Noise from F15s after adding crowns + ultimax - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 27 Old 07-22-2018, 09:13 PM - Thread Starter
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Noise from F15s after adding crowns + ultimax

I haven't even started trouble shooting but though I would ask ahead of time.

Finally finished my dual ultimax 18s in 4 ft flat packs. Dual bridged crown xls 2002 via rca @ .775v to SR7010. Speakon at the sub. Wired at the crown.

The noise/hiss from my F15s is bad. Only unplugging the crowns stops it.

I can easily move the crown power to its own 20a circuit. That's my first guess.

Other items shared on circuit. Emotive xpa 3, TiVo, k8500, roku.

This was just a quick test up. But thought I would ask before I start chasing crazy.


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post #2 of 27 Old 07-22-2018, 09:20 PM
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Try a cheater plug on the crown to see if lifting the ground fixes it. If it does, you can look to see where the amp is picking up the hum. The most common culprit is a cable box on the same line. Cable coax runs great distances next to power lines picking up a hum. separating their power sources is a good start.

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post #3 of 27 Old 07-22-2018, 09:34 PM - Thread Starter
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Quote:
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Try a cheater plug on the crown to see if lifting the ground fixes it. If it does, you can look to see where the amp is picking up the hum. The most common culprit is a cable box on the same line. Cable coax runs great distances next to power lines picking up a hum. separating their power sources is a good start.


Thanks. I've had other sub amps on the same line, which makes it a little weird.

The other circuit I will run it on will be farther away. Hope that helps

Ran out of time mess around. Update tomorrow night


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post #4 of 27 Old 07-23-2018, 02:09 AM
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grounding can vary from amp to amp and there is some other electrical strangeness that can introduce noise.

ensure proper wiring of the cable from avr to amp.

an isolation transformer can be placed in between the avr and the sub amp, which will allow the signal to pass magnetically but will block the ground loop by breaking the physical wiring.

there are cheapies that may not pass the lows and/or may distort. art zdirect is a decent option. jensen is the premo/expensive option.

the same kind device is available for the cable line if disconnecting that solves the problem.

having all equipment plugged into a single receptacle may help as well.

Listen. It's All Good.
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post #5 of 27 Old 07-23-2018, 05:53 AM
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@klimo , I discovered a similar problem myself just yesterday with two of my four subs. They have been free of hum for years, but suddenly have hum. After troubleshooting backwards and not finding a definitive cause, I moved to what I suspected was then the cause. I simply disconnected the TV cable (Cox) from the Contour DVR. Hum gone. Reconnect cable to DVR, hum returned. It is likely that some work in the neighborhood changed the grounding somewhere. So @LTD02 is right that there are mysterious changes and effects. In my case, my two powered subs have zero hum. The pair with the separate amp has the hum. Go figure.

I'm trying this before the Jensen. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It arrives tomorrow, so I'll install it right at the DVR, then try to come back and post results.
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post #6 of 27 Old 07-23-2018, 06:12 AM - Thread Starter
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Quote:
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@klimo , I discovered a similar problem myself just yesterday with two of my four subs. They have been free of hum for years, but suddenly have hum. After troubleshooting backwards and not finding a definitive cause, I moved to what I suspected was then the cause. I simply disconnected the TV cable (Cox) from the Contour DVR. Hum gone. Reconnect cable to DVR, hum returned. It is likely that some work in the neighborhood changed the grounding somewhere. So @LTD02 is right that there are mysterious changes and effects. In my case, my two powered subs have zero hum. The pair with the separate amp has the hum. Go figure.

I'm trying this before the Jensen. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It arrives tomorrow, so I'll install it right at the DVR, then try to come back and post results.
Wow. thats weird.

so, you're placing that device at the dvr location and not where the the cable comes into the house?

I did use some old cheepo rca for one of the subs i had laying around. I'm wondering if a better quality rca might help.

Do balanced connections help alleviate these problems?

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post #7 of 27 Old 07-23-2018, 06:40 AM
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Wow. thats weird.

so, you're placing that device at the dvr location and not where the the cable comes into the house?

I did use some old cheepo rca for one of the subs i had laying around. I'm wondering if a better quality rca might help.

Do balanced connections help alleviate these problems?
Yeah, quite the coincidence.

Cox is also providing high-speed internet. Filters ahead of the modem and router could cause issues, so I'm installing the filter downstream at the DVR. We'll see.

If your line-level runs are not long (10' maybe) and don't run along power cables, RCA usually does fine.
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post #8 of 27 Old 07-23-2018, 10:32 AM
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Another simple and cheap idea is to ground the chassis of the amp to the receiver with some wire. I'm not 100% on the circuit characteristics, but you might consider if you are bypassing any device protection by doing this.

Even so, I like this more than the idea of cheater plugs. Best of luck!
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post #9 of 27 Old 07-23-2018, 11:10 AM - Thread Starter
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Quote:
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Another simple and cheap idea is to ground the chassis of the amp to the receiver with some wire. I'm not 100% on the circuit characteristics, but you might consider if you are bypassing any device protection by doing this.

Even so, I like this more than the idea of cheater plugs. Best of luck!
definitely on my list! thanks!

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post #10 of 27 Old 07-24-2018, 07:20 AM - Thread Starter
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Tried grounds and different RCAs etc. No help.

I did trace it to the TiVo though. Ordered a ground loop isolater. Hope that fixes it.

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post #11 of 27 Old 07-24-2018, 09:56 AM
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Many devices that are powered by cheap china dc wallwarts which inject hf noise into the hdmi or rca ground.

They do make optical hdmi and usb cables, but they are expensive, and I've never used any of them.

The ground wires meant to protect people from lethal voltages are also the very same thing that causes loop hums. That's because they are in parallel rather than in series.

XLR doesn't help if the noise is upstream or caused by the power cords of any/every device in the system/house.

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post #12 of 27 Old 07-24-2018, 10:45 AM
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This one fixed the louder hum from my coaxial cable:

https://www.amazon.com/TII-220-Groun...+isolator+coax
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post #13 of 27 Old 07-24-2018, 03:36 PM - Thread Starter
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Yeah, quite the coincidence.



Cox is also providing high-speed internet. Filters ahead of the modem and router could cause issues, so I'm installing the filter downstream at the DVR. We'll see.



If your line-level runs are not long (10' maybe) and don't run along power cables, RCA usually does fine.


Any luck???


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post #14 of 27 Old 07-24-2018, 03:52 PM
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Any luck???


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I think UPS just delivered in the last hour. Haven't dug into it yet. Plan to by tonight.
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post #15 of 27 Old 07-24-2018, 04:03 PM - Thread Starter
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I think UPS just delivered in the last hour. Haven't dug into it yet. Plan to by tonight.


Great. Anxiously waiting. I ordered one. Will be here tomorrow.


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post #16 of 27 Old 07-24-2018, 05:09 PM
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Great. Anxiously waiting. I ordered one. Will be here tomorrow.


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Works like a champ! Zero hum. I can't find a TV station with a problem.
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post #17 of 27 Old 07-24-2018, 05:31 PM - Thread Starter
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Works like a champ! Zero hum. I can't find a TV station with a problem.


Great news!!


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post #18 of 27 Old 07-25-2018, 03:31 PM - Thread Starter
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It's fixed. Thanks!!!


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post #19 of 27 Old 07-26-2018, 05:31 AM
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It's fixed. Thanks!!!


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Yay! Did we get the same filter? It sucks we have to spend money to correct the cable company's issue, but the $23 or so investment in the filter is not bad.
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post #20 of 27 Old 07-26-2018, 06:16 AM - Thread Starter
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Yay! Did we get the same filter? It sucks we have to spend money to correct the cable company's issue, but the $23 or so investment in the filter is not bad.
Yep. I ordered the same one you had. Really happy it's all fixed. It was basically unusable with how loud the hiss was.

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post #21 of 27 Old 07-26-2018, 06:17 AM
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I swapped/upgraded DirecTV boxes last month and started getting a BAD hum. Nothing else was changed and the coax/dish is grounded at the wall where it comes into the house. I added a coax ground block at the back of the DTV box that grounded to the center screw on the dedicated receptacle for my amps. The hum is completely gone. I've done this in previous houses and asked DTV installers, as well as electricians about any potential problems. They've all said it's a good idea and won't present any problems. I got the ground block for free from the last DTV installer.

I just wanted to throw out another option that doesn't require lifting the ground or buying a filter.

https://www.amazon.com/Coaxial-Groun.../dp/B001I5610E
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post #22 of 27 Old 10-14-2018, 04:48 PM - Thread Starter
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Thought I would update this a bit.

Found out that an extension cord one of the crown amps I had was a huge problem. I purchased a "high quality" extension cord since the crown power cords are only like 3 ft long.

Just one more thing to check if you have noise issues.


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post #23 of 27 Old 10-15-2018, 04:59 AM
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Extension cord. Who would've thought? What's different about the new one?
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post #24 of 27 Old 10-16-2018, 07:16 AM - Thread Starter
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Extension cord. Who would've thought? What's different about the new one?
I'm not currently using one. I need an extension cord to make it to the outlet on a different circuit, so right now, I have quit a bit on 1 circuit.

In the market for another "high quality" cord.

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post #25 of 27 Old 10-16-2018, 08:52 AM
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Search "nema power cord" and I've seen some 14 ga 25 foot versions pretty quickly. I'd go with nothing less than the 14 ga rated for 15 amps. Since the amp consumption is usually a burst, I don't think you'd lose much or any if you can't find a cord rated for 20a service.
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post #26 of 27 Old 10-16-2018, 01:04 PM
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Sure it's not loop related? A power cord won't do that on it's own.
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post #27 of 27 Old 10-17-2018, 03:33 AM
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Sure it's not loop related? A power cord won't do that on it's own.
It's possible that the the extension cord has been cut by a lawnmower and taped back together, or just old and moldy, or just a loose/bad ground/neutral wire connection made worse by bass vibrations or running/biting animals.
Could be a number of things.

What fixed it was likely fresh copper, properly secured.
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