What Oscilloscope specs for audio work, diagnosis and repai

[K Fodder]

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...

 

[bob urz]

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...

I would recommend getting a dual trace scope. Minimum 20/30MHZ
bandwidth. You should be able to get a used one reasonable.
($50 to $200 dollars) I like Tektronix, but a older BK, Hitachi, Kikutsi
or such would be fine. There are some newer imports that MCM electronics
carrys.

Since audio only goes up to 20Kilo Hz or so, you really don't need
a lot of input bandwidth. But for looking at transients and other
things it can be helpful.

I have little plastic boxed function sweep generators. You can also get
CD's with audio tones and sweeps on them. For quick and dirty, download
the CD to a small MP3 player and thats about as small as it gets.
If your trying to do THD tests or such thats another ball game to
get a low THD sine source. Depends on what your doing...

bob

 

[N_Cook]

K Fodder <abc@123.com> wrote in message
news:4bb741a5$0$7727$c3e8da3@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...

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.
By the same reasoning an old 10 or 20 MHz scope with repair manual and
usually no custom items in there, and make sure it easy to take apart for
repairing it, plus perhaps a dead one of same model for spares. Get one that
you remove one cover and almost everything is accessible. At least 10 or 20
M b/w usually means not a load of difficult to remove can screening
involved.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm

 

[Phil Allison]

"Kannon Fodder"

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?

** DO NOT BUY A DIGITAL SCOPE !!!!!!!!!!!!!

Almost any ANALOGUE scope with bandwidth of 5 MHz or more is OK - DC
coupled or not.

Digital scopes absolutely SUCK for audio work.



...... Phil

 

[K Fodder]

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?

 

[Phil Allison]

"Kannon Fodder"

** Hey pal !!!!!!!!!!!!!!!!!!!!

DO NOT DELETE THE NAME OF WHO YOU ARE REPLYING TO

IDIOT !!!!!!!!!!

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?

** No - fuckwit.

The stupid pommy ASS is alluding to a 10:1 divider probe.

Look that up if you have no idea what it is.



..... Phil

 

[Jim Yanik]

K Fodder <abc@123.com> wrote in
news:4bb75ca6$0$14752$c3e8da3@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

 

[Jim Yanik]

K Fodder <abc@123.com> wrote in
news:4bb741a5$0$7727$c3e8da3@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

 

[Bennett Price]

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...

 

[Jeff Liebermann]

On Sun, 4 Apr 2010 01:55:47 +1100, "Phil Allison" <phil_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@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[N_Cook]

K Fodder <abc@123.com> wrote in message
news:4bb75ca6$0$14752$c3e8da3@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

 

[K Fodder]

To All

Thanks for your help. Looks like I might be able to pickup up
a tektronic 465 (100mhz) cheaply so does that sound ok or was
there a newer 100mhz tektronic model more realible or easier to
service? If not I'll go for it.

I'll investigate the digital option down the track.
Thanks for the other advicr given so far, I've noted it all down.





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------------------- ----- ---- -- -

 

[Phil Allison]

"Bennett Price Top Poster"

Distortion has to be pretty awful to see it on a scope

** Absolute bullshit.

and if you see
it (on a dual trace scope comparing input to output) how will you quantify
it,

** By how it looks on the screen - fool.

Peak clipping looks like peak clipping.

Crossover distortion looks like crossover distortion.

Square wave testing reveals response anomalies, instability and slew
limiting instantly.


..... Phil

 

[Phil Allison]

"Jeff Liebermann"
"Phil Allison"

** 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?

** There is no way to prove the point to fools like YOU by posting
messages on a newsgroup.

Buy anyone familiar with the use of analogue scopes for audio test and
repair work will find using a DSO to be mighty irritating and tedious - at
best.

The displayed traces on a DSO are often very misleading and hence useless
for many test procedures that analogue scopes do just perfectly.



..... Phil

 

[Jeff Liebermann]

On Sun, 4 Apr 2010 12:03:59 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Jeff Liebermann"
"Phil Allison"
** 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?

** There is no way to prove the point to fools like YOU by posting
messages on a newsgroup.

Got it. You can't explain why a digital scope is not usable for
analog work. Perhaps I can help jog your memory. See below.

Have you ever actually used a digital scope? A sound card based
scope? You really should try it some time. I think you'll be
pleasantly surprised.

Drivel: iPod Touch based sound analysis instruments:
<http://www.faberacoustical.com/products/iphone/signalscope/>
I'm really tempted.

Buy anyone familiar with the use of analogue scopes for audio test and
repair work will find using a DSO to be mighty irritating and tedious - at
best.

Long ago, in my mis-spent youth, I worked in a repair shop that did
mostly audio. Not audiophile, but production line warranty repair for
various manufacturers of various audio related equipment. The lead
tech never used a scope. He would just listen to whatever was coming
out of the speakers, scribble down what stage or device was blown, and
move on to the next machine. My job was to do the unsoldering and
replacement. His batting average was about 80% correct. I couldn't
even come close to that level of accuracy, especially without a scope.
One day, I saw him try to use a scope, and fail. He didn't know how.

40+ years later, I still can't do it with audio equipment. I gotta
have my test equipment, white noise, pink noise, sweeper, distortion
analyzer, and all important oscilloscope. However, I can do something
like that with 2way radios. I've heard enough of them on the air to
be able to diagnose problems by simply listening to the audio.

Moral: Use your ears first, then use the scope.

The displayed traces on a DSO are often very misleading and hence useless
for many test procedures that analogue scopes do just perfectly.

Oh? Misleading in what way? What measurements are misleading? How
will using a digital scope produce a misleading diagnosis?

I use a digital storage scope for doing the all important square wave
test. Instead of the fuzzy blur of high frequency ringing and
oscillations seen on the analog scope, I see the digital equivalent,
which looks like a jitter infested trace in the same area (top of
leading edges). By superimposing multiple stored traces on top of
each other, ringing and oscillations are fairly obvious, even if they
exceed the frequency response and resolution accuracy of the A/D
converter.

DC related phenomenon are a problem with a PC sound card based scope.
There's no DC response, and the lower limit is about 20Hz. Low
frequency display during the square wave test will show up as a "sag"
in the horizontal part of the waveform even with a DC coupled audio
amplifier. Scope probe compensation also shows the same "sag". I
partly compensate with the scope probe compensation, and just remember
what the "sag" looks like when the scope is directly connected to the
square wave generator. In other words, I ignore the low freq sag.

High frequencies are more of a problem.
<http://en.wikipedia.org/wiki/Slew_rate>
Slew rate testing is difficult with a digital scope, unless the scopes
usable bandwidth is more than 5 times the highest frequency of
interest. For a 2MHz bandwidth digital scope, that limits the maximum
frequency to about 400KHz, which should be more than adequate for any
slew rate testing. That's NOT the case with bottom of the line sound
card based scopes, which are bandwidth limited to about 22KHz. The
96KHz 24bit sound cards are much better.

There are probably other areas where an analog scope is better than
digital. Tuning and tweaking in real time is much easier with a fast
responding analog scope than on a more slothish digital equivalent.
Seeing oscillations and ringing at tiny points during a frequency
sweep is somewhat easier to see on an analog scope.

Did I miss anything on why an analog scope is superior to digital?


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 03 Apr 2010 10:52:49 -0500, Jim Yanik <jyanik@abuse.gov>
wrote:

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.

Ummm.... I now have 3ea T922 (15MHz) scopes. One works, but the other
two have blown flyback xformers. I've been unable to find a
replacement or substitute flyback. Both failed while they were being
used on my bench. The problem seems to be that the scope does not
have a fan and the flyback was probably overheating. There's a
perforated grill and location for a fan on the lower back, but no fan.
So, I added one on my working T922, which seems to be surviving so
far. There's not much air circulation in the upper section (where the
flyback lives) so I added some holes in the top cover (under the
handle) to improve circulation.

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.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Phil Allison]

"Jeff Liebermann = total FUCKWIT "

"Phil Allison"

Digital scopes absolutely SUCK for audio work.

Why duz it suck?

** There is no way to prove the point to fools like YOU by posting
messages on a newsgroup.

Got it.

** You have certainly have GOT some horrible diseases in your brain.

Congenital ones for sure.

You can't explain why a digital scope is not usable for analog work.

** Never said they were "unusable for analog work"

You sure are ONE vile fucking LIAR !!!

Have you ever actually used a digital scope?

** Yep - that is why I am very certain about my comments.

But anyone familiar with the use of analogue scopes for audio test and
repair work will find using a DSO to be mighty irritating and tedious -
at
best.

** Why does this fool not reply to the points already made ?

Cos he is an autistic fuckwit - of course.

Long ago, in my mis-spent youth, I worked in a repair shop that did
mostly audio. Not audiophile, but production line warranty repair for
various manufacturers of various audio related equipment. The lead
tech never used a scope. He would just listen to whatever was coming
out of the speakers, scribble down what stage or device was blown, and
move on to the next machine.

** What a pile of utterly unbelievable FUCKING BULLSHIT !!!

My job was to do the unsoldering and replacement.

** Even that is too technical for a RETARD like this cunt.

Moral: Use your ears first, then use the scope.

** That is no moral.

That is purest BOLLOCKS !!!

The displayed traces on a DSO are often very misleading and hence useless
for many test procedures that analogue scopes do just perfectly.

Oh? Misleading in what way?

** There is no way to DEMONSTRATE the point to an arrogant FUCKWIT like
YOU by posting messages on a newsgroup.

Cos you do not WANT to know.

Did I miss anything on why an analog scope is superior to digital?

** A whole lot of things, actually.

Cos you have no fucking idea how to use an analoge scope to advantage with
audio testing and trouble shooting.

Go DROP DEAD

you RABID FUCKING NUT CASE !!



...... Phil

 

[Jeff Liebermann]

On Sun, 4 Apr 2010 14:08:00 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

You can't explain why a digital scope is not usable for analog work.

** Never said they were "unusable for analog work"
You sure are ONE vile fucking LIAR !!!

Message-ID: <81qhlaFqohU1@mid.individual.net>
"Digital scopes absolutely SUCK for audio work."

Unless someone forged your signature, those are your words. I
substituted "unusable" for "SUCK" because my proof reader doesn't like
profanity.

I realize that you disagree with literally everything I could possibly
offer about analog versus digital scopes. So, instead of arguing in
favor of digital (which is my preferred position), I supplied several
reasons why an analog scope is superior to digital for audio testing,
thus providing you with at least a foundation to build upon. All you
had to do was agree and expand upon what I posted. I was genuinely
interested in WHY you thought digital scopes were unsuitable for audio
testing and troubleshooting. Instead, all you could do is spew
profanity and insults. I appreciate the benefits of your attention,
but I'm more interested in the technology than your exercise of
elementary skool language skills.

So, I'll try again... Why do you think digital scopes absolutely SUCK
for audio work?


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Phil Allison]

"Jeff Liebermann Radio Ham FUCKHEAD & TROLL "

** Another really vile, know nothing Yank PSYCHOPATH

You can't explain why a digital scope is not usable for analog work.

** Never said they were "unusable for analog work"

You sure are ONE vile fucking LIAR !!!

"Digital scopes absolutely SUCK for audio work."

** Clearly a very different comment - plus taken out of context.

I was genuinely
interested in WHY you thought digital scopes were unsuitable for audio
testing and troubleshooting.

** That is a BLATANT FUCKING LIE.

You are simply TROLLING like CRAZY and itching to pick a fight.

Cos you are just another sickening pile of autistic, septic SHIT.

( septic = septic tank = Aussie slang for Yank )

So, I'll try again... Why do you think digital scopes absolutely SUCK
for audio work?

** Same answer as before - CUNTHEAD !!

" There is no way to prove the point to fools like YOU by posting
messages on a newsgroup.

Buy anyone familiar with the use of analogue scopes for audio test and
repair work will find using a DSO to be mighty irritating and tedious - at
best.

The displayed traces on a DSO are often very misleading and hence useless
for many test procedures that analogue scopes do just perfectly. "



..... Phil

 

[Jeff Liebermann]

On Sun, 4 Apr 2010 15:22:07 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

So, I'll try again... Why do you think digital scopes absolutely SUCK
for audio work?

** Same answer as before - CUNTHEAD !!

" There is no way to prove the point to fools like YOU by posting
messages on a newsgroup.

Probably true. You can't. However, I'm not asking you to prove
anything. I'm asking you why you think digital scopes absolutely SUCK
for audio work? That's your statement, and I'm asking for some
substantiation. You need not try to convince me of anything, just
explain your allegations. So there's no misunderstanding, I don't
really care for your opinions and allegations. However, I do care why
you think so.

Buy anyone familiar with the use of analogue scopes for audio test and
repair work will find using a DSO to be mighty irritating and tedious - at
best.

Nice cut and paste including the typo error.

I'm familiar with the use of analog, digital, PDA based, and PC based
scopes. Each has their place. I don't find the digital scopes to be
irritating or tedious. They do require a bit of a learning curve to
understand their operation, but that's true for any piece of test
equipment. What I find tedious is setting up a scope and other
instruments for a specific test, such as a frequency sweep. With an
analog scope, I have to it all from memory and each time I run the
test. With digital, I just punch a button or load a setup macro. My
PC based scope has numerous macros for specific 2way radio tests and
measurements that I do constantly. If I had to setup the tests
individually, as I would with an analog scope, that would certainly be
irritating and tedious.

The displayed traces on a DSO are often very misleading and hence useless
for many test procedures that analogue scopes do just perfectly. "

Displayed traces of what measurements are misleading? What audio test
procedures are useless to perform with a digital oscilloscope? As far
as I can tell, there's very little that can't also be done on a
digital scope (within the limitations of bandwidth and DC coupling).

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558