Recording live with laptop - Buzz problem cause & Fix? (Ground or RF possibly)

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Hi,

I've been reading up on this here and cannot find the answer, so I'm
humbly asking for your help.
I play music in two bands and have been making successful (decent =
listenable; not great by any means) recordings for us to listen to
using two mics for a room sound. It works fine and has fullfilled our
primary purpose thus far, which was just to hear how we sounded for
our own private improvements. We also used some of the recordings for
demos, but they're nowhere near as nice as I'd like for public
listening and its time for us to get a website...not to mention a
Radio DJ at one of our gigs asked me for a demo to play on his show.


So now that I've establised that I'd like to start making some better
quality live recordings, I'm going to tell you how I've already been
trying to do so (with mixed results). That is, I've decided to try
and also get a single channel mono board feed to mix with the room
mics to fill in some sonic gaps. Shouldn't be a huge deal, right?

Well, I know its possible with my rig because I made a pretty nice
recording with my simple system (stereo room mics + board matrix) at a
gig where the soundman gave me an XLR board feed. It was super easy -
I made sure the signal from the board wasnt too hot (while the drummer
was playing kick & snare) and started with that. I did have to ask
him to lower the level quite a bit before I got a useable signal.
THen, I just added in the two XRL cables from the mics (panned left
and right) and mixed them into the board line until it sounded good.
Unfortunately, I haven't been able to duplicate this on my own at
other venues.

Here's my extrememly simple recording rig for getting a live room
sound:

Yamaha MG 10/2 mixer
(2) C1000 room condenser mics
laptop computer
Audacity software


I usually just get a mix of the drums or bass/ drums together to make
sure things wont get too loud, and then hit record to get one long
track for each set we play (which I save after and start with a fresh
track next set). I break apart the songs and edit at home if needed,
but since I'm playing in the band I can't really mix anything there -
just basically taking a print as I heard Monty say.

So here's the problem. I've tried mixing in the board feed again
exact same way on numerous occasions and I almost always get a buzz
entered into the mix along with the instruments from the board feed.
I tried to work with this by mixing the room mics higher and turning
down the board feed figuring I would still get a crispier drums and
vocals from the board. Upon listening back, its really too bad
though...the background buzz eventually renders the music
unlistenable. So I've gone back to making just room mic recordings,
which are fine, but not good enough.
This is frustrating, becuase I know what this little system is capable
of having gotten the good show - but I simply can't get it...


On some of the smaller gigs where we run our own sound I use a Yamaha
Mg 16/6 that I've tried to get a board feed from to mix into the
Yamaha MG 10/2 room mics setup, with zero success. I've tried this at
three different places, (all bars so it could be ground issue as one
has only one outlet to run everything or RF signals with neon sign
interference) and using different approaches from the Yamaha 16/6.

I've tried getting the feed from an Aux out via 1/4" to 1/4"
instrument cable (which would be ideal because I could send a low
enough signal for each instrument channel not to overpower anything),
from the "record out" RCA out (RCA - 1/8 inch with 1/4 inch
connector), and I've even tried to take the feed from the headphones
out. Nothing, always get overwhelming humdrum buzzing.

There have also been occasions where I've tried to get a board feed
from our regular soundman at larger gigs (another musician who just
happens to have better gear and larger setup, but not necessarily a
knowledgeable engineer) but this has also given me the buzz that I've
grown to hate. And at different places with his same gear and various
methods as well. First I tried just taking an XLR-XLR feed from the
left main out while he mixed the show in mono from the right main
out. No go. Headphones out...nothing better. Also tried taking
direct outs from each channel (via 1/4 - 1/4 instrument cables) of his
board to my Yamaha 16/6 Insert I/O inputs, which I then sent a XLR
feed from to the little MG 10.

Not sure what else to do. I've tried doing different outlets when
possible, but if it is a ground issue I dont even know if its being
caused by soundmans board/ equipment, my little mixing board or other
equipment, or by someones amplifier. Could even be a cell phone thing
I've read, but its happened too many times now in different
circumstances for it to be coincidence. I've also been looking at
various possible gadgets like this one, but even then, which device is
causing the problem and do I need 3 or 4 of these converter plugs?

http://www.swee****er.com/store/detail/HumX/



I'm wondering how to fix this. Any ideas would be appreciated!


gratiously yours,



Dan

[DeeAa]

> wrote in message
oups.com...

> I'm wondering how to fix this. Any ideas would be appreciated!
>
Have you tried doing it so that you'd just use the mixer as usual, but also
put the room mics onto it - without sending the signal from those to the
mains.

Then you can adjust the room sound and send it to one of the AUX busses, and
also mix in each channel's signals via the same bus, just by sending them to
that same AUX bus as well in addition to the mains mix.

I'm not sure how many auxes you can run but I'd venture even a small mixer
would have a mains outlet, at least one FX bus and another AUX bus to run
the monitors or something. That you could use for recording, but if you need
monitor auxes, then u need a bigger board in the first place...but anyway, I
wouldn't use two mixers to do it, because just one will do fine?

[Richard Crowley]

> wrote ...
> Not sure what else to do. I've tried doing different outlets when
> possible, but if it is a ground issue I dont even know if its being
> caused by soundmans board/ equipment, my little mixing board or other
> equipment, or by someones amplifier. Could even be a cell phone thing
> I've read, but its happened too many times now in different
> circumstances for it to be coincidence. I've also been looking at
> various possible gadgets like this one, but even then, which device is
> causing the problem and do I need 3 or 4 of these converter plugs?
>
> http://www.swee****er.com/store/detail/HumX/

You can try it. Especially if they will take it back if it
doesn't work. Not clear what is inside that thing.
The very thing that is required for safety (a hard-
connected green-wire ground) is the same thing
that is frequently the source of ground loops.

> I'm wondering how to fix this. Any ideas would be appreciated!

Not clear if you are running your laptop on internal
batteries or using an AC adapter? First thing I would
do is to try it on batteries to see if the AC adapter is
contributing anything. I have found the AC brick to be
a significant source of hum/buzz when trying to use my
laptop even for playback connection to any other line-
powered equipment.

If you can reproduce the problem "at home" with your
mixer, etc. then you have the laboratory setup you need
to go step by step and find out exactly which connection
will affect the noise.

I may have missed some details in your lengthy narration.
Might be better to stick to the technical details and leave
the narrative about your band to some other forum.

Note also that posting a few seconds of sample WAV or
MP3 online somewhere would allow us to hear the noise
for better diagnosis.

[Scott Dorsey]

> wrote:
>So here's the problem. I've tried mixing in the board feed again
>exact same way on numerous occasions and I almost always get a buzz
>entered into the mix along with the instruments from the board feed.
>I tried to work with this by mixing the room mics higher and turning
>down the board feed figuring I would still get a crispier drums and
>vocals from the board. Upon listening back, its really too bad
>though...the background buzz eventually renders the music
>unlistenable. So I've gone back to making just room mic recordings,
>which are fine, but not good enough.

You have a grounding issue. Get a transformer isolation box, and put
it between your system and the other guy's system. This will allow you
to break the signal grounds safely and cleanly and it will prevent finger
pointing about who is responsible for what noise where.

There is a good introduction to ground loops and grounding in the FAQ.

The Ebtech Hum Eliminator is an okay cheap transformer box. Jensen makes
some much better ones that are more expensive. You can make your own with
a 600:600 transformer and some XLR connectors in a Bud box.
--scott

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