Press mult box

[Andy[_13_]]

Anybody ever try building your own passive press train? I have a gig
coming up that will require one, but not enough anticipated future use
to justify putting one in inventory at full price. I know I could
probably rent one, just curious if anyone had ever built one.

Andy

[Mike Rivers]

Andy wrote:
> Anybody ever try building your own passive press train? I have a gig
> coming up that will require one, but not enough anticipated future use
> to justify putting one in inventory at full price.

Beggars can't be choosy, and given that your need is rare, you probably
aren't going to get high class beggars who expect a full blown distribution
ampllifier (even if they don't know what that is).

The important thing that you need is enough isolation at each output so
that someone's shorted cable or unusually low impedance input doesn't
take down everyone else's level. A 1K ohm resistor in series with each
output leg is usually adequate. To prevent shorting out the low side of
a differential output if someone connects it to an unbalanced input, you
probably should make your balanced outputs single-ended with a resistor
between the low side and ground (equal to the source impedance of the
hot output) to provide a balanced source.

If you want to be really nice, you can make a few stereo mini jack outputs
with 20 dB lower output than the line level outputs so they can be connected
to mic inputs on cheap recorders or video cameras.

To be good to yourself, you could put a transformer on the input so that
someone's noisy ground won't affect your system.

All in all, unless you like to build stuff and have some decent metalworking
tools and skills (it's mostly about making a bunch of holes in a box)
you would
probably be better off renting one. If the people who are plugging into your
feed are in any way "professional" it has to look good. Nobody wants to bet
his feed for the 11 o'clock news on a home-made-looking box.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me here:
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[blackburst]

On Aug 6, 10:46*pm, Andy > wrote:
> Anybody ever try building your own passive press train? I have a gig
> coming up that will require one, but not enough anticipated future use
> to justify putting one in inventory at full price. I know I could
> probably rent one, just curious if anyone had ever built one.
>
> Andy

Nearly every big city has a pro-video rental house, and many of them
will rent you a press box at a decent rate. If not, approach the
engineering staff of a local TV station, and they may rent you one.

[Richard Crowley]

"Andy" wrote...
> Anybody ever try building your own passive press train? I have a gig
> coming up that will require one, but not enough anticipated future use
> to justify putting one in inventory at full price. I know I could
> probably rent one, just curious if anyone had ever built one.

Yes, I have. There are some tradeoffs to be made depending on
specific details of your circumstance. Primarily, what will be driving
the mult box, and how many outputs will you need? If you are
driving it with something with a good +4 output, you can likely get
away with driving half a dozen outputs with iso resistors in each leg
(~1K as Mike suggests).

If you don't have a beefy source, or you need a lot more outputs,
you could go the route of feeding the box with line level and giving
the users mic-level. That would give you a lot more gain structure
to play with, driving more loads with effective isolation against faults.

[philper]

On Aug 7, 8:31*am, "Richard Crowley" > wrote:
> "Andy" *wrote...
> > Anybody ever try building your own passive press train? I have a gig
> > coming up that will require one, but not enough anticipated future use
> > to justify putting one in inventory at full price. I know I could
> > probably rent one, just curious if anyone had ever built one.
>
> Yes, I have. *There are some tradeoffs to be made depending on
> specific details of your circumstance. *Primarily, what will be driving
> the mult box, and how many outputs will you need? *If you are
> driving it with something with a good +4 output, you can likely get
> away with driving half a dozen outputs with iso resistors in each leg
> (~1K as Mike suggests).
>
> If you don't have a beefy source, or you need a lot more outputs,
> you could go the route of feeding the box with line level and giving
> the users mic-level. That would give you a lot more gain structure
> to play with, driving more loads with effective isolation against faults.

I built some small ones, and they worked fine. For a "real" bridge,
like with 20-30 outputs to be used at a real press "gang-bang" I'd
rent.
To do a really good job with the isolation and gain for that many
outputs that could be plugged into an infinite variety of flaky target
devices with
questionable cables and that is rugged enough to handle abuse by
people who cover breaking news would be A LOT of work. In my early
days
in the sound biz I worked in news and many of the press bridges I saw
were home made, but nowadays all the sound companies just buy them--
the off-the-shelf ones work great and are far cheaper than even just
buying quality parts to make your own, not even including the box
fabrication.

Philip Perkins

[Scott Dorsey]

Andy > wrote:
>Anybody ever try building your own passive press train? I have a gig
>coming up that will require one, but not enough anticipated future use
>to justify putting one in inventory at full price. I know I could
>probably rent one, just curious if anyone had ever built one.

Audisar will sell you a transformer with a 600 ohm primary and four or five
600 ohm secondaries. Put it in a box with some connectors and ground lift
switches and you're good to go.

I recommend also adding 600 ohm termination resistors with switches as
well, since we live in a world where most sinks aren't 600 ohms any more,
and since these transformers aren't so well-behaved. Plus you can terminate
unused outputs.
--scott

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

[Andy[_13_]]

On Aug 8, 6:10*pm, (Scott Dorsey) wrote:
> Andy > wrote:
> >Anybody ever try building your own passive press train? I have a gig
> >coming up that will require one, but not enough anticipated future use
> >to justify putting one in inventory at full price. I know I could
> >probably rent one, just curious if anyone had ever built one.
>
> Audisar will sell you a transformer with a 600 ohm primary and four or five
> 600 ohm secondaries. *Put it in a box with some connectors and ground lift
> switches and you're good to go.
>
> I recommend also adding 600 ohm termination resistors with switches as
> well, since we live in a world where most sinks aren't 600 ohms any more,
> and since these transformers aren't so well-behaved. *Plus you can terminate
> unused outputs.
> --scott
>
> --
> "C'est un Nagra. *C'est suisse, et tres, tres precis."

Thanks everyone.

Andy

[WillStG]

On Aug 6, 10:46 pm, Andy > wrote:
> Anybody ever try building your own passive press train? I have a gig
> coming up that will require one, but not enough anticipated future use
> to justify putting one in inventory at full price. I know I could
> probably rent one, just curious if anyone had ever built one.
>
> Andy

Rent. Many people already do not trust Press Boxes much, and if
home built this will be even more so. And I always find it irritating
when people who haven't much of a clue come to you begging for a
direct console feed because their boss told them not to use the press
box. And expect you to have all the patch cables they need too....

Anyway a good press box has both mic and live level outputs, well
labeled. But if you build one and there are problems with it, that's
not good for your career. If you rent that (should be) one less thing
to worry about. Of course if they mismatch their levels, that's their
fault.

Will Miho
NY TV/Audio Post/Music/Live Sound Guy
"The large print giveth and the small print taketh away,.." Tom Waits

[Andy[_13_]]

On Aug 9, 9:57*pm, WillStG > wrote:
> On Aug 6, 10:46 pm, Andy > wrote:
>
> > Anybody ever try building your own passive press train? I have a gig
> > coming up that will require one, but not enough anticipated future use
> > to justify putting one in inventory at full price. I know I could
> > probably rent one, just curious if anyone had ever built one.
>
> > Andy
>
> * Rent. *Many people already do not trust Press Boxes much, and if
> home built this will be even more so. *And I always find it irritating
> when people who haven't much of a clue come to you begging for a
> direct console feed because their boss told them not to use the press
> box. *And expect you to have all the patch cables they need too....
>
> * *Anyway a good press box has both mic and live level outputs, well
> labeled. But if you build one and there are problems with it, that's
> not good for your career. *If you rent that (should be) one less thing
> to worry about. *Of course if they mismatch their levels, that's their
> fault.
>
> Will Miho
> NY TV/Audio Post/Music/Live Sound Guy
> "The large print giveth and the small print taketh away,.." Tom Waits

Following the general wisdom of the esteemed members of the group, I
have secured the use of a commercially built press box. Thanks again
to all who responded.

Andy