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 Hum issues with my DOD G7

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EricHaven
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PostSubject: Hum issues with my DOD G7   Sat Oct 31, 2009 1:11 pm

I'm frustrated almost to tears over this. Can anyone offer any advice?

My used DOD G7 has a really horrendous hum, and I know that it shouldn't be there from having owned a couple before. It is present no matter what patches or modes or used. In clean settings, it's still in the background, and with the compressor and distortion settings up, it's really annoying. Even with the noise gate at full, it still cuts through. The hum resonates around a "B" note, and is so bad that when I play an E or B, I can hear the note phase out-of-tune with the hum tone.

I did notice that the hum spikes worse when I jiggle the power cord at the input. This thing uses an ungrounded two-prong wall transformer, and the jack seems to be a little loose.

I pulled the unit out of the case, and tried to find anything that appeared loose or broken. Everything seems to be attached fine, and the circuit board has no cracks that I can see.

I've scoured the web looking for similar issues, and I have read things about bad power supply regulating capacitors causing hum.

It hums no matter which of the two stereo outputs I use, and even through the headphone jack. All of the patches and switches work perfectly. In addition to trying it through my new QSC power amp, I also tried running it through Linda's guitar amp, as well as my little bass practice amp, and it is the same no matter which amp I use.

So far, the seller is avoiding me, so I might have to take it up with eBay and/or PayPal.

Does this sound familiar to anyone?

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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 1:41 pm

The plot thickens....maybe. scratch

A little more digging reveals that the lowest B note on a piano resonates at frequency intervals starting right around 30 cycles per second. Since standard 120 volt AC runs at 60 cycles per second, then AC hum should resonate with any note that comes close harmonically. And the second B on a piano would fall almost dead center at 60 cycles per second.

If my problem is related to AC hum, this would makes sense, since I can hear B notes on my bass clash with the hum tone.

Naturally, I'm not sure what to do with this little bit o' information. scratch

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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 2:01 pm

I'm pretty sure its AC hum. And I don't think there's nothing wrong with your unit in particular. From what it sounds like, the unit should have been designed with a grounded 3 pronged power cord, but wasn't. I'm not going to claim to be an expert on this stuff, but you should look into getting something like this. I think that should help. That ones a little pricy, but you can probably find different model for cheaper, and there's always eBay.
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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 3:12 pm

Thanks, KS. I did consider going this route, but I just want to be sure that it's not something internal before buying one. I hope that's all it would take! Laughing

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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 3:48 pm

Could somebody else please confirm what I said? Because I'm not exactly an expert at this. I just saw "ungrounded two-prong wall transformer" and "the hum spikes worse when I jiggle the power cord at the input" and took a guess. I'm not even sure the plug thing I suggested will help, even if I'm right about what the problem is. I don't want Eric to go out and buy on something that won't help, and then have to spend even more money fixing the real problem.
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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 4:42 pm

Fear not, KS. After spending all day frittering over this issue, and pouring over page after page after page on the web, I have decided to throw in the towel on the G7. It has come to my attention that it might very well have to do with our power grid here in Birch Bay, and there might not be anything I can do about it.

So I have decided to go another avenue.

Since the POG did not do what I wanted it do, I posted it on eBay, and it sold today. I then took the winnings from that auction, and I just bought another Behringer V-Amp Pro, only this time I got the guitar version. So now my rig will consist of the QSC GX3 power amp for muscle, the Behringer V-Amp Pro Bass preamp for my low/clean channel, and the Behringer V-Amp Pro Guitar preamp for my distortion channel.

So now you might be asking how it is that I believe the Behringer will work for my distortion channel. Simple experience. I am familiar with Behringer's guitar products having owned a V-Tone GMX 212 before, and Linda currently owns a V-Tone GMX 210. In fact, since I did not have my full rig for our last rehearsal, I used Linda's amp for my distortion channel, and I was blown away by how well it worked. The distortion tone screamed, and pulling feedback took no effort whatsoever. And get this. I had no problem keeping up with my guitarists Marshall rig volume-wise. The GMX 210 is a 60 watt amp, and I only had the volume control at midway! Go figure!

And all of the reviews I read about Behringer products going up in smoke focused almost exclusively on their bass amps. But every single review I read about the V-Amp Pro series had nothing but heaps of praise for them. And even the Behringer site seems to indicate that the folks who designed and built the V-Amp Pro units put a lot more time and effort into their design than they might have with some of their other products. So I feel pretty secure with this decision.

Whew! After so many months losing sleep over getting a working rig together, I can finally rest easy. Cool

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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 5:46 pm

^ You should have told us you were selling the POG. I would have bid on it

Great to hear about the rig finaly coming together. The Behringer sounds pretty cool. And come to think of it, as much as people complain about their amps and sometimes pedals dying on them, I've heard of a V-Amp dying, and those are pretty popular too.
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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 6:27 pm

Kugelspot wrote:
^ You should have told us you were selling the POG. I would have bid on it

I did! I posted that I had it up for sale in the Amps thread. I figured that no one was interested. Sorry, Bro! I would have offered it to you first if I had known. silent

Yeah, I think that every piece of gear out there has some horror story attached to it. And I have heard of V-Amps going out, but those stories are few in comparison to the stories of how much players love them. Same with their power amps and pro audio gear. I know more than a few snobby audiophiles who absolutely swear by Behringer's mic preamps, feedback zappers, and power amps, but wouldn't be caught dead recommending their bass amps. For every good review I've found, there are nearly a dozen bad ones.

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PostSubject: Re: Hum issues with my DOD G7   Sat Oct 31, 2009 6:59 pm

Behringer has notoriously bad quality control, if you get a good one it will work till you sell it....

2 of the 3 Behringer boards I have owned have had channel 1 stop working, but never had an issue with the 2 compressors or virtulizer ( rev/echo/chorus ).

as far as hum goes though, usually a power supply change will remove it, if it does not then the internal board on the device's filtercaps are shot and not power supply or "device" will remove it.

My BOSS oem power supplys always hummed and I now use aftermarket supplies with the pedals, and have never had a problem no matter where I plug them in.
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