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.
