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Old May 17th, 2020, 08:44 PM   #1
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in need of some expertise and guidance

I've been doing voiceover for some years as a sideline to my acting & video work, usually 4 to 6 jobs a month off local studios or upwork.

I use to have a walk-in robe is a spare room lined with soundproofing and it worked quite well till the wife wanted her storage back - kicked out for for some linen!

So.. I build a booth in my office. Marine ply around a frame with rubber sound deadening & acoustic insulation. it's pretty dead, perhaps a bit too dead but it's been working okay *pic & recent pickup for job attached

in the old location I used an M-Audio Fast Track to convert to usb into the computer. in the new booth I've added a pre-amp.

My current setup is a Rode NT1-A to the DBX 286svia XLR then to the M-Audio via XLR then to the computer via USB and seems to be working okay to my tired old ears.

With no video or acting work I really need to step up my game with voice over,which brings me to my point. In checking my settings I noticed a hum when I bypassed the DBX - it's a low hum. If I remove the DBX completely and run from the Rode to the M-audio - I get a high hum?? *sound test attached

I'm not really sure where to go from here, is this something I need to sort out? can I leave the DBX to eliminate it?

any suggestion will be gleefully accepted

here's something I'm also working on - https://drive.google.com/open?id=1tA...Msg1JsNdlkhMds
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in need of some expertise and guidance-booth.jpg  
Attached Files
File Type: wav Ripple effect Series 2 pickup.wav (4.43 MB, 10 views)
File Type: wav sound test.wav (5.18 MB, 8 views)
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Old May 17th, 2020, 09:56 PM   #2
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Re: in need of some expertise and guidance

Nasty resonances you've got happening there. You sounds like a right Aussie. :-)

Seriously, the Google Drive video snippet sounds really good for the voice. Just had a very quick spot listen.

Andrew
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Old May 17th, 2020, 10:08 PM   #3
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Re: in need of some expertise and guidance

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Originally Posted by Paul Mailath View Post
I noticed a hum when I bypassed the DBX - it's a low hum. If I remove the DBX completely and run from the Rode to the M-audio - I get a high hum?? *sound test attached
Clearly the second part of your track has a lot of mains (and related harmonics) hum. I'm a bit confused about your use of the term "bypass" in your sample track. On the dBx, "bypass" means you are bypassing all the processing (in other words using just the preamp section). So "bypass" is not a thing in itself. "Bypass" is the absence of something (i.e. the absence of processing). So to say your are "turning bypass off" is confusing. You are turning off off.

So to clarify ... in the second section of your track, which affects the noise sample from 14.0 to 18.5 seconds, you say you are going to "switch the bypass off." Do you mean you are taking the dBx out of "bypass" mode ... in other words engaging all the processing sections? Or do you mean you turning off the processing sections, by engaging the "bypass" mode?

As far as the third part of your track, with the noise sample from 24.0 seconds to the end, the high pitched tone is almost surely a bunch of noise from the digital converter in the M-Audio box. It's too high in frequency to be related to your mains power. Did you have that noise all along (before you added the dBx to the signal path)? If all Fast Tracks have that amount of noise, I'd say they're not suitable for serious use. If this occurs only with your setup, I'd guess your Fast Track is defective. (Slim chance it's a shielding or grounding issue with your mic, but given that we don't hear it with the dBx in line, I think it's more likely the mic preamp in the Fast Track.)

- - -

The Ripple Effect sample has so much editing going on that it's hard to tell too much about the audio (aside from making the pacing sound unnatural). However, there are three very obvious bits of noise. One is after "Queensland" at 16.3 seconds. The second is after "thinking" at 22.57 seconds. The third is after "paddock" at 23.55 seconds. In all three cases, immediately after the word, I hear hum and hiss start to fade up. (which you immediately snip out presumably by means of editing) That indicates to me that you have some compression engaged, so, in the absence of desired voice, the compression is raising the system gain, bringing up the noise.
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Old May 17th, 2020, 10:54 PM   #4
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Re: in need of some expertise and guidance

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Originally Posted by Andrew Smith View Post
You sounds like a right Aussie. :-)
it's hard to miss eh! while I can tone it down, the majority of my VO work is 'the aussies farmer/ butcher etc - you work with what you've got

I do need to broaden my range but the 1st thing is to get the technical stuff right

Winston Churchill said that the Australian accent was ‘The most brutal maltreatment that has ever been inflicted on the mother-tongue of the great English-speaking nations.”
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Last edited by Paul Mailath; May 17th, 2020 at 11:34 PM.
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Old May 17th, 2020, 11:29 PM   #5
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Re: in need of some expertise and guidance

Hi Greg,

you're quite right - I had it the wrong way round
0-14 processing is on
14-18.5 processing is off
24-28 DBX is removed from the process - mike goes straight to the M-audio

The M-audio is pretty old so I'm happy to bin that and find another xlr to USB converter - I can get the Shure X2U XLR-to-USB locally.

As far as the mains & related harmonics hum is concerned - I'm not sure what that means but could it have something to do with the power cable for the DBX being connected to a powerboard with a mass of battery chargers for all my cameras? Perhaps I should run a lead to a powerpoint wiht nothing else connected.

If I can get rid of the noise/hum then perhaps I can minimise the processing from the DBX (I know it's a fairly cheap model but it has served it's purpose. I've really been dialing in settings at random to get what I think is a reasonable output (and obviously that's not been good)
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Old May 18th, 2020, 07:56 AM   #6
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Re: in need of some expertise and guidance

Paul,

The dBx cannot remove any noise originating in the M-Audio. I don't hear any noise in the first section. Therefore I assume you are sending a line-level signal from the dBx to the line input on the M-Audio. Since that sounds fine, I think we can just ignore the M-Audio for the moment.

While the noise in the second section sounds terrible, the important measurement is the signal to noise ratio usually expressed in dB. In other words, how loud is the noise relative to the desired signal. Just hearing a section of noise, without knowing all the conditions producing the noise, is not terribly helpful.

I would like to hear a new test with the mic going through the dBx preamp, but with all processing bypassed. (The processing can fool us and make the noise sound louder or softer than its actual level.) With that configuration, record some voice at a proper level. Then without changing anything, just stop talking for 20 - 30 seconds so we can hear and measure the noise (relative to the level of the speech).
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Old May 18th, 2020, 07:30 PM   #7
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Re: in need of some expertise and guidance

Hi Greg,

here's the 2nd test - all processing bypassed with a quick read and 30s of silence - recorded in Audition, no effects.

The noise floor (is that what it's called?) still has that hum

The file is too big for DVinfo so here's a link:
https://drive.google.com/open?id=1w2...pI6lCOM_NVaHFm
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Old May 18th, 2020, 11:04 PM   #8
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Re: in need of some expertise and guidance

Thanks, Paul, that is a very useful sample track.

Your voice peaks are around -5dBFS, which is OK (although perhaps a bit higher than some folks would like). It leaves 5dB of headroom before the gear starts clipping, so you daren't record any hotter than that. The noise peaks fall around -52dBFS which is rather high. That puts the noise ~ -47dB below the voice peaks. That is not adequate S/N (signal to noise) ratio. So yes, this problem should be addressed.

What I hear is a harmonically rich hum related to your 50Hz power mains. By harmonically rich, I mean that, like a piano string, or most musical instruments in general (perhaps excepting a Theramin), there are harmonics that are mathematically related to the 50Hz fundamental frequency. In this case I also see 100Hz, 150Hz, 200Hz, etc. and the harmonics continue, at varying levels, up into the thousands of Hz. Indeed, that could be originating from switching-type AC power adapters or battery chargers. Many countries now insist that all AC adapters are switching-type because they are more energy efficient. So unless you have some fairly old chargers, I'll bet most of them are this type.

Lamp dimmers can also cause the same kind of noise related to mains power and harmonics. Are there any lamp dimmers in use, especially near the sound gear?

As a general rule, all audio gear that is interconnected should get its power from the same outlet if possible. So I suggest you plug the dBx AC adapter into the same outlet where your computer is plugged. And, if possible, get all the chargers away from that outlet. (Of course they might still end up on the same circuit, because of your house wiring; but at least get them physically separated.)

Also, in theory, the preamp, M-Audio converter, and computer should have their earth connections tied together. But this is often overlooked and sometimes even difficult to do, given the present state of computer wiring. Let's pass over this for now, but keep it in the back of our minds.

It is also possible that this AC mains noise is being picked up by the wiring between your mic and the preamp. Is that mic cable properly shielded? Does it properly ground the mic? Is it a reasonable length? Is it physically separated from all those AC adapters and other AC power wiring? If it's absolutely unavoidable to keep the mic cable from crossing over a power cable, they should cross at right angles.

Incidentally, I recall that when the mic was connected directly to the M-Audio input, the signal contained a lot of high frequency noise that I'd associate with computer gear. If there's something wrong with your mic cable, that might cause the two different types of noise to be picked up in the two different scenarios. So don't rule out the mic cable as the culprit.

Of course the mic itself should not be near any power supplies. Also, some computer screens radiate a fair amount of AC noise, so consider whether the mic (or wiring) is close to a display.

*** By the way, your noise sample also contains significant content around 120Hz. This is not a component of the 50Hz mains power. It might be related to a computer display with 60Hz or 120Hz scan rate. So be sure to consider proximity of the mic to any display! God help you if you have an old plasma TV nearby ... they radiate crap all over the spectrum.

Lots of things to try. You can change one thing at a time, to try to scientifically find the source of the problem. Try listening while you move things around, plug and unplug things, turn things on and off, etc. Or you can just use the "shotgun approach" ... change a whole bunch of stuff at once and see whether you've killed the offending noise.

I'll be interested to hear what you find out.

Good luck!

Last edited by Greg Miller; May 18th, 2020 at 11:36 PM.
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Old May 19th, 2020, 12:34 AM   #9
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Re: in need of some expertise and guidance

Remember that most VO artists are not technically advanced, their income from their voice just needs clarity, no room and no noise. When they submit work, it needs simply to be EQ'able and clean. That's all!
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Old May 19th, 2020, 12:58 AM   #10
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Re: in need of some expertise and guidance

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Remember that most VO artists are not technically advanced, their income from their voice just needs clarity, no room and no noise. When they submit work, it needs simply to be EQ'able and clean. That's all!
I would think that "clean" includes fixing the -51dB hum from the power mains frequency & harmonics.
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Old May 19th, 2020, 01:09 AM   #11
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Re: in need of some expertise and guidance

Absolutely, but my thinking is that the simplest path is often the best for many. Mic, modest interface, laptop - done! Hums aren't part of clean.
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Old May 19th, 2020, 01:12 AM   #12
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Re: in need of some expertise and guidance

wow! thx Greg - lots to work on there

I'll test and get back to you

I'm actually now concerned with the amount of electronic gear I have in the room which could be affecting things:
2 large desktop computers, 4 screens & 1 laptop
3 synology servers with 3 UPS backup units, printer and the aforementioned shitoad of battery chargers.

I might have to take the cupboard back - not looking forward to that battle.
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Old May 19th, 2020, 01:13 AM   #13
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Re: in need of some expertise and guidance

If you read the previous posts in this thread, the OP had heard high frequency noise with his simpler setup, and when he added the new preamp the noise changed to mains hum. He's asking how to get a clean recording. All my answers were directed toward his getting a clean recording.

Since his previous combination of mic, simple interface, and PC did not yield "clean," what do you suggest other than the sort of trouble-shooting as I have recommended?
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Old May 19th, 2020, 01:17 AM   #14
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Re: in need of some expertise and guidance

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3 synology servers with 3 UPS backup units
I'll bet you dollars to donuts the UPS units are the problem. Almost all of them put out square waves, which by definition are full of harmonics. They get into audio, and can even wipe out AM radio reception. Get away from those and I'll wager your noise will be much less. By all means your preamp, and ideally your audio PC, should not be powered from those.

(Indeed, you can get much more expensive UPS units that have true sinewave output, rather than typical square wave or "stepped sine wave." But you will pay a lot more for those.)

Beyond the UPS units, every computer, every server, and every monitor has a switching power supply in it. That is a hell of a lot of electrical noise to have inside your live mic studio.
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Old May 19th, 2020, 02:16 AM   #15
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Re: in need of some expertise and guidance

Small switch mode power supplies are usually the culprit for many noise related issues - Why not start with as clean a path as you can arrange, and gradually add your other items to see if it's one of them causing it, or the cumulative effect of all of them.

Rode - M Audio - Computer. everything else disconnected. Then add the DBX. If this causes the noise to ramp up - try disconnecting pin 1 on the XLR cable to the M Audio. If all is well, add the other stuff and repeat.

EDIT
Just noticed you mentioned UPS. Some designs regenerate the mains voltage, while others don't - it's possible your noise source emanates here?
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