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safety track with attenuators

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Eric Hansen
safety track with attenuators
on Mar 1, 2010 at 5:03:59 pm

i have a Zoom H4n and i would like to record a mic (either boom or wireless lav) to track 1 at a normal level and track 2 (or 3 or 4) at a reduced level as a safety track. the Zoom won't let you redirect a single input to 2 tracks with 2 different levels like most camcorders though. a few months ago i used it to record a boom mic and the output of the mic was too low, so i'm looking to add something like the Sound Devices Mixpre or MP-1 to get a good level into the H4n with low noise. so here's what i'm thinking:

mic to MP-1 (or Mixpre)
output split to 2 XLRs
one XLR goes to track 1
second XLR goes through attenuator and then into track 2 (or 3 or 4)

can i split an XLR signal like this? is it now line level coming out of the SD? how much attenuation should i use? i would like to ride the levels to keep track 1 in the sweet spot, but then have the safety track available in case something loud happens that i can't control. has anyone used tracks 3 and 4 on the Zoom? i would have to get an adapter to use the 1/8" TRS for tracks 3 and 4 on the Zoom, but i think it should work.

thanks guys

e

Eric Hansen - The Audio Visual Plumber - http://www.avplumber.com


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Jon Goodman
Re: safety track with attenuators
on Mar 2, 2010 at 12:56:11 pm

Hi Eric. I run a zoom H4N in my bar with a SD 302 as a back up recorder. I found that the line in is not a +4 dbu level and needs padding. I found some variable pads that work well for me made by Rapco. cvpblox variable pad blox. Here's a link. http://www.rapcohorizon.com/products/devices/blox/Default.aspx
Hope this helps.
Jon


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Rodney Morris
Re: safety track with attenuators
on Mar 3, 2010 at 11:18:41 pm

If you use the MixPre, then you will plug the mic into one of the input channels and set the pan for that input to center. This will give you an output on both the L and R XLR outputs of the mixer, no need for a split. However you want to pad the outputs of the mixer is up to you, but understand that the line input on the Zoom is on the 1/4" connector, not the XLR (at least that's the case with the H4, not positive about the H4n). So you could put line to mic attenuators on the the XLR and record on the mic level, XLR inputs of the H4 or you could pad the outputs of the MixPre with simple line level attenuators and adaptors/cables to turn the XLRs into 1/4". The H4 allows you to set levels on the inputs independently. In other words you can set Ch. 1 of the H4 at one level and then set Ch. 2 at a higher/lower level in increments of 1 db. This is accomplished through one of the input menus of the recorder.

I use my H4 for lots of recordings using the mic level XLR inputs. I use it with my SD 442 and set the outputs to mic level. Yes I know I'm using the mic pres on both units, but for the stuff I'm recording you'll never hear the difference. When I try to pad/adapt my way into the line level inputs of the H4, I always run into problems (adapters not fitting properly).

Hope this helps.

Freelance Sound Technician/Mixer


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Ty Ford
Re: safety track with attenuators
on Mar 4, 2010 at 12:51:08 pm

Jon, Rodney,

Aa always, thanks for being here with your thoughtful posts and deep experience. About the line level inputs of the H4; do you suspect they are -10 consumer line level rather than 0 dB line level?

I've run into this with some gear and have found, fortunately, that my Sound Devices 442 mixer has three outputs levels, mic, -10 and pro line. That -10 has saves my butt on more than one occasion.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Rodney Morris
Re: safety track with attenuators
on Mar 4, 2010 at 2:48:12 pm

According to the specs on the H4n from their website:

unbalanced input = +2 to -32dBm

I would go with a -10 db setup on the 442.

As for the MixPre, your best bet is to pad the outputs with line level attenuators (from memory, I think the Shure attenuator has switches for -10, -15 and -20) and use female XLR to male mono 1/4" adapter cables to go into the line level inputs of the H4n.

Freelance Sound Technician/Mixer


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Eric Hansen
Re: safety track with attenuators
on Mar 4, 2010 at 4:11:29 pm

thanks for all your help guys

Rodney wrote: The H4 allows you to set levels on the inputs independently

this might be an area where the H4n and H4 differ. in Stereo mode, the Zoom doesn't allow you to change the levels of the channels independently. in 4 channel mode, you still can't adjust the levels independently, but you can go into the Mixer and adjust the pan. so if i use 4 channel mode, i'm gonna end up recording 2 blank tracks (3 and 4) and end up with half the card space. i don't know if i'm missing something, but this is what i'm seeing.

i saw this in the manual -

Inputs
INPUT [1] [2]
XLR (balanced input) / standard phone (unbalanced input) combo jack
Input impedance
(using balanced input) 1 kΩ balanced, pin 2 hot
(using unbalanced input) 480 kΩ unbalanced
Input level
(using balanced input) −10 dBm _ −42 dBm
(using unbalanced input) +2 dBm _ −32 dBm


so i guess it's not an XLR/TRS combo jack like i thought.

Rodney wrote: If you use the MixPre, then you will plug the mic into one of the input channels and set the pan for that input to center. This will give you an output on both the L and R XLR outputs of the mixer, no need for a split.

my thinking was i didn't want to use a MixPre for just one channel, since its a 2 channel mixer. if i have one microphone and want 2 XLR outs, it would be half as much money to get a MP-1 with a splitter. i was thinking MixPre so i could have 2 sources and split them out to 4 tracks, if this is even possible.

Rodney wrote: I use my H4 for lots of recordings using the mic level XLR inputs. I use it with my SD 442 and set the outputs to mic level. Yes I know I'm using the mic pres on both units, but for the stuff I'm recording you'll never hear the difference

so with the Zoom and SD mixer, this is the setup that you would recommend? when would you not recommend this?

Rodney wrote: As for the MixPre, your best bet is to pad the outputs with line level attenuators (from memory, I think the Shure attenuator has switches for -10, -15 and -20) and use female XLR to male mono 1/4" adapter cables to go into the line level inputs of the H4n.

so this is to bring the high line level of the MixPre down to the consumer line level of the 1/4" unbalanced inputs on the H4n? I'm sorry if this question seems obvious, i always get confused by the different audio levels

one final question: the H4n has a 1/8" stereo mic input for channels 3 and 4 which take over from the built-in microphones. has anyone tried to use this input? i'm wondering if i can use this as tracks 3 and 4 from a mixer, using something as simple as a stereo RCA to 1/8" cable. here are the specs from the manual:

EXT MIC Input impedance  2 kΩ
Input level  −7 dBm _ −47 dBm

i wonder how clean it would be. i looks like i would have to have the mixer outs set to Mic level. but is the impedance too high?

thanks

e

Eric Hansen - http://www.erichansen.tv


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Rodney Morris
Re: safety track with attenuators
on Mar 4, 2010 at 10:24:34 pm

There has to be a way of adjusting the levels independently of each other. That would be a major oversight.

I downloaded the manual for the H4n and looked up setting the levels. When the unit is recording in Stereo mode (2 recording tracks), you should have the inputs set as mono inputs (in the MTR menu). If you have the inputs set as stereo inputs, then I could see how you might not have independent level control. Again, double check to make sure in the MTR menu that you have not selected stereo inputs. (Page 048 of the manual).

Your H4n unit does indeed have the XLR-1/4" combo jack. The balanced input is the XLR and the unbalanced input is the 1/4", thus the differing levels in the specs.

Using the MixPre to output two source mics into 4 tracks will be a mess of adapters/splitters/pads. It can be done, but it won't be pretty, nor would it be ideal.

Yes, the attenuator pads on the outputs of the MixPre would bring the level down from +4 dB to the range which the recorder wants to see.

I use the SD and H4 combo because that's what I have. Yes there are better recorders on the market, but I initially bought the H4 for transcription purposes. I used to record to a mobile ProTools unit (Mbox2), but I get similar results with the H4 and it's much more mobile. I've used it to record audio for many purposes - from radio spots, tv voiceovers, to audio for greeting cards (Hallmark). It's certainly a versatile little recorder. I would not use this unit for recording audio that needed to be absolutely pristine (reference quality), but for the purposes I've described, it's been more than adequate.

One of the gripes that I have with the H4 is that it's not initially user friendly, especially when you are trying to record external microphones. You really need to spend some time with the recorder and the manual to fully utilize the features of it. (That wasn't meant to be a "RTFM" statement. I purchased it thinking it would be a breeze to just pick up and go with it. I needed to bury my nose in the manual a bit to get it working the way I wanted.)

Good luck with it.



Freelance Sound Technician/Mixer


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Eric Hansen
Re: safety track with attenuators
on Mar 5, 2010 at 3:39:41 pm

thanks for all the help Rodney. i've been over and over this manual, so i know exactly what you're talking about.

Rodney writes: I downloaded the manual for the H4n and looked up setting the levels. When the unit is recording in Stereo mode (2 recording tracks), you should have the inputs set as mono inputs (in the MTR menu). If you have the inputs set as stereo inputs, then I could see how you might not have independent level control. Again, double check to make sure in the MTR menu that you have not selected stereo inputs. (Page 048 of the manual).

there are 3 modes with the H4n: Stereo (2 channel), 4 channel and MTR. MTR is mainly a remix mode. if you're recording in MTR mode, it will only record 2 tracks at 44.1k/16bit WAV. it's designed to take stuff you've already recorded, maybe add some effects, and remix a new stereo track. or other things i would rather do with a DAW than a recorder. so you can't set up mono inputs or set levels in the MTR menu when you're in Stereo or 4 channel mode, because they're not there. btw, i could record 2 channels with this mode and set the levels independently, but 44.1k is not ideal since i need 48k for video editing.

its strange, but when the H4n is in either Stereo or 4CH mode, inputs 1 and 2 are always locked together level-wise. this is why i think i need to pad the signal before going into the H4n to create a safety track (if i want to use tracks 1 and 2). i keep mentioning tracks 3 and 4 as an option because in 4CH mode, the H4n allows you to control the levels in groups (track 1 and 2 together, and track 3 and 4 together). if i'm sending my main audio to track 1 and split that off to track 3 using an XLR splitter, then i can drop tracks 3 and 4 to be lower than tracks 1 and 2, creating my safety track. the negative is that tracks 3 and 4 use a 1/8" stereo input and it just adds more cabling and splitters. it's too bad the Zoom can send the input of track 1 to track 3 with a lower level like most camcorders can. maybe in the H4n^2.

Rodney writes: Your H4n unit does indeed have the XLR-1/4" combo jack. The balanced input is the XLR and the unbalanced input is the 1/4", thus the differing levels in the specs.

i'm sorry, what a meant in my previous post is i thought all XLR-1/4" combo jacks had balanced TRS 1/4" and not unbalanced TS 1/4". i was surprised that the 1/4" was unbalanced and that the XLR was always Mic Level and the unbalanced 1/4" was always Line Level.

thanks for letting me know what you're using the H4 for. it's always interesting to me to hear how people are using this equipment.

Eric Hansen - http://www.erichansen.tv


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