Simi Odd Ruby Question

[chi_boy]

This may be just a little off topic.

I want to make a small amp to use with headphones only.  The odd part about the project is that in input will NOT be a guitar.

The input source is actualy a television.

I need to connect headphones to a newer TV that doesn't have a headphone jack.  I wired a line out from the TV to a jack and the output is audible, but there is no volume control, and the fixed volume is really low.

I was thinking about building a Ruby as shown at GGG with a fixed gain and headphones only per the instructions.  My concern is with the input side.  Obviously I don't want to blow up my TV.

What should I start to look for to see if the input will be e problem?  Is the a standard maximum impedance for line out?  Or could I measure the resistance through the headphones and match the imput resistor on the Ruby?

Any help or insight is aprecieated.

Just for the record, this is the Ruby I'm looking at: http://www.runoffgroove.com/ruby.html
Cheers,
George

[PRR]

> a line out from the TV

"Line Out" really should be around 1 volt and able to drive 10K load.

So dump the FET, the 10K pot is fine.

Lose the gain-boost. Even if the TV Line Out is below consumer conventional 0.3V average 2V max, the LM386's bare gain-of-10 will bump it to the full 3V output you can get on a 9V battery.

Fix the bass-cut, intended for max useful guitar racket on teeny speakers.



At 9V, you do not need to care if your headphones are 8 ohm or 100 ohm, you will have plenty of volume. If you have the super-loud type sold for deafening iPod users, and hiss is audible even when turned to zero, stick 47 or 100 ohms between the amp output and the headphone jack.

[chi_boy]

This is why I like this place.

Thanks for the help.

Cheers,
George