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Audio Woes

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Mark Welch
Audio Woes
on Apr 3, 2012 at 12:25:45 am

I've been podcasting for several years doing at times three shows. I have always experienced poor audio recordings from my mic/system.

Here is the setup:
Heil PR 40 mic going thru either a Symetrix 528e voice processor or a Golden Gate Pre 73 pre amp.

Signal then goes out to an Allen & Heath 24 channel mixer then via USB to my computer. I'm running Soundtrack Pro recording software on a 24" iMac.

You would think that the recorded audio would be pretty good with this setup. It isn't. It's noisy and in the broadcast sense, unusable. I've been trying to isolate the problem for over a year now with no luck. Should I go with a Mac Pro and use its soundcard instead?

If anyone would like to hear a sample file and give a professional opinion, I would be more than happy to send.

Thanks,
Mark


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Mark Welch
Re: Audio Woes
on Apr 3, 2012 at 1:35:21 am

Interesting discovery. I lugged out my old non Intel Mac G4and routed the USB cable right from the console and recorded on an ancient version of Soundtrack. Clean as can be. Noise floor extremely low - practically imperceptible through headphones.

This tells me that the USB input or audio circuitry on the back of the iMac is inferior. Any ideas?

This rules out the Heil, A&H mixer and pre amps - whew!

Thanks


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Jordan Wolf
Re: Audio Woes
on Apr 3, 2012 at 6:00:17 am

Mark,

What interface are you using to go from the A&H mixer to your computer? Is it one of the ZED series boards?

You've got some nice gear there, and I'd like to assume that your gain structure is set up correctly, but assumptions are where troubleshooting should begin - so:

Would you mind sharing how you set the gain for each device in your signal chain?

Wolf
<><


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Mark Welch
Re: Audio Woes
on Apr 3, 2012 at 12:45:07 pm

Jordan,

I'm taking USB output from the ZED 24 right into the iMac.

For monitoring playback (during video or audio editing) , I am running computer headphone output back to the A&H mixer and monitoring through one of the channels. However during recording, I turn that channel off and monitor through headphones which I believe are monitoring the USB.

As far as gain, there never seems to be enough. I have input set to max in the mac's system preferences, levels on the board set to normal levels, (channel gain set midway). If I crank up the channel gain on the A&H too much it gets real noisy.

Thanks


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Richard Crowley
Re: Audio Woes
on Apr 3, 2012 at 5:27:16 pm

What happens if you plug the mic directly into the A&H?
Are you saying that you are using your (unidentified) A&H mixer as the analog to digital conversion via USB?
What happens if you just run the audio from the Symetrix or Golden Gate unit directly into the audio input of your Mac?

It seems like you have a lot of stuff there and the more you have to go wrong.

Certainly start with Mr. Wolf's suggestion about making sure the gains are set properly on EACH and EVERY part of the audio chain.

USB inputs cannot add (or remove) noise. But different computers can have power supplies that are friendly or hostile to connecting audio devices, as your experiment shows.

Good move substituting the computer. Now do similar experiments with the rest of the system. A 24-input A&H mixer seems like vast overkill as simply an analog-to-digital converter.


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Mark Welch
Re: Audio Woes
on Apr 3, 2012 at 9:53:06 pm

The mic needs to be pre-amped before going into the mixer, that's why I run it through the Symetrix. I also use the Symetrix for voice proc.

I think it has more to do with the computers power supply.

The A&H ZED 24 is used because we have musicians which we interview and record live for a podcast as well as an internet radio operation going on for another client. The board gets used up pretty quickly depending on type of show and who all we have in studio,

The old G4 will work for an audio recorder for the time being. Just wish I had a better non Intel version of Soundtrack Pro to run on the G4.

I needed to split up the audio and video editing workstations up anyway.

Thanks!!


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Richard Crowley
Re: Audio Woes
on Apr 3, 2012 at 11:36:05 pm

It is not clear why you get noise from your Heil mic, but not from the other mics into the ZED24?
The ZED24 has mic preamps, why do you say that the Heil needs to be pre-amped before going into the ZED24?
It sounds like your computer is compatible with the ZED24, but not with the other outboard processing stuff. Does it produce the same noise with the Symetrix as it does with the Golden Gate? Are these plugged into the same mains power source as the ZED24 and the computer?


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Mark Welch
Re: Audio Woes
on Apr 4, 2012 at 12:35:28 am

If I attempt to use the ZED 24 to pre-amp the Heil, I have to crank the gain way up, about 75-80% full and additional noise is introduced. Bob Heil himself told me a while back they use the Symetrix 528e to demo the PR-40 at the factory. It is a good compliment to the mic.

Other mics in this configuration with the iMac are just as noisy. Yes, the outboard stuff is using the same power circuit. Although I did try isolating the outboard gear at one time. Guess I should iso the Mac from everything (power wise).

Thanks for the help.

Mark


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Richard Crowley
Re: Audio Woes
on Apr 4, 2012 at 5:15:21 pm

"If I attempt to use the ZED 24 to pre-amp the Heil, I have to crank the gain way up, about 75-80% full and additional noise is introduced. Bob Heil himself told me a while back they use the Symetrix 528e to demo the PR-40 at the factory. It is a good compliment to the mic."

That seems VERY odd. The manufacturers' published specifications show that the PR-40 is essentially the same sensitivity as something like a Shure SM58 (-53.9 dB vs. –54.5 dBV, assuming they are both using the same method) The TWiT.TV network uses dozens of them in their studios and they plug them directly into the mixer, etc. Likely the same at radio stations around the planet.

I would assume something to be broken if I had to crank the gain up that far for the PR-40.


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Jordan Wolf
Re: Audio Woes
on Apr 6, 2012 at 3:41:27 am

Richard,

From routine use on various consoles, I'll vouch for needing to crank the gain with the venerable SM58. The PR40, I've never mixed with (would like to), but the PR35 and PR22 I own/use don't require THAT much gain.

Wolf
<><


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Bill Davis
Re: Audio Woes
on Apr 4, 2012 at 6:58:26 pm

[Mark Welch] "Here is the setup:
Heil PR 40 mic going thru either a Symetrix 528e voice processor or a Golden Gate Pre 73 pre amp.

Signal then goes out to an Allen & Heath 24 channel mixer then via USB to my computer. I'm running Soundtrack Pro recording software on a 24" iMac."


SNIP


Mark,

With due respect, this is a very "old style"audio chain in modern terms.

While the equipment is all fully professional and proven, audio has come a long, long way since the days that this much gear was necessary to get a high quality audio signal recorded of something as simple as a human voice.

I do dozens of professional Voiceovers a year and have done thousands over the past 30 years. - and for many of those years I used signal chains like you describe above.

It's all gone.

Now my entire studio chain is a Neumann TLM-103 into a Zoom H4N. That's it. Period. The card gets read into my laptop - and if I feel it needs some signal enhancement like compression, it's applied in post with a click. I get BETTER results with this than I did with thousands of dollars in hardware in the past.

That replaced a simple USB pre from Centronics (MicPortPro), that did the Mic to USB conversion in real time with monitoring for under $200 bucks. And the only reason I switched is that I use the Zoom for other field recording and it was easier to just use the same system for everything.

The point is that there's no longer a need for complexity or expense to get quality audio signals digitized and manipulated.

Digital is simple, vastly less expensive, and a whole lot easier than Analog for the kinds of things you need to do.

There are scads of A/D mic to USB/Firewire zero latency solutions with EQ and compression out there today for a few hundred bucks. That's ALL you need. Not boards and boxes, and dozens of cables and ground loop eliminators and all that complexity.

You're making it much, much harder than it needs to be, in my opinion.

FWIW.

"Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions."-Justice O'Connor


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Ty Ford
Re: Audio Woes
on Apr 5, 2012 at 9:31:06 pm

Hello Mark and welcome to the Cow Audio Forum.

The A&H 24 channel mixer has no preamps? What model is that?

I'd begin by suspecting the mic and the mic cable and go right on down the line from there.

Yes, do post a sound sample.

Regards,

Ty Ford
Audio Forum Leader


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


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Mark Welch
Re: Audio Woes
on Apr 6, 2012 at 1:49:49 am

Yes the A&H does have preamps - 24 of them. I'm just saying that the Heil seems to need much more gain for whatever reason. That isn't my main problem. I just have an unacceptable noise floor on all my recordings.

Trying to identify what is introducing the noise. I suspect it has something to do with either the power source or the iMac itself.

Thanks


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Ty Ford
Re: Audio Woes
on Apr 6, 2012 at 1:52:56 am

Mark,

Then either the mic's broken or the cable's bad. Which A&H mixer? Try another mic, try another cable.

Regards,

Ty Ford


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


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