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Headphone to Line Input Transformer Adapter?

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April 19, 2005 5:15:00 AM

Archived from groups: rec.audio.pro (More info?)

It's easy to find male headphone jack-to-female line-level input jack
adapters at Radio Shack, etc. But where can I find one that actually
transforms typical headphone jack output levels (30 ohms and below) to
those acceptable to line-level inputs (1 kohms and above)?

Explanation:

I need to pipe some audio from the headphone output of an audio device
to the line-level input of a sound card. Because of the higher average
voltage and lower impedance of headphone outputs (vs. line-level inputs),
doing this usually requires nothing more than a cheap Radio Shack jack
adapter, and keeping the headphone output volume set low, so as not to
overload the recording device's line-level input.

But the source device I'm using is funky. It's headphone output suffers
from a high, fixed noise floor. With the device's volume control all the
way down, there's lots of soft hiss. As the volume control is turned up,
the hiss level remains FIXED while the audio increases above it -- until
the audio finally reaches a point where it satisfactorily overcomes that
fixed noise floor, for my tastes.

The problem is that I can't "crank" the volume of a headphone output going
into a line-level input. Doing so overloads the line-level input and I'm
left with subtle distortion. And I have no choice but to use THIS device.
(Too much work to explain why; just trust me.)

So: I need some kind of transformer adapter as described above. Something
that would reduce the level of the headphone output, thereby creating the
headroom needed to "crank" the headphone output's audio above its fixed
noise floor without overloading the sound card line-level input. I hope
you "get" what I mean. <g>

Where can such a widget be found?

Thanks in advance.
Anonymous
April 19, 2005 5:15:01 AM

Archived from groups: rec.audio.pro (More info?)

Why not just turn it up and use a resistive divider to accommodate the
input of the following device?

Kal

On Tue, 19 Apr 2005 01:15:00 GMT, "Mars" <nospam@invalid.com> wrote:

>It's easy to find male headphone jack-to-female line-level input jack
>adapters at Radio Shack, etc. But where can I find one that actually
>transforms typical headphone jack output levels (30 ohms and below) to
>those acceptable to line-level inputs (1 kohms and above)?
>
>Explanation:
>
>I need to pipe some audio from the headphone output of an audio device
>to the line-level input of a sound card. Because of the higher average
>voltage and lower impedance of headphone outputs (vs. line-level inputs),
>doing this usually requires nothing more than a cheap Radio Shack jack
>adapter, and keeping the headphone output volume set low, so as not to
>overload the recording device's line-level input.
>
>But the source device I'm using is funky. It's headphone output suffers
>from a high, fixed noise floor. With the device's volume control all the
>way down, there's lots of soft hiss. As the volume control is turned up,
>the hiss level remains FIXED while the audio increases above it -- until
>the audio finally reaches a point where it satisfactorily overcomes that
>fixed noise floor, for my tastes.
>
>The problem is that I can't "crank" the volume of a headphone output going
>into a line-level input. Doing so overloads the line-level input and I'm
>left with subtle distortion. And I have no choice but to use THIS device.
>(Too much work to explain why; just trust me.)
>
>So: I need some kind of transformer adapter as described above. Something
>that would reduce the level of the headphone output, thereby creating the
>headroom needed to "crank" the headphone output's audio above its fixed
>noise floor without overloading the sound card line-level input. I hope
>you "get" what I mean. <g>
>
>Where can such a widget be found?
>
>Thanks in advance.
Anonymous
April 19, 2005 5:15:01 AM

Archived from groups: rec.audio.pro (More info?)

"Mars" wrote...
> It's easy to find male headphone jack-to-female line-level input jack
> adapters at Radio Shack, etc. But where can I find one that actually
> transforms typical headphone jack output levels (30 ohms and below) to
> those acceptable to line-level inputs (1 kohms and above)?
>
> Explanation:
>
> I need to pipe some audio from the headphone output of an audio device
> to the line-level input of a sound card. Because of the higher average
> voltage and lower impedance of headphone outputs (vs. line-level inputs),
> doing this usually requires nothing more than a cheap Radio Shack jack
> adapter, and keeping the headphone output volume set low, so as not to
> overload the recording device's line-level input.
>
> But the source device I'm using is funky. It's headphone output suffers
> from a high, fixed noise floor. With the device's volume control all the
> way down, there's lots of soft hiss. As the volume control is turned up,
> the hiss level remains FIXED while the audio increases above it -- until
> the audio finally reaches a point where it satisfactorily overcomes that
> fixed noise floor, for my tastes.
>
> The problem is that I can't "crank" the volume of a headphone output going
> into a line-level input. Doing so overloads the line-level input and I'm
> left with subtle distortion. And I have no choice but to use THIS device.
> (Too much work to explain why; just trust me.)
>
> So: I need some kind of transformer adapter as described above. Something
> that would reduce the level of the headphone output, thereby creating the
> headroom needed to "crank" the headphone output's audio above its fixed
> noise floor without overloading the sound card line-level input. I hope
> you "get" what I mean. <g>

You already have a low impedance source and a high(er)
impedance ("bridging") load. No impedance conversion is
necessary. Or likely desirable, either, as it would only add
distortion unless you used expensive transformers.

If you have more than enough amplitude on the headphone
output, (and gain on the line input) and want to mitigate the
noise floor, a simple pad would appear to be what you require.
This is rather a common method of doing the interface you describe.
Related resources
Anonymous
April 19, 2005 5:15:01 AM

Archived from groups: rec.audio.pro (More info?)

Mars <nospam@invalid.com> wrote:
>It's easy to find male headphone jack-to-female line-level input jack
>adapters at Radio Shack, etc. But where can I find one that actually
>transforms typical headphone jack output levels (30 ohms and below) to
>those acceptable to line-level inputs (1 kohms and above)?

You don't need to. There's no reason not to run a low-Z output into a
high-Z input.

>I need to pipe some audio from the headphone output of an audio device
>to the line-level input of a sound card. Because of the higher average
>voltage and lower impedance of headphone outputs (vs. line-level inputs),
>doing this usually requires nothing more than a cheap Radio Shack jack
>adapter, and keeping the headphone output volume set low, so as not to
>overload the recording device's line-level input.

That's a level issue rather than an impedance issue. Just use a pad. If
you're going into an XLR input, having a bunch of the Shure adjustable
XLR pads around is probably a good idea anyway.

>But the source device I'm using is funky. It's headphone output suffers
>from a high, fixed noise floor. With the device's volume control all the
>way down, there's lots of soft hiss. As the volume control is turned up,
>the hiss level remains FIXED while the audio increases above it -- until
>the audio finally reaches a point where it satisfactorily overcomes that
>fixed noise floor, for my tastes.

That's bad, and I would say it's probably worth having a tech clean up
the output stage, or add an output jack before the gain control. But if
you absolutely have to work this way, use a pad.

>The problem is that I can't "crank" the volume of a headphone output going
>into a line-level input. Doing so overloads the line-level input and I'm
>left with subtle distortion. And I have no choice but to use THIS device.
>(Too much work to explain why; just trust me.)

Use a pad.

>So: I need some kind of transformer adapter as described above. Something
>that would reduce the level of the headphone output, thereby creating the
>headroom needed to "crank" the headphone output's audio above its fixed
>noise floor without overloading the sound card line-level input. I hope
>you "get" what I mean. <g>

You don't need any transformer adaptor. Use a pad.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
April 19, 2005 6:15:37 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 19 Apr 2005 01:15:00 GMT, "Mars" <nospam@invalid.com> wrote:

> It's headphone output suffers
>from a high, fixed noise floor. With the device's volume control all the
>way down, there's lots of soft hiss. As the volume control is turned up,
>the hiss level remains FIXED while the audio increases above it -- until
>the audio finally reaches a point where it satisfactorily overcomes that
>fixed noise floor, for my tastes.

Doctor, when I hit myself on the head with a hammer it hurts.
What can I do?

Chris Hornbeck
6x9=42 April 29
Anonymous
April 19, 2005 10:05:42 AM

Archived from groups: rec.audio.pro (More info?)

Mars wrote:
> It's easy to find male headphone jack-to-female line-level input
jack
> adapters at Radio Shack, etc. But where can I find one that
actually
> transforms typical headphone jack output levels (30 ohms and below)
to
> those acceptable to line-level inputs (1 kohms and above)?
>
> Explanation:
>
> I need to pipe some audio from the headphone output of an audio
device
> to the line-level input of a sound card. Because of the higher
> average voltage and lower impedance of headphone outputs (vs.
> line-level inputs), doing this usually requires nothing more than a
> cheap Radio Shack jack adapter, and keeping the headphone output
> volume set low, so as not to overload the recording device's
> line-level input.
>
> But the source device I'm using is funky. It's headphone output
> suffers from a high, fixed noise floor. With the device's volume
> control all the way down, there's lots of soft hiss. As the volume
> control is turned up, the hiss level remains FIXED while the audio
> increases above it -- until the audio finally reaches a point where
> it satisfactorily overcomes that fixed noise floor, for my tastes.
>
> The problem is that I can't "crank" the volume of a headphone output
> going into a line-level input. Doing so overloads the line-level
> input and I'm left with subtle distortion. And I have no choice but
> to use THIS device. (Too much work to explain why; just trust me.)
>
> So: I need some kind of transformer adapter as described above.
> Something that would reduce the level of the headphone output,
> thereby creating the headroom needed to "crank" the headphone
> output's audio above its fixed noise floor without overloading the
> sound card line-level input. I hope you "get" what I mean. <g>
>
> Where can such a widget be found?

What you need is a simple attenuator, as others have already
indicated.

I suspect that one of Radio Shack's line-mounted headphone volume
control gizmos will do what you need.
Anonymous
April 19, 2005 4:48:15 PM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> Doctor, when I hit myself on the head with a hammer it hurts.
> What can I do?

Duuhh! You use a *pad* of course!

PapaNate
Anonymous
April 19, 2005 6:22:59 PM

Archived from groups: rec.audio.pro (More info?)

On Tue, 19 Apr 2005 01:15:00 GMT, Mars <nospam@invalid.com> wrote:


> But the source device I'm using is funky. It's headphone output suffers
> from a high, fixed noise floor. With the device's volume control all the
> way down, there's lots of soft hiss. As the volume control is turned up,
> the hiss level remains FIXED while the audio increases above it -- until
> the audio finally reaches a point where it satisfactorily overcomes that
> fixed noise floor, for my tastes.

As others have said, you don't need anything to go from a normal headphone
output to a line input. But I don't think that you've told us all the
relevant details here.

I would guess that you're trying to send the output of a laptop into a
desktop computer and that you're finding that you're getting noise. This
is due to a ground loop and in this case a transformer is going to be the
easiest way out of the problem.

If it isn't a ground loop then you might get away with using an inline
headphone volume control box which you might find at Radio Shack.

Cheers.

James.
Anonymous
April 20, 2005 2:37:10 PM

Archived from groups: rec.audio.pro (More info?)

In article <oYY8e.9799$go4.7290@newsread2.news.atl.earthlink.net> nospam@invalid.com writes:

> It's easy to find male headphone jack-to-female line-level input jack
> adapters at Radio Shack, etc. But where can I find one that actually
> transforms typical headphone jack output levels (30 ohms and below) to
> those acceptable to line-level inputs (1 kohms and above)?

A headphone ouput is acceptable to practically any line level input,
particularly a "sound card."

> But the source device I'm using is funky. It's headphone output suffers
> from a high, fixed noise floor.

No "converter" is going to fix this.

> With the device's volume control all the
> way down, there's lots of soft hiss. As the volume control is turned up,
> the hiss level remains FIXED while the audio increases above it -- until
> the audio finally reaches a point where it satisfactorily overcomes that
> fixed noise floor, for my tastes.
>
> The problem is that I can't "crank" the volume of a headphone output going
> into a line-level input. Doing so overloads the line-level input and I'm
> left with subtle distortion.

A simple resistive attenuator is all you need. It will reduce the
level of the signal + noise. A direct box (DI) will also do it, but
most of them don't have an adjustable output level.

> And I have no choice but to use THIS device.
> (Too much work to explain why; just trust me.)

Can you at least name the "device" to satisfy our curiosity?


--
I'm really Mike Rivers - (mrivers@d-and-d.com)
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 here: double-m-eleven-double-zero at yahoo
!