Active USB Cable... need some clairification please!

[mydeadpresidents]

I'm planning to purchase a 16' Active USB cable that ends in a female A
type end. I understand that 5 meters (just over 16') is the max
length of USB cable before signal corruption occurs. I have a few
quick questions:

1. Does an "active" USB cable require some kind of power source? Does
it draw power or CPU processing power or anything like that? Is there
a quick and easy description on how it works?

2. At the output end of the active USB cable, can I attach a passive
USB cable or am I required to use active USB cables from then on? If
I can use passive cables, am I right to assume I can go another 16 feet
before needing another active cable?

3. I have a three foot USB cable that ends in a hub (four female A
types). I assume it's passive. Can I plug this into the output end
of my 16' active cable and continue on with passive cables as needed so
long as I don't go over 13 feet? (16 allowed minus 3 feet for the hub
extension leaves 13 feet to work with).

4. Has anyone heard of a 16' Active USB that ends in a hub? (and
allows me to continue with passive cable)

5. Is a ferrite (at both ends) still beneficial to a Active USB cable?
Is there anything wrong with salvaging ferrites from an older USB
cable and using them on a new one?

6. While I've got ya here, I'm looking for a 25' KVM cable (ps2 and
15pin monitor d-sub). Is there any rule about length and performance
on these types of cables or will 25' still work without errors?

Thanks if you can help clear this up for me. I did some research but
I'm still a little unclear about the details.

 

[Guest]

I'm planning to purchase a 16' Active USB cable that ends in a female A
type end. I understand that 5 meters (just over 16') is the max
length of USB cable before signal corruption occurs. I have a few
quick questions:

1. Does an "active" USB cable require some kind of power source? Does
it draw power or CPU processing power or anything like that? Is there
a quick and easy description on how it works?

USB has 5v power on the cable. Active cables use that power source.

2. At the output end of the active USB cable, can I attach a passive
USB cable or am I required to use active USB cables from then on? If
I can use passive cables, am I right to assume I can go another 16 feet
before needing another active cable?

Yes you can mix passive with active cables. Don't use more 5m passive in
total.

3. I have a three foot USB cable that ends in a hub (four female A
types). I assume it's passive. Can I plug this into the output end
of my 16' active cable and continue on with passive cables as needed so
long as I don't go over 13 feet? (16 allowed minus 3 feet for the hub
extension leaves 13 feet to work with).

Depends on the hub and cables. Probably ok, if the hub is suitable.

4. Has anyone heard of a 16' Active USB that ends in a hub? (and
allows me to continue with passive cable)

I haven't.

5. Is a ferrite (at both ends) still beneficial to a Active USB cable?
Is there anything wrong with salvaging ferrites from an older USB
cable and using them on a new one?

Ferrite rings increase the line impedance to noise frequencies. Unless
you are suffering from noise interference, they are not needed and
certainly you do not need to add extra. Yes, if you are suffering from
noise interference, they willl possibly help - eg, if you are running
cables next to the microwave, wrapping them around cordless phones, etc..

6. While I've got ya here, I'm looking for a 25' KVM cable (ps2 and
15pin monitor d-sub). Is there any rule about length and performance
on these types of cables or will 25' still work without errors?

Keyboard and mice will be fine. 25' of monitor lead will need cable and
a KVM/ line amplifier designed to drive that much cable - otherwise you
will be limited to the resolution that can be displayed and get
blurring/ghosting of the image.

 

[mydeadpresidents]

Hi Sue,

Thank you for the help!

Yes you can mix passive with active cables. Don't use more 5m passive in
total.

Okay just to be crystal clear, that's 5 meters beyond the output end of
the active cable. That's what I figured.

Depends on the hub and cables. Probably ok, if the hub is suitable.

Well, there's nothing special about the hub. Just a simple extension
with hub built in and rated for 2.0 usb. All passive from what I can
tell.

Ferrite rings increase the line impedance to noise frequencies. Unless
you are suffering from noise interference, they are not needed and
certainly you do not need to add extra. Yes, if you are suffering from
noise interference, they willl possibly help - eg, if you are running
cables next to the microwave, wrapping them around cordless phones, etc..

Is it fair to say it certainly won't hurt to put them on?

Keyboard and mice will be fine. 25' of monitor lead will need cable and
a KVM/ line amplifier designed to drive that much cable - otherwise you
will be limited to the resolution that can be displayed and get
blurring/ghosting of the image.

Hmm... glad you mentioned that. Any idea what the limit is for d-sub
video cable before performance declines? 15'? 20'? If I end up
needing a 25' solution, do they make the amplifier INLINE as part of
the cable or is it purchased as a separate unit? Is this mostly a
matter of conductor length or shielding? (I don't NEED a KVM cable.
If necessary I don't mind buying separate cables for K, M, and video).
Oh, and one last thing just to be clear... am I saying it right when I
equate d-sub with 15 pin?

Sue

Thanks again Sue. That's just the information I was looking for.

 

[Guest]

Hi Sue,

Thank you for the help!






Okay just to be crystal clear, that's 5 meters beyond the output end of
the active cable. That's what I figured.




Well, there's nothing special about the hub. Just a simple extension
with hub built in and rated for 2.0 usb. All passive from what I can
tell.




Is it fair to say it certainly won't hurt to put them on?

No. It certainly can hurt - eg a ferrite ring intended for filtering a
low bandwidth signal (eg a USB 1 cable) may easily cause unacceptable
attenuation of some of the components of a high bandwidth signal ( eg a
USB 2 cable)...

Hmm... glad you mentioned that. Any idea what the limit is for d-sub
video cable before performance declines? 15'? 20'? If I end up
needing a 25' solution, do they make the amplifier INLINE as part of
the cable or is it purchased as a separate unit? Is this mostly a
matter of conductor length or shielding? (I don't NEED a KVM cable.
If necessary I don't mind buying separate cables for K, M, and video).
Oh, and one last thing just to be clear... am I saying it right when I
equate d-sub with 15 pin?

How long is a piece of string? Performance declines with /any/ length of
cable - it tends only to become observable when you have a very high
quality monitor capable of processing and displaying these very high
frequency components. On a low quality monitor, you never notice what
you are losing with the cable..

Yes, they do make amplifiers for driving long cables. Yes, you can get
monitors with rgb synch bnc connectors that correctly terminate the
cable with a matching impedance, so work better with longer cables.
Noise (eg interference visible on the screen) can be helped by better
shielded cable. Blurring (eg loss of higher frequency components) can be
helped by an amplifier and/or lower loss cable. A KVM cable is not
necessarily high loss or poorly screened. A good quality KVM cable is
better than cr*p separates.. eg

http://www.lindy.com/uk/productfolder/03/33/33736/index.php

But I wouldn't expect much better than 1024 x 768 75Hz over that sort of
distance..


D type sub miniature connectors come in a variety of sizes, eg the 9
pin d sub used for serial ports, 25 pin d sub used for parallel ports,
37 pin d sub used for multiple serial port and 15 pin used for display
interfaces.

 

[mydeadpresidents]

Thanks Sue. My original plan was to put the whole case in the closet
to eliminate noise then bring the bare essentails out to the desk...
and maybe some sort of external enclosure for a DVD player. Given the
high cost of good cable and the questionable performance (I have a good
quality monitor), I'm rethinking things a bit. Might be better just to
make a small enclosure for sound dampening. I'm off to find good air
flow/fan specs. So many I've seen so far seem to contradict each
other...

Thanks for you help.

 

[slowpoke]

6. While I've got ya here, I'm looking for a 25' KVM cable (ps2

Keyboard and mice will be fine. 25' of monitor lead will need cable
and a KVM/ line amplifier designed to drive that much cable -
otherwise you will be limited to the resolution that can be
displayed and get blurring/ghosting of the image.

Actually, high resolution 25 foot cables for the display are readily
available, but don't bother with the ones on the shelves in the discount
stores. I've found the indicator of good quality, is the size of display
the cable is recommended for use on. The good cables will say they are
for use on displays larger than 15". My 25' cable works just fine at all
resolutions with my Sony 18" display.

regards,
Joe

 

[~hpXH535~]

joe,
where'd you get the cable?
Mike

Actually, high resolution 25 foot cables for the display are readily
available, but don't bother with the ones on the shelves in the discount
stores. I've found the indicator of good quality, is the size of display
the cable is recommended for use on. The good cables will say they are
for use on displays larger than 15". My 25' cable works just fine at all
resolutions with my Sony 18" display.

regards,
Joe

 

[slowpoke]

Sorry about the slow reply, I don't check this group as often as some
others.

I ordered it over the net, from MWave. It's a Belkin KVM cable. I
think I paid about $65 for it.