How do I check the output of an amp with a scope?

  • Thread starter fynnashba@yahoo.com
  • Start date
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fynnashba@yahoo.com

Guest
Hello'
I have built a mic amp and wanted to check the wave form on a
scope but when I connect the probes to the o/p of the amp the power
supply trips (The Mic operates on 9 volt single rail.) I connected the
scopes ground probe to the -ve (common) and the output to the other
probe. the scope works alright with a signal generator. The Mic also
works on a power Amp but with some noise.
What might be the problem?
 
On Jun 30, 11:38 am, "fynnas...@yahoo.com" <fynnas...@yahoo.com>
wrote:

      I have built a mic amp and wanted to check the wave form on a
scope but when I connect the probes to the o/p of the amp the power
supply trips (The Mic operates on 9 volt single rail.)
Click to expand...
Is one of your scope probes a GROUND connection? Couple to the
microphone amp output through a coupling transformer, see if that
helps.

Which power supply trips, the scope, or the microphone amp? What
are the specifications of that power supply?
 
On Jun 30, 8:15 pm, whit3rd <whit...@gmail.com> wrote:
On Jun 30, 11:38 am, "fynnas...@yahoo.com" <fynnas...@yahoo.com
wrote:

      I have built a mic amp and wanted to check the wave form on a
scope but when I connect the probes to the o/p of the amp the power
supply trips (The Mic operates on 9 volt single rail.)

Is one of your scope probes a GROUND connection?  Couple to the
microphone amp output through a coupling transformer, see if that
helps.

Which power supply trips, the scope, or the microphone amp?  What
are the specifications of that power supply?
Click to expand...
Thanks
no the ground connection of the scope is connected directly to the
Amp
Its the power supply connected to the amp that trips or reads about 4
volts instead of 9v
The current of the PSU was set to 1 Ampere.
Please, generally, how do you check the responds of an audio Amp on
the scope? I mean how the probes are connected.
 
<fynnashba@yahoo.com> wrote in message
news:3f09618b-db62-4f12-a3de-f130b2b6920b@u26g2000yqu.googlegroups.com...
On Jun 30, 8:15 pm, whit3rd <whit...@gmail.com> wrote:
On Jun 30, 11:38 am, "fynnas...@yahoo.com" <fynnas...@yahoo.com
wrote:

I have built a mic amp and wanted to check the wave form on a
scope but when I connect the probes to the o/p of the amp the power
supply trips (The Mic operates on 9 volt single rail.)

Is one of your scope probes a GROUND connection? Couple to the
microphone amp output through a coupling transformer, see if that
helps.

Which power supply trips, the scope, or the microphone amp? What
are the specifications of that power supply?
Click to expand...
..Thanks
.. no the ground connection of the scope is connected directly to the
..Amp
..Its the power supply connected to the amp that trips or reads about 4
..volts instead of 9v
..The current of the PSU was set to 1 Ampere.
..Please, generally, how do you check the responds of an audio Amp on
..the scope? I mean how the probes are connected.


Do you have a two channel scope? Can you invert and add one of the
channels? If so, make a differential connection to the output with the scope
ground connected to the chassis ground of the amp. Put the inverted probe
on the low side of the output and the non-inverted probe on the high side.
The vertical gain for both channels must be the same and in the calibrated
mode.





--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
I suspect the original poster doesn't know much about electronics. We should
stop trying to help him, and ask that he find someone "local" (in his own
country) who can explain how to use test equipment.
 
On 6/30/2010 4:47 PM William Sommerwerck spake thus:

I suspect the original poster doesn't know much about electronics. We should
stop trying to help him, and ask that he find someone "local" (in his own
country) who can explain how to use test equipment.
Click to expand...
Don't you think it's just a mite too early to give up on him (her)? Ask
some more questions. They obviously didn't provide us with enough
information; we know how to easily fix that problem.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
 
I suspect the original poster doesn't know much about electronics.
We should stop trying to help him, and ask that he find someone
"local" (in his own country) who can explain how to use test equipment.

Don't you think it's just a mite too early to give up on him (her)? Ask
some more questions. They obviously didn't provide us with enough
information; we know how to easily fix that problem.
Click to expand...
He's obviously making some gross error, but can't explain exactly /what/
he's doing. That's all the more reason for asking him to look for local
help.

This is not unlike trying to explain to someone on the other side of the
world how to tie shoelaces.
 
On Wed, 30 Jun 2010 17:40:49 -0700, William Sommerwerck ǝʇoɹʍ:

I suspect the original poster doesn't know much about electronics. We
should stop trying to help him, and ask that he find someone "local"
(in his own country) who can explain how to use test equipment.

Don't you think it's just a mite too early to give up on him (her)? Ask
some more questions. They obviously didn't provide us with enough
information; we know how to easily fix that problem.

He's obviously making some gross error, but can't explain exactly /what/
he's doing. That's all the more reason for asking him to look for local
help.

This is not unlike trying to explain to someone on the other side of the
world how to tie shoelaces.
Click to expand...
Bunny Ears
Probably the most common method for teaching kids to tie their own shoes
is the "Bunny Ears" method.

Tell the child that he needs to make his shoe laces into "bunny ears."
First, he needs to secure a knot for the bunny's head. Take the laces and
cross them over to make an "X". Then, pull one ear through the bottom of
the "X" and pull tight.

Say, "Now we need to give bunny some ears." Loop the laces into "bunny
ears".

Tell the child that now we need to "make the bunny ears tight so they
don't fall off". Then make another "X" using the "bunny ears", slide one
"ear" under the "X" and pull tightly.

Plagiarized from:
http://kidsfashion.about.com/od/doityourselfstyles/tp/kidstieshoes.htm
 
On 6/30/2010 5:59 PM Meat Plow spake thus:

On Wed, 30 Jun 2010 17:40:49 -0700, William Sommerwerck ǝʇoɹʍ:

This is not unlike trying to explain to someone on the other side of the
world how to tie shoelaces.

Bunny Ears
Probably the most common method for teaching kids to tie their own shoes
is the "Bunny Ears" method.

Tell the child that he needs to make his shoe laces into "bunny ears."
First, he needs to secure a knot for the bunny's head. Take the laces and
cross them over to make an "X". Then, pull one ear through the bottom of
the "X" and pull tight.

Say, "Now we need to give bunny some ears." Loop the laces into "bunny
ears".
Click to expand...
[...]

Ackshooly, the way I heard it taught over here (U.S.) was similar, but
more along the lines of making a bunny (to make the first loop), then
"chasing the bunny around the stump" to complete the tie.

Dang, now I won't be able to tie my shoes at all ...


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
 
On 01/07/2010 03:46, David Nebenzahl wrote:
On 6/30/2010 5:59 PM Meat Plow spake thus:

On Wed, 30 Jun 2010 17:40:49 -0700, William Sommerwerck ǝʇoɹʍ:

This is not unlike trying to explain to someone on the other side of the
world how to tie shoelaces.

Bunny Ears
Probably the most common method for teaching kids to tie their own
shoes is the "Bunny Ears" method.

Tell the child that he needs to make his shoe laces into "bunny ears."
First, he needs to secure a knot for the bunny's head. Take the laces
and cross them over to make an "X". Then, pull one ear through the
bottom of the "X" and pull tight.

Say, "Now we need to give bunny some ears." Loop the laces into "bunny
ears".

[...]

Ackshooly, the way I heard it taught over here (U.S.) was similar, but
more along the lines of making a bunny (to make the first loop), then
"chasing the bunny around the stump" to complete the tie.

Dang, now I won't be able to tie my shoes at all ...
Click to expand...
riiight... now he can tie his shoes, all that remains is to tell him
how to hook his scope across the output of his amp!

Sheesh
 
Bunny Ears
Probably the most common method for teaching kids to tie their own shoes
is the "Bunny Ears" method.

Tell the child that he needs to make his shoe laces into "bunny ears."
First, he needs to secure a knot for the bunny's head. Take the laces and
cross them over to make an "X". Then, pull one ear through the bottom of
the "X" and pull tight.

Say, "Now we need to give bunny some ears." Loop the laces into "bunny
ears".

Tell the child that now we need to "make the bunny ears tight so they
don't fall off". Then make another "X" using the "bunny ears", slide one
"ear" under the "X" and pull tightly.
Click to expand...
I think PETA would object.
 
On 7/1/2010 5:15 AM William Sommerwerck spake thus:

Bunny Ears
Probably the most common method for teaching kids to tie their own shoes
is the "Bunny Ears" method.

Tell the child that he needs to make his shoe laces into "bunny ears."
First, he needs to secure a knot for the bunny's head. Take the laces and
cross them over to make an "X". Then, pull one ear through the bottom of
the "X" and pull tight.

Say, "Now we need to give bunny some ears." Loop the laces into "bunny
ears".

Tell the child that now we need to "make the bunny ears tight so they
don't fall off". Then make another "X" using the "bunny ears", slide one
"ear" under the "X" and pull tightly.

I think PETA would object.
Click to expand...
But no bunnies were harmed in this metaphorical example ...


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
 
Tell the child that now we need to "make the bunny ears
tight so they don't fall off". Then make another "X" using
the "bunny ears", slide one "ear" under the "X" and pull
tightly.

I think PETA would object.

But no bunnies were harmed in this metaphorical example ...
Click to expand...
It's the principle of the thing!

"I say unto you, that whoever harms a bunny in his thought, has as much
harmed the bunny in its body."
 
On Jun 30, 1:38 pm, "fynnas...@yahoo.com" <fynnas...@yahoo.com> wrote:
On Jun 30, 8:15 pm, whit3rd <whit...@gmail.com> wrote:

On Jun 30, 11:38 am, "fynnas...@yahoo.com" <fynnas...@yahoo.com
wrote:

      I have built a mic amp and wanted to check the wave form on a
scope but when I connect the probes to the o/p of the amp the power
supply trips (The Mic operates on 9 volt single rail.)

Is one of your scope probes a GROUND connection?  Couple to the
microphone amp output through a coupling transformer, see if that
helps.

Which power supply trips, the scope, or the microphone amp?  What
are the specifications of that power supply?

Thanks
 no the ground connection of the scope is connected directly to the
Amp
Its the power supply connected to the amp that trips or reads about 4
volts instead of 9v
The current of the PSU was set to 1 Ampere.
Please, generally, how do you check the responds of an audio Amp on
the scope? I mean how the probes are connected.
Click to expand...
need a good explanation of what is in that power supply

or, how about float the power supply, even better, use a battery.

then you should be able to connect your scope ground anywhere on the
circuit. just make sure your mike, amplifier, and power supply are all
floating.

Usually one connects the ground of the scope to the system's reference
point, also called ground, and connects the input of scope to the
output of the amplifier. If the output of the amplifier is an 'H'
drive, you will need two input probes, one for each output leg.

If you get the amplifier up and running there's a way to use your
sound card in your PC to explore what is happening at different
frequencies and what the bandwidth of your system is.
 
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