Nylon String Guitar Recording Problems (Intermodulation Distortion?)

[daithif]

Hi,

I've been recording a good quality Nylon String Classical Guitar using two Rode NT1's through my Digi 003 Rack. I keep getting a distorted, almost overdriven sound at times even though the volume never peaks and there is no digital clipping apparent in the file. I've tried all sorts of mic positions and recording at different volumes but I still get it.

Am I experiencing intermodulation distortion?

If so how can I fix the problem? Or is there some other reason this might be happening?

Cheers

Daithi

[KingFish]

Hey Daithi, welcome to the DUC -

Well, could be a few things.

- You using the Digi 003 Pre's and Phantom for the NT1's ?


Distortion can happen at the Capsule of the microphone, the Output of those Pre's, or in the Mix Bus of Pro-Tools, either in a Plugin, Internal Mixer, or the 003's Main Outputs being over driven.

Everything in your session well below -0db Unity? INCLUDING any master Faders?

Do you have Plugins in the tracks when you listen to playback?? if so, Disable them to see if the distortion goes away.

I'd check the signal path, from Mic to Speaker, Out and In the box.

If you import a pre recorded track into pro tools and play it, is it clean??

Perhaps, if you can't find it, you could explain to US, ALL settings, don't think ANY detail is too simple to leave out.

Something like

NT1 --> 003 Pre 1 @ 12:00 O'Clock, --> Input A1 on track in pro-tools shows Level peaking at -10db --> No Plugin --> No Master Fader

-- Main Outs of 003 Feed Sound Craft K1 Mixer Channels 1 & 2 - Gains at -15db No Clipping - Main Outs of SoundCraft K1 feed a pair of Genelec 8020's Turned Wide Open


You get the idea - The more thorough the info, the better chance someone has of making suggestions.

MY suggestion is to keep the ENTIRE signal path as SIMPLE and Bare as Possible to troubleshoot.

Plug Mics into 003, gain up - record your classical guitar on 2 new tracks in a fresh session, pull each track down to BELOW 0db (-5 should be fine) plug a Pair of headphones in, and see if the distortion is still there.

If it is... can you post an Audio Clip for us to download and hear - some distortions are easy to "Identify" others, not so much.

Good luck.

[daithif]

Thanks for that advice Kingfish. I think I've discovered from your help that there's a problem with the output on my computer that's causing the distortion. No matter where I send the output either via the pro-tools inbuilt headphones socket to headphones or speakers or through the computers own headphone socket to the speaker or headphones, the distortion occurs.

I've double checked by importing the aiff files into Audacity and checking mp3's of other records.

Still not sure exactly where the distortion generates from because it occurs at volume levels that aren't particularly loud.

I'm using Sennheiser HD 215 cans which are normally able to take high volume without distortion so I guess there's something wrong between the interaction between pro-tools and my iMac (OSx 10.4.11 2ghz Intel core 2 duo processor, 2gb ram)

Any ideas?

[Larold]

You might check the impedance of your headphones. SOme are 600 ohms, and I think the Mac is set for 8. I may be wrong, but that popped into my head from a similar problem many years ago.

[KingFish]

Well I'm not sure if I have this straight, but you should definitely NOT be routing the 003's AUDIO Path THROUGH your iMac.

I have an LE / iMac / 002 setup, that all feeds a Mixer, and the Mixer feeds the Speakers.

Headphone Jacks are for "Headphones" - you should not use the 003 Headphone jack for anything but.

For now, I'd connect the 003 DIRECTLY to your speakers for Pro-Tooling - and although a royal p.i.t.a use the Digi Core Audio in System Preferences (003) as OS X's outputs so that computer Audio is routed through your 003 to the speakers. you Can NOT have pro tools running though, when playing System Audio... for this reason... the BEST setup, is to get yourself a little Mixer.

there are lots of little 8 Channel Mixers for under $100.00 bucks on E-Bay

Here's an 8 Channel Soundcraft Spirit for $68.00 with 5 hours left on the auction

Really, having an external Mixer with your LE rig is handy, you can monitor Pro-Tools Outputs, your Computers Outputs, you get an extra headphone amp out of the deal, and you can monitor OS X and system audio while Pro-Tools is open.