KVM Worthwhile for audio switching?

I'm in need of a way to swtich audio between two different machines to
accomodate my wireless Sennheiser headphones. As of now, I use a radio shack
RCA A/B switch, but this seems to degrade the signal. Also, I don't have to
have RCA. In fact, 1/8" jack will do, given that I use an adapter to plug
into the sound cards on the computers.

My current set up is a Belkin Omni Cube 4 port to switch the keyboard and
mouse between 2 different machines. I use the VGA and DVI inputs on a
2405fpw to share the monitor between the 2 machines. I've been meaning to
check into new KVMs anyway. Do the new audio supporting KVMs maintain an
acceptable audio swtching quality? I was thinking about the Belkin OmniView
SOHO Series F1DS104T.

Thanks for any info,
Alex

On Sat, 24 Jun 2006 15:43:55 -0500, "Alex Moreau"
wrote:

I'm in need of a way to swtich audio between two different machines to
accomodate my wireless Sennheiser headphones. As of now, I use a radio shack
RCA A/B switch, but this seems to degrade the signal.

I'm not sure where to draw the line here, since your
wireless Sennheiser headphones also degrade the signal.
Treble is just bad relative to Senns with a cord.

What kind of degradation do you feel it is?
If you wiggle the switch a little does that help, suggesting
it's just not making good contact? Is the switch in a metal
case and/or is it near a strong magnetic field such as next
to a wall-wart or other psu?

You could build your own A/B, as fancy as you want it...
double sided copper clad, silver plated, silver/teflon
wiring or all-on-pcb with gold plated jacks and
blahblahblah, bling. It may not sound any different, than
using more modest parts or regardless of the parts,
depending on the cause of the degradation.

Can you pop open the Rat Shack box and take a piece of
jumper wire or similar (leaving box in the same location
it's used in) and jumper between the switch input and output
pins to see if that improves the signal?

Also, I don't have to
have RCA. In fact, 1/8" jack will do, given that I use an adapter to plug
into the sound cards on the computers.

Ok, and there are some that curse at RCA, but overall it's
at least better than a bunch of 1/8" minijacks as minijack
contacts tend to degrade over time.


My current set up is a Belkin Omni Cube 4 port to switch the keyboard and
mouse between 2 different machines. I use the VGA and DVI inputs on a
2405fpw to share the monitor between the 2 machines. I've been meaning to
check into new KVMs anyway. Do the new audio supporting KVMs maintain an
acceptable audio swtching quality? I was thinking about the Belkin OmniView
SOHO Series F1DS104T.


I wouldn't run an analog signal into a digital switchbox and
expect it to be a "good" thing, not with the typical budget
constrained designs put into PC parts. Even so, if all else
fails it's worth a try to buy it from someplace with a good
return policy, and just send it back if it degrades the
sound too much as this is a very reasonable objection to
product performance.

"kony" wrote in message
...
On Sat, 24 Jun 2006 15:43:55 -0500, "Alex Moreau"
wrote:

I'm in need of a way to swtich audio between two different machines to
accomodate my wireless Sennheiser headphones. As of now, I use a radio
shack
RCA A/B switch, but this seems to degrade the signal.

I'm not sure where to draw the line here, since your
wireless Sennheiser headphones also degrade the signal.
Treble is just bad relative to Senns with a cord.

What kind of degradation do you feel it is?

Volume degradation seems to be somewhat of an issue at times, but overall,
I'm looking for the best way to retain the most quality. I'm not very
knowledgeable regarding such devices, and perhaps the A/B switch is the best
I can do.

If you wiggle the switch a little does that help, suggesting
it's just not making good contact? Is the switch in a metal
case and/or is it near a strong magnetic field such as next
to a wall-wart or other psu?

You could build your own A/B, as fancy as you want it...
double sided copper clad, silver plated, silver/teflon
wiring or all-on-pcb with gold plated jacks and
blahblahblah, bling. It may not sound any different, than
using more modest parts or regardless of the parts,
depending on the cause of the degradation.

Yes, and I do have the ability for such endeavors, but not the time. Truth
is, I'm busy most of the time, so buying a solution is better than building
one at this point in time.

Can you pop open the Rat Shack box and take a piece of
jumper wire or similar (leaving box in the same location
it's used in) and jumper between the switch input and output
pins to see if that improves the signal?

Also, I don't have to
have RCA. In fact, 1/8" jack will do, given that I use an adapter to plug
into the sound cards on the computers.

Ok, and there are some that curse at RCA, but overall it's
at least better than a bunch of 1/8" minijacks as minijack
contacts tend to degrade over time.

I don't mind using RCA. I just thought using 1/8" jacks rather than adapters
or hybrid cabling might provide a lesser rate of degradation.



My current set up is a Belkin Omni Cube 4 port to switch the keyboard and
mouse between 2 different machines. I use the VGA and DVI inputs on a
2405fpw to share the monitor between the 2 machines. I've been meaning to
check into new KVMs anyway. Do the new audio supporting KVMs maintain an
acceptable audio swtching quality? I was thinking about the Belkin
OmniView
SOHO Series F1DS104T.


I wouldn't run an analog signal into a digital switchbox and
expect it to be a "good" thing, not with the typical budget
constrained designs put into PC parts. Even so, if all else
fails it's worth a try to buy it from someplace with a good
return policy, and just send it back if it degrades the
sound too much as this is a very reasonable objection to
product performance.

OK. So with the information I've given, what would you do, if anything, to
limit signal loss? Any advice is welcome as long as it's not a solution that
requires building.

Thanks,
Alex

Alex Moreau wrote:
"kony" wrote in message
...
On Sat, 24 Jun 2006 15:43:55 -0500, "Alex Moreau"
wrote:

I'm in need of a way to swtich audio between two different machines to
accomodate my wireless Sennheiser headphones. As of now, I use a radio
shack
RCA A/B switch, but this seems to degrade the signal.

I'm not sure where to draw the line here, since your
wireless Sennheiser headphones also degrade the signal.
Treble is just bad relative to Senns with a cord.

What kind of degradation do you feel it is?

Volume degradation seems to be somewhat of an issue at times, but overall,
I'm looking for the best way to retain the most quality. I'm not very
knowledgeable regarding such devices, and perhaps the A/B switch is the best
I can do.

If you wiggle the switch a little does that help, suggesting
it's just not making good contact? Is the switch in a metal
case and/or is it near a strong magnetic field such as next
to a wall-wart or other psu?

You could build your own A/B, as fancy as you want it...
double sided copper clad, silver plated, silver/teflon
wiring or all-on-pcb with gold plated jacks and
blahblahblah, bling. It may not sound any different, than
using more modest parts or regardless of the parts,
depending on the cause of the degradation.

Yes, and I do have the ability for such endeavors, but not the time. Truth
is, I'm busy most of the time, so buying a solution is better than building
one at this point in time.

Can you pop open the Rat Shack box and take a piece of
jumper wire or similar (leaving box in the same location
it's used in) and jumper between the switch input and output
pins to see if that improves the signal?

Also, I don't have to
have RCA. In fact, 1/8" jack will do, given that I use an adapter to plug
into the sound cards on the computers.

Ok, and there are some that curse at RCA, but overall it's
at least better than a bunch of 1/8" minijacks as minijack
contacts tend to degrade over time.

I don't mind using RCA. I just thought using 1/8" jacks rather than adapters
or hybrid cabling might provide a lesser rate of degradation.



My current set up is a Belkin Omni Cube 4 port to switch the keyboard and
mouse between 2 different machines. I use the VGA and DVI inputs on a
2405fpw to share the monitor between the 2 machines. I've been meaning to
check into new KVMs anyway. Do the new audio supporting KVMs maintain an
acceptable audio swtching quality? I was thinking about the Belkin
OmniView
SOHO Series F1DS104T.


I wouldn't run an analog signal into a digital switchbox and
expect it to be a "good" thing, not with the typical budget
constrained designs put into PC parts. Even so, if all else
fails it's worth a try to buy it from someplace with a good
return policy, and just send it back if it degrades the
sound too much as this is a very reasonable objection to
product performance.

OK. So with the information I've given, what would you do, if anything, to
limit signal loss? Any advice is welcome as long as it's not a solution that
requires building.

Thanks,
Alex

if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.


NT

wrote in message
oups.com...
Alex Moreau wrote:
"kony" wrote in message
...
On Sat, 24 Jun 2006 15:43:55 -0500, "Alex Moreau"
wrote:

I'm in need of a way to swtich audio between two different machines to
accomodate my wireless Sennheiser headphones. As of now, I use a radio
shack
RCA A/B switch, but this seems to degrade the signal.

I'm not sure where to draw the line here, since your
wireless Sennheiser headphones also degrade the signal.
Treble is just bad relative to Senns with a cord.

What kind of degradation do you feel it is?

Volume degradation seems to be somewhat of an issue at times, but
overall,
I'm looking for the best way to retain the most quality. I'm not very
knowledgeable regarding such devices, and perhaps the A/B switch is the
best
I can do.

If you wiggle the switch a little does that help, suggesting
it's just not making good contact? Is the switch in a metal
case and/or is it near a strong magnetic field such as next
to a wall-wart or other psu?

You could build your own A/B, as fancy as you want it...
double sided copper clad, silver plated, silver/teflon
wiring or all-on-pcb with gold plated jacks and
blahblahblah, bling. It may not sound any different, than
using more modest parts or regardless of the parts,
depending on the cause of the degradation.

Yes, and I do have the ability for such endeavors, but not the time.
Truth
is, I'm busy most of the time, so buying a solution is better than
building
one at this point in time.

Can you pop open the Rat Shack box and take a piece of
jumper wire or similar (leaving box in the same location
it's used in) and jumper between the switch input and output
pins to see if that improves the signal?

Also, I don't have to
have RCA. In fact, 1/8" jack will do, given that I use an adapter to
plug
into the sound cards on the computers.

Ok, and there are some that curse at RCA, but overall it's
at least better than a bunch of 1/8" minijacks as minijack
contacts tend to degrade over time.

I don't mind using RCA. I just thought using 1/8" jacks rather than
adapters
or hybrid cabling might provide a lesser rate of degradation.



My current set up is a Belkin Omni Cube 4 port to switch the keyboard
and
mouse between 2 different machines. I use the VGA and DVI inputs on a
2405fpw to share the monitor between the 2 machines. I've been meaning
to
check into new KVMs anyway. Do the new audio supporting KVMs maintain
an
acceptable audio swtching quality? I was thinking about the Belkin
OmniView
SOHO Series F1DS104T.


I wouldn't run an analog signal into a digital switchbox and
expect it to be a "good" thing, not with the typical budget
constrained designs put into PC parts. Even so, if all else
fails it's worth a try to buy it from someplace with a good
return policy, and just send it back if it degrades the
sound too much as this is a very reasonable objection to
product performance.

OK. So with the information I've given, what would you do, if anything,
to
limit signal loss? Any advice is welcome as long as it's not a solution
that
requires building.

Thanks,
Alex

if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.


That's all I need to know...thanks!

Alex

On Sat, 24 Jun 2006 16:30:44 -0500, "Alex Moreau"
wrote:



OK. So with the information I've given, what would you do, if anything, to
limit signal loss? Any advice is welcome as long as it's not a solution that
requires building.

Let me put my answer in context...

I regularly participate in 3 different headphone oriented
forums. I build my own headamps and happen to have
transisters scattered all over the floor at the moment so I
can match gain on them. The sound card I use for headphone
listening has RCAs added to the card mounting bracket (tight
fit, but on some cards it is possible to add them) and a few
topology and parts alterations. The output goes directly to
a headamp, I would not switch it between systems at all
unless I had hand-built a switch.

That's just "what I would do". I opened my prior post
mentioning the minor degradation from the wireless(ness) of
the headphones because I can't decide for you what degree of
degradation is acceptible to _your_ ears... it is a
subjective thing and I can't hear your resultant sound
either way, though I have A/B compared wireless Senns.

There are studio quality headphone distribution and/or amp
boxes but they're not cheap. What would you budget and how
often do you find you're needing to switch? Is it a problem
that with a KVM, you will necessarily be switching the audio
when you switch the rest... can't be using one system and
listening to the other unless you did it manually which
somewhat defeats the whole purpose.

I would first determine what is causing the signal loss to
more directly combat it. As I'd mentioned previously,
opening up the switch and shorting it out of the circuit as
well as considering it's location are a couple of thing to
try. For all we know you could just buy another switch and
swap it in for the (potentially) poor one currently in the
Radio Shack box... or buy another box that looks pretty
similar but doesn't have the problem. If on the other hand
you had a very noisey environment and the extra cables were
a problem (I've no idea if very long cable runs to the Senn
transmitter could foul up transmissions), shorter cables,
better shielded cables, or re-routing the cables might help
(if not a combination of these).

On 24 Jun 2006 14:37:11 -0700, wrote:



if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.



It's not so hard to degrade low level analog signals. There
was a time when a lot of Radio Shack gear was tailored
towards simplistic kid's hobby use, the box could be
operating as it was designed to, was never intended to be a
"great" isolator of signal.

kony wrote:
On 24 Jun 2006 14:37:11 -0700, wrote:



if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.



It's not so hard to degrade low level analog signals. There
was a time when a lot of Radio Shack gear was tailored
towards simplistic kid's hobby use, the box could be
operating as it was designed to, was never intended to be a
"great" isolator of signal.

but how would a switchbox degrade a headphone signal? Series R has no
effect until it gets into fault proportions, capacitance ditto on a
8-35 ohm line, and parallel R again has no effect until it gets well
and truly into fault territory. Higher impedance lines sure, but not
headphones.


NT

On 25 Jun 2006 07:06:05 -0700, wrote:

kony wrote:
On 24 Jun 2006 14:37:11 -0700, wrote:



if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.



It's not so hard to degrade low level analog signals. There
was a time when a lot of Radio Shack gear was tailored
towards simplistic kid's hobby use, the box could be
operating as it was designed to, was never intended to be a
"great" isolator of signal.

but how would a switchbox degrade a headphone signal? Series R has no
effect until it gets into fault proportions,

Define "fault proportions".
The statement is generally untrue.
Series resistance causes a very easily detectable change in
analog audio on any reasonably good (including consumer
grade) equipment. In fact it is one of the reasons many
people will use a separate amplification stage instead of
using the headphone-out on a power amp (with the series
resistance to the HP jack).

capacitance ditto on a
8-35 ohm line,

Where are you getting this *information*?
Cable capacitance is not only an issue but will make some
outputs instable altogether. A series resistance here can
help (not sound, but stability) or a ferrite bead, or other
resolutions chosen in the design stage (given the target
use) but capacitance is a significant issue. Typical audio
cabling is a trade-off of low cost and size, flexibility.

and parallel R again has no effect until it gets well
and truly into fault territory. Higher impedance lines sure, but not
headphones.

Define "fault territory". Will "some" audio signal get
through? Yes, and you are observing that some does right
now. Will the signal be preserved as much as possible
(reasonably so)? No.

If analog signal was so easily preserved there would be
little point to digital transmissions.

As stated previously, if you want to find where your fault
is, you need to isolate the variables such as moving the
box, shorting out the switch. That you are having this
issue in the first place is a sign it is not as simple as
you suggest. It might just be a bad or worn switch but...
(it might not).

kony wrote:
On 25 Jun 2006 07:06:05 -0700, wrote:
kony wrote:
On 24 Jun 2006 14:37:11 -0700, wrote:

if your switchbox is degrading quality or volume, its because its
faulty. Its quite a challenge to build a device like this that will
degrade headphone signals. Replace the switch or leads if necessary.

It's not so hard to degrade low level analog signals. There
was a time when a lot of Radio Shack gear was tailored
towards simplistic kid's hobby use, the box could be
operating as it was designed to, was never intended to be a
"great" isolator of signal.

but how would a switchbox degrade a headphone signal? Series R has no
effect until it gets into fault proportions,

Define "fault proportions".

theres really no need. headhones are routinely driven via many ohms
series R, a functional switch will not get that into that order of
magnitude of contact resistance. If it does its thoroughly stuffed.


The statement is generally untrue.
Series resistance causes a very easily detectable change in
analog audio on any reasonably good (including consumer
grade) equipment. In fact it is one of the reasons many
people will use a separate amplification stage instead of
using the headphone-out on a power amp (with the series
resistance to the HP jack).

2 different things there. Series resistance of many ohms magnitude will
change the frequency response since the phones dont have constant
impedance at all freqs. But a switch of milliohms resistance is not
going to make a detectable difference.


capacitance ditto on a
8-35 ohm line,

Where are you getting this *information*?

Its what I'm qualified in. Capacitance isnt a problem because the
impedance is so low. Different matter on high impedance lines, or at
frequencies way above audio, or on very long lines. But a headphone
lead is none of these.


Cable capacitance is not only an issue but will make some
outputs instable altogether. A series resistance here can
help (not sound, but stability) or a ferrite bead, or other
resolutions chosen in the design stage (given the target
use) but capacitance is a significant issue.

but this has nothing to do with degrading audio quality, so long as the
amp is capable of driving the load sensibly. I've not come across any
good quality kit that goes unstable when loaded with a headphone lead -
if it did it would be junk grade. Novelty goods etc.


Typical audio
cabling is a trade-off of low cost and size, flexibility.

plus durability/reliability and marketing considerations.


and parallel R again has no effect until it gets well
and truly into fault territory. Higher impedance lines sure, but not
headphones.

Define "fault territory". Will "some" audio signal get
through? Yes, and you are observing that some does right
now. Will the signal be preserved as much as possible
(reasonably so)? No.


Lets put numbers to it. A leaky switch might have 500k resistance, and
this is across a line with load of 35 ohms and line impedance of
anything from 35 ohms downwards. And this R consists of carbon, which
is ohmic.

The ratio of leakage R to line R is 14300:1, so the line level will be
thus reduced to 0.99993 times its original voltage level. Since carbon
is ohmic there is no distortion thus introduced.

Now lets say the C is heavily contaminated with copper dust that has
oxidised, forming a network of rectifying distorting resistance
elements. In practice there will be more C than Cu, and the R of the C
is much lower than that of Cu oxide. Lets be generaous and say there is
10% distortion of the current flowing across this leaky switch. This
will give us a distortion of 0.0007%.

No human being can hear that, and other system disortions will swamp
this one.

BTW I'm looking at the switch section of a catalogue, which for an
ultraminiature switch, ie a cheap type, gives a min insulation of 1000
Mohms.



Now lets spin numbers for series R.

Again using low quality switches not intended for analogue use at all,
contact R spec is 200mohms.

With 32 ohm headphones fed via a 100 ohm R, typical of consumer audio
amps, and amp output impedance of say 0.2 ohms, we get a line
impedance of 100.2 in parallel with 32 = 24.254 ohms.

Now when we add the flimsy switch of at worst 0.2 ohms, we get 100.4
ohms driving 32 ohms instead of 100.2 ohms. You only need look at the
resistance vs frequency plot of any moving coil driver to see there
wont be any detectable difference. A typical 8" 8 ohm LS has impedance
that varies from 1.5-2 ohms upto 20 - 30 ohms, in series with voice
coil R of typ 5 - 6 ohms. This can only be approx since they vary
somewhat, but this is fairly typical. The effect of any switch
resistance is lost orders of magnitude below the various types of
distortion inherent in moving coil loudspeakers.



If analog signal was so easily preserved there would be
little point to digital transmissions.

This doesnt back up what youre claiming above, as its not significantly
related to it. Preseving analogue quality at af over a 2m 25 ohm line
is elementary, preserving it over transmission paths is a very
different matter with entirely different problems and solutions.


NT