Hi guys, just need some quick expert advice.
I have a mono 1/4 inch jack that has two prongs, one I guess is for the
tip, the other for the shield (called common sometimes too?)
My problems was I had to use stereo mic cable because I'm in Chile and
it's a pain to go to get other cable.
So, how would everyone recommend I wire the connection?
Should I solder both cables to the tip? Or just one and not use the
other cable?
Or should I solder one to the tip, and solder the ground and the other
wire to the common (ground) connection?

Thanks, sorry if this is a bit confusing English.

David M wrote:

Hi guys, just need some quick expert advice.
I have a mono 1/4 inch jack that has two prongs, one I guess is for the
tip, the other for the shield (called common sometimes too?)
My problems was I had to use stereo mic cable because I'm in Chile and
it's a pain to go to get other cable.
So, how would everyone recommend I wire the connection?
Should I solder both cables to the tip? Or just one and not use the
other cable?
Or should I solder one to the tip, and solder the ground and the other
wire to the common (ground) connection?

Thanks, sorry if this is a bit confusing English.

What are you going to connect using this cable?

--
ha

The cable you describe is not a stereo one but I believe it's an overall
screened twisted pair.
The 1/4" jack: The 2 "prongs" you refer to are known in the trade as tip and
sleeve.
I should ask, what is it to be used for? X factor. So I'll cover two
eventualities....

If you are using this cable to span to another 2-pole interface:
Join both internal conductor wires to the tip and terminate (screw or
solder) screen to the sleeve of jack. Same convention at other end!

If you have a 3-pole (or more!) connector to span to:
then here the 2 conductor wires are for the programme circuit and the screen
goes to screen/ground - and at the jackplug end, join one of those wires to
screen at sleeve, the other to tip, making the wiring known as "unbalanced".

Hope it's clear.
Jim

"hank alrich" wrote in message
. ..
David M wrote:

Hi guys, just need some quick expert advice.
I have a mono 1/4 inch jack that has two prongs, one I guess is for the
tip, the other for the shield (called common sometimes too?)
My problems was I had to use stereo mic cable because I'm in Chile and
it's a pain to go to get other cable.
So, how would everyone recommend I wire the connection?
Should I solder both cables to the tip? Or just one and not use the
other cable?
Or should I solder one to the tip, and solder the ground and the other
wire to the common (ground) connection?

Thanks, sorry if this is a bit confusing English.

What are you going to connect using this cable?

--
ha

In article .com writes:

I have a mono 1/4 inch jack

My problems was I had to use stereo mic cable because I'm in Chile and
it's a pain to go to get other cable.
So, how would everyone recommend I wire the connection?
Should I solder both cables to the tip? Or just one and not use the
other cable?

By "stereo mic cable" I guess you mean a cable with two conductors
inside a shield. How you wire it depends on what the other end is
going to.

If what you need is an "unbalanced" cable, that is one with a mono
plug on both ends, use one of the conductors and let the other one
float. Of course be sure you use the SAME conductor on both ends.
Usually the two conductors have different colors of insulation so you
can identify them. Other than the color of the insulation they're
identical so it doesn't matter which one you use. Oh, and connect the
center conductor to the tip, and the shield to the "sleeve", the other
terminal on the plug.

If you're rewiring one end of a mic cable (with its original XLR
connector on the other end), take apart the XLR end and see which wire
goes to Pin 2. On the 1/4" plug end, connect that wire to the tip.
Connect the other wire and the shield to the sleeve.

However, one little caution. If you're planning to plug a conventional
professional type microphone into a 1/4" unbalanced jack. it may not
work.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

"Mike Rivers" wrote in message
news:znr1108646929k@trad...

In article .com
writes:

I have a mono 1/4 inch jack

My problems was I had to use stereo mic cable because I'm in Chile and
it's a pain to go to get other cable.
So, how would everyone recommend I wire the connection?
Should I solder both cables to the tip? Or just one and not use the
other cable?

By "stereo mic cable" I guess you mean a cable with two conductors
inside a shield. How you wire it depends on what the other end is
going to.

If what you need is an "unbalanced" cable, that is one with a mono
plug on both ends, use one of the conductors and let the other one
float. Of course be sure you use the SAME conductor on both ends.
Usually the two conductors have different colors of insulation so you
can identify them. Other than the color of the insulation they're
identical so it doesn't matter which one you use. Oh, and connect the
center conductor to the tip, and the shield to the "sleeve", the other
terminal on the plug.

If you're rewiring one end of a mic cable (with its original XLR
connector on the other end), take apart the XLR end and see which wire
goes to Pin 2. On the 1/4" plug end, connect that wire to the tip.
Connect the other wire and the shield to the sleeve.

[Be careful! If it's an XLR at far end, do not always accept XLR pin 2 to
be HOT.
It could turn out to be pin 3 - found on some unconventionally-wired
gear. We still do not know if it's unbalanced or
"balanced". Ideally, still wanting to hear a description of the other
interface connector/s, their function/s, and what length of this
2-core cable is proposed.
Jim]

However, one little caution. If you're planning to plug a conventional
professional type microphone into a 1/4" unbalanced jack. it may not
work.
[How true! Jim]


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Hi Everyone,
Thanks a lot for the responses, I appreciate it.
The cable is like this
http://www.colomar.com/Shavano/2cable.gif
The connectors I'm connecting look like X and Y on the page:
http://www.colomar.com/Shavano/xlr_sn_c.gif
(or another pic at http://www.highlystrung.co.uk/acatalog/jsw2.jpg )
They're the same type used in a guitar I assume, a mono 1/4 inch socket
with 2 'prongs' to solder the cable to, I guess you'd call them. Sorry
I don't know the English vocabulary.
I'm putting one socket one one side of a wall, the other on the other
side of the wall. like this

(female mono 1/4" socket) --- |||| wall ||| --- (female mono 1/4"
socket)

They'd be connected with the cable mentioned above.

Thanks everyone!
dav=EDd

David M wrote:

Hi Everyone,
Thanks a lot for the responses, I appreciate it.
The cable is like this
http://www.colomar.com/Shavano/2cable.gif
The connectors I'm connecting look like X and Y on the page:
http://www.colomar.com/Shavano/xlr_sn_c.gif
(or another pic at http://www.highlystrung.co.uk/acatalog/jsw2.jpg )
They're the same type used in a guitar I assume, a mono 1/4 inch socket
with 2 'prongs' to solder the cable to, I guess you'd call them. Sorry
I don't know the English vocabulary.
I'm putting one socket one one side of a wall, the other on the other
side of the wall. like this

(female mono 1/4" socket) --- |||| wall ||| --- (female mono 1/4"
socket)

They'd be connected with the cable mentioned above.


If you use a stereo 1/4" in the walls, you'll have that connection if
you ever need it, and mono 1/4" cables will work fine, too.

"Prong" is usually the sticking-out part of a connector (like an AC
power connector) or a point on a fork, "terminal" or "solder lug" is the
part you solder to. But you got your point across just fine.

David
The cable you illustrated is a screened, twisted pair. Use both colours
(line 1 + line 2) together as one conductor to (signal) centre of the next
item....
X and Y as illustrated are known as 1/4" mono jacksockets. (I had thought
earlier you were talking about the jackplugs!)
Is this the type of cable with which you're linking the sockets? You could
use cheap antenna cable if it's only about a metre.
If to be mounted in a metal box, for safety's sake make sure the jacksocket
floats (no connection to shield) and ground the box metalwork at a corner by
a wire to a suitable, permanent earth (ground) point.
If housing in a plastic or wooden box, no grounding is needed.
Or you could even try to run the apparatus' external cable through the wall
(if holes can be hidden from view) and omit the wall sockets!
You have still NOT mentioned what the wall sockets lead to/from at their
other ends. Can you say what will be their function? If you are trying to
link high- or medium-impedance (AC resistance) circuits, there is,
unfortunately, a limit to cable length due to its self-capacitance per metre
which affects progressively audio high-frequencies. Yet if the sending
impedance is low ohms, ie below 150ohms, no problema.

Jim

"David M" wrote in message
oups.com...
Hi Everyone,
Thanks a lot for the responses, I appreciate it.
The cable is like this
http://www.colomar.com/Shavano/2cable.gif
The connectors I'm connecting look like X and Y on the page:
http://www.colomar.com/Shavano/xlr_sn_c.gif
(or another pic at http://www.highlystrung.co.uk/acatalog/jsw2.jpg )
They're the same type used in a guitar I assume, a mono 1/4 inch socket
with 2 'prongs' to solder the cable to, I guess you'd call them. Sorry
I don't know the English vocabulary.
I'm putting one socket one one side of a wall, the other on the other
side of the wall. like this

(female mono 1/4" socket) --- |||| wall ||| --- (female mono 1/4"
socket)

They'd be connected with the cable mentioned above.

Thanks everyone!
davíd

In article writes:

[Be careful! If it's an XLR at far end, do not always accept XLR pin 2 to
be HOT.
It could turn out to be pin 3 - found on some unconventionally-wired
gear. We still do not know if it's unbalanced or
"balanced".

He didn't ask about the other end. I'm assuming it's a normal mic
cable and either he's going to rewire both ends, just salvaging the
piece of cable, or he'll have to dope out the "hot" issue himself if
the first way he hooks it up doesn't work.

How's he going to find out if he has a Pin 3 hot Pin 2 not device
anyway? If he said it was an Ampex MX10, then we'd know. He doesn't
need too much information at this point.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Hi guys, ok, sorry about the lack of information...I'll try to do a
small diagram if possible and then explain more in English....here it
goes...


(INSIDE VOCAL BOOTH) (WALL) (OUTSIDE -- MOTU 828mkII input)

guitar-----1/4" mono jacksocket-----cable---1/4" mono jacksocket
-----cable ----MOTU input

So basically, I have a small vocal booth I've built, with a selection
of different jacksockets on each side of the wall of the booth. one of
the jacksockets is the mono 1/4" jacksocket. The problem is, I'm in
Chile and it's difficult to find all professional level supplies, so I
have to use stereo cable as illustrated above. I have other XLR
jacksockets for microphones, and stereo jacksockets for headphones, but
I figured I'd install one mono jacksocket in case someone wanted to
bring a guitar or something else into the booth. I would have
installed extra stereo but I thought the mono signal would short out
the stereo jacks....this isn't true? Is it the other way around? does
a stereo signal short out mono jacks? I remember a teacher of mine
warned me much about this, but it was a couple of years ago so I'm not
sure.
Anyways, so the signal chain would start with a guitar (or another mono
instrument), plug into the 1/4" mono jacksocket, travel through stereo
wire (illustrated above) through a wall of a couple inches, transfer to
another mono 1/4" jacksocket, then through a cable to my 828 mk II.

If we understand your descriptions properly, you are wiring
a short (~6 inches?) connection between two female, 1/4",
2-conductor ("mono"), panel-mount phone jacks.

1) Use shielded ["screened"] cable.
2) Connect the shield/screen to the terminals on the jacks that
connect to the outside barrel.
3) Take both of the inner wires and connect them to the
remaining ("hot") terminal.

You may find this reference useful.
http://www.rane.com/note110.html
Although it shows only wiring cable-end connectors (not panel-
mount). But the principles are the same.

For such a short distance it doesn't really matter how you assign
the inner conductors.

For a longer cable, I would wire it as if it were balanced (with
one inner conductor to the "hot pin" and the other one grounded).
That way, if you needed to change the connector at one end (like
replacing a phone plug with XLR, etc.) the cable would be ready
for it.

Purists would say that you should try to get some low-capacitance
cable made for high-impedance ("Hi-Z") applications like guitar
pickups. But your cable may be OK for such a short distance.

I would use 3-conductor "stereo" jacks rather than mono. That
way you can also use your interconnection point for things like
balanced lines or stereo headphones, etc. It would still work
fine for mono jacks like guitar pickups, etc.

David
What length in total of cable (crucial to know) from the actual
guitar-mounted socket to your MOTU 828 Mk ll,
whatever that is (a model of mixer?). Does it have a high impedance (roughly
50kohm) line input?
Has the route already been tried out successfully without this extension
work? Or is the guitar going to route into a guitar amp first?
If not, and you intend it going into a mixer, you may need a Direct Inject
isolation transformer device to step down both signal impedance and signal
voltage, inserted between the instrument pickups and the mixer input at Mic
level. One "DI Box" normally serves only one instrument into one channel.
Jim

In article .com writes:

I would have
installed extra stereo but I thought the mono signal would short out
the stereo jacks....this isn't true?

Well, yes, but this is exactly what you want it to do. Short between
the ring and sleeve.

But pehaps you need a lesson in terminology (not English). You're not
talking about stereo or mono jacks, plugs, and cables you're talking
about single or two-conductor parts. If you want to use the incorrect
but more easily understood terms, you can call them "unbalanced" and
"balanced" where you've been using "mono" and "stereo."

Anyways, so the signal chain would start with a guitar (or another mono
instrument), plug into the 1/4" mono jacksocket, travel through stereo
wire (illustrated above) through a wall of a couple inches, transfer to
another mono 1/4" jacksocket, then through a cable to my 828 mk II.

That's how it works. Imagine that your piece of mic cable has only one
conductor inside the shield rather than two. Use one conductor and
ignore the other one. This is better than connecting the two
conductors together when the source is likely to be a guitar, because
the capacitance (which is a function of the relationship of the
diameter of the conductor to the diameter of the shield) will be lower
than if you use both conductors in parallel. Lower cable capacitance
will make the guitar sound better (or less worse).



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

3) Take both of the inner wires and connect them to the
remaining ("hot") terminal.

And I say use just one, for the sake of reduced capacitance between
the signal conductor and the shield. But for a wall thickness, it
really doesn't matter. He could use a piece of lamp cord and probably
get away with it.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

wow, thank you everyone for the replies. the MOTU 828 mk II I'm
referring to is a computer input/output interface (I think this is the
correct terminology). A webpage with more information is
http://www.motu.com/products/motuaudio/828/body.html/en
I'm not sure of the impedence of everything, actually, I'm a bit
unclear about what impedence really means in the acoustic sense, it
seems like a difficult concept for someone new to all this like me.

thank you everyone for the responses, you are all very kind...
david

David
I had found out from my AppleMac musician mate what a MOTU 828 is - he
thought I *should* have known such a thing! Clicked on your url to Motu. Yes
a very streamlined interface, you guys are spoilt nowadays.

Small theory lesson for beginners...
Not acoustics.
Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.
Jim

On Sat, 19 Feb 2005 11:35:40 GMT, "Jim Gregory"
wrote:

David
I had found out from my AppleMac musician mate what a MOTU 828 is - he
thought I *should* have known such a thing! Clicked on your url to Motu. Yes
a very streamlined interface, you guys are spoilt nowadays.

Small theory lesson for beginners...
Not acoustics.
Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.
Jim



Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

If you are going to post theory, at least make it right.

d

Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message
...
On Sat, 19 Feb 2005 11:35:40 GMT, "Jim Gregory"
wrote:

David
I had found out from my AppleMac musician mate what a MOTU 828 is - he
thought I *should* have known such a thing! Clicked on your url to
Motu. Yes
a very streamlined interface, you guys are spoilt nowadays.

Small theory lesson for beginners...
Not acoustics.
Impedance is basically resistance in Ohms but at AC frequencies:
mains,
audio, RF, UHF, etc - so it varies electrically according to what part
of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its
conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.
Jim



Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

Don't work with video much, do you?

Don Pearce wrote:

"Jim Gregory" wrote:
snipitty doo dah

Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.


Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

If you are going to post theory, at least make it right.

Cat **** in your tea this morning or something, Don? Glasses fogged?

Read this, which Jim wrote above; I requote it since you missed it:

Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in!

Now wash the teapot and start your day anew.

--
ha

On Sat, 19 Feb 2005 06:19:35 -0800, "Richard Crowley"
wrote:


"Don Pearce" wrote in message
...
On Sat, 19 Feb 2005 11:35:40 GMT, "Jim Gregory"
wrote:

David
I had found out from my AppleMac musician mate what a MOTU 828 is - he
thought I *should* have known such a thing! Clicked on your url to
Motu. Yes
a very streamlined interface, you guys are spoilt nowadays.

Small theory lesson for beginners...
Not acoustics.
Impedance is basically resistance in Ohms but at AC frequencies:
mains,
audio, RF, UHF, etc - so it varies electrically according to what part
of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its
conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.
Jim



Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

Don't work with video much, do you?

Plenty - this applies at audio, video and RF.

d

Pearce Consulting
http://www.pearce.uk.com

On Sat, 19 Feb 2005 16:46:35 GMT, (hank alrich)
wrote:

Don Pearce wrote:

"Jim Gregory" wrote:
snipitty doo dah

Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in! This is why a cable with an internal
capacitance (inherent charge attraction sandwiched between its conductors,
linear value per metre) reaches a point where the HF top response is
compromised noticeably compared with the LF and mid-band behaviour.
Kept shorter than that, its bandwidth is fine.


Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

If you are going to post theory, at least make it right.

Cat **** in your tea this morning or something, Don? Glasses fogged?

He writes that the capacitance of a cable causes some kind of
fundamental limit to the top end of a cable - "noticeably compromised"
are his words. As I said - utter nonsense. I can take that same cable
he claims to compromise the top end of audio, and pass 1GHz through it
with minimal loss.

Read this, which Jim wrote above; I requote it since you missed it:

Impedance is basically resistance in Ohms but at AC frequencies: mains,
audio, RF, UHF, etc - so it varies electrically according to what part of
the spectrum it is placed in!

Now wash the teapot and start your day anew.

And what has t this to do with anything I wrote?

d

Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:
Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

Don't work with video much, do you?

Plenty - this applies at audio, video and RF.

Except, of course, that characteristic impedance is something different
and shouldn't even be called "impedance" at all. But half the time it
is what people are talking about when they talk about impedance.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 19 Feb 2005 13:09:21 -0500, (Scott Dorsey) wrote:

Don Pearce wrote:
Utter nonsense. Every cable used in audio is good for at least
1,000MHz virtually without attenuation. This is down to matching the
cable's IMPEDANCE with the source and load - nothing to do with the
capacitance, which can be any value you like as long as it is balanced
by an appropriate inductance.

Don't work with video much, do you?

Plenty - this applies at audio, video and RF.

Except, of course, that characteristic impedance is something different
and shouldn't even be called "impedance" at all. But half the time it
is what people are talking about when they talk about impedance.
--scott

Well, characteristic impedance and termination impedance are what give
you a flat frequency response. The post I was replying to made it
sound like a cable was some sort of lowpass filter.

d

Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:

Well, characteristic impedance and termination impedance are what give
you a flat frequency response. The post I was replying to made it
sound like a cable was some sort of lowpass filter.

A cable _can_ be a lowpass filter when it's short enough to be modelled
as a lumped-sum device.

A cable can _also_ have ringing and reflection problems when it's long
enough to be modelled as a transmission line.

When a cable is short enough to be considered a lumped-sum device, you
care only about the series impedance and shunt capacitance, and the
cable really doesn't have a characteristic impedance. This is basically
the case when the length of the cable is less than half a wavelength.

When a cable is long enough to be considered a transmission line, you
care only about the characteristic impedance. This is basically the
case when the length of the cable is longer than half a wavelength.
(You also do have high end rolloff because of shunt capacitance here,
but you can't think about it as a lumped sum thing.... this is why
the data sheets for coaxial cables have attenuation curves instead of
just scalar numbers).
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 19 Feb 2005 13:46:56 -0500, (Scott Dorsey) wrote:

Don Pearce wrote:

Well, characteristic impedance and termination impedance are what give
you a flat frequency response. The post I was replying to made it
sound like a cable was some sort of lowpass filter.

A cable _can_ be a lowpass filter when it's short enough to be modelled
as a lumped-sum device.

A cable can _also_ have ringing and reflection problems when it's long
enough to be modelled as a transmission line.

A cable does not ring. A network, of which a cable may or may not be a
part, can ring. And there is no lower limit to the length you can
model as a transmission line. As a microwave engineer I used routinely
to use transmission line models for cables as short as one hundredth
of a millimetre.

When a cable is short enough to be considered a lumped-sum device, you
care only about the series impedance and shunt capacitance, and the
cable really doesn't have a characteristic impedance. This is basically
the case when the length of the cable is less than half a wavelength.

The lumped approximation is simply something you can do if a cable is
short enough. The cable itself knows nothing of this, and remains
firmly a transmission line - nothing magic happens to it on account of
being short.

A cable can not be a lowpass filter. A cable can, however form part of
a network which makes a low pass filter.

When a cable is long enough to be considered a transmission line, you
care only about the characteristic impedance. This is basically the
case when the length of the cable is longer than half a wavelength.
(You also do have high end rolloff because of shunt capacitance here,
but you can't think about it as a lumped sum thing.... this is why
the data sheets for coaxial cables have attenuation curves instead of
just scalar numbers).
--scott

Exactly. And those attenuation curves assume that you have matched the
thing properly.

d

Pearce Consulting
http://www.pearce.uk.com

I was talking there only about losses incurred by *long* cables from
*medium* Z going into medium Z or high Z (a useful practice likely inherited
from valve/tube grid days). Very few calls to *match* impedance anymore in
Audio. Leaving out power amps and PSUs which work on current amplification,
I always think in terms of off-load source voltage, routeing path, and
at-load voltage, giving an insertion loss figure from spot freq tests made
across the whole 22Hz-22kHz range.
Low into High - that's our watchword.
Eg, 150 or 200 Ohm mics look into a Z of at least 1k2 (sometimes1k6) Ohms on
channel input for maximum level transfer. Can be run floating or "balanced"
for
1000 metres easily. If source Z were matched (impossible at whole AF range),
the gain after receiving would have to be stepped up about 6dB and there
would be a
*noticeable* lack of harmonic overtones. As far as I am aware there is no
such thing as screened twisted-pair 200Ohm mic cable!
600 Ohm Line Source (probably less than 70 Ohm nowadays) is happy to see
8kOhm or much higher and would be measured in dBU.
Termination by resistive 600 Ohm (in dBm) is usually for fulfilling a
calibrated voltage match.
Not only does capacitance/metre characteristic play its part, but in
high-gain high Z stages, the wrong type of unclamped cable can be heard to
behave
microphonically.
Any cable catalogue list will quote the capacitance figure in pF /metre for
each specific type (and sometimes for each core).... and dB /100m loss in
data/RF cables. Why, do you think?
Not many bandwidth problems happen from low Z into 50 or 75 Ohms with decent
RF co-ax cable! But then the sending level is usually bumped up to arrive at
a proper usuable level.
Jim

In article writes:

He writes that the capacitance of a cable causes some kind of
fundamental limit to the top end of a cable - "noticeably compromised"
are his words. As I said - utter nonsense. I can take that same cable
he claims to compromise the top end of audio, and pass 1GHz through it
with minimal loss.

You won't lose any power to standing waves if the characteristic
impedance matches all along, but the electrical resistance of the
cable (which is a function of its length) doesn't go away just because
you're terminating it with the correct load. All coaxial cable has
loss rating in dB per 1000 feet.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

On 19 Feb 2005 18:19:58 -0500, (Mike Rivers)
wrote:


In article writes:

He writes that the capacitance of a cable causes some kind of
fundamental limit to the top end of a cable - "noticeably compromised"
are his words. As I said - utter nonsense. I can take that same cable
he claims to compromise the top end of audio, and pass 1GHz through it
with minimal loss.

You won't lose any power to standing waves if the characteristic
impedance matches all along, but the electrical resistance of the
cable (which is a function of its length) doesn't go away just because
you're terminating it with the correct load. All coaxial cable has
loss rating in dB per 1000 feet.

Please don't introduce red herrings. Nobody here is discussing
resistive losses. The post I was replying to was about the capacitance
of the cable causing a loss at the top end of audio. If you want to
discuss resistive loss, of course I am happy to, but for goodness sake
don't make it sound as if you are thus contradicting what I wrote.

d
Pearce Consulting
http://www.pearce.uk.com

In article writes:

I was talking there only about losses incurred by *long* cables

Well, since the question that started this thread was about a short
cable, the length being just enough more than the thickness of a wall,
perhaps it's time to start another thread.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

"Mike Rivers" wrote in message
news:znr1108855310k@trad...

In article
writes:

I was talking there only about losses incurred by *long* cables

Well, since the question that started this thread was about a short
cable, the length being just enough more than the thickness of a wall,
perhaps it's time to start another thread.


--
This was my point, I was trying to indicate that there could be HF loss that
may result from the total cable run.
Jim

In article writes:

Please don't introduce red herrings. Nobody here is discussing
resistive losses. The post I was replying to was about the capacitance
of the cable causing a loss at the top end of audio.

Well, it does, when the source impedance (regardless of the
characteristic impedance of the cable) is high compared to the
capacitive reactance of the cable at the frequency you're considering.
There's no way to get around that. Technically it's not a CABLE loss,
it's a SYSTEM loss, but the cable means nothing if there's nothing
driving it. It doesn't even have to be there.

I thought you introduced the red herring when you started talking
about RF and microwave engineering and the question was about an audio
connection with less than a foot of cable. But Usenet is like that.
You talk about what you know, and somehow try to make it fit into a
discussion.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo