[taylor]

I am putting together an amp that uses a JM4556 and is... err... similar to a certain commercial amp.

So, 3 questions:
One of the 0.1uf decouping caps broke, and I don't have any spares. Should I keep it with one decoupling cap, run it without decoupling caps, get another cap that is a different size, or et 2 new caps of a different size?
I was too cheap to use a real amp power supply, so I raided an old pc and took the power supply from it. I cut off the AT harnesses and just used the +12v and -12v rails. I think it has caps, so caps in the amp should be redundant?

For the casing, I didn't have one of those fancy Hammond cases. So I got this old parallel printer switch, ripped out the guts, drilled new holes, and sanded the paint off for a metal finish that will look nice with my imaginary PS-1s. But 2 days later, it's starting to rust. Should I go for the "ghetto-fi" theme or is there an easy way to make it not rust?

The amp itself is not loud and sounds very staticy. Is it just because of my subpar components or is there a more serious problem?

And, my closing thought "Why didn't I save myself 20+ hours of work and just buy a CMoy?"

 

[eyevancsu]

Maybe you should try buying some clear coat paint from Rust-O-Leum, thats the stuff i use when i sand down to bare metal. Its only a few bucks, so id say its worth a shot.

Quote:

The amp itself is not loud and sounds very staticy. Is it just because of my subpar components or is there a more serious problem?

It shouldnt be because of sub-par components.

Quote:

And, my closing thought "Why didn't I save myself 20+ hours of work and just buy a CMoy?"

Because DIY sounds so much better and is much more satisfiying, or so ive heard...

-ivan c.

 

[taylor]

Quote:

Originally Posted by eyevancsu It shouldnt be because of sub-par components.

Because of the broken decoupling cap maybe?

 

[PinkFloyd]

Quote:

Originally Posted by taylor I am putting together an amp that uses a JM4556 and is... err... similar to a certain commercial amp. So, 3 questions: One of the 0.1uf decouping caps broke, and I don't have any spares. Should I keep it with one decoupling cap, run it without decoupling caps, get another cap that is a different size, or et 2 new caps of a different size? I was too cheap to use a real amp power supply, so I raided an old pc and took the power supply from it. I cut off the AT harnesses and just used the +12v and -12v rails. I think it has caps, so caps in the amp should be redundant? For the casing, I didn't have one of those fancy Hammond cases. So I got this old parallel printer switch, ripped out the guts, drilled new holes, and sanded the paint off for a metal finish that will look nice with my imaginary PS-1s. But 2 days later, it's starting to rust. Should I go for the "ghetto-fi" theme or is there an easy way to make it not rust? The amp itself is not loud and sounds very staticy. Is it just because of my subpar components or is there a more serious problem? And, my closing thought "Why didn't I save myself 20+ hours of work and just buy a CMoy?"

Hi Taylor,

It's not rusting it's starting to oxidise. To prevent rust you'll have to clean the oxidisation (the brown stuff) back to bare metal with some 000 grade steel wool.

If you're going to hand paint the enclosure then go for an all in one like Hammerite. If you're spray painting it then go for a red oxide primer followed by your top coat. If you want to keep the appearance "bare metal" then strip the board out and spray the entire enclosure with 3 or 4 light coats of semi sheen lacquer...... that'll seal the metal and will prevent oxidisation (ingress of moisture)

Follow the instructions on the spray pain tin and build up using fine coats instead of one heavy coat. If you want a really professional finish, let the lacquer set for 2 months and then buff it up with some rubbing compound finishing with a good quality silicone car polish.

Mike.

 

[Sal]

I like gloss spray polyurethane for coating enclosures. In your case, you sand down the enclosure, don't touch it with fingerprints but immediately clean it with alcohol or something to remove grease and spray with polyurethane.

I get the spray polyurethane at Home Depot or any hardware store in the paint dept. Makes your amps shiny.

 

[taylor]

I got some Rust-Oleum clear spray paint that I will use, now I need to find some steel wool.

 

[PinkFloyd]

Quote:

Originally Posted by taylor I got some Rust-Oleum clear spray paint that I will use, now I need to find some steel wool.

1200 grade wet or dry sandpaper will also do the job.

 

[kevin gilmore]

You cannot use a pc power supply for this. The power supply expects
a significant load on the 5 (and possibly 3.3) voltage lines. Many
power supplies won't even start up without a 5 volt load.