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Vox AC30


Anderson Council Sound

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Hey everyone, I'm mostly a recording engineer, so I don't know much about amps and such, but I have a problem with my friends AC30 that we can't seem to pin down.

 

Basicly, there is a very loud and intrusive mechanical rattle that happens whenever we turn the amp up loud. It does not come thru the speakers, but it is loud enough to be picked up by any microphone we place on the cab, no matter the positioning. We've looked the amp over for any loose screws or anything that could be rattling, and no luck. We also just had the amp overhauled, replaced the tubes, etc., and altho we told the guy about the rattling, when we brought it back to the studio, it was still there.

 

Anyone have this happen before, or could make and suggestions? We are going to start recording soon, and we really need to use this amp, but as it is now, it's useless. We are taking the amp back this friday, but the tech seemed perplexed as to what may be causeing this. I figured I'd stop by here and see if anybody has any words of wisdom for us. Thanks!

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Posting this question in the "Ask Myles" thread will get you the answer. Myles is the -- and I mean THE -- expert on amps.

 

In the mean time, here is what I'm thinking.

 

I would not just look for loose screws but tighten up anything that might be a problem. I'd pick up the amp and give it a gentle but quick "up down" shake, pick it up, then raise it like another 8 inches kinda quickly and bring it back down to the "start" point, and see if you hear anything rattle. Obiviously be gentle.

 

If there is a reverb tank (I guess that is what there called) in it, maybe something is bouncing around in there.

 

Finally, this may also be as obvious as the rest of what I typed, but make sure it is the amp and not something in the room vibrating sympathetically.

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Pad the handle(s). I have had them vibrate on a number of combo amps if the amp is running loud enough. Just stick something soft, like a folded-up washcloth, between the handle and the cabinet. Sometimes, if you pull the handle out all the way, like you're lifting the amp by it, it will stay that way, and that would kill the rattle too. But if the amp vibrates enough, it could slip back into place against the amp and you'd have the problem back, possibly right in the middle of a take.

 

If that isn't it, look for anything else loose in the amp, especially anything that's bolted into place, like the speaker or the chassis, or even the baffle board the speaker is mounted on, and make sure the bolts aren't hangin' loose or something. If all else fails, sit the amp itself on a padded surface, and see if the bottom of the cabinet or the feet(if they are hard instead of rubber) are causing the rattle.

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Thanks for the replys guys, I copied the post in the Miles thread.

 

As far as your suggestions, we have gone over the thing with a fine toothed comb, and nothing. A Vox AC30 is actually very hard to get inside, so that was our main reason to bring it to a tech, we didn't want to mess anything up. But as far as what we can do to the outside/inside, there is nothing loose. The handle is the first thing I grabbed too, no luck. We were hoping the tech would have gone over any screws/bolts on the inside, but it doesn't sound like he did. :-(

 

The vox does not have a reverb tank inside. And altho it is hard to pinpoint exactly where the rattle is comming from while it's on "11", it seems to definitaly be comming from inside the amp. In fact, if we turn it up loud and just knock on the top of the amp, you will hear it rattle.

 

We spent $375 getting the amp overhauled, and it still rattles. We replaced the tubes because a) we thought it may be the problem and b) they hadn't been changed in years. But in reality, the amp sounds awsome, and it didn't really need new tubes. But $375 later, it still rattles, so needless to say it is a bit of a disappointment!

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Someone already pointed this out...but to use a variation of good ole Occam's Razor: "The explanation requiring the fewest assumptions is most likely to be correct."

 

You pick up the case. No rattle

It doesn't rattle at low volume.

Rattles at high volume (hint, hint, hint!)

 

Is it possible that the amp is just shaking up and down on the floor and rattling? Or, the case and contents itself is rattling (harmonic motion or some such Physics concept).

 

Put the thing on a bed of pillows and crank 'er up and see what happens.

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Try a process oif elimination: does it make this rattle sound if you connect a different speaker-cab to it, instead of the internal speakers?

 

Are you sure it isn't a snare-drum's snares rattling sympathetically? Or something else in the room? Have you experienced this rattle in different places, under varying conditions??

Ask yourself- What Would Ren and Stimpy Do?

 

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Anderson Council

This is a strange one, but a guy who i jam with most weeks has just suffered very similar with his really quite new Vox ac30, after 2 returns to the shop for "repair" now he is borrowing one my amps as the fault cant be found and he is waiting on a new amp and not a Vox as he has the hump about it.

so cant really help and never solved it, at least you and he are not alone, i know its small comfort. Hope you can solve it.

G

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Yes, the first thing we did was remove the snare drums and such...we always have the amp isolated off the floor...it is def. comming from the amp, and it is not connected to the volume of the amp. You can knock on the top of the amp and hear it rattle without playing anything, the thing is just too heavy to shake and see if that works.

 

We are taking it back to the tech on Fri, and hopefull he will go over the whole thing better.

 

I asked the question here cause I thought that maybe it was something common to the AC30. That sux your friend couldn't figure out his problem, hope we can ours. This paticular Vox is also a rare red one. Not sure how many were produced, but it was a very limited run. The thing sounds great, just need to find the rattle!

 

Thanx again everyone!

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Best of luck anderson.

have you tried holding any of the knobs when you can here the rattle, i did have an amp that used to shake one of the knobs on the control panel when being cranked??? sorry cant be more help.

G

Love life, some twists and turns are more painful than others, but love life.....

 

http://www.soundclick.com/bands/pagemusic.cfm?bandID=592101

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