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Post subject: 68 Mustang - Feedback Problem
Posted: Tue Aug 25, 2009 4:35 pm
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I run my 68 Mustang through Vox AC15. I get mad feedback when I am near a mic.

It seems that I have to turn down my pickup volume pot a lot to reduce the feedback - my guitar ends up too quiet, even with the amp cranked.

Any way to help with this? Would a pickup booster pedal help? Is this normal for stangs?

Also, I have some buzzy grounding issues - buzz goes away when I grab my cable/input jack. Opened up the electronics, and nothing seemed horribly out of place - anyone have any ideas or a schematic?

I'm also looking for information on mustang electronics in general - what exactly am I working with..

Thanks!


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Post subject: Re: 68 Mustang - Feedback Problem
Posted: Tue Aug 25, 2009 6:38 pm
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spaniel wrote:
I run my 68 Mustang through Vox AC15. I get mad feedback when I am near a mic.

It seems that I have to turn down my pickup volume pot a lot to reduce the feedback - my guitar ends up too quiet, even with the amp cranked.

Any way to help with this? Would a pickup booster pedal help? Is this normal for stangs?

Also, I have some buzzy grounding issues - buzz goes away when I grab my cable/input jack. Opened up the electronics, and nothing seemed horribly out of place - anyone have any ideas or a schematic?

I'm also looking for information on mustang electronics in general - what exactly am I working with..

Thanks!


Welcome!

Apparently, your pickup or pickups need to be potted, even if there are indications that they already were. What is happening is that the coil in at least one of your pickups is loose and when the sound coming out of your amplifier hits the coil, it causes it to vibrate and that in turn, causes that nasty feedback. This situation is certainly not uncommon. Potting involves the pickup being given a wax bath until the coil is saturated and then it is allowed to cool. As the wax now permeated throughout the coil resolidifies, so does the coil.

Lowering the guitar's volume and using a booster pedal literally puts you right back where you started so that's right out.

Decreased buzz or hum when touching anything metal on an electric guitar is believe it or not, normal. This hum or buzz is more predominant with single coil pickups such as your's. Many people will tell you to shield your entire guitar which will help cut down on the hum. I, for one, have not seen ANY dramatic results on any guitar that has been shielded as the most common source where hum originates is through the pickups themselves which in your particular situation, typically do not get any shielding. The guitar MIGHT quiet down a little if the pickups are screwed down low as this puts the pickups partially through the pickguard where the back of it is shielded and so, a portion of the pickups MAY get some benefit but that's about it. To give you a balanced presentation, others will surely disagree on this whole shielding issue yet, I still stand by what I've said..

As to the electronics of your Mustang, here's a diagram:

http://www.jag-stang.com/MrMaxima/gpphotos/SDmust.html

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Post subject:
Posted: Tue Aug 25, 2009 6:50 pm
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Thanks for the detailed answer!

This guitar buzz is a lot louder than the normal hum - not a problem when on stage, but when recording, or even talking over it, it drives me mad. Other folks also seem to think it is louder than average - any other ideas why? I suppose I can try lowering the pickups... I do believe my cables are shielded, but even if they're not, my other guitar doesn't give me any problems (dano).

I think I understand what you say about the amp vibrations causing the coils to vibrate, thus causing feedback. I'm confused, however, at how the vocal mic works into this. If I'm just jamming, no mics, I have no feedback problem. When I try to sing - be within a foot of the mic really - the problems start. It is somewhat alleviated by not being super close to the amp, but I've still had this problem in the studio from 12 feet from my amp. Is this still a pickup potting problem?


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Posted: Wed Aug 26, 2009 5:34 am
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spaniel wrote:
Thanks for the detailed answer!

This guitar buzz is a lot louder than the normal hum - not a problem when on stage, but when recording, or even talking over it, it drives me mad. Other folks also seem to think it is louder than average - any other ideas why? I suppose I can try lowering the pickups... I do believe my cables are shielded, but even if they're not, my other guitar doesn't give me any problems (dano).

I think I understand what you say about the amp vibrations causing the coils to vibrate, thus causing feedback. I'm confused, however, at how the vocal mic works into this. If I'm just jamming, no mics, I have no feedback problem. When I try to sing - be within a foot of the mic really - the problems start. It is somewhat alleviated by not being super close to the amp, but I've still had this problem in the studio from 12 feet from my amp. Is this still a pickup potting problem?


Your welcome.

Yes, the feedback is a potting problem. The (re)potting of your pickups in your situation sounds vital!

Lowering your pickups is a waste of time.

Note: The fact that the Dano doesn't give you any problems leads me to overwhelming believe that the problem is inside your Mustang. Specifically, a component is not grounded or wired backwards. It could also be one of your pickups is outright failing too.

Not being there to experience it first hand, the chief other possibilities for the buzzing might be the lighting and/or the 'house' wiring where you play, causing or at the very least, contributing to this buzz. This, coupled by the fact that your pickups aren't humbucking could also exacerbate the situation. Again though, I HIGHLY suspect the problem lies inside the Mustang.

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