shielding on L2500

[pbass2]

Hi,
I don't remember the last time I tried the preamp in my 2004 US L2500--I've always just used passive. It is DEAD quiet in passive. Well I flicked on the pre today in my home studio where the electrical is pretty darn "clean", plugged into my CMD121P) and man that sucker was pretty darn noisy. I changed the battery just to check--still the same. I did notice that on mine, there's no shielding of any kind on the inside of the plastic control cavity cover.
Think it would help if I put something on there? Shielding paint, foil, etc.? I'm a dummy about that stuff, but I don't want to pay my tech to do something if it's a simple fix.
I've never used active hardly ever, because tonally, it's SO close to passive, so I don't even recall if I've encountered the noise in other settings----but I'd like to know I've got the beast as quiet as I can get it.

 

[Ken Baker]

Here's an image of the cavity from an L-2000 I used to have.

http://www.bassesbyleo.com/images/g&l_tech/l-2000/l2k_control_cavity.jpg

The black paint in the cavity is shielding paint. I cut small copper foil strips and stuck them onto the shielding paint extending over the cover screw holes. I then shielded the entire back of the cover. Once screwed down, the cover is grounded. The self-adhesive foil is available at Stew-Mac.

I've also done this with my new L-2500. It does help to quiet the bass when active.

Another thing that will help is to back off the volume control on this, or any other, active bass. If you run it wide open, it will tend to be noisy.

Hope this helps.

Ken...

 

[pbass2]

Here's an image of the cavity from an L-2000 I used to have.

http://www.bassesbyleo.com/images/g&l_tech/l-2000/l2k_control_cavity.jpg

The black paint in the cavity is shielding paint. I cut small copper foil strips and stuck them onto the shielding paint extending over the cover screw holes. I then shielded the entire back of the cover. Once screwed down, the cover is grounded. The self-adhesive foil is available at Stew-Mac.

I've also done this with my new L-2500. It does help to quiet the bass when active.

Another thing that will help is to back off the volume control on this, or any other, active bass. If you run it wide open, it will tend to be noisy.

Hope this helps.

Ken...

Very helpful---I can handle that. Now, how is the back of the cover shielded in that pic? It just looks like the plastic(?)
Man, my cavity in my bass is a MESS compared to yours! Wires goin' every which-way!

 

[Ken Baker]

Very helpful---I can handle that. Now, how is the back of the cover shielded in that pic? It just looks like the plastic(?)

Not well lit - sorry. Yes, it's shielded with the self-adhesive copper foil that I mentioned above. The whole of the back (in) side is covered. Aluminum shielding foil would also work, but should not be "mixed" with other metals due to the possibility of corrosion caused by electrolysis. Copper tape is easily available, so I'd recommend that.

Man, my cavity in my bass is a MESS compared to yours! Wires goin' every which-way!

That one was much messier before I had to replace the preamp. Not by choice, mind you (it was my fault), but it gave me a reason to clean things up in there a little.

Ken...