[sci.electronics] impedance mismatch?

tg@cs.toronto.edu (Tom Glinos) (03/16/91)

I've got a set of headphones that can handle about .2 watts at 300 ohms.
The specs on my cd-rom player state .7 volts at 30 ohms.

The sound volume is pretty low. How can I make things louder?

joeld@hpnmdla.hp.com (Joel Dunsmore) (03/20/91)

In sci.electronics, tg@cs.toronto.edu (Tom Glinos) writes:

>    I've got a set of headphones that can handle about .2 watts at 300 ohms.
>    The specs on my cd-rom player state .7 volts at 30 ohms.
>
>    The sound volume is pretty low. How can I make things louder?

Somewhat out of my field, but:

.7 volts into 30 ohms => 16.33 mW.  Assumed matched, so Vdrive=1.4 volts.

1.4 volts => 300 ohms from 30 ohm source gives: 5.3 mWatts delivered to load.

With a 3:1 transformer, you would get 3 times more power delivered to your
headphones.  I think.

Joeld

P.S. High voltage side goes to the headphones.

al@qiclab.scn.rain.com (Al Peterman) (03/21/91)

In article <91Mar15.161948edt.552@smoke.cs.toronto.edu> tg@cs.toronto.edu (Tom Glinos) writes:
>I've got a set of headphones that can handle about .2 watts at 300 ohms.
>The specs on my cd-rom player state .7 volts at 30 ohms.
>
>The sound volume is pretty low. How can I make things louder?

3 choices that I see..

Get lower impedance headphones.  Your current setup will only 1.6 mw of
the 200 that the heaphones could handle.  That's not enough, in fact
it's 30db down form what you should be able to get..  With 8 ohm
heasets that player should develop about 60 mw..

Get a transformer.  Kind of a kludge, and decent audio performance may
be questionable - but it's cheap and doable.  Get a 20-600 ohm or so
and it ought to help the problem.

Get an amp - this is the "right" way..



-- 
Alan L. Peterman                                   (503)-684-1984 hm
                       al@qiclab.scn.rain.com
It's odd how as I get older, the days are longer, but the years are shorter!