Attn: Jeorg - How goes the digital recorder install?

[Charlie E.]

Hi Jeorg,
How did that unit work out for your church? The city here is
considering changing over from that combination CF/CD unit, as it is
too complicated for the clerks to use properly.

Thanks,
Charlie

 

[Joerg]

Hi Jeorg,
How did that unit work out for your church? The city here is
considering changing over from that combination CF/CD unit, as it is
too complicated for the clerks to use properly.

So far so good. The Marantz is programmed to automatically record
worship services and the resulting MP3 is transferred to the server
immediately afterwards. The front panel controls are blocked so nobody
can mess with the machine. We will probably unblock them once we have an
audio team scheduled and, most of all, well trained. Manual operation is
rather simple once it's programmed right. Hit the record button and it
begins to spool audio onto MP3, later hit stop and that's it.

We do have some issues with the CAT-5 spitting out EMI into pastor's
wireless mike receiver (Shure Marcad) but that thing has problems with
just about any noise source. Light switches and such. The Sennheiser
receivers perform much better so some day we want to switch everything
to that system.

Before we make this permanent and stop backup tape recordings we will
have to clean up all the cabling. Holes are mostly drilled already,
cable trays are installed, and I cut the 19" rack to custom height. But
we don't want to risk a major hickup for the Christmas services so our
IT guy and I will tackle that job right after Christmas. Run cables
properly, install shielded CAT-5, some ferrites, spread audio and power
runs apart, ground everything. It is unbelievable but even high end
stuff like the Marantz recorder or the Sennheiser wireless does not have
ground terminals (%^#&!!). So I'll have to take the drill and some
self-tapping screws.

 

[Charlie E.]

So far so good. The Marantz is programmed to automatically record
worship services and the resulting MP3 is transferred to the server
immediately afterwards. The front panel controls are blocked so nobody
can mess with the machine. We will probably unblock them once we have an
audio team scheduled and, most of all, well trained. Manual operation is
rather simple once it's programmed right. Hit the record button and it
begins to spool audio onto MP3, later hit stop and that's it.

We do have some issues with the CAT-5 spitting out EMI into pastor's
wireless mike receiver (Shure Marcad) but that thing has problems with
just about any noise source. Light switches and such. The Sennheiser
receivers perform much better so some day we want to switch everything
to that system.

Before we make this permanent and stop backup tape recordings we will
have to clean up all the cabling. Holes are mostly drilled already,
cable trays are installed, and I cut the 19" rack to custom height. But
we don't want to risk a major hickup for the Christmas services so our
IT guy and I will tackle that job right after Christmas. Run cables
properly, install shielded CAT-5, some ferrites, spread audio and power
runs apart, ground everything. It is unbelievable but even high end
stuff like the Marantz recorder or the Sennheiser wireless does not have
ground terminals (%^#&!!). So I'll have to take the drill and some
self-tapping screws.

Thanks Jeorg!
What is the separation between the Marantz and those wireless
receivers? Same rack? All my Shure wireless are in the back, but the
recorder is in the front, so I shouldn't have any noise problems...

Charlei

 

[Joerg]

Thanks Jeorg!
What is the separation between the Marantz and those wireless
receivers? Same rack? All my Shure wireless are in the back, but the
recorder is in the front, so I shouldn't have any noise problems...

Yes, in the same rack, about 2ft from the diversity antennas to the
CAT-5 jack of the Marantz. If you guys ever need new mikes take a look
at Sennheiser. The only things too flimsy on those are the mute buttons.
Sennheiser said that pastors use those too often. Well, they advertized
them for worship use. Duh! Maybe more of their engineers should go to
church ...

 

[Joerg]

Is this perhaps because so few people would know what to do with a ground
terminal? I've read through the proper way of grounding using nice, wide,
low-inductance braid, but of all the "grounded" systems I've seen, many just
use something like 12ga. wires that are run many feet to some star ground...
and that sort of wire is already not that great of a "ground" by the time you
hit high HF, much less VHF or UHF.

True, but even 12AWG can work wonders on a crackling audio problem. As
long as you keep the run short, under 1ft or so. Now we have to drill
each and every one of the boxes, vacuum the burrs out, screw back
together. I guess that'll take all morning. It is also quite
disappointing that "high tech" gear comes with anodized aluminum panels
and 19" racks are powder-coated. The only method to get a decent ground
there is the Dremel tool and then it doesn't look good anymore.

 

[Joerg]

Joerg

mm, not sure about that Marantz, but I grounded my Chinese 10inch amp by using
the XLR input, ground pin (do not normally use that input).
So just plug in ground.
As you can see, those XLR are grounded real good (yellow green wire goes to case):
ftp://panteltje.com/pub/PA3000/xlr_rear.jpg

Well, we use that XLR jack and I don't have much faith these days that
the desiners knew how to route that peoperly on the inside. Nothing
beats a good old ground stud.

 

[Charlie E.]

Well, we use that XLR jack and I don't have much faith these days that
the desiners knew how to route that peoperly on the inside. Nothing
beats a good old ground stud.

Except, of course, when using the ground stud adds in ground loops
throughout the rack. Had that happen to me once in a big
installation. Ended up going through the entire rack and adding
insulation between the rack ears and the rack on each piece of
equipment... :-(

Charlie

 

[Joerg]

Except, of course, when using the ground stud adds in ground loops
throughout the rack. Had that happen to me once in a big
installation. Ended up going through the entire rack and adding
insulation between the rack ears and the rack on each piece of
equipment... :-(

That can quickly lead to a hazard. In that case I always go the iso xfmr
or DI route. Sometimes Radio Shack has decent audio transformers,
sometimes autoparts stores do, and if it has to be really good there is
MuxLab.

 

[Nico Coesel]

Before we make this permanent and stop backup tape recordings we will
have to clean up all the cabling. Holes are mostly drilled already,
cable trays are installed, and I cut the 19" rack to custom height. But
we don't want to risk a major hickup for the Christmas services so our
IT guy and I will tackle that job right after Christmas. Run cables
properly, install shielded CAT-5, some ferrites, spread audio and power
runs apart, ground everything. It is unbelievable but even high end
stuff like the Marantz recorder or the Sennheiser wireless does not have
ground terminals (%^#&!!). So I'll have to take the drill and some
self-tapping screws.

Proper audio equipment never has ground terminals to avoid ground
loops. At least that's what I've been told when working at a company
that did a lot of similar audio systems in churches. Usually the
amplifier was the only thing that was grounded.

 

[Nico Coesel]

Yes, in the same rack, about 2ft from the diversity antennas to the
CAT-5 jack of the Marantz. If you guys ever need new mikes take a look
at Sennheiser. The only things too flimsy on those are the mute buttons.
Sennheiser said that pastors use those too often. Well, they advertized
them for worship use. Duh! Maybe more of their engineers should go to
church ...

There are special mixer amplifiers that can use a microphone to mute
the pastor automatically when the organ plays. If I may promote one I
designed: http://sti.dma.nl/files/downloads/ZLV_2081-B_STI.pdf (in
Dutch).

 

[Charlie E.]

That can quickly lead to a hazard. In that case I always go the iso xfmr
or DI route. Sometimes Radio Shack has decent audio transformers,
sometimes autoparts stores do, and if it has to be really good there is
MuxLab.

Yeah, but problem occured when project had three racks, on in booth,
one stage left, one stage right, on at least two different phases,
plus various other equipment in other locations. We measured 1-3VDC
between the various portions of the same room's ground!

Charlie

 

[Joerg]

Yeah, but problem occured when project had three racks, on in booth,
one stage left, one stage right, on at least two different phases,
plus various other equipment in other locations. We measured 1-3VDC
between the various portions of the same room's ground!

Wow, that would be a good time to get to the ground of that. Since this
is probably a place of public jurisdiction a certified electrician
should be called. Before a current heats up a signal wire and something
catches fire.

 

[Joerg]

Proper audio equipment never has ground terminals to avoid ground
loops. At least that's what I've been told when working at a company
that did a lot of similar audio systems in churches. Usually the
amplifier was the only thing that was grounded.

That belief is IMHO founded on a lot of misconceptions. It is how
situations like this happen, to be exact it was last Saturday at 4:30pm
at our church: A women's choir used it for a public performance. They
had invited a tenor singer doing an a capella sans microphone. He's
obviously quite famous so photographers were there. One of them stood
next to the audio booth, fired off his camera .. brrrzzzzt ... *POCK*
.... rat-tat-tat ... phsssss. EMI straight into the ("professional")
audio gear, from the flash circuitry of his camera. So here's me doing a
mad dash from 3rd row to the back and turning down all slide pots,
hoping I'd remember how they were set for when the women's choir starts
again. Whew!

I sure wish audio engineers were taught at least a wee bit of RF
know-how. It would save us from a lot of grief. A ground terminal _is_
important. Here's another reason: Most racks are painted, and of course
nobody ever bothers to tape the threads. So is most gear. Now you screw
all this into the rack. Some of it makes contact, some not, other gear
maybe a little but only when there is a full moon. All depending on
chance. IMHO that is most certainly not a professional setup but,
unfortunately, a very common scenario.

Another test you can do: Take a GSM cell phone and turn it off. Walk up
to a running audio rack, then turn the phone back on and listen. You'd
be surprised how many audio engineers do not know that opamps with
bipolar inputs such as the nice low-noise NE5532 have parasitic RF
rectifiers right at the inputs, the BE junctions:

http://focus.ti.com/lit/ds/symlink/ne5532.pdf

Someone turns that big battery of fluorescents on, RF pulse comes along
.... *POCK*.

 

[Charlie E.]

Wow, that would be a good time to get to the ground of that. Since this
is probably a place of public jurisdiction a certified electrician
should be called. Before a current heats up a signal wire and something
catches fire.

It was at UCSB, and there was a lot going on, including inter-building
ties (video and audio) and you-name-it A/V. (Theatrical lighting,
sound board, video/data projection, movie projectors, slide
projectors...)

Easier just to insulate the racks...

Charlie