Discussion in 'General Electronics Chat' started by t-bone, Apr 4, 2008.
could some one explain what motor boating is?
Generally means an oscillation, or instability condition.
p.s.- there are some non-technical explanations which are pretty funny, but I'll leave them out
It is a very slow oscillation in an audio circuit so it makes a sound like a mororboat. Putt, putt, putt etc.
It is exactly as Audioguru described, and it is quite often caused by a weak or totally open electrolytic filter capacitor in the power supply. When the filter caps aren't doing their job, this can sometimes allow audio signals from the output stage to feed back to the low-level input stages, causing a low-frequency "motor-boat" sound in the speakers.
It's most often associated with vacuum tube circuits. I had an amp that had that problem, and was temporarily cured by a new 12AT7. I got an Archer lifetime tube and just swapped a new one in every two weeks or so.
I have played with this, when you get a chance, get a good sound generator (if you use mac, I believe the website is like hitsquad.com, something like that, you can google it) and look for signal scope pro, it has a decent free trial. Use the square wave setting at like .5 Hz and you will really here the putt. If you use windows, I'm sorry, but I don't have any software suggestions
Also, according to a friend of mine, motor boating can be caused by having AC out of phase, since it will provide positive feedback instead of negative..
That's a new one by me! I've heard of AC phasing causing hum, but not motorboating.
On second thought.... are you speaking of AC power Mains phasing? Or are you referring to some other type of phasing such as speakers, audio transformers, etc???
No, the mains transformer, it is driving a tube amplifier of some sort..