just built first DIY sub help! (1 Viewer)

[Philip_G]

Ok
I just got my new shiva 12" and an adire 250 watt plate amp, cut a hole in the back of an MCM electronics box big enough for the amp, screwed it in place, stuffed the box with poly fill (completely full) plugged in the sub, screwed it in, and all I'm getting is a REALLY loud hum.
there aren't any directions with the amp, so I'm assuming the red and black wires off the back are the + and - speaker connections, so I hooked them up to one side of the sub, and connected the other set of terminals to them to parallel both voice coils (could this be my problem?) there's a right and left RCA input, I tried my sub cable in both of them, then hooked up a speaker lead from the left main to the high level ins to check, and it still hums.
Any thoughts? it's got to be something retarded I did..
with no input hooked up, there's no hum, the sub cable is an acoustic research 25' I unplugged the sub cable when I plugged in the high level ins, the hum seems about the same on both.

 

[Geoff L]

Not sure but belive the Parts Express 250 and the Adire 250 are the same amp. If so there is a voltage type switch at the bottem of the amp. (in the lower right hand corner next to the power plug connection) Be sure it is set to 115v and not 215v --- as mine came with the switch set to overseas current.
Mine also came with both stye power cords.
Take a look see! Dont know if this would cause your hum if current switch is set incorrectly and your useing the proper cord as its the only on that going to fit in your wall, so pretty hard to screw that up. But if your switch is set correctly and speaker polarity is correct might be ground loop problem.
If wired as you say load should be fine and not causeing your problem.
Give everything the once over again and see if you missed something. Others may offer ideas if your hum continues.
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Smoothe

 

[Philip_G]

Geoff-
I checked the voltage selector briefly, but I didn't get right down and look at it REALLY close so it's very possible it wasn't where I thought it was. I'll definetly check again! thanks!

 

[Gregg Roszkowski]

Hey, if your receiver has an LFE out hook it up to the line in, right or left, doesn't matter. That's all you have to do.

 

[Philip_G]

I have been using the LFE out, that's the RCA out/in I've been using. I used the high in's just to see if it was a problem with the cable or LFE output on the deck.

 

[Gregg Roszkowski]

Oops, but leave the red and black wires hooked up the way you have them and keep keep it in parallel.
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Who Dat!

 

[Gregg Roszkowski]

Sounds like it could be a cable problem. Are you using a single phono plug or a dual red and white rca plug?
If you have the speaker hooked up in parallel and it is hooked up to the terminal cup on the inside of the sub, just take the red and black wires of of the amp and hook them up accordingly. I think you already have it that way? The last thing to do is connect the LFE out to the line in on the amp and you should rockin'.
I bought the wrong type cable that wouldn't insert fully into the RCA jack and the same thing happened. Try a spare set of RCA cables and see if that doesn't work.
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Who Dat!

 

[Philip_G]

it's just a single plug, no different from a standard RCA though, just only one of em
the amp is mounted to the back of the cabinet, so there's no terminal cup, the amp plugs into one set of terminals on one voice coil, then I soldered a speaker wire from the other side, to the other set of terminals on the side the amp is plugged into.

 

[Gregg Roszkowski]

"it's just a single plug, no different from a standard RCA though, just only one of em"
Are you sure? Check the length of the plug with another set of RCA cables.
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Who Dat!

 

[Philip_G]

I've tried 2 different cables (totally different) and the problem persists, I'm pretty sure it isn't the cable, especially since the hum persists with no sub cable, and just the speaker level inputs plugged in.
here's a super crude diagram of how it's wired from the amp to the sub, I double checked my solder joints for quality and polarity, everything seems to be in order, double checked the voltage switch, and (unplugged the amp first) switched it between 115 and 220 then back to 115 to make sure it was "in" the detent.

I'm starting to wonder if they sent me a bum amp

 

[Dustin Haug]

Phillip I responded to your email. From your drawing it appears that the wiring is right. Does the sub make any noise at all other than the hum, or is the hum all that you can hear? Since you are in GF if you can't get it going maybe sometime you could bring it by and I could look at it. Post or email if you need anything.
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My DIY sub page

 

[John E Janowitz]

Philip,
this is a common problem with these amplifiers, as well as the PE ones, and the Amp350 that I sell. Just use one of those cheater plugs to go from the 3 prong grounded plug to the 2 prong when you plug the amp into the wall. This should solve the humming problem. Also, use the bottom of two outlets. If you plug the 2 prong adapter into the top of the two outlets, often the little metal tab will ground with the screw and the ground loop will still be there.
Was the hum your only problem? Do you get output from the subwoofer?
John

 

[Harold A]

I had the same problem when I first got mine hooked up. The cheater plug will take care of it. The humm was so loud on mine that I thought it was broken. The cheater plug took care of it.

 

[Philip_G]

Ok, I'll drop by radioshack and grab a cheater plug today.
I get very little music output and a LOT of hum, you can barely distinguish the music, and the hum is only there when there is some input, if I turn the receiver off, no hum.

 

[Philip_G]

YUP you guys are right, a cheater took care of it!
I never would have thought of that!
Thanks!
it's sounding pretty impressive

 

[Jones_Rush]

Can anyone please explain in plain english what a
"cheater plug" is ? how much does it cost ?, and can
I order it online ?
I searched Radioshack.com for a "cheater plug" and got no
results.

 

[Philip_G]

it's just one of those little adapters that allows you to plug in a 3 prong, grounded cord, into a socket without a ground, like an extension cord, any hardware store should have them for like $2.
if you were brave I suppose you could clip off the ground on the cord if you couldn't find one. Though I wouldn't in a million years

 

[Patrick Sun]

Home Depot has cheater plugs for $0.97. Go look in the electrical department (outlets, plugs, power extension cords, etc).
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PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; Link Removed

 

[Geoff L]

Phil,
Glad things are working for you now! Thought the ground prong might be it but wanted to make sure your voltage switch was correct, as mine came slid over to 250. Hoped you didnt over look this!
Tried to get on line all day and problem with server kept me off line. Was curious to how things were going for you.
Anyway---All my plate amps --- I've snapped of the ground prong! As long as the amp is fused protected. NEVER have had a problem blowing fuses or running into a problem later down the road.
Biggest thing-- NEVER a HUM.
Someone may post info that may stop my anti hum {fix-it} style, but as I see it more or less running a cheater plug is basicly the same thing.
RIGHT?

Please correct me if Im nuts.
So Phil how she sound?
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Smoothe

 

[Philip_G]

sounds pretty good
I ran a test sweep that I burned off an MP3 that somone posted a bit ago from 15hz to 80hz and it seems ok, haven't had time to watch a movie, but I've run through some CD's and haven't bottomed it out yet

it doesn't shake the whole room quite as much as I'd like (I think a twin in the other corner of the room would produce the desired effect though.. soon :bg , but it puts my dad's MK 12" sub to shame.
here's a few quick pics I snapped.