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Main => Audio/Jukebox/MP3 Forum => Topic started by: General Zod on September 07, 2004, 09:34:28 pm

Title: Annoying HUM in my speaker
Post by: General Zod on September 07, 2004, 09:34:28 pm

Having almost completed my MAMEcab , just adding a few finishing touches. I'm noticing a very profound hum coming from the cabinet speaker.

I'm running the + & - from the hacked speaker, into the + & - terminals on the jPac. The cabinet speaker itself is already wired to the jamma harness.

The hum goes away when I turn off the hacked speakers, but then so does my sound!  :-\

Any advice on what to do for eliminating the hum?

Thanks in advance.

Michael

Title: Re:Annoying HUM in my speaker
Post by: clonestar on September 10, 2004, 01:28:47 pm

Try this at your own risk (and maybe see if anyone else agrees with me before you do):

Run a wire from the j-pac ground to a screw on the pc case to earth it.  Might well make it go away.

Title: Re:Annoying HUM in my speaker
Post by: Craig on September 16, 2004, 04:22:33 pm

Keep all your audio signal and speaker wires away from any voltage wiring. ;)

Title: Re:Annoying HUM in my speaker
Post by: CM on September 29, 2004, 10:07:34 pm

Also (I am assuming you are using amplified speakers) turn down the PC's audio line-out volume very low.  Use the speakers' volume instead.

Title: Re:Annoying HUM in my speaker
Post by: General Zod on September 30, 2004, 09:39:15 am

It's been a while since I posted .... ( storms around here and such ) ... but after trying a few different wiring configurations, and also having talked to a couple of people , the problem still persisted.  >:(   Until ....

I dug a little deeper in the ol'research department and found out that my being thrifty when it came to audio solutions was my biggest problem. Cheap, unshielded wiring was to blame in the mysterious, annoying hum.  ;)

Lesson learned , and the moral is ..... Don't buy cheap speakers, but try finding decent speakers at a cheap price.  :D ( moreover if you plan on hacking them as a source of powering the existing cabinet speakers. )

Title: Re:Annoying HUM in my speaker
Post by: gap on October 05, 2004, 09:06:27 am

I've got a hum that goes away when the fluorescent marquee light is turned off.

The placement of audio components will be difficult to change, so is there something else I can do?  I'll ditch the fluorescent and install incandescent before screwing around with the audio stuff.

Here's a pic of the back of my speaker panel, which is mounted diagonally below the marquee:

http://www.mamegap.com/images/speakerpanelback.jpg

It contains:
- A 10x10 watt stereo amp kit (http://www.circuitspecialists.com/prod.itml/icOid/194).  The dangling cable on the left connects to a 20' extension cable (1/8" phono, shielded but sorta thin, $8 at Radio Shack).  The right dangling cable (unshielded) goes to a 12V power source (old PC power supply) mounted in the bottom of the cab.

- Two 4" shielded Happ speakers, connected by short (10" or so) fairly thick unshielded speaker wire.

- An Oscar-inspired volume control setup (http://www.oscarcontrols.com/volume/index.shtml), using a 100K stereo pot before the amp.  That's the thing up top, mounted to an aluminum z-bracket.

Any suggestions?  The fluorescent light is a GE fixture, about 5 years old.  I read something about electronic vs. magnetic ballast thing-a-majigs.  Would an electronic ballast eliminate the hum?

How about a metal shielding box around the amp board and/or volume control pot?

Any ideas appreciated.