Getting a LOT of noise on FMX-20, possible problems?
- Thread starter OK&L Ent.
- Start date
JordanBlock
Well-known member
In general, Azden gear tends to be rather noisy.
Is there a way to reduce or eliminate the noise?
Steve House
Veteran
You said "noise when monitoring." Is the noise present on the tape or just in the headphones when monitoring?
Sorry I wasn't specific. It's for sure noticeably present on tape too.
SMuir
Well-known member
Commerical noise-removal plugins (eg. DINR, Soundsoap) and EQ can help manage the noise on a recording, but they almost always do so at the expense of quality and transparency. Another strategy is to manually or automatically "gate" the signal, so that the overall level drops between lines of dialogue. The down side of gating is that the noise may become more apparent every time someone starts talking. It may take a combination of noise reduction, EQ and gating to bring about a subtle improvement in the track.
Frankly, the most effective way to reduce noise is not to record it in the first place. Mic self-noise is pretty much unnavoidable (quantum mechanics and whatnot), but an innexpensive mic will generally have a pretty high noise-floor. The same goes for other components in the signal chain; cables, preamps, mixers, effects units, and A-D converters (not to mention headphone amplifiers) can all add noise to the signal. The trick is to select high-quality gear and use it in such a way that the noise is kept to a minimum, preferably burried deep in the track.
JordanBlock is quite right about Azden gear, but the mixer may not be weak link in your signal path. It would help if you provide more information about your recording gear (mic, camera, etc.)
Rode NTG-2 -> (Forgot Cable Brand, for some reason) 15 Ft XLR Cable wrapped around pole -> Azden FMX-20 Mixer w/ Headphones -> (Forgot Brand Again) 6 ft XLR Cable -> DVX-100B
Note: The set up works fine if I go just Rode -> 15 ft Cable -> DVX-100B or Rode -> 6ft XLR Cable -> DVX-100B
Steve House
Veteran
Sounds like you've identified your problem - what's out of the chain when it sounds good that's in the chain when it sounds bad (and cables don't count)? You get what you pay for.
JordanBlock
Well-known member
If the setup works fine without the Azden in the loop, it's pretty clear where the problem lies.
Are you using the same settings on the camcorder for both situations?
Going straight in with the Rode suggests that you're using the camcorder on the MIC setting.
Are you using the MIC setting while using the mixer?
You probably want to use the camcorder on the LINE setting when coming out of the Mixer. These types of mixers are designed to drive high output levels. So, the output stage amplifier has a corresponding noise level. If you turn down the master volume control to get the signal level so it works with the MIC input setting on the camcorder, then the signal is not high enough compared to the output stage noise. So, you get a poor signal-to-noise ratio. This would also be the case with the more expensive Sound Devices mixers.
There are mixers with output stages that are designed to interface with MIC level inputs on camcorders (primarily used with camcorders like the HV30, but can be used with camcorders like the DVX-100 to add additional XLR inputs):
http://www.juicedlink.com/index_files/CX_camcorder_XLR_microphone_adapter_audio_mixers.htm
Hope this helps you out ...
-R
I'm responding to you at 3 am on the East Coast, so I'mma try this when I get a chance during the day. Thanks for the info though!
I've got a MixPre, and I know that I can't take the line level XLR outputs into a mic level receiver without TONS of hiss (for the reasons above).
If my only option is a mic level receiver, then I need to use at least 30dB of attenuation between the MixPre and the receiver, so I can gain up in the MixPre to get the signal above the noise level its the output drivers.
I've never used the FMX-20. But, I think I would first try to use the equipment properly, before dropping coin on more expensive equipment (and getting the same poor result ... by still using the equipment improperly).
-R
If my only option is a mic level receiver, then I need to use at least 30dB of attenuation between the MixPre and the receiver, so I can gain up in the MixPre to get the signal above the noise level its the output drivers.
I've never used the FMX-20. But, I think I would first try to use the equipment properly, before dropping coin on more expensive equipment (and getting the same poor result ... by still using the equipment improperly).
-R
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You were completely right. After changing it to line, all noise was gone, it my sounds transparent now. Thank you so much!
These quotes aren't entirely accurate. They may work in practice, but it's really important to understand the reasoning (and the math) behind the practice.
First, mic-level signals and line-level signals are two completely different creatures that should never be intermingled from output to input. Line-level signals run a voltage of -10dBv (unbalanced/consumer) or +4dBv (balanced/professional). Mic-level signals run (+/-) -58dBv. That's a difference of nearly 60dBv. Now, some mic-level signals are slightly hotter, and a -50dB pad can convert a line-level signal to a workable mic-level signal.
Second, if you do run a line-level signal into a mic-level input, without in-line attenuation (a pad), and you compensate by driving the mixer's output at a barely-metered signal level, the noise is also coming from the camera's pre-amps as you have to bring the signal back up at the camera. That adds noise, and amplifies any noise coming from the mixer.
You also need to understand that there is no such thing as mic-level recording. A pre-amp's function is to bring mic-level signals up to line-level for proper recording. The signal is always line-level when it hits the tape. Period.
This all boils down to proper gain-staging. Every point along the signal chain that allows the user to adjust the level is a gain stage. The best option is to bring any mic signals up to line-level as early in the signal chain as possible. This is why mixers have pre-amps on the inputs. But if the signal gets hosed at any point in that chain, it cannot be fixed anywhere downstream. It has to be fixed at the same place where it was messed up. This would also be why we have tone generators and VU meters. Match your line-level outputs to the inputs, zero all the meters with tone, and you're unified. That will help avoid many issues with gain staging, since it calibrates almost all the stages in the chain to the same recording levels.
Know your gear, and always match line-level output to line-level input, and mic-level out to mic-level in. Yes, there are times when you may find yourself feeding a mic-level-only device. I keep in-line pads (XLR barrels) for that occasion.
And if you're working with wireless mic systems, know that most wireless systems add two gain stages to the chain: the transmitter and the receiver. Both usually have level adjustments, and both offer potential for the signal to over-modulate.
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With camcorder set to "manual" so camcorder preamp gain is fixed:
1) MixPre into mic level input on camcorder -> tons of noise
2) MixPre through 40dB pad into the same mic level input on camcorder -> clean
In case 2, you're going through the exact same camcorder preamps, set at the same gain level.
Case 2 is better because you've boosted the signal level inside the MixPre, so the signal level is high relative to the noise of the MixPre line output amps.
You're right. It's all proper gain staging. But that includes the various gain stages contained inside the mixer
-R
1) MixPre into mic level input on camcorder -> tons of noise
2) MixPre through 40dB pad into the same mic level input on camcorder -> clean
In case 2, you're going through the exact same camcorder preamps, set at the same gain level.
Case 2 is better because you've boosted the signal level inside the MixPre, so the signal level is high relative to the noise of the MixPre line output amps.
You're right. It's all proper gain staging. But that includes the various gain stages contained inside the mixer
-R
Isn't that pretty much what I said? Any point where you can adjust levels is a gain stage. That would include the mixer's inputs and outputs.
I never suggested that your setup was wrong, or that it wouldn't work. It's just that the reasoning behind it wasn't exactly on. I was merely clarifying the "why" to your "how." It's very helpful to understand the values of mic-level and line-level signals in order to think through the signal chain.
And potentially lots of over-modulation. The other risk involved in running line-level out to mic-level in is that you completely destroy your safety range. It's very easy to clip the signal when the levels are improperly mixed like this, since a line-level signal can (and usually will) overload the pre-amp's handling capacity.
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