ICs that are out of production. But they have good reliability. I have a 2213. -- Jim Yanik jyanik at localnet dot com
From: Bennett Price on 3 Apr 2010 13:12 Distortion has to be pretty awful to see it on a scope and if you see it (on a dual trace scope comparing input to output) how will you quantify it, (e.g., 5%THD, 7%IM)? On 4/3/2010 6:24 AM, K Fodder wrote: > Hi can someone please help me with what scope I should get for > Audio equipment repair? I need to have flexibility so I wont > have to buy another for a while. A benchtop model is fine. > > I want something specifically to cover tube/valve amps. > I need to be able to check the performance of amp and see if > my input signal is distorting, deteriorating, has interference > or other types of problems that plague audio. > > What the max MHZ range would I need to aim for? > What other features would it need or be handy? > Do you know a specific brand and model? > Do you think I need any other equipment? > Whats a good brand/model function generator? > > Lastly I have read suggestions that I should get an older analog > scope for this work. And then read the digital ones "can" do the job. > It is a bit of conflicting information what do you think? > > What would be best for audio and offer the most flexibility? > Or has there been a scope that covers both digital and analog well? > > Detailed answers are fine. Learning... :) >
From: Jeff Liebermann on 3 Apr 2010 14:00 On Sun, 4 Apr 2010 01:55:47 +1100, "Phil Allison" <phil_a(a)tpg.com.au> wrote: >** DO NOT BUY A DIGITAL SCOPE !!!!!!!!!!!!! Why? >Almost any ANALOGUE scope with bandwidth of 5 MHz or more is OK - DC >coupled or not. > >Digital scopes absolutely SUCK for audio work. Why duz it suck? I don't do much audio work. Just the audio processing sections (mic amp -> compressor -> limiter -> modulator -> demodulator -> demphasis -> speaker amp) of two way radios. The ability of digital scopes to do the grunt work of sweeping the frequency and amplitude range, measuring SINAD directly, and frame grabbing the results, have been a big plus. I may not be able to see distortions, high frequency ringing, and subtleties because of the dynamic range limitation of the A/D converter, but everything else is much better and easier. If I'm looking for high frequency oscillations, I use one of several 100Mhz scopes. If you have the money, I would get both a digital and an analog scope. Article on the limitations of digital scopes: <http://www.syscompdesign.com/AppNotes/scope-specs.pdf> So despite the unsubstantiated warnings of digital doom and disaster, I'll recommend Visual Analyzer: <http://www.sillanumsoft.org/prod01.htm> for a (free) PC based software oscilloscope. This is what I use for most of my tinkering and light weight waveform sniffing. It should give you a clue as to the limitations of 8bit 44KHz (or 24bit 96KHz) sampling PC based scopes. With a 24bit sound card (Startech 7.1 for $20), I can see noise down to about -80dB (-120dB theoretical) below max input. For a USB scope, this is my current favorite: <http://www.syscompdesign.com/CGR101.html> $200. Note the open source software. The only problem is that I share it with a friend and don't quite own it yet. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: N_Cook on 3 Apr 2010 14:44
K Fodder <abc(a)123.com> wrote in message news:4bb75ca6$0$14752$c3e8da3(a)news.astraweb.com... > >You should also get a potential divider for when working on the o/p area as > >you are bound to have the attenuator set on the wrong scale ,some time, and > >at least blow the first transistor. > > You mean like a varible resistive dummy load for the output? > > Another consideration for valve stuff especially, ie big kit, is the ability to use the scope at the amp so being able to position it face up , floor standing, is useful. A valvetester and also for personal safety a variac plus isolation transformer and ELCB/RCCD/ GFCI -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://diverse.4mg.com/index.htm |