KVM Worthwhile for audio switching?

[Alex Moreau]

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

 

[kony]

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.

 

[Alex Moreau]

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?


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.

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

 

[meow2222]

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.


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.


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.



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

 

[Alex Moreau]

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

 

[kony]

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).

 

[kony]

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.

 

[meow2222]

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

 

[kony]

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).

 

[meow2222]

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.

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.

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

 

[kony]

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.

You are attempting to explain away all possible problems,
with the only result being that your switchbox must work ok.
See the problem with this logic?

Fact is, just a few ohms of resistance will degrade the
sound. One need not have "golden ears" to hear it either.
Will you still get sound? Yes, but we cannot hear what your
degraded sound, sounds like.

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.

Again you are making assumptions based on everything being
properly working- clearly something isn't.

We don't know that there is only milliohms of resistance,
nor whether all solder joints are good or further resistance
or capacitive couplings, or if unshielded wire or case is an
issue, or (anything at all actually, you might have a
defective switch for all we know, since you can't be
bothered to just do the simple tests I suggested).

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.

I'm sorry but you are not qualified in this, if you feel you
can jump to such a conclusion. First we would need to know
the output stage of the driving source (sound card?), what
stability it has at driving capacitive loads. It could be
that it uses a series resistance, or a low speed, low
quality opamp that is quite stable at typical cable
capacitances... or it might not be. Higher quality outputs
do tend to be more sensitive.

I don't believe you are qualified either if you are having
this kind of dilemma in resolving a relatively simple
problem, merely an inline switchbox degradation. This is
something anyone with a year of college electronics would
find trivial, even boring.

but this has nothing to do with degrading audio quality, so long as the
amp is capable of driving the load sensibly.

Quality is directly effected, the issue is not only pushing
the voltage and current through the wire. Every single
audio product on earth (that sounds different) is evidence
of this.

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.

Actually most gear is made to reduce customer RMA, work in
the broadest situations possible. Truely high performance
gear has to have HF/bandwidth limitations and measurements
taken to reduce capacitive load just enough to be stable,
while not degrading quality too much. If you start tacking
on multiple series cables you are depending on the design to
have been made stable (or that it was inherantly by low-spec
design) in that scenario.

We are not talking about "a headphone lead" though,
obviously any headphone driving product is meant to do that.
Didn't yours also sound ok in contrast to what you now
describe as degradation? Again you try to discount
everything but that leaves nothing, you must then be
imagining the problem? It is in fact likely to be the
switch but you aren't looking to resolve this it seems,
rather than ????

I suspect you WANT a KVM audio switch but it is the reason
in itself for your post, not just to resolve a problem with
a switchbox. If that is the goal, fine/good/great/etc, but
it would be good to just cut to the chase and make that
clear instead of detailing issues with the switchbox.

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.

If your switch has 500k, there is no question that it will
degrade audio quality. I'd be surprised if it can produce
reasonable sound at all in such a scenario.

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.

You don't know thing:1 about electronics do you? 500K
resistance and 0.99993? No.

Since carbon
is ohmic there is no distortion thus introduced.

You are completely wrong. The resistance causes it, AND the
carbon does too, AND "ohmic thus none" is just
non-applicable, it doesn't account for any other sources of
distortion. Anyone with extensive hands-on audio
electronics experience can tell you that just switching
between carbon and metal resistors will change the sound.
Not one of those voodoo "golden ears" types of things
either, a blind A/B blahblahblah, scientifically valid
conclusion.

Now lets say the C is heavily contaminated with copper dust that has
oxidised, forming a network of rectifying distorting resistance
elements.
n practice there will be more C than Cu, and the R of the C
is much lower than that of Cu oxide.

Where is this copper supposed to be? You should have no
bare copper contacts anywhere to oxidize.

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. I don't know what you think you are qualified in, but
it sure as heck isn't analog audio.

First of all, it does not form any rectifying network, it is
a simple series RC. That is, IF you had bare copper which
you should not. Are you just making this up as you go
along?

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

So it's all settled then, it can't be the cables and it
can't be the switch, it must be your imagination.

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.

Did it ever occur to you that this is with a PROPERLY
working switch?

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.

You might find 100 Ohm on a piece of junk but not on any
decent gear. Granted, a typical sound card may be a piece
of junk. Why the theories on your part though, have you
bothered to actually check your equipment? If not, no
wonder you still have a problem, you aren't actually DOING
anything to resolve it.

Also, it would be surprising to find that your wireless Senn
transmitter has 32 ohm impedance, or rather, not at all
likely.

Now when we add the flimsy switch of at worst 0.2 ohms,

You feel comfortable arbitrarily declaring 0.2 Ohms? You
shouldn't, if the switch is worn or defective it may easily
be higher- remember that you ARE having a problem with
(something).

we get 100.4
ohms driving 32 ohms instead of 100.2 ohms.

Not quite, you can't just add up the resistances without
considering the other passive elements in the audio path.

You only need look at the
resistance vs frequency plot of any moving coil driver to see there
wont be any detectable difference.

It would go from poor, to poor, so yes that's about the
same.

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.

So you're trying to drive loudspeakers with your sound card
line out? It would be good for you to stick to the issue at
hand that you still can't resolve as it was a rather simple
one.

This doesnt back up what youre claiming above, as its not significantly
related to it.

Quite the opposite.

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.

Apparently it is for me- I don't have this distortion
problem that you do.

 

[meow2222]

(e-mail address removed) wrote:

This is a discussion about whether a correctly functioning switchbox in
the lead to heapdhones could degrade audio quality. (I'm assuming here
the switchbox is designed for the purpose, and not eg a 100kW motor
switchbox etc). We seem to have gotten sidetracked at places, but
hopefully after this post we'll be back to the point.




You seem to have gotten very confused. For a start I'm not the OP and
would be unlikely to be asking for help solving a distortion problem
due to leads, switchbox, etc, if I had one. If it were due to software
drivers I might well, I'm not no expert in those.

Second I dont think you've paid enough attention to follow what was
being said at various points. I'm not sure why. I'll add some notes
which may help clear some misunderstandings up.

You are attempting to explain away all possible problems,

havent tried that at all, have only refuted your claim that a switchbox
could degrade a heaphone signal

with the only result being that your switchbox must work ok.
See the problem with this logic?

Yes: I dont have such a switchbox, and your imagination has come up
with the wrong guess.

Fact is, just a few ohms of resistance will degrade the
sound. One need not have "golden ears" to hear it either.
Will you still get sound? Yes, but we cannot hear what your
degraded sound, sounds like.

Feel free to back this up with some numbers.

Again you are making assumptions based on everything being
properly working- clearly something isn't.

I think youve misunderstood, Im explaining why a properly functionng
switchbox cant degrade the sound.

We don't know that there is only milliohms of resistance,

if its not faulty we do, and thats what I'm discussing.

nor whether all solder joints are good

if not, its faulty

or further resistance
or capacitive couplings,

in a headphone or speaker switchbox that would be unlikely.

Switching a mix of headphones and speakers on bridged output amps is a
bit more complex, but I dont think theres much chance of the OP's
switchbox being designed to handle that.

or if unshielded wire or case is an
issue,

it isnt, not at 30 odd ohms, a.f. and a volt or more. If you think it
is I'd start to wonder just what your skill level is on this.

or (anything at all actually, you might have a
defective switch for all we know, since you can't be
bothered to just do the simple tests I suggested).

I have no access to the op's switchbox.

I'm sorry but you are not qualified in this,

wrong again

if you feel you
can jump to such a conclusion. First we would need to know
the output stage of the driving source (sound card?), what
stability it has at driving capacitive loads. It could be
that it uses a series resistance, or a low speed, low
quality opamp that is quite stable at typical cable
capacitances... or it might not be. Higher quality outputs
do tend to be more sensitive.

Well I simply dont agree. If its not capable of driving headphones then
its not fit for purpose. I havent come across any commercial analogue
audio amp with such a problem in a long time. Very old equipment yes,
home made kit yes, faulty kit yes, but not modern commercial equipment.
Any company putting out kit that bad would soon go bust. Imagine the
cost, lost business and destroyed reputation that would result from 5%
of shipped equipment going unstable.

I don't believe you are qualified either if you are having
this kind of dilemma in resolving a relatively simple
problem, merely an inline switchbox degradation.

I'm not attmpting to solve a switchbox or distortion problem.

This is
something anyone with a year of college electronics would
find trivial, even boring.

I dont agree. I've worked with many of them in the lab and you might be
surprised how clueless most are. Too often students learn on paper
without knowing how those concepts relate to the physical practical
world, and without having the more basic concepts that should come
before the sort of stuff thats typically taught at degree level. I've
seen a lab full of students taught the concepts needed to construct a
radio receiver yet not have a clue where to begin.

Hint: dont get me started on the shortcomings of degree courses

Quality is directly effected, the issue is not only pushing
the voltage and current through the wire.

Youre welcome to show us the numbers/maths that back your claim up. I
dont think they will.

Every single
audio product on earth (that sounds different) is evidence
of this.

clearly it isnt.

Actually most gear is made to reduce customer RMA, work in
the broadest situations possible.

This is why we can assume whatever amp is driving the switchbox and
lead will work, and why we can condsider discussion of instability not
relevant to non-faulty equipment.

Truely high performance
gear has to have HF/bandwidth limitations and measurements
taken to reduce capacitive load just enough to be stable,
while not degrading quality too much. If you start tacking
on multiple series cables you are depending on the design to
have been made stable

of course, as every competent design is. If its decent quality it wont
be only just stable. Thats more likely to be a property of bottom end
kit.

We are not talking about "a headphone lead" though,

I was. Still am.

obviously any headphone driving product is meant to do that.
Didn't yours also sound ok in contrast to what you now
describe as degradation? Again you try to discount
everything but that leaves nothing, you must then be
imagining the problem?

maybe youre imagining the problem.

It is in fact likely to be the
switch but you aren't looking to resolve this it seems,
rather than ????

no, because its not my problem.

I suspect you WANT a KVM audio switch

what for?

but it is the reason
in itself for your post, not just to resolve a problem with
a switchbox. If that is the goal, fine/good/great/etc, but
it would be good to just cut to the chase and make that
clear instead of detailing issues with the switchbox.

Youre lost in deep jungle here. I dont have a distrortion problem, dont
want to buy a switchbox, and if I did I cant imagine any reason to be
posting about it.

If your switch has 500k, there is no question that it will
degrade audio quality. I'd be surprised if it can produce
reasonable sound at all in such a scenario.

Pay attention. 500k is leakage resistance, not contact resistance.

You don't know thing:1 about electronics do you?
yes


500K
resistance and 0.99993? No.

ok, offer us your maths. You tell me.

You are completely wrong. The resistance causes it, AND the
carbon does too, AND "ohmic thus none" is just
non-applicable, it doesn't account for any other sources of
distortion.

it wasnt meant to, it was meant to show that ohmic lekage doesnt cause
distortion. Pay attention.

Anyone with extensive hands-on audio
electronics experience can tell you that just switching
between carbon and metal resistors will change the sound.

nonsense. The problems with non-blind A/B tests are well known.

Not one of those voodoo "golden ears" types of things
either, a blind A/B blahblahblah, scientifically valid
conclusion.

there are cases where it will, since carbon is higher noise and WW
inductive and capacitive, but in most cases it makes no detectable
difference. It wont change anything in a heaphone switchbox. Do you
have a link to some evidence for what you say? Or some verifiable
numbers and maths?

Where is this copper supposed to be? You should have no
bare copper contacts anywhere to oxidize.

you've misunderstood entirely. The copper dust comes off the switch
contacts due to wear, and settles on the insulating parts of the switch
mechanism. This slowly oxidises, and Cu/CuO is known for its tendencey
to rectify. Thus the presence of copper dust in the leakage resistance
material can cause non-ohmic resistance.

No. I don't know what you think you are qualified in, but
it sure as heck isn't analog audio.

yes it is.

First of all, it does not form any rectifying network, it is
a simple series RC. That is, IF you had bare copper which
you should not. Are you just making this up as you go
along?

the problem is that you have failed to follow what was said.

So it's all settled then, it can't be the cables and it
can't be the switch,

I didnt say that, I said a non-faulty switchbox would not be the cause

it must be your imagination.

Do me a favour here. If we're going to discuss things, pay attention,
otherwise its pointless.

Did it ever occur to you that this is with a PROPERLY
working switch?

yes, I took it as stone obvious.

You might find 100 Ohm on a piece of junk but not on any
decent gear. Granted, a typical sound card may be a piece
of junk.

Suggest looking up junk in a dictionary.

Why the theories on your part though, have you
bothered to actually check your equipment?

no, why would i?

If not, no
wonder you still have a problem, you aren't actually DOING
anything to resolve it.

there is no problem with my equipment to resolve

Also, it would be surprising to find that your wireless Senn
transmitter has 32 ohm impedance, or rather, not at all
likely.

I dont have a Senn transmitter. And whether the headphones were 3 ohm
or 80 ohm would not change the argument enough to be significant. Even
if the transmitter had 10k input R it still wouldnt make enough
difference to change any of the conclusions.

You feel comfortable arbitrarily declaring 0.2 Ohms?

where do you get the notion that its arbitrary? Its the worst contact R
spec of all the low grade switches I looked at.

You
shouldn't, if the switch is worn or defective it may easily
be higher-
obviously


remember that you ARE having a problem with
(something).

No I'm not.

Not quite, you can't just add up the resistances without
considering the other passive elements in the audio path.

what other elements? The cable/switchbox capacitance is of no
significance, nor is its inductance. AFAIK we shouldnt have a carbon
arc in the chain, not at headphone voltage - cant think of any other
passive impedance that could be there.

It would go from poor, to poor, so yes that's about the
same.

So you're trying to drive loudspeakers with your sound card
line out?

Are you really that confused? Are you aware that headphones use moving
coil drivers, as do loudspeakers? Do you understand I'm saying the
impedance/frequency plot of a headphone moving coil driver will be
similar to that of a loudspeaker?

It would be good for you to stick to the issue at
hand that you still can't resolve as it was a rather simple
one.

I am, the issue being your claim that a correctly functioning switchbox
could degrade the sound.

Quite the opposite.



Apparently it is for me- I don't have this distortion
problem that you do.

I dont have any distortion problem. I suggest paying a lot more
attention.

If you have some numbers and maths to back up your belief that a
correctly functioning switchbox on a headphone lead could degrade audio
quality, lets see it. Or any other form of verifiable evidence. So far
you've produced none.


NT

 

[kony]

This is a discussion about whether a correctly functioning switchbox in
the lead to heapdhones could degrade audio quality.

Is it? You seemed to suggest it may not be a correctly
functioning switchbox, else what would be the point of
replacing it?

(I'm assuming here
the switchbox is designed for the purpose, and not eg a 100kW motor
switchbox etc).

Ok, but what purpose would this serve, to assume something
not yet evident? I'm not really trying to argue on this
topic but you are posing hypotheticals when there instead
the real McCoy right there which is the problem you wish to
resolve.

We seem to have gotten sidetracked at places, but
hopefully after this post we'll be back to the point.





You seem to have gotten very confused. For a start I'm not the OP and
would be unlikely to be asking for help solving a distortion problem
due to leads, switchbox, etc, if I had one.

That is a reasonable point, but then what is the purpose of
the thread if not to address the OP's situation?

Second I dont think you've paid enough attention to follow what was
being said at various points. I'm not sure why. I'll add some notes
which may help clear some misunderstandings up.

I would tend to disagree, do you always make such random
assumptions when someone disagrees?

havent tried that at all, have only refuted your claim that a switchbox
could degrade a heaphone signal

My claim is that the implementation of the switchbox is what
the OP is claiming IS degrading the signal. What are we to
do, call him a liar?

It would seem more productive to address the possible
reasons rather than trying to second-guess that.

Yes: I dont have such a switchbox, and your imagination has come up
with the wrong guess.

You are correct that I should not have written "your", it
should be "his". It still applies though, of course we
could claim everything is in *perfect* working order and
thus it can't be happening... and yet it is.

Feel free to back this up with some numbers.

I can do one better, I have a headamp right here in front of
me and can clearly hear the difference. Output impedance is
not just contrasted to driver impedance, or seen additively.
The two are separate and must be treated as such.

So if you want a number, ok...

Output impedance of 0.2 Ohm. Add anything to that you want.
1 Ohm? 20Ohm? Both degrade the signal, only question is if
it's below the threshold of human perception.

I think youve misunderstood, Im explaining why a properly functionng
switchbox cant degrade the sound.

You'd tried to, and practically speaking if the switchbox is
working properly there shouldn't be much series resistance
at all but we don't know that it IS properly designed and/or
working properly.

You may also be completely ignoring noise pickup if it isn't
shielded properly, and that this isn't driving 32 Ohm
headphones, it's driving a wireless transmitter for
headphones.

if its not faulty we do, and thats what I'm discussing.

Then why are you discussing it, since there is obviously a
problem or are you second-guessing the OP's description of
the situation. If you are, fair enough, I had already
suggested he try to isolate the problem so we know for sure.

if not, its faulty

yes, it goes without saying.
It's still a mystery though why you are taken to
presupposing the switchbox /wouldn't/ potentially be faulty
given that there is a problem being reported.

in a headphone or speaker switchbox that would be unlikely.

Depends on what's inside. Do we even know if this is a
passive unit?

Switching a mix of headphones and speakers on bridged output amps is a
bit more complex, but I dont think theres much chance of the OP's
switchbox being designed to handle that.


it isnt, not at 30 odd ohms, a.f. and a volt or more. If you think it
is I'd start to wonder just what your skill level is on this.

Do you know it's 30 odd ohms? That's a random guess I
suppose, one that might apply to this hypothetical,
non-applicable scenario but not to this thread addressing
the OP's gear.

wrong again

You may know what you think we're talking about but
apparently you don't know what the thread is about.

OP has WIRELESS headphones. Do you see the difference?
The thread is not only about the narrowly defined parameters
you are supposing, it's about the actual equipment the OP
has. You are trying to describe dissimilar gear and if you
do that, it seems do you do not know the significance of
wireless headphones, which could be interpreted as not being
qualified.

Well I simply dont agree. If its not capable of driving headphones then
its not fit for purpose.

Depends on what you mean by "driving headphones" though,
there are plenty of sound cards out there with no output
stage at all but an opamp capable of a few dozen mA, if
that. Many would argue that the audio-out line on many if
not most sound cards is not actually fit for driving many
headphones.

It wouldn't apply here though, OP has wireless headphones.

I havent come across any commercial analogue
audio amp with such a problem in a long time.

Well it's a sound card, yes? We're talking integrated
voltage gain stage after a DAC, not a power amp.

Very old equipment yes,
home made kit yes, faulty kit yes, but not modern commercial equipment.
Any company putting out kit that bad would soon go bust. Imagine the
cost, lost business and destroyed reputation that would result from 5%
of shipped equipment going unstable.

Oh? You can't infinitely string any transport without
problems. Same applies to a digital signal, but with analog
we're going to have to define some kind of threshold for
what is deemed an instable signal since it could be gradual.
That is, unless it has a high value resistor on the output.
If you can't see why that degrades sound I feel you need to
build a few (or a few more) amps without such a high
impedance.

I'm not attmpting to solve a switchbox or distortion problem.

Then why are you posting in the thread?
Perhaps you have misinterpreted my reply. It is made in the
context of the thread it is placed in, not an overview of
every possible audio circuit nor of one unlike what the OP
has, one which has already been described as problematic.

 

[meow2222]

it seems no longer constructive.

NT