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Old January 19th, 2005, 04:22 PM   #1
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Mixing internal mic with external mic?

I have an AT4073a + Beachtek DXA-6 + Panasonic PV-DV953. Is it possible to record both mics simultaneously?

My attempts at trying the various settings on my DXA-6 have ended in failure. When I use the mono setting the right channel is dead. When I use the stereo setting the channels are identical.

Secondly, how do I do the attenuation trick? I want the second channel to be an attenuated copy of the first. The knob seems to have no effect.
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Old January 19th, 2005, 05:20 PM   #2
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You can't as far as I know, use both the internal and external mics at the same time on that camera. That's typical of any mini-jack camera.
Your description of the Mono versus Stereo switch is backwards from the way it's supposed to work. Either your BeachTek is defective or you're describing the situation incorrectly. The mono switch position should route both inputs to both outputs. This is typically used to send a single mono mic (like your 4073a) to both output channels equally. It would also allow you to, for example, send two lavs to both outputs equally so that both people would be "centered" without having to do any post-production on the tape.
The stereo switch position keeps each input routed only to the matching output. You use this to keep two sources separated to their individual channels. It can't create stereo out of a mono signal, it simply enables the recording of a stereo (or two channel mono) signal from two individual mic elements.
You can't do the attenuation trick with this setup either. You have to have individual control of the two channels. I don't think you have that on the 953 and the Beachtek won't allow it either since the two inputs are being mixed when in mono mode. This mixes the effect of the two pots too, so you can't control them individually.
Do you have a newer DXA-6 with phantom on both channels or the older version that only has one phantom channel?
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Old January 19th, 2005, 05:25 PM   #3
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I have the new one. I will check whether I described the mono/stereo behavior correctly.
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Old January 19th, 2005, 08:20 PM   #4
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Emre, with the cam you have I don't think it is possible!
The moment you plug in external mic or the Beachtek you disable the internal mic.
You can mix onboard mic of the sort of higher end cams (where the mic is conected to a mic input on the cam).
In your case you just need one more cheap exteranl mic (equal or better to the internal) and rout it to the second channle of the DXA-6.
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Old January 21st, 2005, 07:49 AM   #5
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Re: Mixing internal mic with external mic?

<<<-- Originally posted by Emre Safak : I have an AT4073a + Beachtek DXA-6 + Panasonic PV-DV953. Is it possible to record both mics simultaneously?

My attempts at trying the various settings on my DXA-6 have ended in failure. When I use the mono setting the right channel is dead. When I use the stereo setting the channels are identical.

Secondly, how do I do the attenuation trick? I want the second channel to be an attenuated copy of the first. The knob seems to have no effect. -->>>

What trick? To protect from overload? This is sort of a pet peeve for me. Why not just use a mixer with a good limiter so you don't have to do that?

Regards,

Ty Ford
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Old January 21st, 2005, 06:21 PM   #6
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Re: Re: Mixing internal mic with external mic?

<<<What trick? To protect from overload? This is sort of a pet peeve for me. Why not just use a mixer with a good limiter so you don't have to do that? -->>>

Well... my reasoning is that I have to record in stereo anyway, but I am only using one channel, so why not do something useful with the second?
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Old January 21st, 2005, 06:54 PM   #7
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This Y cable together with your BeachTek in stereo mode will allow you to record the same mic in the two channels at different levels.

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=134134&is=REG
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Old January 21st, 2005, 07:47 PM   #8
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Except it's a phantom powered mic and he has the dual-phantom version of the DXA-6. At the minimum he'd have to cut Pin 1 on one of the male ends of the Y (or use an inline ground-lifter if the Y is long enough to allow this additional length on one side).
Then you'd still have to test to make sure the DXA-6 isn't getting some kind of bad reaction or leakage with the phantom power that's present but hopefully not flowing into the input where pin 1 was lifted.
If all that worked out, then that would be the way to get differential control.
If he was using a mic with an internal battery, or he put an external phantom supply between the mic and the Y, then all would be well without having to lift any pins of the XLR's.
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Old January 21st, 2005, 08:30 PM   #9
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Are you sure, Jay? I can't visualize any DC short circuits or any other circuitry problems with powering the mic from one of the channels through the unaltered adaptor and listening to the mic with both. Why cut a wire? If there were any power leakage path, say through a reverse biased rectifier diode in the unpowered channel, it would be miniscule, and even that could be eliminated by turning phantom on in both channels.
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Old January 22nd, 2005, 02:10 PM   #10
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Y cable okay with phantom power from DXA-6

To set the record straight I checked with Harry Kaufmann at BeachTek. He agrees that there is no problem phantom powering a single mic through a Y adaptor that applies the signal to both channels. You can turn on one channel's phantom power or both, but he thinks you may use slightly less power if you just turn on one.

He also thinks it's a very wise practice to record the same signal at two levels about -20 dB apart.
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Old January 22nd, 2005, 03:01 PM   #11
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Re: Y cable okay with phantom power from DXA-6

<<<-- Originally posted by Fred Retread : To set the record straight I checked with Harry Kaufmann at BeachTek. He agrees that there is no problem phantom powering a single mic through a Y adaptor that applies the signal to both channels. You can turn on one channel's phantom power or both, but he thinks you may use slightly less power if you just turn on one.

He also thinks it's a very wise practice to record the same signal at two levels about -20 dB apart. -->>>

Huh?

First off, using a Y connector for mics is NOT a good idea because of the way in which a mic matches with the input impedance of the preamp. Throwing two mics (presumably in parallel) across a mic input that is expecting a signal at at a certain level and impedance (and not getting it) is asking for trouble.

20 dB difference? Why would you want to do that? One signal would be down in the noise floor. If you pay attention to setting good levels in the first place, or use a professional mixer with a good limiter, you don't have to play safe and end up with more noise than you wanted.

The difficulty phantom powering two mics with y connectors is still there and iffy. Also, please remember that some mics require a full 48 V DC phantom with a good current, while other work with less.

Concernedly,

Ty Ford
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Old January 22nd, 2005, 03:42 PM   #12
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Oops, I didn't realize there were two phantom switches on the new DXA-6. I thought there was no choice but to have phantom power on for both channels with a single switch. Yes, if you can activate just one of the channel's phantom power circuits using a switch for each one, then you should be okay.
Ty, in this case he wanted to split a single mic to two input channels, which still isn't a great idea, but shouldn't be much of a problem using the AT4073a.
I do agree that a 20db difference is way too much. Between 4 and 8 db depending on how wide the dynamics are is what I use if I have to do this.
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Old January 22nd, 2005, 04:24 PM   #13
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Re: Re: Y cable okay with phantom power from DXA-6

Replies to comments originally posted by Ty Ford :

Huh?

First off, using a Y connector for mics is NOT a good idea because of the way in which a mic matches with the input impedance of the preamp.....
Not an issue according to the manufacturer, who recommends the hookup. Incidentally, no preamp in the DXA-6

....Throwing two mics (presumably in parallel) across a mic input that is expecting a signal at at a certain level and impedance (and not getting it) is asking for trouble....
Not two mics to one input, rather one mic to two inputs. Again, the idea is endorsed by the manufacturer of those inputs.

....20 dB difference? Why would you want to do that? One signal would be down in the noise floor....
Because the noise would probably sound better than clipping. Nice to have available in post.

...If you pay attention to setting good levels in the first place...
Sometimes there isn't a good level for a huge source dynamic range. Avoid clipping, get noise. Avoid noise, get clipping.

...or use a professional mixer with a good limiter...
There's the ticket, IF you can afford the equipment.

.. you don't have to play safe and end up with more noise than you wanted...
If you can't afford a pro mixer, this technique at least allows you to set a level high enough for low noise and then fix loud passages in post

...The difficulty phantom powering two mics with y connectors is still there and iffy...
Again, not trying to do that.

...Also, please remember that some mics require a full 48 V DC phantom with a good current, while other work with less.
Emre's mic will get the full 48V and current.


Your points are all well taken, they just don't completely mesh with the thread.
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Old January 22nd, 2005, 04:31 PM   #14
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Yeah, 20 dB does sound like a lot, now that you mention it.
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Old January 22nd, 2005, 05:38 PM   #15
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Re: Re: Re: Y cable okay with phantom power from DXA-6

<<<-- Originally posted by Fred Retread : Replies to comments originally posted by Ty Ford :

Huh?

First off, using a Y connector for mics is NOT a good idea because of the way in which a mic matches with the input impedance of the preamp.....
Not an issue according to the manufacturer, who recommends the hookup. Incidentally, no preamp in the DXA-6

++It's still an input stage and it has impedance characteristics. Well I guess if the single mic cords that bridge two inputs will work, this may as well. Guesss I missed the original drift.

....Throwing two mics (presumably in parallel) across a mic input that is expecting a signal at at a certain level and impedance (and not getting it) is asking for trouble....
Not two mics to one input, rather one mic to two inputs. Again, the idea is endorsed by the manufacturer of those inputs.

++One mic to two inputs -- right, better...as above. I missed that.

....20 dB difference? Why would you want to do that? One signal would be down in the noise floor....
Because the noise would probably sound better than clipping. Nice to have available in post.

++A signal 20 dB in the noise floor sounds horrid. When you normalize it or raise it's gain in any way, the noise comes right up with it. I've done it with 5dB as a precaution on my DAT machine. In fact, the Panasonic DAT machine defaults to a staggered level in one mode, but not 20 dB.

...If you pay attention to setting good levels in the first place...
Sometimes there isn't a good level for a huge source dynamic range. Avoid clipping, get noise. Avoid noise, get clipping.

...or use a professional mixer with a good limiter...
There's the ticket, IF you can afford the equipment.

+++There are many advantages to investing in a good mixer in addition to those things discussed in this post.

.. you don't have to play safe and end up with more noise than you wanted...
If you can't afford a pro mixer, this technique at least allows you to set a level high enough for low noise and then fix loud passages in post

++ as long as you have no hopes for it to sound seamless, because using that -20 dB track section pumped up is going to be quite a bit noisier.

Your points are all well taken, they just don't completely mesh with the thread. -->>>

Perspective is a funny thing isn't it?

Smiles,

Ty Ford
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