Spike filter for Soundcard>home stereo hookup?


L

Lee

I need some kind of filter... something to go between my soundcard and
stereo receiver to prevent spikes. Not sure if such a thing exists, but
here's my story and hope someone can help: My soundcard is connected
directly to my receiver's VCR input (I use it as an AUX) via RCA cables.
The problem is: the sound will sometimes mute (and playback will stop),
when the stereo's switches are used. The only fix is a reboot. If the
stereo is on before powering up the PC, the sound might not work at all.
Or, if I listen to music and change something on the stereo (such as check
the radio for a sec), same problem could occur. Other fuctions of the PC
would still work, but no sound until reboot! The problem sometimes depends
on the weather, too-- the more hot/humid it is, the worse it gets. And I've
found that cleaning with anti-static spray (i.e. the Kensington brand)
helps, but I still worry about any spikes from my stereo to the PC. Since
I'll be getting a new computer soon, I would like to get this ironed out
beforehand, so as not to damage my brand new machine!

The PC and stereo are connected to two identical (cheap) Belkin surge
protectors. Both are plugged in to the same double outlet. Also, the
hardware is in a room with carpeting.

Does anyone know of some device that will work? Or any ideas for this
situation please? I'd really like to get this done before getting my dream
machine.

Thank you
Lee
Brooklyn NY
 
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Z

Zypher

Why (just wondering) do you think its a voltage spike or ground spike
problem? Is the stereo amp grounded? At least the receptacle you've
plugged the amp into grounded? Correctly? You computer grounded?

If you asked me, personally, I'd say the RCA cable you were using is junk.
For a small amount of $$ you can pick up a GFI (ground fault interrupter)
checker, which when plugged into a receptacle will tell you if the
receptacle is grounded properly, and polarized properly.

I'm not understanding why if you change the stereo why the computer would be
affected.
 
L

Lee

Although I haven't tested them, I am confident the outlets are grounded.
I'm in an apt building, and the wiring was upgraded to 220 about 15 yrs
ago. (That was before I moved in though.) All stereo and PC components are
plugged into 2 Belkin surge protectors. My Kenwood receiver (where the
cable is connected) is around 15 yrs old, and have a few other old
components hooked up as well. Some have polorized plugs, some not. (The
kenwood has.) But everything goes directly into the surge protector.
Components are in stackable oak containers made for stereo equipment.
Bottom container rests on carpet. PC is on top of metal desk, with the main
box resting on anti-static bags. Desk is on same carpet.

I have a feeling it's something to do with static electricity. When I give
all components (stereo and computer) a Kensington anti-static cleaning, it
gets much much better. I figure a filter between stereo and PC would
isolate them from eachother and prevent any sudden voltage changes to leak
through. Maybe what I'm looking for is an isolation transformer type
device, but on a much smaller/simpler scale.

It's strange about the weather... when the AC is powered up, problem isn't
that bad. But when room is warm (i.e. 80 deg) and humid, it's almost
impossible to play music!

You're right about the RCA cables.. they are cheap generic junk! But
they're only 2 or 3 feet long. Would higher quality cables be better, even
for short distances? And if so, what cables are both good and... cheap:)

I'm getting a new mobo in a couple months, and dread the idea of damaging
it!!!

Thanks
Lee
 
G

Guest

Lee said:
My soundcard is connected directly to my receiver's VCR input
(I use it as an AUX) via RCA cables. The problem is: the sound
will sometimes mute (and playback will stop), when the stereo's
switches are used. The only fix is a reboot. If the stereo is
on before powering up the PC, the sound might not work at all.
Or, if I listen to music and change something on the stereo
(such as check the radio for a sec), same problem could occur.
Other fuctions of the PC would still work, but no sound until
reboot! The problem sometimes depends on the weather, too-- the
more hot/humid it is, the worse it gets. And I've found that
cleaning with anti-static spray (i.e. the Kensington brand)
helps, but I still worry about any spikes from my stereo to the
The PC and stereo are connected to two identical (cheap) Belkin
surge protectors. Both are plugged in to the same double outlet.
Also, the hardware is in a room with carpeting.

The anti-static spray doesn't really help; it's just a coincidence.

The cheap RCA audio cables are fine, contrary to what Monster would
like us to believe. I get all my audio and video cables from a
99-cent store and have no problems.

You may want to try running a ground wire between the VCR chassis to
the wall outlet ground (a 2-3 prong AC adapter can help here). But if
that doesn't work, I blame the badly designed sound card for not
tolerating pops properly. this happens with outputs that are directly
coupled, as opposed to coupled through capacitors. The pops can be
eliminated by adding coupling capacitors (try 10-50 uF, 50VDC,
nonpolarized -- Radio Shack sells them for speakers) and grounding the
free side through a 50,000-100,000 ohm resistor. The resistor drains
off the DC that builds up when the capacitor isn't connected to
anything. This is an old solution to pops that occur when stereo
equipment is switched.
 
D

Dave

The Kenwood is probably double insulated, not earthed, as is the rest of the
stereo system. On the back does it have an earth terminal near the AM
input? If so make sure a short earth cable is hooked to it and the other
end is connected to a copper clad iron 4+ foot stake driven into the soil.
The earth cable should be as heavy as possible, even as heavy as car jumper
cable. DO NOT CONNECT the antenna earth to a power socket earth.
 
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L

Lee

Actually the anti-static spray isn't coincidence -- I tried it so many
times with and w/o that it can't be! I sometimes have the tendency to rub
against the desk with my sock (100% cotton no less), and have noticed the
sound mutes about 5 seconds later. So I do believe this is related to
static electricity.

My PC has a SB Pro card. It is 5 yrs old, but still works.

That cap circuit sounds like a good idea. Any web sites out there with the
schematic?

Thanks a lot for the help




(e-mail address removed) (do_not_spam_me) wrote in
 
W

w_tom

Earth ground is not required to solve this noise transient
problem. Components must share a common ground. A point
where all component's grounds come together. This ground need
not connect to anything else. However your single point
ground may be connected to outlet safety ground. To eliminate
sudden voltage differences between 'floating' audio
components, connect those component grounds together to a
common point. Earth ground is not required and will not solve
this noise problem

Additionally, an earth ground rod must be 8 feet anyway. 4
feet ground rods are insufficient and violate the code.
Connecting appliances to a separate earth ground rod would
also violate code. Furthermore, do not connect those grounds
to a cold water pipe. Connections to 'dump' electricity in
water pipes are undesirable. You need a single point ground
between all interconnected components.

Those Belkins don't do anything for you. They do nothing
until voltage exceeds 300+ volts. Their internal filters are
so trivial as to almost not exist. You are suffering from low
voltage noise - not differential mode surges. Solution is to
discharge or short those noise voltages. Belkin does nothing
nor even claims to address your solution.

Also the GFCI recommendation is bogus. GFIs do not report a
missing ground nor do they care if ground exists.

do_not_spam_me has provided good ideas including debunking
those cable myths.

Static spray indicates that your body is discharging static
electric currents through audio components. Discharge path is
taking audio paths because a circuit to discharge your shoes
through grounds was not (yet) installed. Just another reason
why the single point ground with a connection to outlet safety
ground is required. Static electric current travels down your
arm, through single point ground and outlet ground, into
carpet or tile floor, to discharge bottom of your shoe. Again
no earth ground is required. Just simple grounding so that
the discharge does not take a noisy path through audio cables.
 
D

Dave

Depending on how old your apartment is the water pipe could also be used for
the power main earth connection. To complicate things, some cold water
pipes may only go into the soil 300mm/12 inches or so and then be joined to
plastic pipe to the mains. To further complicate things, while the main
electrical earth may be connected to an approved ground spike, some electric
hot water heaters may be earthed to a cold water pipe instead of the ground
circuit.

If you can borrow a digital multimeter check the resistance between the
earth socket and the cold water pipe and if the reading is less than a few
ohms then I would strongly suspect the pipe was used as a ground. Of course
if you can see that the earth is connected to a ground spike then the cold
water pipe should be OK. Obviously it would be much better if you had
access to the wiring plans.

30-40 years ago, it was quit common for a cold water pipe to be used as the
earth connection but now it is illegal in most places for that practice
because of ELBs. If you do have ELBs then I'm reasonably sure the cold
water pipe should be OK but you should really check. You should be able to
access the information for mains wiring/earth connection through the
relevant state/national building standards. If you can get to the meterbox
then there may even be a compliance sticker in there for the new
(15yo)wiring, quoting the relevant compliance code and that would make it a
lot easier to track it down. There may also be a sticker on the fuse box if
you have one in the apartment and the meterbox is elsewhere.

I say not to use the earth connection to ground the radio as it is illegal
to do so in most places.

I have a shortwave radio and have used the electrical earth as a temporary
ground (for testing) but I found that introduced too much noise, especially
from computers. But short wave radios are much more sensitive than the
typical receiver.
 
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L

Lee

30-40 yrs... that's just how old the building is. So the cold water pipe
might not be the safest way then. My multimeter needs fresh batteries,
will check resistance when I pick them up. I think grounding the PC and
stereo (and the desk as well) to a common point might be the trick. I'll
experiment to see and get back later in the week. By the way, what are
ELBs?

Thanks to everyone for the suggestions!
Lee
 

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