I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure that the
device is putting out without having to connect it to another device with
a headphone amp.

a) Portability is paramount--ideally no larger than the connectors and an
inline bump.

b) Quality is secondary. It doesn't have to be loud or especially
accurate. This is a test for output, not a critical listening
experience.

c) It must be passive. I don't want to depend on (or wait on connecting
to) a power supply, be it batteries or house current.

Can I make do with just a pair of transformers? Showing a load of 10K
for 8-ohm headphones, that means a 1000 to 1 transformer? Any particular
suggestions?

Or does someone have an entirely different solution I should be
considering?

This came up last week when I was trying to record a keyboard. I plugged
into the line out and got no signal. I spent several minutes trying to
discover my error (bad connection? incorrectly plugged? some switch set
wrong?) before I realized that the keyboard line out was defective.

Carey Carlan wrote:
I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure that the
device is putting out without having to connect it to another device with
a headphone amp.

So, make a cable with a female 1/4" on one end and two RCA connectors on
the other end. It won't be loud and the response won't be as flat as possible,
but it'll work fine with an efficient pair of phones like the Sony MDR-V6.

This came up last week when I was trying to record a keyboard. I plugged
into the line out and got no signal. I spent several minutes trying to
discover my error (bad connection? incorrectly plugged? some switch set
wrong?) before I realized that the keyboard line out was defective.

Keyboard line out should have been a 1/4" jack. You can just plug a pair
of headphones in there. If it's a mono TS output, you'll hear sound in
one ear. If it's a balanced TRS output, you'll hear it out of phase in
both ears.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Sun, 13 Mar 2005 14:46:18 GMT, Carey Carlan
wrote:

I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure that the
device is putting out without having to connect it to another device with
a headphone amp.

a) Portability is paramount--ideally no larger than the connectors and an
inline bump.

b) Quality is secondary. It doesn't have to be loud or especially
accurate. This is a test for output, not a critical listening
experience.

c) It must be passive. I don't want to depend on (or wait on connecting
to) a power supply, be it batteries or house current.

Can I make do with just a pair of transformers? Showing a load of 10K
for 8-ohm headphones, that means a 1000 to 1 transformer? Any particular
suggestions?

As Scott says, most "line outs" directly to headphones should drive
them audibly (unless there's an electric guitarist or drummer in the
room), but transformers will give the device's output a "reasonable"
load and possibly be substantially louder (if the line-out's impedance
is too high or doesn't have the current capability to drive 8 ohms
directly).
Also, keep in mind that the impedance ratio of a transformer is
equal to square of the voltage ratio. So if you have an old unused
wallwart with 120VAC input and 8VAC output (hmm, Alesis...), the
impedance ratio is (120/8)^2 or 225, which (with 120V primary to line
out and secondary to phones) turns 8-ohm phones into 1800 ohm phones.
That may not be the perfect load, but it's a lot closer to 10k than it
is to 8 ohms.

Or does someone have an entirely different solution I should be
considering?

This came up last week when I was trying to record a keyboard. I plugged
into the line out and got no signal. I spent several minutes trying to
discover my error (bad connection? incorrectly plugged? some switch set
wrong?) before I realized that the keyboard line out was defective.

-----
http://mindspring.com/~benbradley

In article writes:

I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure that the
device is putting out without having to connect it to another device with
a headphone amp.

Whirlwind used to make a gadget like that, and maybe they still do. I
think it was called the Q-Box. Here it is:
http://www.whirlwindusa.com/test.html

c) It must be passive. I don't want to depend on (or wait on connecting
to) a power supply, be it batteries or house current.

Sorry 'bout that. Batteries required.

Can I make do with just a pair of transformers? Showing a load of 10K
for 8-ohm headphones, that means a 1000 to 1 transformer?

That might work. Actually the impedance ratio is the square of the
turns ratio, so you'd want a 35:1 transformer which is a little more
practical but you can probably do with less. Or you might just hunt up
a high impedance set of headphones and try hooking them across a line
output. I frequently plug headphones into an output jack to see if
anything's coming out. Since you just want to know if there's a signal
present (and what signal) it doesn't need to be ear-bleeding loud.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

"Scott Dorsey" wrote in message

Carey Carlan wrote:

I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure
that the device is putting out without having to connect it to
another device with a headphone amp.

So, make a cable with a female 1/4" on one end and two RCA connectors
on the other end. It won't be loud and the response won't be as flat as
possible, but it'll work fine with an efficient pair of phones like
the Sony MDR-V6.

Sounds like something I've done and had work well.

MDR-V6s have pretty low impedance - what 32 ohms? The Sennheiser HD 580s
have similar voltage sensitivity, but with more like 450 ohm impedance. They
seem like the better choice.

On Sun, 13 Mar 2005 14:46:18 GMT, Carey Carlan
wrote:

Or does someone have an entirely different solution I should be
considering?

No, I think you have a really good solution. Nothing is as fast
and as convincing as actually hearing the signal.

I keep an old pair of Sennheiser 414's (2000 ohms) and a variety
of adapters just for that purpose. There are also several 600
ohm phones that are modern and otherwise useful.

If I were really smart (fat chance), I'd also have a portable
signal source and adapters. Maybe a portable CD player. Always
wanted one anyway.

Good fortune,

Chris Hornbeck

"Mike Rivers" wrote in message
news:znr1110735271k@trad...

In article
writes:

I'd like to add a gadget to my emergency kit to let me plug a pair of
headphones into a -10 stereo line out. I just want to make sure that the
device is putting out without having to connect it to another device with
a headphone amp.

Whirlwind used to make a gadget like that, and maybe they still do. I
think it was called the Q-Box. Here it is:
http://www.whirlwindusa.com/test.html

c) It must be passive. I don't want to depend on (or wait on connecting
to) a power supply, be it batteries or house current.

Sorry 'bout that. Batteries required.

When I was a youngster 60 years ago, I connected an LP player to a pair of
Brush crystal headphones, with no amplification. It worked quite well.

Norm Strong

In article writes:

When I was a youngster 60 years ago, I connected an LP player to a pair of
Brush crystal headphones, with no amplification. It worked quite well.

I connected a set of crystal headphones to a galena crystal detector
and listened to the radio. No batteries required.

Fidelity? What's that?

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article znr1110844387k@trad, Mike Rivers wrote:
In article writes:

When I was a youngster 60 years ago, I connected an LP player to a pair of
Brush crystal headphones, with no amplification. It worked quite well.

I connected a set of crystal headphones to a galena crystal detector
and listened to the radio. No batteries required.

Fidelity? What's that?

I bet a nickel that the frequency response of that combination was flatter
across the band than a typical AM table radio today. Not much selectivity,
though.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
In article znr1110844387k@trad, Mike Rivers wrote:

I connected a set of crystal headphones to a galena crystal detector
and listened to the radio. No batteries required.

I bet a nickel that the frequency response of that combination was flatter
across the band than a typical AM table radio today. Not much
selectivity,
though.

You're not kidding about the selectivity. When I built my first crystal
radio, there was an AM station's antenna across the valley from me. It
didn't matter how I adjusted the variable condenser, I could only get that
one station.

Hal Laurent
Baltimore

In article writes:

You're not kidding about the selectivity. When I built my first crystal
radio, there was an AM station's antenna across the valley from me. It
didn't matter how I adjusted the variable condenser, I could only get that
one station.

You had a variable condenser in your crystal radio? You must have
built the advanced version. Mine all had a fixed capacitor (mica, of
course) and a coil of enameled wire wound around an oatmeal box. I
don't remember the slider arrangement, but it must have involved a
strip of metal mounted on a board sliding across a sanded-off strip
along the length of the coil.



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo