Amp Buzz

[dude]

I just built a ruby amp the other day (go to http://www.runoffgroove.com/ruby.html for a schematic) and it works well save for a LOT of buzz. I imagine if I ground the metal box I've got it in it will help, and also the pot cases, but I'm not sure that's it. For one thing, the buzz gets louder when I touch the strings or anything else connected to the ground in the circuit. Anybody know what to do to fix it?

[Samba Pa Ti]

it could be the lack of shielding, the amp could be picking up RF noise and the guitar (and lead) is acting like a massive antenna (a bigger one when you touch the strings).

[JoeAArthur]

Sounds to me you have your input jack wired incorrectly - like the "ground" and hot lead is backwards.

[dude]

Thanks. I did notice that there was less buzz downstairs, so Samba is probably right.

As for JoeAArthur's hypothesis, I'm going to try that, too, though it doesn't make sense to me. I thought the signal coming from a guitar was an alternating current, and therefore it shouldn't matter which contact goes where. But, You undoubtedly know a lot more about this than I do, and it really isn't any trouble to try your solution, so I'll go for it. Thanks!

(Edited a spelling error)

Edited June 15, 2007 by dude

[Geo]

Thanks. I did notice that there was less buzz downstairs, so Samba is probably right.

As for JoeAArthur's hypothesis, I'm going to try that, too, though it doesn't make sense to me. I thought the signal coming from a guitar was an alternating current, and therefore it shouldn't matter which contact goes where. But, You undoubtedly know a lot more about this than I do, and it really isn't any trouble to try your solution, so I'll go for it. Thanks!

(Edited a spelling error)

The signal is AC, but you still have to pick one side to be ground. With the wires reversed, you've basically decided that the strings are no longer grounded but are now an antenna. It also makes all the shields in your shielded wires antennas.

So it's not so much that there is a real "correct" ground side, just that you've connected some things that must be grounded (shields, pot lugs, ground tab on jack) to one side.

[CrazyManAndy]

Once you get rid of the buzz, let me know how it sounds. I've been contemplating building one myself.

CMA

[dude]

I switched the input jack. There's almost no buzz now. Thanks for the help!

CMA, I'm really not the person to ask how it sounds. It sounds good to me, but my experience in this area is extremely lacking (I've never owned an amp before). It was a fun project, though. Good way to kill an afternoon.

[Geo]

I switched the input jack. There's almost no buzz now. Thanks for the help!

CMA, I'm really not the person to ask how it sounds. It sounds good to me, but my experience in this area is extremely lacking (I've never owned an amp before). It was a fun project, though. Good way to kill an afternoon.

Hey, that's pretty cool if the first amp you've owned is one you've built!

[CrazyManAndy]

I know what you mean dude. I only have a second-hand practice amp (Peavey Rage 158) and I don't even have a guitar to play through it (never actually played an electric).

CMA