B450 Resurrection and Intro

**Old Joe** · #1 07-29-2011, 08:47 AM

Hello TB. I've been lurking and making comments here and there but this is my first thread here on the site. I guess a formal introduction is in order.

I got involved in music from an early age, when I was six. Can play a bit of keyboard, guitar, flute, and of course bass. Took a long vacation from music to concentrate on college and forming a family. Played regularly at church for about 10 years, in the school's band for about 5 years, and with friends at jam sessions. I am starting to get back into music and want to concentrate on bass. My plan is to get real good so when the kids hopefully go off to college I am ready to start or join a band and play regularly. Kids are still young, so I have plenty of time to get better.

Now that the intro is out of the way, I wanted to share a recent "resurrection" I did on an Acoustic B450 combo amp. I already owned a Carvin R600 and a 410 cab which I use on the second floor of our house. I've been wanting a cheap combo to practice while on the first floor of our house so I don't have to lug that beast downstairs when my kids are sleeping. The local GC had this combo listed as having a cracked frame and had been there since February of this year. I called and was told that the electronics where not working. So I figured, if the speakers are in good shape, and I get a good price, I can at
least get a 210 cab. Went to the store to take a look. The guy that I talked to was very nice and upfront about the problems with it. He plugged it in and flipped the switch. The head turned on and made the familiar click sound when the amp starts to feed power to the speakers, but no sound. I checked the speakers and the cones where not torn. Pushed them a bit and they didn't appear to be blown. Now I am ready to buy this thing. After some haggling I got it for $70 plus tax, which I think was a fair deal.

Here is the cab as I started stripping it:

The insides looked OK:

The head seemed fine inside:

Here was the problem with it. The cables that feed the speakers had come loose from the crossover board which was located in the head:

MODS: If this thread is in the wrong area please move it. This looked like the right place to make the thread. If it is not, my apologies.

**Old Joe** · #2 07-29-2011, 09:11 AM

The crossover is in a board by itself in the head. I wanted to move this to the cab since I want the cab and head separate from each other.

Got some Speakon connectors for the amp output.

Not the cleanest job but it works and keeps the whole project as cheap as possible.

**Old Joe** · #3 07-29-2011, 09:37 AM

Mounting crossover board and jacks on the plate.

**Old Joe** · #4 07-29-2011, 09:43 AM

This is my first time really using a router so the cutouts for the plates and handles did not come out too clean. I attempted making some templates but got impatient. If I ever do a project like this again I'll definitely make some templates.

I used 7-ply 3/4 inch thick birch plywood. In hindsight could have used 1/2 inch but I wasn't going for a light weight cab anyway. This one's staying at home.

I was able to salvage the port tubes on the original cab but managed to destroy them while checking for fit on the new one.

**Old Joe** · #5 07-29-2011, 09:51 AM

Since I used screws I got to test the cab before committing to glue. Sounded pretty good at this point and it helped me get excited to finish it.

Rounded the edges off. Time for some PL Premium goodness...

I left one side off to make it easier to glue the foam in. Didn't really need to do that...

**Old Joe** · #6 07-29-2011, 09:59 AM

After reading some threads here I decided to go with the mattress padding that Walmart sells. I did just one layer at this point but later found out I needed more. Ended up stuffing the old padding in and that seemed enough to really get the air moving out of the cab.

After this I closed the open side and gave it a poly finish. I used speaker gasket tape on the speakers, jack plate, and handles. Had some rattling when testing it and determined that I needed to get the speaker screws really tight. I didn't want to damage the frame so I was a bit timid about getting them tight at first. But after I did the rattling went away.

**Old Joe** · #7 07-29-2011, 11:07 AM

After waiting for the paint to dry and assembling it, this is what it looks like. I made a case for the amp too.

Not perfect but sounds good enough to practice with. I even added the cab to my Carvin setup and it sounds extremely loud and punchy.

**Old Joe** · #8 07-29-2011, 11:19 AM

Some more pics:

**Old Joe** · #9 07-29-2011, 11:43 AM

I ordered some ports to help with projecting the lows a bit more. It sounds good but definitely needs a bit more fullness in the lower range.

I do have a question for those who have worked with amps before. The amp is not the cleanest one. There is some slight hiss to it, which I am fine with. But I noticed that when I get the pickups close to the amp on the side where the toroidal transformer is located, I get some noise. Not exactly a hum. But the kind of noise you hear when you get near big electrical substations.

I don't have this problem with my Carvin amp and thought it might be because the Carvin amp is completely enclosed in a metal case. Thinking it was a shielding problem I lined the head case with aluminum foil to electrically enclose the amp. But that didn't do much to eliminate the problem. The foil is doing its intended job. I can trace an electrical connection from any point in the foil to the amp's ground on the electrical plug on the back.

It's no biggie since the noise only occurs when I am about a foot away from the amp and only on the side where the transformer is. But since this is a learning project for me, I'd like to know if anyone has a possible solution. If anyone can give suggestions on this feel free to do so.

Jimmy P. · #10 07-29-2011, 06:44 PM

Good work! It looks great! Regarding the source of the noise, don't overlook your guitar -- is it shielded? (With either copper foil or EMF paint...)

**B-string** · #11 07-29-2011, 07:07 PM

The noise from the trans will more than likely overcome a thin piece of foil.
Nice job BTW.

Immigrant · #12 07-29-2011, 10:43 PM

Congrats on the job well done. That thing has style now.

**Old Joe** · #13 07-30-2011, 01:00 PM

Thanks for the props guys. Could have been better but this is my first try at something like this so I'm taking it easy on myself.

Quote:

Originally Posted by Jimmy P.

Good work! It looks great! Regarding the source of the noise, don't overlook your guitar -- is it shielded? (With either copper foil or EMF paint...)

I tried with a bass I recently shielded with copper foil and an EMG equipped bass. The results were the same.

Quote:

Originally Posted by B-string

The noise from the trans will more than likely overcome a thin piece of foil.
Nice job BTW.

That's what I'm thinking. I used two layers but it might not be enough. That is a big transformer and it's seating very close to the edge of the case.

If I remember correctly, on my Carvin amp, the transformer is sitting almost in the middle of the case. The case is completely closed and made of fairly thick gauge metal. Probably steel but don't quote me on that.

It is what it is. And I'm happy with the overall results.

**B-string** · #14 07-30-2011, 01:13 PM

You could cut up a steel can like from canned veggies as a shield. Just remember the trans needs air flow too.

**Old Joe** · #15 07-30-2011, 01:41 PM

Quote:

Originally Posted by B-string

You could cut up a steel can like from canned veggies as a shield. Just remember the trans needs air flow too.

But, then I would have to eat the vegetables. That's more work than I'm willing to put into this.

The foil was a quick and cheap attempt at shielding it. But I didn't cover the vents. I rather have it hum than burn down the house.

lfh · #16 08-13-2011, 12:01 PM

Very cool project! Thanks for sharing in detail!