Resources for the Recording Musician
September 11, 2007

Guitar Recording Question

so far I only recorded voice in my studio with my Amek recording pre-amp/eq (9098) and a Neuman U87 microphone. today I set up my fender amp in my studio and miked it with the Neuman running through the Amek recording pre-amp, but I ran into the following problem which I can't figure out: the lowest input setting on my Amek 9098 pre-amp is 0db and when talking into the mike at this setting nothing can be heard anymore, but in front of my Fender amp (with the guitar amps level set to 6) still a lot of signal is coming through/out of the Amek pre-amp. is this normal ? also when increasing the input just a bit the signal is distorted big time. Does this have something to do with the fact I am using a condensor mike and not a dynamic one ? on the other hand I've seen people miking amps with the same Neuman mike so how is it done properly without distortion ? thanks for any kind of help with this !

Yes, as you've just figured out, guitar amps can be MUCH louder than a voice, especially when you've got the microphone right up on the guitar amp.

The typical first choice microphone for a guitar amp is usually the very inexpensive Shure SM-57, which is a dynamic microphone.  Sometimes that is complimented by another dynamic microphone, such as the Sennheiser MD-421.  Really, dynamic microphones are the only ones you would ever want right up against the grill of the cabinet, but there are no rules and you can do whatever sounds good to you.  Dynamic microphones aren't as sensitive and don't have as hot of output levels as most condenser microphones, so you can get away with putting them up close on a loud amp.  Also, they aren't as fragile as some condenser microphones, and especially ribbon microphones.  But, the U87 is robust enough to be right up close to the amp.

Usually, if you are going to use a condenser microphone, or a ribbon microphone, on a guitar amp, it will be set back further from the amp... A good starting point is about 12 inches away.  Sometimes these will just supplement the dynamic microphones that are right up on the grill.  Another use is to put the condenser or ribbon microphone even further back to get more of a room tone to blend in with the closer microphones.

There are many ways that you can get unwanted distortion when recording loud signals, such as a guitar amp.  First, you might simply be overloading the microphone's own electronics.  Many microphones, such as the U87, have a built-in PAD/Attenuation switch, to help in these cases.  So, there's one way to bring the signal level down... switch in that pad on the U87.  If that still doesn't help, then you'll have to either move the microphone further away or turn down the amp.

The next place down the line is the microphone pre-amp itself.  Most higher end pre-amps also have a pad/attenuation switch on them which will help you if the output is being distorted.  Depending on where the pad is in the circuit path, it may or may not help if its the input to the pre-amp which is being distorted (sometimes the pad is on the input, and sometimes it's on the output of the pre-amp).  Most of the time the pad is on the input.  If your pre-amp doesn't have a PAD switch on it, you can also buy those little inline attenuator pads that have XLR connections on both ends, that you simply plug-in between the microphone and the pre-amp.  Those are quite handy to have around.  Again, you can also turn down the amp or move the microphone further away.

Microphone position itself is crucial to the sound you capture.  Putting the microphone right dead center in front of the speaker will give you the brightest, and loudest, sound.  With a condenser microphones, such as the U87, that would probably be too bright and crunchy for most applications.  Moving the microphone off to the side of the speaker cone will give you a more mellow tone.  Sometimes people even put a microphone BEHIND the guitar cabinet (usually an open back type cabinet) for a different and more mellow sound.  Then, also play with the distance the microphone is away from the cabinet, as this will have a huge effect as well on the sound, especially if you are combining the sounds of more than one microphone (then you start dealing with finding the best phase relationship by adjusting positions).

Lastly, as already mentioned, turn down the guitar amp, or get a much smaller wattage guitar amp for recording.  If you aren't going for full blown distortion, you probably don't need the amp cranked up super loud.  Many engineers have discovered that very low wattage amps can actually be MUCH better for recording because you can turn the amps all the way up for maximum distortion and speaker excursion while still having very reasonable volume levels which won't overdrive your microphones (or bug your neighbors as much).

Hope this helps a bit.


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