solved: audio crackle in mame cab - any ideas?

[Jimbo]

Hey all,

I've got my mame cab running great with groovyarcade.  I'm getting slight audio-crackle and a bit of buzz/hum from the speaker (it's an electrocoin midi with a single speaker in the marquee area).  The crackle/buzz is slight and seems to be linked to activity on screen.  For example, the buzz seems to happen in sync with a flashing logo etc.

Here's my setup: -

 - Motherboard directly mounted to plywood base in the cab.
 - audio amp, JPAC, hantarex polo/3 15Khz CRT monitor.
 - Cab wired for Jamma with a J-PAC
 - audio out of PC goes to audio amp (stereo mini jack)
 - mono audio out of amp goes to J-PAC speaker inputs
 - 12v amp is powered by the same ATX PSU powering the motherboard.
 - Also has a suzo-happ switching PSU powering marquee and various button bulbs etc.

I'm thinking it is probably a grounding issue, but not sure what the best things to test/try are.

Any ideas?  Aside the occasional crackle and buzz, the audio sounds great, but this small thing is niggling me.

Cheers - James

[Mike A]

It could be the amp and PC sharing the power supply.

Try powering the amp with a different power supply.

That is an easy and quick test.

[Jimbo]

Hah - that solved it - thanks Mike!

[Mike A]

I try to start simple. That tends to fix most problems.

I am glad I could help.

[Gilrock]

So is this for JimboVision?  I just stumbled onto that thread 2 days ago when searching for rotating monitors.  Read the whole thread and then it seemed to die out but I noticed you were still active.

[DaOld Man]

I was going to suggest same but Mike beat me to it.
I had same problem with my first jukebox, which speaker bar tapped onto atx power supply.
Seemed it got worse if i turned up volume. (Would start to crackle and even cut out.)
New power brick dedicated to speakers fixed it.

[Jimbo]

Heeey...

Jimbovision...

Hmmm....

Things have changed a lot for me since I started that project.  I went from a small house with hardly any space, and needing to fit all my gaming needs into 1 cabinet, to having a bit more disposable income and a larger house with a decent sized garage.  I've since bought a few cabs and no longer have the need to have everything in one.  I really enjoyed that project though and I learned a lot.  I still have the sketchup plans if anyone wants them, heh.  Right now I'm looking at building up the cabs in my garage gameroom.  I have a few originals (recently restored an Out Run), but I still have the urge to scratch-build stuff - and I haven't really done anything since my Videotron bartop project.  My next scratch build will probably be a multi-vector machine.  Hopefully later this year as I am still trying to get these Electrocoin Midi's restored and mamed up with groovyarcade.  They've been a fun project actually, maybe I'll post about those too!

Thanks for the interest anyway.   I still have the control panels for Jimbovision. but I never got further than the rotating controls unit.  My guess is they will be pilfered for controls over the next few years  

[Gilrock]

Thanks for the update.  I don't think I would build the rotating control panel but it was a cool design.  I'm wanting my next cab to have the ability to swap out control panels though.  I want to make it jamma compatible and run multiple items like a BitKit, Mister, and anything else jamma compatible.  I had thought about trying to make the monitor rotate but MikeA says I should just build 2 panels...lol.

[Mike A]

2 cabs minimum.
1 horizontal and one vertical.

[Jimbo]

Agree with Mike!  If you have the space - that's the way forward

Your idea sounds cool Gilrock.  I've also considered a Mister, but I'm not convinced it would be good for an arcade cab where kids and friends/relative will be left alone with it.  The Mister frontend is basic but it looks like it could be messed up by someone fairly easily going into the settings etc.  Also with groovyarcade and a CRT and nicely configured framedelay settings etc, you really can get it close to real hardware, at least so it's hard to really tell the difference for normal folk!

[Gilrock]

Yeah it would mainly be my play toy.  I've had tons of people at my house of various ages and most will look at my room full of games and not even make a comment about it.  I have to drag people in there to try to show off anything.  So I don't seem to have to worry about anything being used without my guidance...lol.

[csnow]

2 cabs minimum.
1 horizontal and one vertical.

Agreed.  Even better if you can swing four so you can have 4/8 way of both horizontal and vertical.  Just say no to the Franken panels.

[Zebidee]

2 cabs minimum.
1 horizontal and one vertical.

Agreed.  Even better if you can swing four so you can have 4/8 way of both horizontal and vertical.  Just say no to the Franken panels.

These numbers can start increasing very quickly if you add-in factors like one-player vs two-player, trackballs, spinners, driving games (they have different control styles too). If you don't like frankenpanels or swapping out control panels, then a decent basic arcade setup could easily be a dozen or more machines.