Loud Source, Noisy recording, what gives?

I’m wondering if anyone can give some hints, tips, what have you as to what may be causing the weird electronic background noise in the short clip below. In case it matters, the mic is Sennheiser MD421-II recording a very loud JBL speaker, preamp is ART USB Dual Pre, into Audacity (Realtek sound card on Windows 7 laptop). Nothing is clipping from pre to Audacity and it seems like a clean signal but then there are those bad artifacts. BTW, I don’t want to turn down…I want to record the LOUD source :wink:


What say ye?

It seems clean to me, too past some minor peak distortion. I don’t hear anything odd or unusual. How are you listening to it? Can you listen on somebody else’s computer as a test.

I hear a “room echo” effect like a “stage” or “concert” setting. Did you intend that? It’s rough to record guitar speaker without getting the room in the mix. If you need a dry recording, you might split the headphone feed and record that.

As a test, don’t play the guitar. Just clap once loudly. Does it sound like an auditorium? That’s your room.



It’s got reverb pretty high, as intended. If you listen at 5 secs and 8 secs I think you can hear some kind of quiet, fizzy distortion that trails off over 1/2 second or so. Almost like a kind of nasty overtone, a muted buzzing sound. I exported it to my iPhone and can hear it there too so I don’t think it’s the computer. See if you can hear it…I swear it’s there! :confused:

Are you listening to the track on headphones from the computer? One of the ways we diagnose problems is to split the system apart and see if each part works like it’s supposed to.

All I hear – on quality headphones – Is you doing fancy fingering on a guitar. I can hear string squeak, harmony strings and melody line. Nothing like half-second weird electronic background noise.

I’m trying to build your system in my head. Try listening to the track on headphones just to test. If you’re on speakers there are some sound pathways that can cause trouble.

Oh, and yes, I think you have feedback – on playback. Everybody who performs is familiar with microphone feedback …eeeeEEEEE. Computer systems can feed back, too, but they can be seriously freaky because of the delays inside the machine.


Koz - it’s like a barely audible but persistent “electronic sizzle” that seems to be most apparent when the notes hit peaks and then it rapidly decays. I’ve listened to it on computer, iphone, ipod all through 3 different sets of headphones. Sounds the same so this seems like a recording artifact. Maybe its feedback in the computer system as you suggest? But a different kind of feedback than I’m used to. In any event, to me it’s very distracting and nasty sounding. Oh yeah, I had my wife listen and she immediately heard it (and hated it). I don’t think I’m crazy, but I am at a loss!

OK, you did the legwork. The recording does sound harsh and you can get that if you overload the microphone or the mic channel. Most microphones can’t sit in front of a guitar cabinet running full steam. They’re going to overload something. This system is designed to gracefully record your grandma reading folk tales quietly at five feet. It won’t put up with an industrial grade change in volume.


The Sennheiser is a dynamic, moving coil microphone, so that will not overload. Do you get the overload lights on the front of the Art preamp? Can you force them to come on? Part of the discovery process is forcing something to break – sometimes discovering in the process that it’s already broken.

I don’t know what the inside of the Art looks like, but most preamplifiers have a very sensitive sound amplifier inside that you can’t control. It’s not connected to the knob. That amplifier is supposed to be connected to the overload light, but sometimes they’re wired different.

Are you going through a USB hub? Are you going through a very long USB cable or a USB extension cable?

Are you playing in a tiny closed room? I was going to suggest as a test that you back the microphone off – at least double the distance from the cabinet, but that’s not going to work if you start getting close to a wall in the room. The volume is just going to go up again.

You don’t have one of these, do you?


You chug that between the microphone and the preamp. We use those in News Gathering when we have to record something very loud and the volume controls aren’t enough.

There is the possibility that you’re microphone is working just fine and you’re listening to the cabinet overload. Where is the microphone and where is your head while you’re playing?

I can’t stress enough how much juice you can generate with that microphone. We did a test once where we connected a dynamic (moving coil) microphone to an electronic system without a preamp. Somebody screamed into the microphone and we could clearly measure the signal. The preamp was cowering in terror under the table.


Koz - thanks for the thoughtful replies. I think you’re right that something is overloading. The ART preamp seems to be behaving okay, green light only, no red clipping light coming on. USB cord from ART preamp is probably 6ft or so. The room isn’t extremely tiny, typical bedroom/office size. I don’t have an attenuator but because the ART preamp seems to be acting fine I’m hoping it’s not necessary. But it could be the case that the MD421 doesn’t agree with the ART preamp and is just feeding it too strong a signal…but wouldn’t it clip the preamp? I’m probably 5-6ft from the cabinet while recording, nothing unusual there, how I’ve always done it.

Your last comment does make me wonder if there’s some problem with that large diaphragm mic sending too strong/complex a signal to the ART…or maybe the sound card can’t handle it? Maybe I don’t have enough processing power to handle the signal cleanly? Or maybe it could be electrical interference, that’s just occurring to me now?

This weekend I’m going to work on it some more, do some troubleshooting. I’ll report back if I can make progress. Thanks!

That’s what’s so darn much fun about this. Everything is working but not quite right.

You did say a couple of things needing comment.

that large diaphragm mic sending too strong/complex a signal

Conventionally, Condenser Microphones are called large, medium and small diaphragm depending on their construction and expense. It’s entirely optional depending on the goal of the designer. Those work by moving tiny pieces of metal film around with the sound. You can destroy a condenser microphone with loud sound. Blow into one and the sound engineer might let you live. Might not.

Your microphone is a “dynamic” or moving coil microphone. Nobody I know refers to them as Large Diaphragm because you can’t have a dynamic microphone without one. I see where the Sennheiser web site calls it that.

Yours works by the sound moving a very light metal plate connected to a coil of wire around a powerful magnet. You can set a small, personal thermo-chemical explosion next to one and it will just go with it and keep right on working. We had one come back from a shoot in two pieces. It was working when we put it back together. It’s still working.

ART USB Dual Pre, into Audacity (Realtek sound card on Windows 7 laptop).

Just so I’m clear, you’re not using the digital USB sound from the Art Dual Pre? When it’s working properly, you don’t need a sound card at all. The DualPre is the sound card. That might be where some of your distortion is coming from. The sound card in most Windows laptops is floor sweepings.


Koz - thanks for correcting me on the technical details. I don’t know what I’m talking about :slight_smile:

I spent some time today trying to remedy the problem. No luck. Link below is to another clip (this time using a 1st gen MD421 mic). Basically the same idea. I hear a persistent digital “sizzling” pretty much throughout when notes are peaking, like it’s just over the top of the notes quickly trailing off. See if you can hear what I’m talking about here? About the Dual Pre, I have it running with XLR input out thru USB into the computer. I think normal operation. If this isn’t what you were asking, let me know.

Anyway, I’m wondering if it’s somehow overloading the input sensitivity of the Dual Pre or something, causing some kind of distortion? Maybe the signal chain can’t handle this kind of volume without creating weird digital artifacts, despite not doing traditional clipping? I just don’t know…