"Frank Gilliland" wrote in message
...
On Thu, 28 Apr 2005 09:11:08 -0500, "Chad Wahls"
wrote in :


"Frank Gilliland" wrote in message
. ..
On Wed, 27 Apr 2005 10:22:40 -0500, "Chad Wahls"
wrote in :

snip
Most often, even wahat you consider "high end" cards do not have the
audio
sheild grounded properly.


Very good point. Some cards have shield connectors that are DC
isolated from the chassis to prevent ground loops with other audio
equipment. In such cards the shield is coupled to chassis ground with
caps, but line noise can be a problem (and the cap must be shorted)
because the caps may not large enough to fully shunt low frequencies.
But the caps do shunt RF very well, and if they can keep the local AM
broadcast stations out of the soundcard then the neighbor's legal CB
radio shouldn't be a problem.




Problem is that they don't do all that well with AM Broadcast. When I was
a
conglomo radio engineer we had a 50K FM and a 500W AM in a residential
area.
I would get complaints-o-plenty of the AM coming thru computer speakers,
cheapo HT systems and phones.


Sounds like we had similar jobs -- do the daily checks, fill out the
daily reports, then spend the rest of the day making cables, cleaning
cart machines and waiting for something to break?


And spring storms... Arrrgh. Had a ground come loose once and I got the
page "Chad oldie's console is on fire!"

That was the worst electrical storm I have ever seen, My tower got hit 53
times in one day. I went thru an ass load of OpAmps that day! I was
actually second in command, the CE was corporate, so, often in the spring
and summer he was off building stations which put me in charge. It was a
great relationship as the Engineering dept was least hasseled and my "boss"
the CE and I are best friends.

I'm still over there helping out from time to time. BEs are like farmers,
always willing to help each other out, I like that!


Of course we had to do what we could to
eliminate the problem and usually I would pull the sound card, DC ground
it
with 1 ohm 1/4W resistors and the problem went away. 90% of my problems
called in were ratified with proper grounding. Fortunately most of the
construction in the area is newer as that tower used to be outside city
limits but due to urban sprawl it is no longer.

As for my personal soundcards I use pro models with a separate breakout
box
that's balanced. The other card in that computer and other computers in
the
house are SB audigy models with the mini jacks removed and XLR whips out
in
their place. This whip then goes to a breakout box with 6 Jensen
transformers in it 4 for output and 2 for input. The mic input is shorted
down permanently. I have zero noise problems, if you have an Audigy card
it
does sound good! You just have to help it out


I use the Extigy -- it's great because you can locate the box some
distance away from the noisy computer and ground it directly to the
mixer.


Yeah, those are great consumer cards! I went with the original audigy
because they were dirt cheap at the time and sound good. My big sound card
for my mastering system is a MOTU 828mkII. I love it! I recently bought it
to upgrade an old Echo LAYLA, still nice but I wanted firewire.

But for complaints to the station, I got them to order a huge box of
4" jumpers that have pigtails to the shield. Just plug them into the
soundcard (or whatever audio equipment is getting the interference),
screw the pigtail to the chassis, and 'presto' -- problem solved. No
invasive surgery, and you're out of the house in a matter of minutes.


Unfortunately I was across the street from the local community college, so
the surrounding apartments had a lot of student housing. The kids would go
home for the summer and convieninetly loose the jumpers. I had some too
(jumpers) and would use them for the more established residents but for the
kids I would do the solder in to keep from having to come back. I got
pretty quick with it so I could be in and out fast. Took longer to explain
what I was going to do than do it


The transformers....... When radio engineering and upgrading EAS systems
in
all the stations I found that all the old receivers that we were throwing
out were loaded with Jensen transformers! What a salvage find!!!!!


No kidding!


I had
many-o-dumpster diving missions, then adopted a Chad's gotta pilfer it
pile.
Lots of transformers and power supplies were gutted


Those old Bogen and Rauland paging amps have some pretty sweet
transformers, too. One of these days we gotta exchange inventory lists
of our scrounge bins.

My bins are slowly deteriorating as I've been out of the loop a while but I
have another build this summer I said I would help on After that I should
be back in action for a while!

My best find was 3 Invonics AM broadcast processors I think they are
LVP201's. I was a touring sound engineer and I used one for lead vocal and 2
for squashing the drums. I would have the drums on a VCA and then send them
to the "loud drums subgroup" for discretionary use. This would make the
drums "louder" without chewing up subwoofers. Great for a drum solo and
what it did for vocals was amazing. I got some pretty funny looks from
other engineers on the road though

I sold two of them to a local studio and now have one at home on my.... u
guessed it.... CB Talk about loud audio, screw swing, I have NO swing,
the way it should be

I got those units from a dumpster because they had LED's burnt out, HA!

Chad