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Old 13th March 2013, 11:07 PM   #1
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Join Date: Jun 2012
Default larger AC motors and shielding issues? Animated cabinet

I'm working on an animated guitar cabinet- think Leslie, that'll be close enough for now- and I'm wondering about noise and shielding and such.

This is being designed from the ground up. There's a nice cavity in the base of the cabinet that seems to be begging for the tube amp- a designed-to-fit amp with a preamp, not a Leslie amp.

However, the 24v AC variable speed motor that animates things is right there at the base. It operates from about 40-200 rpm and everywhere in between.

So I'm concerned that if I try to put the amp in the base, it will tend to pick up noise from the motor and play it through the speakers. There's certainly a place to put some shielding, but the motor would be within inches of the amp.

I notice in a Leslie amp, there is no preamp- it takes a signal from the speaker out and just maybe this is how they get away with putting those two motors right next to the amp, with negligible issues, and no shielding to speak of. Conceivably I could put the preamp up towards the top of the cabinet, which would be handy for inveterate knob-twiddlers, but then I'm exposing it to the vibrations of the speaker and stringing out some longer wires that are going to be vulnerable to noise as well.

Any insights or information here?

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Old 14th March 2013, 02:10 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
Amplifiers have been made for decades with large iron power transformers right on them. If those don;t present a huge radiated noise problem, I doubt your motor will be any worse. Shield the amp, just as if it were standing alone outside the cab. Make sure your motor has all the proper noise abatement applied so it doesn;t radiate more noise than it has to.
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Old 14th March 2013, 02:48 AM   #3
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Join Date: Nov 2011
In addition to the possibility of electromagnetic interference you have to think about mechanical vibration which may cause microphonic effects as you have already anticipated, especially in tube amplifiers.

Last edited by Bibliophile; 14th March 2013 at 02:56 AM.
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Old 14th March 2013, 11:33 PM   #4
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Join Date: Jun 2012
Originally Posted by Enzo View Post
Make sure your motor has all the proper noise abatement applied so it doesn;t radiate more noise than it has to.
Thanks all- I'm all ears if anyone can describe appropriate noise abatement measures. One thing I'm avoiding like the plague is any kind of motor controller that induces RFI. As to the motor itself, I'm not sure where to start with noise abatement. Other than running a larger motor, geared down farther, slower, to avoid that high pitched whine.
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