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Old 16th June 2009, 03:44 PM   #11
rknize is offline rknize  United States
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Perhaps you have a bad OPT and have DC on the speakers?
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Old 16th June 2009, 04:18 PM   #12
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Such rattle sound may indicate oscillations on high frequencies caused by mods.
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Old 16th June 2009, 10:05 PM   #13
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Default Re: Speaker sounds blown...but isn't

Quote:
Originally posted by bereanbill
I recently aquired a Danelectro DM-10 guitar amp whose speaker had a dropped voice coil. I replaced it with a known good speaker and it still had that "rattle" that is indicative of a voice coil rubbing. I tried 3 different speakers, incuding a new Jensen with the same result. All of these speakers sound fine in other amps...any ideas?

Is the speaker cone fouling the cabinet somewhere ?

Otherwise sounds like an amplifier problem.
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Old 17th June 2009, 04:25 AM   #14
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I was experimenting with my amp and my amp was in a state where layout was pretty sloppy. I heard sounds similar to what you are describing at higher volumes. I confirmed with a scope that the amp was breaking into oscillation every time the amp clipped but would stop when the amp recovered from clipping. Looked wierd on the scope. Sounded exactly like what you are describing.

Cleaning up the layout (making leads very short) cured the problem.
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Old 17th June 2009, 01:49 PM   #15
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Is the speaker baffle warped? If it is, the speaker frame could be getting twisted/warped when you attach it, causing the voice coil to rub.

I'd guess the other suggestions are more likely than this, but thought I'd toss this possibility out there, too.
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Old 17th June 2009, 04:22 PM   #16
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Quote:
Originally posted by SpreadSpectrum
I was experimenting with my amp and my amp was in a state where layout was pretty sloppy. I heard sounds similar to what you are describing at higher volumes. I confirmed with a scope that the amp was breaking into oscillation every time the amp clipped but would stop when the amp recovered from clipping. Looked wierd on the scope. Sounded exactly like what you are describing.

Cleaning up the layout (making leads very short) cured the problem.
Hey...SS..that is the most cohesive reply yet!!! I'll give it a shot. Seems wierd that Danelectro wouldn't bypass the cathodes on this am p when most others are. Maybe a lead dress issue??? THX
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Old 17th June 2009, 04:29 PM   #17
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I would try it with the speaker wired but NOT mounted in the cab.

If it still makes the noise and the speaker is good, it's probably the oscillation mentioned. That happened to me when I removed the "anti-oscillation" cap from my '74 Fender Vibro Champ. (The cap also can reduce some high end.) So I changed the grid wire on that tube to a shielded one and the oscillation was cured.
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