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rattling on a 400+

CDweller

CDweller

Oct 24, 2009
1,212
166
Clearwater, FL
#1
I just purchased a new old stock (they're discontinued) Mesa 400+. The tone is the finest I've heard, to me of course. Yet the top cover of the amp resonates sympathetically when I play, and it vibrates loudly- even to the point where it gets amplified. I am hoping there is a quick fix that someone is aware of before I have to get the factory involved. Killer tone, and if I can get this cover vibration issue resolved, I'm done with new amps:hyper:
 
#5
billhilly66 said:
Tighten the screws maybe?
Click to expand...

Actually removed the screws when the amp was first uncrated to remove the plastic tube protectors. During reassembly, I used blue Loktite on all the screws, and tightened them fastidiously. Not my first rodeo, dont'cha know.

Yeah Johnk, looks like weather stripping is in order, or maybe a bead of silicon along the mating surface, or a 10" or so length of hardwood epoxied edgewise along the area of the cover that rattles the most.

The amp feels light compared to my Reeves 225. I know we can model and what not, but I still stand by my tube amps for tone to the bone!
 
#6
Teething problems with this new amp. I put weatherstripping under the top plate, and that reduced one set of resonance frequencies. But it seems as if another part of the amp's chassis is rattling (An Ab played on the D string does it, thank you) and getting amplified. Frustrating, because this amp has a wonderfully harmonically content getting covered up by this nasty resonance.

I want this amp to be my main live player.

I'm soliciting opinions- I've already started to strip phillip head screws, am dangerously close to stripping screw threads, and have already scratched my new amp.

Back the manufacturer with this amp, or what? Nothing like getting a $40-$70 bill to ship your new amp back to the factory...
 
#8
The first rule of increasing transmission loss of noise/vibration is isolate the source.

Either put the amp on a stand next to the cab or perhaps put a square of thin closed cell foam [like that exercise mat stuff] on top of the cab so when the amp/rack is stacked on the cab it cannot conduct as much vibration in the first place = less likelihood of panel resonances in the amp case + can't be bad for tube life either.


edit - ya, what he said. :-]
 
#9
I think the foam is a good idea. I don't get any rattles, but my 400+ likes to slip-slide around on the top of my cab when we really get rocking. I'm scared I'm gonna vibrate the thing right off the edge onto the floor one of these days. :eek:

Cutting up an old yoga mat might work for both of us.
 
#10
you can also get some sorbothane feet for it, or remove the stock feet and put a disc 1/2"-1" of sorbothane between the feet and the head cabinet (use longer screws of course) and it will isolate it completely from the cab. i've done this before and for me, it works better than anything else. it'll also make the tubes last longer by not transferring any vibrations to them.
 
#11
If it does not have rubber feet already, Mesa will send you some for not much money, and you can get them at the hardware store as well. It has holes for them.

Mine came without rubber feet and I put a towel under it until I got them :)
 
#13
Dang, I'm grateful for TalkBass- you guys are like the cavalry. I greatly appreciate all the suggestions. I'll be getting some foam for under the amp, and the sorbothane material for the feet, as well. Mesa sold a shock-mounting cabinet for the head, but it looks a little wacky to me. I'm thinking I'll get a live-in case for the head, and make sure it's well isolated with foam.

I like the sound of this amp; can't wait 'till it's all dialed in and cooking with gas. I love the smell of tubes working- I think it's ozone, isn't it?
 
#16
Yep- got the idea of not impeding the airflow with any sort of obstruction. I've never owned a rack mount style of amp such as this before, and never had to contend with this issue. All of my previous amps (Walter Woods, Reeves Custom 225, GK, Fender Bassman 50, etc.) have lived happily on top of whatever cabinet without amplifying any chassis resonance.

I'll get the sorbothane for the top and bottom surfaces of the amp, and use some sort of urethane or other elastomer between the mounting nuts,bolts, washers, and rack ears when I get the live in case. Then the case itself will rest on a gramma or other sort of foam. Sheesh, what we do for tone.
 

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