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Zoom H4N Attenuator

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Chris BryanZoom H4N Attenuator
by on Jan 12, 2011 at 1:37:55 pm

What is everyone using for an attenuator for the H4N? I record audio directly out of soundboards at weddings via 1/4 inch cable or rca cable and the audio always clips and sounds horrible. I've been using this 40 db pad from b&H

and it still doesn't do the trick. Even when I set the levels super low on the Zoom, the audio gets quieter, but it still clips. Can someone please direct me to a 50 db attenuator that would work with the H4N, or tell me how you are getting good sounding audio from the H4N?


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Dave HaynieRe: Zoom H4N Attenuator
by on Apr 1, 2011 at 7:12:25 am

You gotta love the gear specs... everyone picks their own favorite units. I'll try to explain how I figured out what to do.. at least what works for me.

The spec for a consumer line-level output... what you might find from an RCA tape monitor output from a mixer, is -12dBV. You can get this output on some mixers, it's maybe the best one available for a stereo tap. The typical output from a submix or other XLR or 1/4" balanced output is probably +4dBu (international studio level). So what does that mean? Well, dBV is decibel relative to a 1V signal... the "V" means "Volt", -12dBV = 0.25V. dBu is a decibel relative to 0.775V, the "u" means "unloaded" ... +4dBu = 1.228V; -12dBV = -9.78dBu. So basically, you need a 15dB pad on a "pro" signal to deliver the same level as you get from a "consumer" signal. So that's the first thing to factor in when you're hooking up... at least, to a line level output.

And of course, if you have the option, you may get to hook up to a studio monitor output, which will probably have a volume control. This is probably expected to drive a studio amp or powered monitor, you'd kind of hope it's limited to +4dBu, but I wouldn't always put money on it, some amps can take inputs up to +24dBu. But if you have access to the volume knob, you can solve your problems there entirely... assuming the sound guy doesn't accidently hit that button during the show.

Now, let's look at the Zoom H4n inputs themselves. Naturally, since these are mic inputs, they're speced in dBm (decibels relative to 1mW... the actual voltage you see depends on the impedance of an attached microphone). So anyway, balanced input is speced at -42dBm to -10dBm at 1K ohms, the 1/4" is speced at -32dBm to +2dBm at 480Kohms, 1/8" input is speced at -48dBm to -7dBm at 2Kohms.

Now of course, an unbalanced line level signal is usually really high impedance, so I actually run the line level (which I want) though a direct box, which delivers a 600 ohm signal to the XLR input on the Zoom... which is about what it's looking for there -- good mics are usually 150-1K ohms, more or less. At 600ohms, my handy dandy dB calculator ( tells me I have 0.25V at -10dBm... which is just that -12dBV. There's definitely some range there in the Zoom, so you could leave some headroom and drop another 10-20dB off the consumer signal, or maybe 30-40dB off the +4dBu output (a 40dB pad is more common, what I've used with the direct box, and what most people seem to recommend... if it's not enough, you probably have a much hotter signal on that mixer).

Of course, given the fact you're running from XLR outputs, you have at least +4dBu, but maybe more, depending on just what that output is. Most direct boxes do have built-in attenuators, and if you flip it around, you could run the XLRs in and the 1/4" out at a known high impedance to the 1/4" input on the Zoom. I'd stay away from the 1/8" input, both because they break too easily, and also, that's a 2K ohm input, not a good match to an unbalanced line level output. In my case, I have a few of the variable XLR pads, as well as the 40dB pad in the direct box, so I could actually cut 80dB from the mixer if necessary... I never needed the extra pads for this stuff, though. But I always bring a bag of audio support stuff... extra cables, adapters, etc. if I have a chance at a sound board tap when recording a show.

The other thing about the direct box is that you can flip a switch to cut ground, which can eliminate hum (you might have a ground loop between the H4n and the mixer, particularly with a stereo tap).


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