Many years ago I built myself an audio "passive preamp". The I/O
switching section consisted of ten pairs of connectors and ten DPDT
center off switches. Each connector was routed to the center "common"
terminal of a switch, and all the "tops" and all the "bottoms" of the
switches were wired together - forming two busses to which any input
or output (or group of I/O) could be connected. Now I have too many
things to connect, and several of them have s-video to be switched as
well. So I'm looking for a bigger, more capable switcher.

I see lots of passive NxN switchers, but it appears they only connect
one input to one output at a time. That is no help in being able to
connect (for instance) VCR out to DVD recorder in, and DVD recorder
out to monitor in simultaneously.

The word "matrix" in the name doesn't seem to improve on that
limitation, but "routing matrix" seems to imply that one can create
more than one connection at a time. Unfortunately, all the routing
matrix switchers I've found are active and have four-digit $ prices. A
price of thousands of dollars is out of the question, and even if it
wasn't, I'd rather not add active devices between my audio components,
several of which are DC-coupled. Plus you are still limited to
dedicated inputs and dedicated outputs - you can't have a single cable
going off to another room and use it for I or O as needed. And you
can't have a single cable to a DV camcorder which swaps its single
connector between input and output.

Yes, I know, normal people use a home theater receiver. But if I'm
suspicious of the effect a multi-thousand dollar pro switcher would
have on my system, there is no way I'm going to inflict a mass-market
receiver on myself.

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

Loren

"Loren Amelang" wrote ...
Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

The nature of video is such that routing a video source to a
variable number of destinations is not possible the way it
is in audio. Most modern audio sources are low-impedance
voltage sources and audio destinations are relatively high-
impedance sinks. This allows one to route an audio output
to several destinations without appreciable loss or distruption.

However, video signals have up to 5,000x more bandwidth
than audio and need properly-matched source and load impedances
to operate properly. A video routing switcher is actually a
combination of a matrix switch and several distribution amplifier
stages.

Note that video matrix switch ICs (some even completely self-
contained with output amps, etc.) are available from vendors
like Maxim, etc. See a listing of them at...
http://www.maxim-ic.com/solutions/cr...x.mvp?pl_pk=50

See particularly MAX453, MAX454, MAX455 (2x1, 4x1,
and 8x1 buffered video multiplexers or the newer
MAX4359, MAX4360, MAX4456 (4x4, 8x4, and 8x8
buffered video crosspoint switch circuits.

Many of their ICs are available in an "Evaluation Kit" where
the chip is already installed on a PC board with all the required
peripheral components to make a working circuit.

I have made myself a couple of video Distribution Amplifiers
by using the Evaluation Kits with first-class performance and
specifications at a cost far less than anything you could buy off
the shelf. Of course I had to provide my own enclosure, connectors,
power supply, etc. so likely not practical for everyone.

Maxim not only makes cool ICs, but they also sell them direct
online (at www.maxim-ic.com) and many of them are available
at vendors like www.digikey.com, etc.

"Loren Amelang" wrote ...
Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

The nature of video is such that routing a video source to a
variable number of destinations is not possible the way it
is in audio. Most modern audio sources are low-impedance
voltage sources and audio destinations are relatively high-
impedance sinks. This allows one to route an audio output
to several destinations without appreciable loss or distruption.

However, video signals have up to 5,000x more bandwidth
than audio and need properly-matched source and load impedances
to operate properly. A video routing switcher is actually a
combination of a matrix switch and several distribution amplifier
stages.

Note that video matrix switch ICs (some even completely self-
contained with output amps, etc.) are available from vendors
like Maxim, etc. See a listing of them at...
http://www.maxim-ic.com/solutions/cr...x.mvp?pl_pk=50

See particularly MAX453, MAX454, MAX455 (2x1, 4x1,
and 8x1 buffered video multiplexers or the newer
MAX4359, MAX4360, MAX4456 (4x4, 8x4, and 8x8
buffered video crosspoint switch circuits.

Many of their ICs are available in an "Evaluation Kit" where
the chip is already installed on a PC board with all the required
peripheral components to make a working circuit.

I have made myself a couple of video Distribution Amplifiers
by using the Evaluation Kits with first-class performance and
specifications at a cost far less than anything you could buy off
the shelf. Of course I had to provide my own enclosure, connectors,
power supply, etc. so likely not practical for everyone.

Maxim not only makes cool ICs, but they also sell them direct
online (at www.maxim-ic.com) and many of them are available
at vendors like www.digikey.com, etc.

Waiving the right to remain silent, Loren Amelang
said:

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not
found the proper search term?

Videonics (if they are still in business) made these. I owned one
which was composite video with stereo audio. They upgraded it to S-
Video at some later time. It was 4x4 and NOT passive. You cannot do
that with video.

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Waiving the right to remain silent, Loren Amelang
said:

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not
found the proper search term?

Videonics (if they are still in business) made these. I owned one
which was composite video with stereo audio. They upgraded it to S-
Video at some later time. It was 4x4 and NOT passive. You cannot do
that with video.

--
Larry Jandro - Remove spamtrap in ALLCAPS to e-mail

Are you a Sound/Video/Lighting/Staging Freelancer..?
If so, think about joining our mail list.
Send an e-mail to:
(Requests from Yahoo & Hotmail will be rejected.)

Loren Amelang wrote:

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

You want a patchbay, with a couple rows set aside for mults. Yes, maybe
someone out there makes a matrix switcher that lets you double-up, but
there's just something very safe-feeling about a patchbay.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Loren Amelang wrote:

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

You want a patchbay, with a couple rows set aside for mults. Yes, maybe
someone out there makes a matrix switcher that lets you double-up, but
there's just something very safe-feeling about a patchbay.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Sat, 4 Dec 2004 14:12:40 -0800, "Richard Crowley"
wrote:

"Loren Amelang" wrote ...
Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

The nature of video is such that routing a video source to a
variable number of destinations is not possible the way it
is in audio. Most modern audio sources are low-impedance
voltage sources and audio destinations are relatively high-
impedance sinks. This allows one to route an audio output
to several destinations without appreciable loss or distruption.

Understood. While I have occasionally connected a single source to two
destinations simultaneously with not totally disastrous results, my
main goal is to be able to make two (or more) simultaneous connections
between single sources and single destinations. The equivalent of the
"tape-monitor" loop in a receiver, for instance.

However, video signals have up to 5,000x more bandwidth
than audio and need properly-matched source and load impedances
to operate properly. A video routing switcher is actually a
combination of a matrix switch and several distribution amplifier
stages.

Is that necessary if you are only connecting a single destination to
any one source? Assuming they are compatible when connected directly,
of course?

Note that video matrix switch ICs (some even completely self-
contained with output amps, etc.) are available from vendors
like Maxim, etc. See a listing of them at...
http://www.maxim-ic.com/solutions/cr...x.mvp?pl_pk=50

See particularly MAX453, MAX454, MAX455 (2x1, 4x1,
and 8x1 buffered video multiplexers or the newer
MAX4359, MAX4360, MAX4456 (4x4, 8x4, and 8x8
buffered video crosspoint switch circuits.

Interesting! I've used several Maxim chips in other projects, and
somehow I had a feeling I would end up building my own switcher.
Thanks!

Maybe "crosspoint switch" is the search term I was looking for?

Loren

On 4 Dec 2004 21:05:02 -0500, (Scott Dorsey) wrote:

Loren Amelang wrote:

Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

You want a patchbay, with a couple rows set aside for mults. Yes, maybe
someone out there makes a matrix switcher that lets you double-up, but
there's just something very safe-feeling about a patchbay.
--scott

I think what I really want is a patchbay with a couple of simple
switches connected to it. Gear that needs to be swapped often or A/Bed
could be patched to the switches, and those odd combinations that are
difficult with switches could still be patched together. I do worry
that every added connection point is a source of eventual problems,
but I guess a patchbay at least concentrates them in one more
accessible place.

Loren

"Loren Amelang" wrote ...
"Richard Crowley" wrote:

"Loren Amelang" wrote ...
Is there really no such thing as a passive matrix switcher with
multiple internal busses, that can make multiple independent
connections among any of its I/O connectors? Or have I just not found
the proper search term?

The nature of video is such that routing a video source to a
variable number of destinations is not possible the way it
is in audio. Most modern audio sources are low-impedance
voltage sources and audio destinations are relatively high-
impedance sinks. This allows one to route an audio output
to several destinations without appreciable loss or distruption.

Understood. While I have occasionally connected a single source to two
destinations simultaneously with not totally disastrous results,

Professional/industrial video equipment usually has high-impedance
inputs with two connectors so that you can "loop-through" the video
signal to additional inputs. Then you put a 75-ohm termination at the
end of the line.

But few (if any?) consumer devices have loop-through inputs.
Connecting a standard 75-ohm ouput to more than one 75-ohm
terminated inputs will significantly degrade the signal, even
reducing the amplitude of the sync portion to the point where
some equipment won't be able to lock to it. NOT RECOMMENDED!

my main goal is to be able to make two (or more) simultaneous
connections between single sources and single destinations.
The equivalent of the "tape-monitor" loop in a receiver, for instance.

In that case, Scott's suggestion of a patch bay may be more like
what you are looking for. I was assuming you were actually
needing an any-to-any solution which would call for a non-
blocking matrix.


However, video signals have up to 5,000x more bandwidth
than audio and need properly-matched source and load impedances
to operate properly. A video routing switcher is actually a
combination of a matrix switch and several distribution amplifier
stages.

Is that necessary if you are only connecting a single destination to
any one source? Assuming they are compatible when connected directly,
of course?

Yes. A properly driven and terminated transmission line is
required for high-quality transport of any high-frequency signal
like video.

In article writes:

Understood. While I have occasionally connected a single source to two
destinations simultaneously with not totally disastrous results, my
main goal is to be able to make two (or more) simultaneous connections
between single sources and single destinations. The equivalent of the
"tape-monitor" loop in a receiver, for instance.

Radio Shack has had a few variations on that. I have one right here in
my office so I can listen to the radio, or play audio from either of
the two computers, or record from the radio or an external source to
either (or both) of the computers. It's all unbalanced on RCA jacks,
but it's two channels (stereo). It's model 42-2115, but unfortunately
it or an equivalent no longer exists at Radio Shack.

I'll bet you could find one on eBay, though. In fact I just did:
http://tinyurl.com/7xbuu or in plain English, Item 5736072044

Thank the seller for his honesty (he says he found it in his basement
and doesn't have any idea what it is or what to do with it), that $9.95
is too much, and he's an asshole for charging a flat $8 for shipping (it
weighs much less than a pound). He doesn't have any bids and it
closes in 3 days. Offer him $5 plus actual US postage. Live it up.
Have him send it Priority Mail. Gotta get tough with those know-nothing
eBay opportunists.

Afterthought, aftersearch. Here's a better deal (also from an apparent
know-knot) Item number: 5735939498 Buy it now for $8.99, flat $5
shipping. Almost not worth arguing about if it's what you want.
Read the owner's manual here (sort of - text without pictures):

http://support.radioshack.com/suppor...oc63/63395.pdf
or, in Spanish, with illustrations:
http://support.radioshack.com/suppor.../doc9/9194.pdf

--
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 ...
Radio Shack has had a few variations on that. I have one right here in
my office so I can listen to the radio, or play audio from either of
the two computers, or record from the radio or an external source to
either (or both) of the computers. It's all unbalanced on RCA jacks,
but it's two channels (stereo). It's model 42-2115, but unfortunately
it or an equivalent no longer exists at Radio Shack.

That would be a great suggestion if he were looking for audio-
only. But I understood that he was asking for audio & video.

In article writes:

Radio Shack has had a few variations on that.

That would be a great suggestion if he were looking for audio-
only. But I understood that he was asking for audio & video.

He may need to buy two devices, or spend more than he was expecting to
get one device that switches both video and stereo audio in one shot -
a "matrix" for sure.

How much is not having to use both hands worth?

--
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 ,
Richard Crowley wrote:
"Mike Rivers" wrote ...
Radio Shack has had a few variations on that. I have one right here in
my office so I can listen to the radio, or play audio from either of
the two computers, or record from the radio or an external source to
either (or both) of the computers. It's all unbalanced on RCA jacks,
but it's two channels (stereo). It's model 42-2115, but unfortunately
it or an equivalent no longer exists at Radio Shack.

That would be a great suggestion if he were looking for audio-
only. But I understood that he was asking for audio & video.

I was also assuming audio-online. If he wants audio and video both, there
is no way to do it without either a DA or a nightmare of termination rules
and loopthroughs.

A patchbay (with a DA for the video and mults for the audio) still seems
the solution to me.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I agree. The lowest cost "real solution" would be to use a small DA for
each source, and a patch bay to send them to their destinations. This is
essentially what a router is, just in one case and with a control
mechanism - - either serial or with a dedicated panel.

If real broadcast quality isn't important, then check out some vendors
associated with the security field. I'm often surprised by the low prices
in the couple of catalogs I happen to get.

Steve



"Mike Rivers" wrote in message
news:znr1102335580k@trad...

In article writes:

Radio Shack has had a few variations on that.

That would be a great suggestion if he were looking for audio-
only. But I understood that he was asking for audio & video.

He may need to buy two devices, or spend more than he was expecting to
get one device that switches both video and stereo audio in one shot -
a "matrix" for sure.

How much is not having to use both hands worth?

--
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 5 Dec 2004 17:11:44 -0500, (Mike Rivers) wrote:

In article writes:

Understood. While I have occasionally connected a single source to two
destinations simultaneously with not totally disastrous results, my
main goal is to be able to make two (or more) simultaneous connections
between single sources and single destinations. The equivalent of the
"tape-monitor" loop in a receiver, for instance.

Radio Shack has had a few variations on that. I have one right here in
my office so I can listen to the radio, or play audio from either of
the two computers, or record from the radio or an external source to
either (or both) of the computers. It's all unbalanced on RCA jacks,
but it's two channels (stereo). It's model 42-2115, but unfortunately
it or an equivalent no longer exists at Radio Shack.

I'll bet you could find one on eBay, though.

Thanks! Looks like a handy gadget to have around. Not sure I'll be
using it with my serious audio system, though... Have to look inside
first, at least.

Loren

Found a definition of "matrix switcher":

http://www.extron.com/product/prodtype03.asp
"Matrix switchers route multiple audio/video sources to multiple
audio/video destinations. Matrix switchers provide the ability to
route any input to any output - or multiple outputs - at any time."

I guess they mean a _buffered_ matrix switcher can route one input to
multiple outputs.


It looks like the key to my terminology question is that when a
switcher offers more than "n by 1" switching, it can specify the
number of available crosspoints. As in:
"Kramer VS-44AV 4x4 (4 Crosspoint) Mechanical CV / Audio Matrix, 220
MHz"

http://www.kramerelectronics.com/indexes/desc.asp?p=VS-44AV
"The Kramer VS-44AV is a high quality mechanical 4x1x4 switcher for
composite video and stereo audio signals. It is designed to route up
to four sources to any one of four available outputs simultaneously.
The VS-44AV is unique in allowing four different cross points of video
and stereo audio to operate at the same time. However, it is important
to note that it cannot distribute an input signal to multiple outputs
simultaneously."

I assume the limitation on "an input signal to multiple outputs
simultaneously" is because it isn't buffered.

I'm still not clear what the "4x1x4" terminology means. It sounds like
a combination of a 4x1 input switch and a 1x4 output switch, but that
would only allow four simultaneous crosspoints if they were all in the
same row or column. I want to be able to put four simultaneous
crosspoints in a diagonal or random pattern. So maybe this still
doesn't do what I imagined. They don't make a passive counterpart for
S-Video, anyway.


Another useful search term is "loop back" (as in the "tape-monitor"
facility of a receiver).

http://www.extron.com/technology/faq.asp
"Video loop back is a feature of Extron system switchers that allows
selected inputs to be looped out of the system switcher to a scaler or
scan converter and then looped back into the System. The result is the
switcher and the scaler or scan converter essentially operate as one
unit."

That would solve one of my problems, but I really want to be able to
switch any appropriate piece of equipment into the loopback position.
That patchbay is sounding better all the time. Especially since I
can't always use "audio follows video" switching. Sometimes the audio
goes to or through additional equipment.

Loren

In article writes:

Radio Shack model 42-2115

Thanks! Looks like a handy gadget to have around. Not sure I'll be
using it with my serious audio system, though... Have to look inside
first, at least.

You know what they say about laws and sausages - If you like them,
you'd better not watch either being made. Just cheap switches and some
resistors.

--
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:znr1102369850k@trad...

In article
writes:

Radio Shack model 42-2115

Thanks! Looks like a handy gadget to have around. Not sure I'll be
using it with my serious audio system, though... Have to look inside
first, at least.

You know what they say about laws and sausages - If you like them,
you'd better not watch either being made. Just cheap switches and some
resistors.

Are you describing the laws or the rat-shack switch boxes? :-)