# SMS-1 causing sub noise?



## keager

HI everybody,

I'm new to this forum and would like some advice. I have a Denon 3311, Velodyne SMS-1, Behringer ep4000, and a DIY maelstrom 18 with dual PR's. They sound great, but with the volume turned down or no source on the receiver, I get kind of a faint hum. I'm not an expert, but I don't think it is the normal ground loop hum from a sub. The noise is not just a single steady tone, it is kinda broken up or gurggling. Hard to describe. I tried to use a cheater plug on all devices with no change. The only way it will go away is to disconnect the the connection to the sms-1. The connector from the SMS-1 to the Behringer is a balanced xlr. I just need to know where to start. Thanks in advance!


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## dahlke2

This sounds like you are hearing electrical noise from the electronics. The output in the SMS-1 might be close to its processing components and it's picking up the small electric fields like an antenna.


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## keager

Thanks for your reply. If that is the case, how would I check/fix that issue?


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## keager

Since my last post, I removed the sms-1 from the cabinet several feet away from all other components, removed all cabling and ran straight to the amp(so inputs were not near power cables etc.) The noise is present with the xlr coonector and power cable hooked up. All other rca's on the sms-1 are disconnected. If I remove the power connector from the sms-1 it goes away. Could my SMS-1 be defective?


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## dahlke2

​You might want to try using a different xlr cable for the output. When I run sound systems for concerts, sometimes a slightly defective xlr cable causes problems. Also, check the settings on the SMS-1 because you may have a setting up really high so that it is amplifying the small background noise too much. Maybe set it back to the default settings. You posted that you tried to use cheater plugs to see if the noise was a ground loop. If that is the only thing you did, try plugging the components into the power in different configurations. Like into the same pair of outlets without a surge protector; into different outlets; both on the same surge protector; if one has just a two-prong plug try flipping it around. 
​Otherwise you might have a defective product. If you can find another one to compare it to that would be great.


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## keager

Thanks, 

I will try different power plug configurations. I have also used a rca with a 1/4 inch trs plug instead of xlr and no luck. I read that the EP4000 should have the front knob turned all the way up because it is a attentuator and not "gain". Is that correct?


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## dahlke2

I don't think it should matter if the gain knob is turned up all the way. The labeling for the knobs is pretty much the same as the amplifiers I use, and they work fine not turned up all the way.


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## thebuckaman

I am having the same issue with a low level gurgling sound out of the subs when volume is really low. I'm running RCA in to SMS from an Onk 805 and balanced XLR out to a Face Audio F1600TX. Nothing seems to be helping. I have tried several different XLR cables and have made some of my own. No change. Any ideas? This is my second SMS-1.


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## keager

The best I have been able to do is minimize it a bit by using rca's out of the sms-1 and then an adapter to a 1/4 inch trs connector. seems a little better but not satisfactory to me.


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## radz

Have either of you had any luck solving this issue yet?

Keagan you have described almost exactly my situation and all I can put it down to is its the sms-1 causing the problem.

Like you I've tried everything I can think of including, different cables, new dedicated power line even an EBTech Hum eliminator in the line but it all makes no difference at all.

From the above it might sound like the hums loud but I can hardly hear it from 2 metres away when my system is paused but its there and shouldn't be.

Another interesting thing I noticed is when I first started using this system it didn't do it. Over the course of about 3 months with no changes it slowly developed. Also when I first power my system up the sub doesn't make the noise but after I play some audio through the sub it appears and won't leave until I swith the sms-1 off.


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## Theresa

Either they are defective or the design is very poor. I would return it for an exchange.


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## radz

Theresa said:


> Either they are defective or the design is very poor.


Thats what I'm thinking to but wondering if anyone has found a solution that doesn't involve returning although if the units broke thats the best solution.


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## keager

I have not had a solution to my noise problem. It almost seems it is a gain structure problem. I got a new amplifier that is extremely powerful, thus meaning I have the gain on the amp turned way down, and now the noise is pretty minimal, but still there. I am going to tweek with adjusting the Avr lfe output and the volume on the SMS to see if any difference. Pretty annoying, but I don't think it is a defective product.


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## thebuckaman

I have found the only way that has minimized it (not remove it) is to use the RCA in and XLR out on my unit. It has greatly reduced the noise, but I am a noise-free freak and am really going crazy with this device.


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## radz

Looks like we are all going to have to learn to live with it.

I was really glad to stumble on this thread and find out I'm not the only one with this issue.

Something else slightly interesting is that I'm using speaker line inputs so something different than both of you. I might try and adapt these to rca and see if it makes a difference.

Over the next month I'm going to try some different wiring from my amp to see if it makes a difference. I've also going to got another sms-1 to test and see of its the same.


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## bmrowe

Wow, I am having this same issue. Onkyo 805 -> SMS-1 -> EP4000. Whenever the sub goes from being used to not used in a movie scene, I hear a slight buzz and then some gurgling. These noises are pretty quiet, but I can hear them from my listening position a few feet away. 

I also hear a slight buzz from the subwoofer all the time when the gain on the EP4000 is turned all the way up. I haven't tried removing the SMS-1 from the chain yet as its late here, but I will try tomorrow. I think I could cut down on the noise by cranking the gain in either the Onkyo or SMS and bringing the EP4000 down to half gain or so. However, from what I have read, the 'gain' on the EP4000 is more like an attenuation control and should be kept at max to provide maximum bandwidth.

This thread is a bit old, has anyone had any advancements here? I had been using this exact setup for months with no issues. Therefore, if it is an SMS-1 issue, I'd think it would be a warranty type thing.


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## radz

bmrowe said:


> This thread is a bit old, has anyone had any advancements here? I had been using this exact setup for months with no issues. Therefore, if it is an SMS-1 issue, I'd think it would be a warranty type thing.


I have never found a solution.

With my subs I really had to go and stand next to the subs with nothing playing to hear it so I decided to live with it for now.


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## bmrowe

radz said:


> I have never found a solution.
> 
> With my subs I really had to go and stand next to the subs with nothing playing to hear it so I decided to live with it for now.


Did you do RCA or XLR from the SMS-1 to your amp? I am doing SMS-1 RCA -> in wall -> RCA to XLR -> Amp -> Speakon -> sub. I also have the SMS-1 at 14 volume and the EP4000 at max.


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## radz

bmrowe said:


> Did you do RCA or XLR from the SMS-1 to your amp? I am doing SMS-1 RCA -> in wall -> RCA to XLR -> Amp -> Speakon -> sub. I also have the SMS-1 at 14 volume and the EP4000 at max.


I had this problem with XLR but RCA had the same problem.

I don't have my sub on at the moment to check but from memory the SMS volume and EP4000 gain didn't make a difference to the problem. 

Since my first post I've changed amp and either it has reduced the noise or I've learned to block it out (maybe I've just gone a bit deaf).


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## Phillips

bmrowe said:


> Did you do RCA or XLR from the SMS-1 to your amp? I am doing SMS-1 RCA -> in wall -> RCA to XLR -> Amp -> Speakon -> sub. I also have the SMS-1 at 14 volume and the EP4000 at max.




I use to own a SMS-1 and had a couple of different subs hooked up.
My expereience was to keep the levels similiar in level, one was a little bit higher.
The general volume/level was controlled by the SMS-1.
Not sure why you would turn the volume to max on the sub, i would think this would introduce noise.
Quite a bit of gear if you turn up the volume can cause hiss or noise.


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## bmrowe

Phillips said:


> I use to own a SMS-1 and had a couple of different subs hooked up.
> My expereience was to keep the levels similiar in level, one was a little bit higher.
> The general volume/level was controlled by the SMS-1.
> Not sure why you would turn the volume to max on the sub, i would think this would introduce noise.
> Quite a bit of gear if you turn up the volume can cause hiss or noise.


With a passive amp (which perhaps is foreign to you), you need to use an external amp to control volume. Setting the 'volume' to max on my EP4000 is essentially putting the attenuation to a minimum. By that, if you turn the 'volume' down any more, you would reduce bandwidth. Many have stated that the volume level on the EP4000 is more of an attenuation control instead of a volume control.


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## bmrowe

I found a solution. I had been using a bare wire from the EP4000 into a speakon terminal at the speaker. I put on a speakon connector on the amp side and noticed that the rumbling had become constant with no LFE content being played.

I did some more searching and found a thread on avs that contained the following:



> The last thing I did yesterday was I decided to run a subsonic filter of 15Hz with a slope of -36db (I was just playing around). So the first thing I undid tonight was the slope of the subsonic filter. Every time I changed the number, the sub made a noise like it was getting feedback from each change. When I got -12db, the noise stopped. I went back to -18db and the rumbling noise came back. So I set it to -12db and saved the changes. When the SMS-1 came back on after the save, the noise started again, but now it was intermittent. So I went back in and changed the number to -6db and the sound is gone, even after the save.
> 
> I even went back in and tried the larger numbers again and the issue is very consistent. -6 is no noise, -12 is intermittent noise, and anything larger is constant noise.


Sure enough, once I adjusted my subsonic filter slope the noise went away. Obviously this isn't a long term solution, but its good to find out exactly what was causing the issue.


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