Speaker to Line Level and Variable Audio - Redux

[jwest1]

Hi, I'm new to this board.  Many thanks in advace for any information or advice I might receive on this topic.  Sorry for the long post.

I have a Plasma monitor which has no Audio Out or Variable Audio Out  >:( , and  I have an older Amplifier (with large capacitors) than I like a lot, driving my home system.  The VCR is used as my tuner and I also have a DVD player.  No cable or satellite box to use as a controller. 

So here's my problem.  I'd like to use the Plasma's remote to control master volume since the amplifier is not remote controlled. The Sony DVD player doesn't have volume control either (though ironically, there is one on it's remote  ??? ) and neither does the VHS.  I can't control volume on the components separately.

The Plasma does have external speaker terminals (16W (8W + 8W) into 6 ohms).  Amplifier is 80W.

So, I'd like to implement the following solution, Speaker Level to Line Level from the external speaker terminals from the Plasma to the amplifier, as a workaround to my particular situation.



Here are my ?'s.

-Will the above work and still be able to provide gain through the Plasma's remote, (variable audio out)?

-Approximately, how much will the sound quality degrade as opposed to connecting audio L/R directly to the amplifier.

-Is there a better/more elegant low cost solution?  I've all ready spent too much money on the Plasma and don't want to buy a seperate remote contolled preamp or A/V receiver, especially when i consider my amplifier to be better quality than many of the units around today.

TIA, Warren

[jwest1]

...don't overwhelm me with the responses. 

Is this thread in the wrong section, or are noobs on this board persona non grata  ;).

How about it fellas, chime in.

[Staigen]

Hi

[audioguru]

Hi Jwest,
I understand that the monitor has 8W into 6 ohms speaker outputs which are remote-controllable, and you want to attenuate them and feed the 80W amplifier.

It should work with your 11:1 attenuators if the 80W amp has an input sensistivity of about 100mV or 200mV. Otherwise the attenuation is too high.

[jwest1]

Thanks for the replies...

Hi  jwest1, and welcome to this forum

I dont get it, first you say the output is (16W (8W + 8W) into 6 ohms), then you
say it is 80W. I would reduce the resistor by a factor of 10 at least, R1=1K and
R2=100 ohms, and also place a 100 ohms resistor across the speaker output of
your plasma monitor to act as a load for that poweramp.

//Staigen

Let me carify Staigen, the speaker terminal output of the Plasma is rated at (16W (8W + 8W) into 6 ohms) whereas my component amplifier is 80W.  I like the idea of using a resistor across the plasma's speaker terminals to act as a load. 

Hi Jwest,
I understand that the monitor has 8W into 6 ohms speaker outputs which are remote-controllable, and you want to attenuate them and feed the 80W amplifier.

It should work with your 11:1 attenuators if the 80W amp has an input sensistivity of about 100mV or 200mV. Otherwise the attenuation is too high.

Yes audioguru, that's exactly what I'd like to happen.  The input sensitivity of my amplifier is 150mV and 50 kohms so it seems by your calculations that the attenuation is about right.

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



However, how about the following as a simpler alternative? 

Use a 10 ohm 5W resistor across the plasma's speaker terminals for load.
Then, cut a 3 foot RCA cable in half, connecting the tinned ends to the plasmas speaker terminals (parallel to the resistor). 
Couple the RCA male ends to a ground loop isolator, and then from the isolator to the component amp.

In your opinions, would this be as good a solution as the first?


.

[Staigen]

Hi

Let me carify Staigen, the speaker terminal output of the Plasma is rated at (16W (8W + 8W) into 6 ohms) whereas my component amplifier is 80W

Ok

Use a 10 ohm 5W resistor across the plasma's speaker terminals for load

Dont you think 10 ohms resistors will give rise to crossover, use at least 47 ohms
resistors.

Couple the RCA male ends to a ground loop isolator, and then from the isolator to the component amp

That will be just fine, but, you must have at least one ground connection between the
two. A little schematic will clarify things.

//Staigen

[jwest1]

Here's the final booty-fab.  Sound quality is good, surprisingly.

The convenience of using the Plasma's remote control as a master gain, is worth the trade-off of any degradation in frequency response, imo.

This is coupled to a Radio Shack ground loop isolator.

There is still a slight but detectable hum, however far less than just using a resistor across the speaker terminals.  Although I can live with it, for the purpose of compulsiveness and elucidation, how can the remaining hum be eliminated?  Or, do you see any improvements that can be made?

Warren