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Welcome to the Forum, Murphy!

You might try floating the ground in the balanced connections (i.e., clipping the shield from the connector at one end), but it sounds to me like your problem is probably “upstream” of the BFD and amp, like maybe a cable TV or satellite dish feed that’s not properly grounded. It won’t do to turn off everything in front of the BFD/amp. It needs to be disconnected from the BFD/amp. I’d first try disconnecting any cable/sat service antenna cables from the system. If that doesn’t isolate the problem, then disconnect each component from the system and then add them back one at a time to see where the noise starts.

Regards,
Wayne
 

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Thanks for the suggestions. I disconnected the Lexicon processor, the TiVo unit, the Z-box, the DVD players. We turned off all computers and wireless networks just in case they were adding in anything. The hum was still there. We do not have cable or satellite only off-air antenna and I disconnected that also. The only things I did not disconnect were the other 4 power amplifiers. The equipment is in a equipment closet and to disconnect the other amplifiers is a major tear down. Is there a different unit that can do the same thing as the BFD with adding in the hum?

Getting desperate and annoyed,
Murphy
 

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Getting desperate and annoyed,
Murphy
The simplest ( though not cheapest ) solution is to provide the offending component ( the Behringer unit in this case ) with Galvanic Isolation ( in the form of ground lifted, audio transformers ) .

(i) Here's a set . You should ( hopefully ) only need them on the output of the 1124 .
- Jensen Transformers are TOTL ( spec wise ) & quite transparent in the circuit ( more so than even the Behringer unit that they would follow :whistling: ) .


(ii) Here's a much cheaper solution at @ 1/5 the price ( though utilyzing the same approach of providing galvanic isolation with ground lifted transformers ) .
- These are just "alright" ( spec wise ) and within a clean circuit ( not yours at the moment ) are apparent ( to the trained ear ) when they are inserted into the signal chain .
- I'd recommend starting with these & then moving on to something better ( if you figure the system warrants the extra monies spent ) .



NOTE : The Urei/JBL 6290 amp ( & the rest of that series ) are pin 3 hot . 6290 OM pdf
- Your Lexicon unit ( like all newer balanced electronics for the last couple of decades ) are pin 2 hot .
- Mixing electrical protocols ( such as you are ) can often lead to hard to trace noise problems / especially with single phase electrical services ( that may already be at a tipping point / current balance wise ) .
- (FWIW ) if those were my amps, I'd modify their front ends & rewire the XLR connectors ( by simply swapping the wires at pins 2 & 3 ).

:sn:
 

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Is there a different unit that can do the same thing as the BFD with adding in the hum?
So you were not having any hum before inserting the BFD into the signal chain?

Most home theater users get the hum with the BFD because they’re inserting a component with a grounded electrical plug into a system that has only two-prong power cords. Since you already have grounded-plug components in your system (the amps), that suggests to me that you might have a defective BFD, or else used bad cables to make the connection.

A couple of other suggestions: Is there a ground cable for your antenna? If so, it should be connected to the house electrical ground stake.

Also - it sounds like you have your amps in one location and your other electronics in another? If so, there’s a good chance the two circuits in use are on different electrical phases. This is a common source of a hum and noise.

Regards,
Wayne
 

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Ok, I spent the money and purchased a Jensen ISO-MAX. I installed it on the output side of the 1124. It did not remove the hum.

Any more suggestions? Please!!
 

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Ok, I spent the money and purchased a Jensen ISO-MAX. I installed it on the output side of the 1124. It did not remove the hum.

Any more suggestions? Please!!
Things to try ;

(i) Locate the 1124 to the location of your amplifiers ( & power the 1124 with the same AC service as the sub-woofer amp ) . Put the ISO-MAX on the input of the 1124 .

(ii) If you bought the 2-chnl ISO-MAX, isolate the input & the output of the 1124 .
- Under those conditions of galvanic isolation , the 1124 should be quiet ( apart from it's inherent circuit hiss ) . If it still produces a loud hum & buzz , then the 1124 either can't work with the AC it's getting ( it happens, but is quite rare ) / or the unit itself is defective ( much higher odds ) .

:sn:
 

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Thanks for everyone's help. I had to get another XLR cable so that is why this replay was delayed.

This is what I did last:
  • I put the equalizer on the same power circuit as the sub-woofer amplifier.
  • The ISO-MAX is 2-channel, so I put the input to the equalizer on the first channel
  • I put the output of the equalizer on the second channel.
The hum/hiss is still there but maybe slightly reduced. So does this mean I have a defective equalizer?

Murphy
 

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Hello everyone. I just joined this group recently when I decided to do some upgrades to my home stereo. After years of powering by NHT 1259 subs with a Carver 225wpc TFM24 I decided is was time to pull the trigger on something with more headroom and also apply some room eq using a FBq1000. I don't mean to hijack this tread but short of reading through all 300+ replies in the hope of finding an answer I was hoping someone here might have already come across this. Anxious to get things up and running I set up the new Behringer EP4000 and FBD last night using a Samson S-Converter to get me from RCA to XLR. The signal path is Preamp Sub Out => Samson => FBD => amp. At power on everything worked as it should except for static (digital noise) on the subs. No problem with hum. To isolate the problem I removed the FBD and ....no noise. Has anyone come across this issue before and figured out a possible cause?

Dan
 

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For starters, the FBQ isn’t especially known for its stellar noise characteristics, and you’re merely boosting the noise with the S-convert. There is no reason to use it merely for RCA to XLR conversion; the downstream equipment, both the EQ and amp, will accept unbalanced connections, so you merely need RCA to 1/4" cables readily available at your local guitar shop. Feeding the output straight from your receiver to the FBQ, you might be able to get away with using its rear panel switches in the quieter -10 dB position. If you end up needing a signal boost for the amp, insert the S-convert after the FBQ, and boost just enough to drive the amp to max, and no more. More details in the article on gain structure you can find in my signature.

Regards,
Wayne
 

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Wayne

Thanks for the reply. I will give your suggestion a try and see how it works. It sounds like I should have maybe done a little more homework before giving this eq a try. I was intrigued by the possibility of using this with REW to improve on sub performance but I guess in practice there are always trade offs. I have a lot of high end equipment which without the BFD is dead quiet. As I see it it's a worthwhile experiment even if I can't find a workable solution. If after 30 days of tinkering I can't quiet this unit it'll be heading back to Parts Express. Thanks again.
 

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Wayne,
I read through your series on gain structure this morning and while I don't pretend to understand all of the technical details I have a pretty good idea of how to go about using the BFD in my system now. I haven't tried this yet but I was planning on testing the noise performance of the BFD using the same connections mentioned in my first post, except using the -10db input setting on the BFD and dropping the gain on the Samson converter. Dropping the gain will undoubtedly limit the power of the EP4000 but frankly, at least for the subs I'm currently running should still be more than enough.


Dan
 

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Dropping the gain will undoubtedly limit the power of the EP4000 but frankly, at least for the subs I'm currently running should still be more than enough.
Dropping the S-Convert gain has no affect on the amp’s power output. You can simply increase the amps gain controls to compensate – that’s what they’re there for, to accommodate a wide variety of input signal levels.

Really, you probably don’t even need the S-Convert. The EP4000 can be driven to maximum power with a mere 1.23-volt input signal. Most modern receivers’ sub outputs generate way more than that. If you’re not sure if yours can, it’s easy enough to determine your output voltage – Part 7 of the gain structure article outlines an easy-to-accomplish process that anyone with a digital volt meter can do.

Regards,
Wayne
 

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For what it's worth I thought I would give a quick update on my progress in trying to solve the noise issue with the BFD. Wayne, as you suggested I removed the S-Convert and used a RCA-to-TR adapter on the input of the BFD. This didn't solve the noise issue but it was one less piece of electronics in the signal path. I still have plenty of output from my preamp/xover to drive the BFD. As a cheap experiment I built an AC box with the reverse polarity parallel N5401 diodes and a 22R parallel resistor to ground to see if I could break the ground loop. FWIW, this is the same scheme used by Nelson Pass in the A-75 amplifier I built 15 years ago. I had high hopes this would solve the problem but after trying several combinations of plugging in the AC using this box the noise was still there. What I found is after powering up everything if I touch the chassis on the BFD the noise level drops, but then comes back again intermittantly. It's not so much a hum as it is just noise. I ordered a ART DTI box today from Sweetwater Music and hope this solves the problem. In the grand scheme of things the fan noise from the EP4000 is much louder than that from the BDF, but that problem will be solved by replacing the fan with one that is quieter. I really like the ability to measure room response using REW and then send the filters to the BFD using the MIDI connection. It would be great to put the BFD before the preamp and correct the entire system but I'm concerned fidelity would suffer. Some day when I have nothing to do I might give it a try.

Dan
 

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I have been living with the hum for years. Recently bought a new surge protector and was plugging all the power cords back in and decided, like Popeye, "That's all I can stands and I can't stands no more". (The cheater plug removes the hum) I want to try making the RCA to XLR plug to try and eliminate the hum. I have a male XLR connector and a Monster Bass 300 RCA Subwoofer cable that I had used before adding the BFD DSP1124P. I have stripped one end of the RCA and after looking at what's inside I am confused as to what connects (and what doesn't connect) to the XLR pins. I will attach a picture. This is a description of Monster Bass 300:

Balanced Subwoofer Cable Improves Bass Response
• More Accurate, Realistic Home Theater Bass w/ Greater Clarity
• 24k Gold Contact Straight-Cut Turbine Design Connectors
• Special Low Frequency Wire Network Delivers Deeper, Tighter Bass
• 12 Ft Length

Any help would be appreciated.
Thanks in advance
Ron
 

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Basically there are only two functioning connections from the RCA: The signal (+), which appears at the connector tip, and the signal (-), which appears at the connector sleeve.

You’ll need an ohm meter to determine where all the wires are showing up on the connector. I expect that the two insulated wires have continuity with the RCA tip, and the two bare wires with the RCA sleeve. However, it’s possible that only one of the insulated wires is actually connected to the tip, ditto with the bare wires and the sleeve.

As far as the XLR connections, the signal (+) will go to Pin 2 and signal (-) to Pin 3, with a jumper to Pin 1. If the hum and noise persists, try disconnecting the jumper.

Regards,
Wayne

 

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Hello Wayne.
Had to run out to the hardware store to get a new multimeter as the one I had has died. Had to watch a short you tube video to get up to snuff on using it as I have never really used it much.
The brown wire goes to the tip by itself. The black, bare silver, and the ground shield are all connected to the sleeve.
So, does this mean that all 3 of the sleeve connecting wires need to go to Pin 3?
Just so you know, my understanding of this kind of stuff is limited!
Thanks,
Ron
 

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Wayne,
I have tried with and without the jumper. The hum is still present. I plugged the cheater in as test, and the hum goes away 100%. I had read through all the posts where the cause of the hum is solely from the BFD and the cheater plug stops it cold. (True for my case) I thought part of this fix was to "leave the ground/shield open". (Page 7 post 68 from Bobqspr). I don't really know what that means but what I have done is connect everything from the RCA to the XLR. Am I supposed to leave somethings unconnected? I have the cheater plug in right now listening to some Pandora and it is so much better without that dag gum hum!
I realize this is a really old topic for everyone but I'm hoping for a solution. Sorry for bringing back such a difficult topic!
Thanks
Ron
 
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