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Old August 24th, 2005, 04:09 PM   #31
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Glad I could help.

Does anyone know for certain what the output of the mixer is? The spec sheet says electrically balanced. The block diagram appears to be impedance balanced but doesn't really show a resistor. If it is impedance balanced it can work fine into a balanced input and still reject noise.

Sam
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Old August 24th, 2005, 04:25 PM   #32
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Jeremy, thanks for the mp3. This is *very* close to the noises I have.

I do have one program - Soundsoap that I've use for occasional cleanup. Simple and easy to use. I've mostly used it for rumble, never for specific higher frequencies... Worth a try. Otherwise re-recording a couple of lines is easy.

Fred (and Sam) - Thanks for the clarification. Looks like the problem is inherent to the equipment. It'll be interesting to do some testing with different equipment configurations.

In the article he mentions a connector by Neutrik that eliminates this problem, even when there is a Pin 1 error. A google search pulls up dozens of Neutrik connectors. Just curious if anyone has used one of these and if it actually works.

Sam also said,
"Transformer inputs like Beachtech uses helps also."

So would this confirm what others here have said about running from the mixer into the Beachtek into the camera or is this suggesting a different setup altogether?

It's also good to know we're talking about 6' to 10' of interference. That's definitely workable with the equipment at hand for the short term.
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Old August 24th, 2005, 05:20 PM   #33
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The problem appears to be in the mixer so anything after the mixer does not help. If you have to leave phones on in the room either get a phantom power supply to go between the mic and the DXA-2 or get a DXA-6. If the phones can be turned off you can probably get by using the mixer into the DXA-2. That way you are balanced until just before the camera.

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Old August 24th, 2005, 06:00 PM   #34
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Thanks! Sounds good.
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Old August 24th, 2005, 06:57 PM   #35
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Patrick, Sam and I are looking at different units. Is yours the UB802 or the MX802A (or something else)?
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Old August 24th, 2005, 07:22 PM   #36
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It's the Eurotrack UB802 (cheap job - $100 retail).
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Old August 24th, 2005, 08:00 PM   #37
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Ah, that's what I suspected. The spec sheet and manual for that one, as I said earlier say that the main outs are not balanced. Yet the spec sheet does say that it is a TRS jack, impying impedance balancing. Another call to that support guy might be in order. As of now, to me all four are suspects--the mic, the mixer, the unbalanced run and the cam.

The mixer can be eliminated, as we've learned, by directly grounding the input and output cables to the housing (if they are not already).

I've queried Audio Techica as to the wiring of the AT3031 (I have two of these myself) vis-a-vis the pin 1 error. I'll let you know what they said tomorrow. I'm also going to experiment with my AT3031s and my cell phones.

If the first two are eliminated and the problem persists, the unbalanced run can be addressed several ways.
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Old August 24th, 2005, 08:04 PM   #38
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The UB802 was the first one I looked at. The users manual says electronically balanced. I take that to mean a balanced differential output. The spec sheet says unbalanced. The block diagram looks unbalanced. Who knows?

Sam
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Old August 24th, 2005, 08:15 PM   #39
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Where does it say electrically balanced? Page 7 of the manual says the mains are unbalanced. Clearly Patrick needs to talk to them again if he wants to find out what the story is.
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Old August 24th, 2005, 08:54 PM   #40
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Hey Fred,
We got to be looking at two different things. I was looking at page 9 of the UB802 Users Manual.

Sam
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Old August 24th, 2005, 11:24 PM   #41
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Interesting...

I see exactly what you guys are talking about. Page 7 says unbalanced. Page 9 says balanced, and the block diagram... well I have no idea how to read that.

Just to make sure I'm on the same page here I've highlighted the offending sections of the manual (Page 7, Page 9 and a scan of the Block Diagram - which I think is easier to read than the PDF)

http://www.cheezwhiz.org/Behringer%20UB802

If it is indeed using unbalanced MONO outs, am I right to think adding the DXA-2 to the equation would have no significant benefit? I mean if it's unbalanced at the MAIN OUT, the unbalanced signal would just sail away until it hit another set of circuits (DXA-2) to run through, only to come out just as unbalanced as before on the other end?

Is it common for cheapo mixers like this to use unbalanced main outs like this? It seems a little weird that a mixer of any kind would do this.
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Old August 25th, 2005, 09:01 AM   #42
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If it turns out the Behringer main outs are truly unbalanced, then the main advantage to putting the BeachTek between the mixer and the camera would be allowing you to use easily obtainable better shielded cables with more durable connectors for longer runs or moving the camera around.
This specific case wouldn't really benefit from this, but for other people's activities using a BeachTek with an 1/8-inch jack camera does offer that physical advantage even with unbalanced signals.
You may also gain some protection from ground loop hums since the Beach has transformers and two-position grounding switches, but this is highly dependent on the specific camera and what you're hooking to it (especially AC-powered video monitors).
In addition, you could use the EDB-1 or the Ebtech Hum Eliminator to make the signal balanced using a short cable from the Behringer. Then send the balanced signal to the BeachTek and camera.
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Old August 25th, 2005, 09:23 AM   #43
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Awesome, thanks. The EDB-1 is about half the price of the Ebtech. They both look like they do the same thing. Is it just a case of you get what you pay for or are they essentially the same thing?
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Old August 25th, 2005, 01:50 PM   #44
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They perform vastly different functions but use similar passive circuitry.
They can both create a balanced signal from an unbalanced one and that would be their function in this example.
The EDB-1 also provides attenuation of 20 (full time), or switchable 40 or 60db. It's a single channel device whose main purpose is to take a hot unbalanced signal and turn it into the equivalent of a balanced mic signal. It's called a "Direct Box" because its original use was to record an electric guitar or guitar amp output directly into a mic input on a mixer, but they are inexpensive and very handy for lots of other functions.
The Ebtech Hum Eliminator has two channels and can use balanced or unbalanced connections in any combination. It doesn't change the signal level. Its primary purpose is to eliminate ground loop hums, but I use mine primarily for making a long balanced run to a DSR-45 DVCAM deck that uses unbalanced inputs. Since this deck is plugged into AC power some distance from my mixer, it could also have a ground loop hum but that's taken care of automatically so I don't have to worry about it.
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Old August 25th, 2005, 02:26 PM   #45
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Thanks again.
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