Headphone attenuator/volume control (EE's, please read)

[Tempus]

I just received my new V6's, and despite some painful long-
term ear pinching, due to my colossal ears, I like them
quite a bit. In fact, I'm hearing things in video games
that I didn't know were there. For example, bass.

Unfortunately, their EXTREME sensitivity has also revealed
the overall Samsunginess of my TV, in the form of
ever-present and unignorable background hiss. The volume
of the hiss remains constant as I adjust the volume on the
TV. Also, the only comfortable listening level, with these
new super-sensitive headphones, is to put the volume on one
click out of 64. (I prefer it pretty quiet. On my old Lil'
Cheapie headphones, I used 3 clicks.)

It has occured to me that both of these problems could be
solved by a simple attenuator hooked in between the TV and
the headphones. Now, I'm fairly handy with a soldering
iron, but not with AC theory, so does anyone here know how
one could go about making an attenuator that doesn't
distort sound or have any particular frequency bias? The
obvious idea is to put two resistors in series with the
left and right sides, respectively, or perhaps just one on
the common, but would this perform as hoped?

 

[blr]

Although I can't answer your question directly, I can suggest a solution.
I've seen cheap extension cords with built in volume controls. Look at the local hardware store. Since you're using it with a TV the small loss in quality due to the cheap cord/attenuator itself will be inaudiable. I know Sennheiser also makes such thing but it's perhaps more expensive (it's Sennheiser after all).

Hope this helps.

 

[kwkarth]

Radio Shack also sells an innexpensive in-line volume control for headphones. It's about 4 bux if I remember correctly.

 

[ponzio]

Just to clarify, are you plugging your headphones into a headphone output of your TV? If not, what are you plugging them into? Without knowing more about your setup, it is difficult to recommend things to make it better.

From your post it appears that you want a filter to remove the "everpresent" hiss, as well as a volume (or gain) control.

How about a small, homemade, battery-powered headphone amp to plug into the line-out of your source (Xbox, portable CD player, soundcard etc.)? For a relatively inexpensive price, this will provide better cleaner amplification, gain control, and may eliminate the hiss you are experiencing (again, I'm not sure what you are plugging your headphones into). You can buy one, build one yourself (good educational exercise), or have one built for you. Do a search for JMT or CMOY amps on this site and you will find many happy users.

Ponzio -- E.E.

p.s. Welcome to the world of hearing new things. It gets better.

 

[Tempus]

kwkarth:
>Radio Shack also sells an innexpensive in-line volume
>control for headphones. It's about 4 bux if I remember
>correctly.

Yes, I found that after I posted the message. It's $5, and
I can't build one properly for less, so I'll probably just
get that.

ponzio:
>are you plugging your headphones into a headphone output
>of your TV?

Yes.

>From your post it appears that you want a filter to remove
>the "everpresent" hiss, as well as a volume (or gain)
>control.

The TV generates hiss. The hiss (noise) volume is
constant, even when I increase the volume of the TV
(signal). Therefore, I can increase the signal to noise
ratio by turning up the volume on the TV, but this would
cause the sound level in the headphones to be deafeningly
loud. If I attenuate this loud signal with a device
installed between the headphone port and the headphones
themselves, I can have the high signal to noise ratio, and
still have a reasonable sound pressure level.

>How about a small, homemade, battery-powered headphone amp
>to plug into the line-out of your source (Xbox, portable
>CD player, soundcard etc.)? For a relatively inexpensive
>price, this will provide better cleaner amplification,
>gain control, and may eliminate the hiss you are
>experiencing

As you no doubt know, being an EE, you cannot increase the
signal to noise ratio by adding a component to an existing
chain of components. I have described, in the above
paragraph, the only way I can improve the S/N ratio.

One COULD make some sort of filter, but no filter will be
able to discriminate between noise and a similar signal.
In other words, if you block the frequency components
present in the noise, you also remove any similar
frequencies from the signal, and therefore have done
nothing to improve the signal to noise ratio.

 

[kwkarth]

Actually, by attenuating the hiss which is constant with the in line volume control and then increasing the output of the TV sound by turning it up to 4 or 5 clicks or more, you WILL greatly improve the signal to noise ratio in your headphones.

Happy listening,

-kevin xEE

 

[ponzio]

Quote:

As you no doubt know, being an EE, you cannot increase the signal to noise ratio by adding a component to an existing chain of components. I have described, in the above paragraph, the only way I can improve the S/N ratio.

After rereading your first post, I believe I understand your situation better now.

You have described a way to possibly improve the S/N ratio while maintaining your present amplification source. Your attenuator solution may work and may very well provide the results you desire, plus, it is extremely low cost. You will increase the volume on your television to a point where the desired audio information outweighs the constant level hiss you are hearing. However, without knowing the exact volume level required, it is difficult to predict whether the volume level you require will cause the amplifier in the TV to distort its output. If distortion of the desired audio information occurs, it cannot be cured.

I believe you misunderstood my response. I did not recommend adding a component to your signal chain. I recommended substituting a component with better S/N characteristics.

You have not answered my question about your source, but since you said you played games, I will assume that your source is a video game console, and that the console has line level audio outputs. If I am mistaken in this assumption, please correct me.

Currently your signal chain is roughly as follows: Source --> cable --> TV --> cable --> headphones. From my experience, I believe that the audio amplification (headphone output) within the TV is causing some or all of your unwanted noise. Another cause may be RF interference from nearby electronics.

In my post, I recommended the following signal chain: Source --> cable --> small amplifier --> cable --> headphones. The amplifier will cost more than $4 and less than $100 (perhaps less than that). It will be small, portable, battery powered, and capable of use with other audio devices. Without having heard your TV, I will say that I believe that, in addition to not having hiss, it will sound markedly better than your TV headphone output. It may even make you smile.

 

[slindeman]

I'm with Ponzio here. It is the headphone jack of your TV that is likely causing the hiss, so a better solution than attenuation (but more expensive) would be to hook up a dedicated headphone amp either to the audio line-out of the original source (x-box, dvd player, vcr, etc.) or if your TV has a line-out on the back you could instead hook it up there. This would completely remove the hiss problem. Not only that, but the sound in general would improve compared to the attenuated TV headphone jack, because the TV's headphone jack likely uses a very cheap opamp or some cheap resistors connected to the cheap amp for the TV's built-in speaker(s). Whether its worth the cost or not would be up to you.

 

[Tempus]

kwkarth:
>Actually, by attenuating the hiss which is constant with
>the in line volume control and then increasing the output
>of the TV sound by turning it up to 4 or 5 clicks or more,
>you WILL greatly improve the signal to noise ratio in your
>headphones.

Isn't that what I said?

I think the point of confusion is this: The addition of the
attenuator to the chain of components does NOT improve the
signal to noise ratio. It is the turning up of the volume
on the TV that does THAT, so my rule about adding
components not improving S/N still holds. (You may consider
this mere semantics, but I'm very literal.)

ponzio:
>I believe you misunderstood my response. I did not
>recommend adding a component to your signal chain. I
>recommended substituting a component with better S/N
>characteristics.
>You have not answered my question about your source, but
>since you said you played games, I will assume that your
>source is a video game console, and that the console has
>line level audio outputs. If I am mistaken in this
>assumption, please correct me.

I'm not using an external tuner. I'm using the internal
tuner of a poorly made TV (when I'm not playing a video
game). I therefore cannot separate the source of the noise
from the rest of the system. I cannot substitute a high
quality amp. All I could do is add a second amp to the
chain, and as I said before, that won't help.

>It may even make you smile.

I only smile online.

slindeman:
>...or if your TV has a line-out on the back you could
>instead hook it up there.

It has line out, but the line out is at least as poorly
designed as the headphone jack, if not more so. I haven't
tested it for hiss, because the last (and only) time I
attached the line out to something (a pair of speakers with
built in amp, known to work fine) it made a loud buzzing
noise come out of the INTERNAL speakers of the TV. Hooking
something up to an OUTPUT of the TV is NOT supposed to make
the TV go nuts, so at that point I decided it would be
better to pretend that the line out didn't exist.

>Whether its worth the cost or not would be up to you.

Regardless of the context, my answer to this question is
almost always "No."

 

[JML]

Is it high-frequency hiss (which most people have assumed) or is it a low-frequency hum?

You might have some noise passed along from the transformers used for your game setup. A filtered transformer ought to cure it. You can try Radio Shack and bring it back if it doesn't work. but disconnect the game hardware first and see if the noise is gone. The other possibility no one seems to have mentioned is noise from the Cable TV hookup if you have one. An in-line cable filter would cure that and also improve the image.

But do you get the noise just from the TV with nothing else connected but the headphones? And I almost hate to ask, but is the TV's minijack mono or stereo?

 

[slindeman]

Quote:

Regardless of the context, my answer to this question is almost always "No."

My solution to the same problem you have (bad sounding TV through its own speakers and heapdhone jack) came in at $80 and a few hours of soldering iron time, and includes the headphones (HD570), portable headphone amp (DIY), and cables. It is also the solution to my crappy sounding computer speakers and their hissy sounding headphone jack. It is also the solution to my hissy portable cd player headphone jack. You'd be amazed at the number of uses you can find for a good inexpensive portable headphone amp. You said you know how to solder. Well you can probably figure out my advice.

 

[pedxing]

Many electronic products have a low line hiss that does not increase at all or very little when the overall volume is cranked up. I have encountered this problem with every single computer speaker I I have tried.

Adding another amplifier right to the TV headphone jack will not solve the hiss problem. It will amplify the hiss itself too. A headphone amp may make the overall signal sound better with his headphone. To solve the base line hiss, an attenuator of some form is required.

I know www.headphone.com sells some harrison lab attenutors for certain interconnects (or you can go to www.hlabs.com to go directly to harrison lab's website). They are not a cheap solution and for a TV, a Radio shack volum controller might be satisfactory.

I have the same problem with my headphone amp. The volume knob does not equalize the left and right channels at very low volumes.

 

[slindeman]

Quote:

Adding another amplifier right to the TV headphone jack will not solve the hiss problem. It will amplify the hiss itself too. A headphone amp may make the overall signal sound better with his headphone. To solve the base line hiss, an attenuator of some form is required.

The whole point is to bypass the crappy headphone jack completely, be it the TV's, the portable CD player's, or the computer speaker's. Not sure why you would think I suggested amplifying the crappy hissy jack. In my experience, the line-outs of my TVs, VCRs, mini-systems, soundcards, portables, etc. are quite decent when connected to a dedicated headphone amp.

 

[ponzio]

Originally posted by Tempus
As you no doubt know, being an EE, you cannot increase the
signal to noise ratio by adding a component to an existing
chain of components . . .

. . .my rule about adding components not improving S/N still holds. (You may consider this mere semantics, but I'm very literal.)

Being an EE, I am familiar with the field of signal processing. I also believe that this "rule" is false.

Noise is removed (and thus S/N increased) from audio signals by communications equipment hundreds of trillions of times per second, every single day.

I am unaware of any rule that says that unwanted portions of signals may not be identified and subtracted from signals. When you know what your noise signal looks like, then you can subtract it. You have a constant hiss. This hiss could be analyzed, reproduced and subtracted from the original signal very effectively.

Granted, this is beyond the scope of your $4 solution, but I have allowed myself to be annoyed by your continued parading of your new "rule", and thus, I reply.

 

[Tempus]

JML:
>Is it high-frequency hiss (which most people have assumed)
>or is it a low-frequency hum?

It's a hiss, not a hum, as implied by my use of the word
"hiss."

It's good, old fashioned white noise.

>You might have some noise passed along from the
>transformers used for your game setup.

No, because if the source were outside the TV, then the
noise would increase when I turn up the volume on the TV,
which it doesn't.

>You can try Radio Shack and bring it back if it doesn't
>work.

I know that an attenuator will work, there was never any
doubt about that.

>But do you get the noise just from the TV with nothing
>else connected but the headphones?

Yes.

>And I almost hate to ask, but is the TV's minijack mono or
>stereo?

Stereo, but I fail to the relevancy to the hiss problem.

slindeman:
>Well you can probably figure out my advice.

Perhaps some time in the future, but it's not worth it
right now. I have yet to encounter a hiss problem in any
of my own equipment that cannot be solved with a simple
attenuator.

pedxing:
>Many electronic products have a low line hiss that does
>not increase at all or very little when the overall volume
>is cranked up. I have encountered this problem with every
>single computer speaker I I have tried.
>Adding another amplifier right to the TV headphone jack
>will not solve the hiss problem. It will amplify the hiss
>itself too. A headphone amp may make the overall signal
>sound better with his headphone. To solve the base line
>hiss, an attenuator of some form is required.

My sincere thanks, pedxing, for being one of the few to
actually grasp the situation in 10,000 words or less.

slindeman:
>The whole point is to bypass the crappy headphone jack
>completely, be it the TV's, the portable CD player's, or
>the computer speaker's.

...which is impossible, because, as I already said, I am
using the internal tuner of the TV, and the line-out ports
are screwed up.

>Not sure why you would think I suggested amplifying the
>crappy hissy jack.

Because it's the only remaining way to get sound out of the
TV and into the headphones? Just a guess.

ponzio:
>Being an EE, I am familiar with the field of signal
>processing. I also believe that this "rule" is false.

In the general case, yes, you can find counterexamples.
For example, if the noise were a precise copy of a Barry
Manilow CD being mixed with the desired signal, then yes,
you could, with a pure copy of said CD, subtract that
component from the mix. But that's not my situation.

Also, if the noise were in frequency ranges outside those
of the signal, it could be removed by means of a band pass
filter. This, too, is not my situation.

Furthermore, if the noise were a repeating pattern, one
could average many copies of it, and extract a close match
to the noise, which could then be subtracted from the
signal. This is also not my situation.

My situation, as I have tried so many times to make clear,
is hiss. Hiss is white noise. White noise is
fundamentally unpredictable. It never repeats. No two
white noises are the name, unless one is a recording of the
other, and I'm fairly certain that my TV does not have a
recording of white noise in it, as that would have cost me
extra.

Now, in the specific case of the noise being WHITE noise,
and the signal being defined in a general sense, such that
you can not make any advance conclusions about the nature
of the signal today, then yes, my "rule" holds true. You
can apply all the digital signal processing you want, but
it's not going to help.

>Noise is removed (and thus S/N increased) from audio
>signals by communications equipment hundreds of trillions
>of times per second, every single day.

...but only by making assumptions about the content of the
noise, the signal, or both.

>I am unaware of any rule that says that unwanted portions
>of signals may not be identified and subtracted from
>signals.

Only in the specific case of a noise and/or signal with
predictable and distinct characteristics, which does not
apply here.

>When you know what your noise signal looks like, then you
>can subtract it.

Which would be great if it weren't for that darn
unpredictability.

>You have a constant hiss. This hiss could be analyzed,
>reproduced and subtracted from the original signal very
>effectively.

In truth, there is nothing constant about a constant hiss,
short of the annoyance factor. In order to reproduce it,
you would first have to isolate it from the signal. It's a
circular solution. We can solve the problem if we start
with the problem already solved, and then work from there.

>Granted, this is beyond the scope of your $4 solution, but
>I have allowed myself to be annoyed by your continued
>parading of your new "rule", and thus, I reply.

Your annoyance is the result of your not understanding.
I'll take one more stab at clarifying this: Have you
considered that the SIGNAL might at times include a
recording of a similar hiss? Tell me how you would isolate
one hiss from the other, given no copy of the clean signal
from which to work.