I want to build an audio amplifier to boost the signal from my DVD
player, connected in-line in the audio lead (phono) between the DVD player
and the TV. I gather that the normal signal level is 0.5Vrms and the input
impedance of the TV audio input should be 10k (presumably at 1kHz?). It
would be very convenient for me to leave the dc (around 6V wrt the signal
return) rather than connect via a capacitor....is the TV certain to have
it's own dc block? It is reading off-scale ohms on my DMM. The TV is a
United Kingdom PAL model, combo, Ferguson, 14" new, with dual tuner (don't
know the model without
uninstalling it from the cabinet in which it has been installed, which takes
some time).

Many thanks for the help, David

Why? The TV's audio inputs should be just fine with the analog output
from the DVD player.

Kal

On Fri, 17 Dec 2004 23:11:37 -0000, "David"
wrote:

I want to build an audio amplifier to boost the signal from my DVD
player, connected in-line in the audio lead (phono) between the DVD player
and the TV. I gather that the normal signal level is 0.5Vrms and the input
impedance of the TV audio input should be 10k (presumably at 1kHz?). It
would be very convenient for me to leave the dc (around 6V wrt the signal
return) rather than connect via a capacitor....is the TV certain to have
it's own dc block? It is reading off-scale ohms on my DMM. The TV is a
United Kingdom PAL model, combo, Ferguson, 14" new, with dual tuner (don't
know the model without
uninstalling it from the cabinet in which it has been installed, which takes
some time).

Many thanks for the help, David

Why? The TV's audio inputs should be just fine with the analog output
from the DVD player.

Actually I have several types of input that I wish to play through the TV
but it seemed easier to just say a DVD player because everyone knows the
type of connection we are talking about. Suffice to say that I do require
this amplifier and would like to know whether the input would already have a
dc block or whether I must block the dc from my amp. It would be much more
convenient not to block the dc on my amp (yes, I do know how to but believe
me, it would be nice not to!). Many thanks.

On Sat, 18 Dec 2004 08:18:19 -0000, "David"
wrote:

Actually I have several types of input that I wish to play through the TV
but it seemed easier to just say a DVD player because everyone knows the
type of connection we are talking about. Suffice to say that I do require
this amplifier and would like to know whether the input would already have a
dc block or whether I must block the dc from my amp. It would be much more
convenient not to block the dc on my amp (yes, I do know how to but believe
me, it would be nice not to!). Many thanks.


Maybe you need a small mixer to do this job properly and flexibly.
Look at the Behringer range.

All inputs, and all the outputs must have DC blocking (cap coupled), because
this is the safety standard for coupling devices together.

If you have to boost the audio level for some reason, you should be looking
for a fault. All these consumer items should work properly together without
added amplifiers in between.

--

Jerry G.
======


"David" wrote in message
...
Why? The TV's audio inputs should be just fine with the analog output
from the DVD player.

Actually I have several types of input that I wish to play through the TV
but it seemed easier to just say a DVD player because everyone knows the
type of connection we are talking about. Suffice to say that I do require
this amplifier and would like to know whether the input would already have a
dc block or whether I must block the dc from my amp. It would be much more
convenient not to block the dc on my amp (yes, I do know how to but believe
me, it would be nice not to!). Many thanks.

"David" wrote ...
Actually I have several types of input that I wish to play
through the TV but it seemed easier to just say a DVD
player because everyone knows the type of connection
we are talking about. Suffice to say that I do require
this amplifier

That fact by itself throws question on one or more parts of
your system. Consumer equipment line levels are pretty well
matched right out of the box. If you require gain, then something
is wrong. You'd be better off fixing it than plastering a bandage
over the problem.

and would like to know whether the input would already have
a dc block or whether I must block the dc from my amp.

It is never safe to assume DC blocking on equipment you don't
have the schematic diagrams for.

It would be much more convenient not to block the dc on my
amp (yes, I do know how to but believe me, it would be nice
not to!). Many thanks.

You'll have to explain that before you will get us to buy into
your scheme.

That fact by itself throws question on one or more parts of
your system. Consumer equipment line levels are pretty well
matched right out of the box. If you require gain, then something
is wrong. You'd be better off fixing it than plastering a bandage
over the problem.

Fixing the problem would have been far more difficult, I am afraid. The
mountings of the TV have been modified to be fitted into my yacht and when
you say "boat", "yacht" or "modified" to people in UK domestic equipment
outlets you might as well say that you have been been using it for target
practice for the past ten years. Besides, there aren't many left in the
high street who know how a TV works, let alone be able to fix one! I can't
obtain the circuits until after the New Year and it is very hard to work on
a modern TV without circuits. Meanwhile we would have been DVD-less (and
without other audio bits) as we live on our boat, all over the festive
season :-(((

So, I have now built a tiny pre-amp with nothing more sophisticated than a
741 op amp and a handful of components that I happened to have on board. I
did manage to find a couple of suitable capacitors in some junk equipment,
so have managed to block the dc OK. Once upon a time I had my own
comprehensive electronics lab with lab technicians - now I live on a boat
:-)

Thankfully it works so we can watch the TV and DVD and listen to some tapes
over Christmas. I'll sort the real problem out in the New Year when I can
get the circuits for the TV.

Thanks for your help, everyone, and a very Happy Christmas!

David

On Sat, 18 Dec 2004 09:17:07 -0800, "Richard Crowley"
wrote:

Consumer equipment line levels are pretty well
matched right out of the box. If you require gain, then something
is wrong. You'd be better off fixing it than plastering a bandage
over the problem.

Well, maybe. Many hi-fi amplifiers have identical line inputs
labeled "Tape", "Tuner", "CD". Some CD players have VERY hot
outputs. I sometimes wonder if people who extol vinyl over CD have
been listening to an overloaded CD input.

Getting the gain structure right is an essential step when connecting
pro audio components, but seems largely ignored in the audiophile
world.

On Sat, 18 Dec 2004 18:10:03 -0000, "David"
wrote:


Fixing the problem would have been far more difficult, I am afraid. The
mountings of the TV have been modified to be fitted into my yacht and when
you say "boat", "yacht" or "modified" to people in UK domestic equipment
outlets you might as well say that you have been been using it for target
practice for the past ten years.

Sharing this essential background information from the outset would
have been sensible.

Sharing this essential background information from the outset would
have been sensible.

I didn't ask anyone how to solve the problem, I said that I wanted to build
a preamp and asked for a confirmation that the input impedance of the audio
input should be 10k and that the voltage should be 0.5V rms. I also asked
whether it is essential to block dc on typical modern TV audio inputs. I
don't really see how all the other background information was necessary at
all, and I only gave it because it seemed un-civil not to, after people had
taken the trouble to help me.

"David" wrote in message
...
Sharing this essential background information from the outset would
have been sensible.

I didn't ask anyone how to solve the problem, I said that I wanted to
build
a preamp and asked for a confirmation that the input impedance of the
audio
input should be 10k and that the voltage should be 0.5V rms. I also
asked
whether it is essential to block dc on typical modern TV audio inputs. I
don't really see how all the other background information was necessary at
all, and I only gave it because it seemed un-civil not to, after people
had
taken the trouble to help me.

The reason being the number of people who come here with
a situation like yours and some pre-determined, hair-brained
"solution" that is more likely to make it worse. If you hung
around here more you would recognize the repeated scenario.

Complaining to people who you are asking for help when they
try to give you a sensible answer hardly seems sporting.

Complaining to people who you are asking for help when they
try to give you a sensible answer hardly seems sporting.

I wasn't complaining - only answering Laurence's remark. But whatever,
please don't let's get off to a bad start....I was grateful for the replies
and I'm an easy-going sort of person who never deliberately offends. :-)

David

"David" writes:

I want to build an audio amplifier to boost the signal from my DVD
player, connected in-line in the audio lead (phono) between the DVD player
and the TV. I gather that the normal signal level is 0.5Vrms and the input
impedance of the TV audio input should be 10k (presumably at 1kHz?). It
would be very convenient for me to leave the dc (around 6V wrt the signal
return) rather than connect via a capacitor....is the TV certain to have
it's own dc block?

I would not count on that....
Maybe it has, or maybe it has not.

Best to install that DC block capacitor!


--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

On Sat, 18 Dec 2004 23:34:09 -0000, "David"
wrote:

Sharing this essential background information from the outset would
have been sensible.

I didn't ask anyone how to solve the problem, I said that I wanted to build
a preamp and asked for a confirmation that the input impedance of the audio
input should be 10k and that the voltage should be 0.5V rms. I also asked
whether it is essential to block dc on typical modern TV audio inputs. I
don't really see how all the other background information was necessary at
all, and I only gave it because it seemed un-civil not to, after people had
taken the trouble to help me.

Sometimes a questioner has correctly defined a problem and needs help
with only one detail.

Sometimes they've incorrectly understood the problem, decided to set
off in a wrong direction to solve it and hit a brick wall, which they
see as only a minor detail :-)

A good shopkeeper listens politely to what the customer WANTS, then
tries to discover what he NEEDS. I wouldn't complain about getting
good service :-)

Laurence Payne writes:

A good shopkeeper listens politely to what the customer WANTS, then
tries to discover what he NEEDS. I wouldn't complain about getting
good service :-)

In this case you failed to discover what this customer needed, so was
it indeed good service? David's comment was appropriate, in my
opinion.

There are indeed those of us who are more-or-less clueless, but there
are also those who are not. Part of the expertise in responding on
usenet is making this determination. I have also had the unpleasant
experience of wading through or attempting to answer responses that
provided a solution I wasn't looking for.
--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

Randy Yates wrote:
Laurence Payne writes:

A good shopkeeper listens politely to what the customer WANTS, then
tries to discover what he NEEDS. I wouldn't complain about getting
good service :-)

In this case you failed to discover what this customer needed, so was
it indeed good service? David's comment was appropriate, in my
opinion.

There are indeed those of us who are more-or-less clueless, but there
are also those who are not. Part of the expertise in responding on
usenet is making this determination. I have also had the unpleasant
experience of wading through or attempting to answer responses that
provided a solution I wasn't looking for...

Yet we've all had the opposite experience; where the OP proposes a solution
without properly explaining the problem, or fixates on a solution which will
not work, or fixates on a solution which 'might' work...given information
which he has not yet provided.

Numerous wasted posts down the line, we discover the problem was totally
different than the OP presumed.

jak