Highly Shielded Audio Cable

[Ralph D.]

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Any good suggestions would be appreciated.


Thanks!

 

[isw]

In article <AL2dncMV16ZBrIDOnZ2dnUVZ_v-dnZ2d@giganews.com>,
"Ralph D." <not@anytime.com> wrote:

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Any good suggestions would be appreciated.

Look for a cable TV-coax (RG-6, maybe) that has a continuous foil shield.

Isaac

 

In sci.electronics.repair Ralph D. <not@anytime.com> wrote:

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly
shielded to connect my audio source to a transmitter across a room.
This cable passes many sources of interference, so the shielding is
critical.

One approach might be to convert from 3.5 mm stereo to dual RCA and
then back, as it seems to be a little bit easier to buy good-quality
stereo RCA cables in many lengths. But the problem then becomes
finding adapters that aren't junk, and I don't have a good answer for
that.

This sort of falls into the "don't ask a barber if you need a haircut"
category, but http://www.bluejeanscable.com/articles/humrejection.htm
discusses the audio hum rejection (60 cycle) of various kinds of cables.
Unfortunately, at least the two best ones in that test are RG-59 coaxial
cables, which are around 0.25" (6.3 mm) outside diameter; the logistics
of feeding two of those cables into a 3.5 mm plug are non-trivial.

That site also sells audio cables which they make themselves; a 20 foot
length of their "MSA-1" cable with 1/8 stereo plugs on each end is $63.
I don't know if this is any good or not, only that it exists. They
claim 1 or 2 day turnaround.

Markertek ( http://www.markertek.com ) sells cables (and a bunch of
other stuff) aimed at the TV and video production industry. They stock
ready-made cables, and also offer cables that they make, but they
claim about a week lead time on those. Their part number SC25MZMZ
might do what you want; it is $27, 25' long, has 3.5 mm stereo plugs on
each end, and is made from Canare "star quad" microphone cable. Again,
I don't know if this is any good or not, only that it exists.

Their ready-made cables are cheaper and will ship quicker, but based on
nothing other than the apparent outside diameter of the cable, they
probably aren't shielded as well.

If you want to look at the cable in person first, you might try a place
that sells electric guitars, amps, etc; they usually stock reasonable-
quality cables, and since MP3 players are popular, they have them with
3.5mm plugs. If you're in the US, the Guitar Center chain has lots of
locations; there is probably a locally-owned equivalent in the nearest
big city.

Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.

Matt Roberds

 

[Mike Tomlinson]

In article <AL2dncMV16ZBrIDOnZ2dnUVZ_v-dnZ2d@giganews.com>, Ralph D.
<not@anytime.com> writes

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

Off-the-wall suggestion: run them through a length of copper pipe or
through that flexible metal conduit used in electrical installations?

You'd probably want to earth (ground) just one end to be sure a ground
current didn't flow, causing interference.

--
(\_/)
(='.'=)
(")_(")

 

[Phil Allison]

"Ralph Dope"

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly
shielded to connect my audio source to a transmitter across a room. This
cable passes many sources of interference, so the shielding is critical.

** I have a sense of "deja vu" about this question ?

Is the signal stereo or mono ?

A 20 foot long 3.5mm two core cable is not gonna be easy to find at all let
alone with different qualities.

BTW:

Do you REALLY have a problem or are you just imagining one ?

How about some details ?

The solution may NOT be what you have guessed it to be.



..... Phil

 

[dave]

On 03/09/2014 08:30 PM, Ralph D. wrote:

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Any good suggestions would be appreciated.


Thanks!

What type of input does the transmitter have? Balanced +6dB? Unbalanced
50 Ohms? If it's Balanced, use transformers at the send end, or a
balanced line driver (aka Direct Box) of some kind (2 for stereo).
Ground only the receive end of your shields. Use as much "send" as you
can get away with; this will reduce noise at the xmtr input.

 

[Cydrome Leader]

In sci.electronics.repair Ralph D. <not@anytime.com> wrote:

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

get some electrical conduit.

 

[D. Peter Maus]

On 3/9/14 23:49 , isw wrote:

In article <AL2dncMV16ZBrIDOnZ2dnUVZ_v-dnZ2d@giganews.com>,
"Ralph D." <not@anytime.com> wrote:

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Any good suggestions would be appreciated.

Look for a cable TV-coax (RG-6, maybe) that has a continuous foil shield.

Isaac

For this application, you'd want a cable with at least a 95% braid shield.

A more effective solution would be to convert the audio to a balanced
line at one end, and then back to unbalanced at the other. Better CMRR.
Shielded twisted pair, here, will get the job done.

 

[RobertMacy]

On Mon, 10 Mar 2014 08:24:12 -0700, D. Peter Maus <dpetermaus@att.net>
wrote:

...snip...
For this application, you'd want a cable with at least a 95% braid
shield.

A more effective solution would be to convert the audio to a balanced
line at one end, and then back to unbalanced at the other. Better CMRR.
Shielded twisted pair, here, will get the job done.

might look into high quality cabling like Belden 1800F
John Woodgate in UK and I worked together to extensively analyze that
cabling and exploring 'weaknesses', have LTspice models and he has a lot
of application data.

 

[William Sommerwerck]

The Lady from Philadelphia suggests...

Have you tried using an inexpensive cable //simply to see what happens//,
rather than assuming you //need// a highly shielded cable?

If it doesn't work, you could encase the cable in braiding, grounding the
braiding at the reception end?

 

[Michael Black]

On Sun, 9 Mar 2014, Ralph D. wrote:

Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly
shielded to connect my audio source to a transmitter across a room. This
cable passes many sources of interference, so the shielding is critical.

Just use coax. Even something small like RG174 likely has better
shielding than many audio cables.

Of course, if there is a real issue here, little stereo plugs end up
leaving an unshielded area for the RF to get in. Changing to something
else would complete the shield. I know I'd use BNC connectors for audio
connectors if that pile of 200 male connectors I found on the sidewalk
had included 200 female BNC connectors as well.

Make sure the output feeding the coax is low impedance, that's not for
feeding the coax, but a high impedance would make it easier for the RF to
be picked up. And terminate at the transmitter end, so that point sees
relatively low impedance.

Make sure the usual low value bypass capacitors are at the input to that
transmitter, so even if there is RF pickup, it is bypassed to ground and
won't be rectified by the input stage. Get some ferrite beads (the tiny
ones, and put them on the lead between the input jack of the trnasmitter
and the first stage, or the traditional method would be an RF choke of
suitable value.

Look in any radio handbook and there should be a section on RF
interference, which would describe how to keep RF out of the first stage
of an audio amplifier.

Michael

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Any good suggestions would be appreciated.


Thanks!

 

[Phil Hobbs]

On 3/10/2014 7:11 AM, Phil Allison wrote:

"Ralph Dope"

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly
shielded to connect my audio source to a transmitter across a room. This
cable passes many sources of interference, so the shielding is critical.


** I have a sense of "deja vu" about this question ?

Is the signal stereo or mono ?

A 20 foot long 3.5mm two core cable is not gonna be easy to find at all let
alone with different qualities.

BTW:

Do you REALLY have a problem or are you just imagining one ?

How about some details ?

The solution may NOT be what you have guessed it to be.



.... Phil

Hack a long HDMI cable.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

On Sunday, March 9, 2014 11:30:08 PM UTC-4, Ralph D. wrote:

Hi,



I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).

Hmm, What kind of interference are you seeing? (can you turn things off and make it go away?) To get rid of electro-static pick-up (display screeens flourescent lights...) get a cable with both braid and a almuinized mylar sheild.
(Driving the cable with a low impedance source should help too.)

60 Hz, magnetic interference is darn hard to shield against (In my limited experience.) Your best bet there is to keep a good distance between transfomeres and the cable.

George H.

Any good suggestions would be appreciated.





Thanks!

 

[dave]

On 03/10/2014 09:56 AM, Cydrome Leader wrote:

In sci.electronics.repair Ralph D. <not@anytime.com> wrote:
Hi,

I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

get some electrical conduit.

There should not be a lot of RF in the radio room, compared to near the
antennas. Do all the other stations use EMT for audio? It really isn't
necessary. You can probably use unshielded twisted pair if you know what
you're doing. The Phone Company doesn't use shielded cable for baseband
audio.

 

[Michael Black]

On Tue, 11 Mar 2014, ggherold@gmail.com wrote:

On Sunday, March 9, 2014 11:30:08 PM UTC-4, Ralph D. wrote:
Hi,



I need a cable (ideally about 20ft), stereo 3.5mm male/male, highly shielded
to connect my audio source to a transmitter across a room. This cable passes
many sources of interference, so the shielding is critical.

I would prefer to get it from Amazon so as to get it quick with Prime
(incredibly narrow window of free-time during a currently very busy
schedule) but would be OK with ordering from one of the Ham sites if
turnaround time is very good. I could not get a good search parameter on
Amazon that didn't turn up thousands of hits that I just don't have time to
sift through right now.

Any good cable with known good isolation would be good. I have ferrite
chokes I can use, but would prefer a cable of suitable quality that did not
need them (current cable is getting interference even with them as this is
not just run-of-the-mill 60cycle stuff).


Hmm, What kind of interference are you seeing? (can you turn things off
and make it go away?) To get rid of electro-static pick-up (display
screeens flourescent lights...) get a cable with both braid and a
almuinized mylar sheild. (Driving the cable with a low impedance source
should help too.)

That's the question most of us missed. I could have sworn he said "rf
interference", but when I looked back after posting, realized he hadn't
indicated any specific bit of interference.

Michael

60 Hz, magnetic interference is darn hard to shield against (In my limited experience.) Your best bet there is to keep a good distance between transfomeres and the cable.

George H.

Any good suggestions would be appreciated.





Thanks!

 

[RobertMacy]

On Tue, 11 Mar 2014 20:02:49 -0700, Michael Black <et472@ncf.ca> wrote:

...snip...

That's the question most of us missed. I could have sworn he said "rf
interference", but when I looked back after posting, realized he hadn't
indicated any specific bit of interference.

...snip....

I assumed stuff like nearby motor drivers, or worse, from those new solid
state ballasts. The cheap ones can get VERY energetic. and coupling
magnetic into audio is not an easy item to stop.

People are so used to 'shielding' with electrostatic shields and lowering
the impedance to reduce high impedance interference, that they are
completely caught off guard when confronted with low impedance noise
sources, like magnetic field. May have noticed that lowering the impedance
makes little difference.

Sometimes, high impedance noise gets 'converted' somewhere to a low
impedance source which is really mindboggling, since you recognize the
noise and expect it to be coming from high impedance.

Best way,...balanced pair, shielded. And I MEAN balanced over the WHOLE
spectrum! DC to GHz, 10GHz if you can do it. That includes termination
circuitry, Tx/Rx, and high quality cabling with very symmetrical conductor
placement and spacings within that cable. That is, if you're goal is 120
dBV, or better 140dBV, down noise floors you had better pay attention to
everything.

 

[dave]

On 03/12/2014 07:58 AM, RobertMacy wrote:

On Tue, 11 Mar 2014 20:02:49 -0700, Michael Black <et472@ncf.ca> wrote:

...snip...

That's the question most of us missed. I could have sworn he said "rf
interference", but when I looked back after posting, realized he
hadn't indicated any specific bit of interference.

...snip....

I assumed stuff like nearby motor drivers, or worse, from those new
solid state ballasts. The cheap ones can get VERY energetic. and
coupling magnetic into audio is not an easy item to stop.

People are so used to 'shielding' with electrostatic shields and
lowering the impedance to reduce high impedance interference, that they
are completely caught off guard when confronted with low impedance noise
sources, like magnetic field. May have noticed that lowering the
impedance makes little difference.

Sometimes, high impedance noise gets 'converted' somewhere to a low
impedance source which is really mindboggling, since you recognize the
noise and expect it to be coming from high impedance.

Best way,...balanced pair, shielded. And I MEAN balanced over the WHOLE
spectrum! DC to GHz, 10GHz if you can do it. That includes termination
circuitry, Tx/Rx, and high quality cabling with very symmetrical
conductor placement and spacings within that cable. That is, if you're
goal is 120 dBV, or better 140dBV, down noise floors you had better pay
attention to everything.

These are pretty darn close to what you need, as long as they are true
balanced. This will put a face on it, any way.

http://www.markertek.com/CATV-Headend-Interface/CAT-5-Transmission-Systems/Composite-Video-Over-CAT5.xhtml

 

[William Sommerwerck]

"RobertMacy" wrote in message newsp.xcl6jxtm2cx0wh@ajm...

Best way,...balanced pair, shielded. And I MEAN balanced over
the WHOLE spectrum! DC to GHz, 10GHz if you can do it. That
includes termination circuitry, Tx/Rx, and high quality cabling
with very symmetrical conductor placement and spacings within
that cable. That is, if you're goal is 120 dBV, or better 140dBV,
down noise floors you had better pay attention to everything.

It's unfortunate that the OP seems limited to 3.5mm connections. There are AR
cables (Master Series) that have a separate shield, grounded at the receiving
end, with identical wires (not the shield) carrying the signal. There is also
a ferrite choke. I use these in my system.

http://www.amazon.com/Acoustic-Research-MS201-Cable-feet/dp/B00008VSJI/ref=sr_1_2?ie=UTF8&qid=1394636624&sr=8-2&keywords=acoustic+research+master+series

They used to be fairly cheap, but have gotten pricey again. (Of course, the
price is still rather lower than "audiophile" cables with the same features.)

 

[dave]

On 03/12/2014 07:58 AM, RobertMacy wrote:

On Tue, 11 Mar 2014 20:02:49 -0700, Michael Black <et472@ncf.ca> wrote:

...snip...

That's the question most of us missed. I could have sworn he said "rf
interference", but when I looked back after posting, realized he
hadn't indicated any specific bit of interference.

...snip....

I assumed stuff like nearby motor drivers, or worse, from those new
solid state ballasts. The cheap ones can get VERY energetic. and
coupling magnetic into audio is not an easy item to stop.

People are so used to 'shielding' with electrostatic shields and
lowering the impedance to reduce high impedance interference, that they
are completely caught off guard when confronted with low impedance noise
sources, like magnetic field. May have noticed that lowering the
impedance makes little difference.

Sometimes, high impedance noise gets 'converted' somewhere to a low
impedance source which is really mindboggling, since you recognize the
noise and expect it to be coming from high impedance.

Best way,...balanced pair, shielded. And I MEAN balanced over the WHOLE
spectrum! DC to GHz, 10GHz if you can do it. That includes termination
circuitry, Tx/Rx, and high quality cabling with very symmetrical
conductor placement and spacings within that cable. That is, if you're
goal is 120 dBV, or better 140dBV, down noise floors you had better pay
attention to everything.

http://muxlab.com/wp-content/uploads/2012/09/VE_Stereo_Hi-Fi_Balun.pdf

 

[dave]

On 03/12/2014 08:10 AM, William Sommerwerck wrote:

"RobertMacy" wrote in message newsp.xcl6jxtm2cx0wh@ajm...

Best way,...balanced pair, shielded. And I MEAN balanced over
the WHOLE spectrum! DC to GHz, 10GHz if you can do it. That
includes termination circuitry, Tx/Rx, and high quality cabling
with very symmetrical conductor placement and spacings within
that cable. That is, if you're goal is 120 dBV, or better 140dBV,
down noise floors you had better pay attention to everything.

It's unfortunate that the OP seems limited to 3.5mm connections. There
are AR cables (Master Series) that have a separate shield, grounded at
the receiving end, with identical wires (not the shield) carrying the
signal. There is also a ferrite choke. I use these in my system.

http://www.amazon.com/Acoustic-Research-MS201-Cable-feet/dp/B00008VSJI/ref=sr_1_2?ie=UTF8&qid=1394636624&sr=8-2&keywords=acoustic+research+master+series


They used to be fairly cheap, but have gotten pricey again. (Of course,
the price is still rather lower than "audiophile" cables with the same
features.)

That is pure audio snake oil. If you are dealing with induced magnetic
fields (hum) you need a competent differential input and balanced lines.
The copper part of the phone company is not shielded. Even the part that
carries high fidelity audio for industry is not shielded.

Big clunky interfaces like that are usually very reactive and do affect
the sound...badly. Try Hosa brand. Spend the difference on better speakers.