strange sounds when recording acoustic guitar with k&k p/u

Dusty Ol' Bones

Dusty Ol' Bones

Full of green dust
Hello, I think I might know the answer to my own question but still wanted to run it by you all. The other day I was attempting to record into a 4 input audio interface and hit a minor snag. It went vocals, banjo line, banjo mic, guitar line. I thought by plugging in the guitar, it would be less headache than using a mic because I have trouble getting the guitar player to sit still while recording. Well, after recording a couple of takes, we reviewed them. During review I kept hearing a whoosh sound and I thought my pop filter was too close or my enunciations had too much wind. Nope. Then I thought the banjo mic was picking something up. Nope. I still couldn't isolate the whoosh until I soloed the last track. I'll be damned if it wasn't the guitar doing it. He normally plays with a pick but sometimes he was hiding his pick and brushing over the strings with his thumb. It was at the thumb brushes that the sound occurred.

The first thing I did was say I don't have time to troubleshoot the electronics on the guitar, so we unplugged and set up a mic. That solved the problem perfectly and after some chastising, my guitar player chilled a bit on the Pete Townsend too. Of course this left me asking myself what caused the problem. I determined it was at least one of four things: 1) his thumb brush technique somehow didn't work well with the the k&k pure mini, 2) the pickup itself was either faulty or installed incorrectly, 3) the cable was old and faulty, or 4) either the interface or that particular input was malfunctioning.

I think it was the cable. The instruments and all the recording equipment are mine but the guitar cable was the only thing that was his. I take care of my equipment but it's not as much of a priority for him. The cable did look old and worn out and he doesn't roll or wind it up for storage. He just tosses it on the floor and however it lands is where it will rest until he uses it again. And I hear people talk about checking the impedance of cables but I have not quite implemented that yet.

Without being there and inspecting my setup, what do y'all think it could possibly be?
 
Thanks mods for moving.
I originally posted this thread in Guitars but decided it was more of a signal chain question than guitar question.

I realized I posted three paragraphs with a little question at the end. The whoosh sound I am describing sounds like someone blowing into a mic. That was why I thought it was the vocal mic at first.

So I think I've narrowed it down to either being the thumb brush technique not interacting well with the piezo pickup or the cable was faulty. The pickup has three pads glued to the underside of the top of my dreadnaught acoustic guitar. Maybe the thumb brush created a vibration that the pickup didn't like. But why wouldn't a pick also create a vibration? I thought it was the cable because when I eliminated it and switched to a mic, the sound was no longer being recorded in subsequent takes. Still not sure.
 
I don't know if related, but piezoelectric pickups need very high impedance termination, on the order of megaohms. The high Z input on an interface might be enough, but I would check the specs. I generally use high quality active DIs for piezoelectric pickups.
 
bouldersoundguy said:
I don't know if related, but piezoelectric pickups need very high impedance termination, on the order of megaohms. The high Z input on an interface might be enough, but I would check the specs. I generally use high quality active DIs for piezoelectric pickups.
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Thank you for the reply and the good info. I forgot to mention that my recording stuff is set up in a spare bedroom. I have a dinosaur DAW desktop that runs XP and I would say my equipment is somewhere between hobbyist and serious hobbyist.

I did a quick search on a retail site and came up with about 80 listings ranging in price from $1,000+ (non-rackmount) down to $45. Do you have any brand/model recommendations for someone recording a Martin dreadnaught but who can't afford a D-28?
 
@bouldersoundguy
As you suggested, I checked the manuals and specs of the pickup and the interface. The pickup said works best with input impedance between 500k and 1 meg. The interface impedance is 1 mega ohm for an instrument in (3 k ohms for mic). Should work, right?
 
rob aylestone said:
Can we hear it? Im struggling to equate a woosh to an impedance issue?
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Thank you for replying. Yeah, sorry. I knew the impedance thing was unrelated to the woosh sound. I figured I would welcome the unrelated advice and run with it.

The project files containing that take are on my DAW desktop, which is currently located in a spare bedroom of my friend's house. I would have to get on that machine and put everything on a thumb drive since my recording computer is not hooked up to internet. Of course, this is all dependent on my friend's work schedule considering it's his house. I'm going over there this week so it might be a few days before I can upload an mp3 to this thread.

Do you know if k&k piezo pickups have issues with certain strumming techniques?
 
No, the only thing they do (and this is just what my friend told me) that is odd is respond badly to things like wrist bands and watch straps - bit they're clicks not longer sounds?
 
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