New iNuke6k causes hum? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 23 Old 09-29-2015, 06:24 AM - Thread Starter
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New iNuke6k causes hum?

I've been using an iNuke6k to power my subs for a few months. This particular 6k has never had a fan mod done to it, since it lives in my equipment closet and I can't hear the fans. However, last week it started doing the power cycle thing about once every 10 minutes. It does it even with no load, while sitting on the kitchen table. So, it is going in for warranty repair. This post isn't about that one.

Since that one was going to be out of service, I ordered a new one via Amazon, 2 day shipping, and it arrived yesterday.

I put it in place of the other one, and after a little while, I noticed that both sub woofers were producing a hum. Probably the classic 60Hz ground loop hum. I can feel the drivers vibrating. I found it odd that the old one didn't have this problem at all.

A bit of troubleshooting turned up this interesting fact. I have 3 circuits in my equipment closet. When I plug the amp into each of the 3 in order it goes - buzz, buzz, quiet. In other words, one of the 3 circuits causes the amp to be as quiet as the old one... I needed to rewire my entire rack to make this work, but now I'm wondering if I should have bothered. Should I just return this amp as defective and hope the next one doesn't exhibit this problem?

Thoughts?

Thanks.
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post #2 of 23 Old 09-29-2015, 12:24 PM
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Originally Posted by KevinG View Post
I've been using an iNuke6k to power my subs for a few months. This particular 6k has never had a fan mod done to it, since it lives in my equipment closet and I can't hear the fans. However, last week it started doing the power cycle thing about once every 10 minutes. It does it even with no load, while sitting on the kitchen table. So, it is going in for warranty repair. This post isn't about that one.

Since that one was going to be out of service, I ordered a new one via Amazon, 2 day shipping, and it arrived yesterday.

I put it in place of the other one, and after a little while, I noticed that both sub woofers were producing a hum. Probably the classic 60Hz ground loop hum. I can feel the drivers vibrating. I found it odd that the old one didn't have this problem at all.

A bit of troubleshooting turned up this interesting fact. I have 3 circuits in my equipment closet. When I plug the amp into each of the 3 in order it goes - buzz, buzz, quiet. In other words, one of the 3 circuits causes the amp to be as quiet as the old one... I needed to rewire my entire rack to make this work, but now I'm wondering if I should have bothered. Should I just return this amp as defective and hope the next one doesn't exhibit this problem?

Thoughts?

Thanks.
I would send it back but, first you could try daisy chaining a wire from the rear of your receiver to a screw on the back of each amp and then grounding it on your power supply. It removed my hum.

But it also could be a bad amp plain and simple. Ordering and returning from amazon is super easy, might give that a try.

"we need more power" - My Wife.

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post #3 of 23 Old 09-29-2015, 01:52 PM
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It sounds like something may be going on with the electrical supply. The hum does not sound like an amp problem if it is quiet on one of the circuits. It is better to not use multiple circuits do to developing a ground loop hum.
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post #4 of 23 Old 09-30-2015, 06:32 AM - Thread Starter
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After a bit more troubleshooting last night, I can safely say that the new amp doesn't have a problem at all.

I moved the new amp back to the circuit that causes it to produce a hum from the subs. Confirmed hum was there.

I swapped back in the bad amp. It was quiet.

I compared the settings on both amps carefully. I noticed that the bad amp was set to stereo mode, low pass filter engaged.

The new amp was set to stereo mode, full range. Sure enough, when I switch the new amp to also engage the low pass filter, the hum goes away.

So, the hum there, but the amp's crossover is being used to filter it out. No big deal. I use a Dirac 88-A, and lots of checking with REW, and the room is very nicely balanced, so no harm in leaving the 6k with the low-pass filter engaged. But it does bring up a number of interesting questions.

1) If this is a 60 hz hum (and, I really think it is). What is the low-pass crossover doing to filter it out? I looked through the manual, and I can't find any specifications on what the low-pass or high-pass filters actually are (frequency or slope). The Dirac, and REW both confirm that my subs are producing plenty of output up to around 200hz, so I can't imagine what the low-pass filter is doing, or how it is affecting a 60hz signal...

2) When the amp is on the circuit that doesn't produce hum (when in low-pass mode), and I switch it to full-range mode, there is still a very faint bit of hum, but I need to get my face right in front of the 18" drivers to hear it. I wonder if it is worth running the amp in full-range mode (and re-doing a room calibration) just to remove one more cross-over from the signal path.

3) I'm thinking that since I have 3 circuits in the closet, with two that are in-phase with each other, I should carefully move all equipment that is in the audio path onto those 2 circuits. That may help get rid of the hum. It's a big undertaking, but I'll probably give it a shot.

I forgot to mention...I did try a wire from the receiver's chassis to the inuke6k chassis. It didn't make a difference. I also made sure all interconnects were firmly seated. I also tried bypassing the 2x4, but didn't try bypassing the 88a. I also didn't (but should have) take note of which circuit the receiver/88a is getting power from in comparison to the circuits that cause hum.

Thoughts?
Thanks!
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post #5 of 23 Old 10-04-2015, 09:52 AM
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Howdy


I had a similar problem when I put my sub system together and got some help here (Thanks again AVS forum!) fixing it. I had two new grounded 20A circuits for my home theater system, all tied into a new grounded service panel, so I was totally flummoxed. The advice I got was to check the grounding for my cable (TV / Internet) and phone lines. Wouldn't you know it, but I had disconnected the ground strap from the cable line while doing some work in the garage. Reconnecting the ground caused my hum to go away (& stay away. Things have stayed dialed for a year + now)!


Hope it's that easy for you...


Cheers,


Jon

Denon AVR-X4000 receiver, Oppo BDP 103 Blu Ray, TiVo XL4 DVR, Panasonic TC-P65VT60 Plasma TV, Infinity Beta 40 FL & FR and Beta C360 center, Definitive Technology UIW RCS II in-ceiling surrounds, dual TC Sounds LMS-15" sealed subs (https://www.avsforum.com/forum/155-di...ble-build.html), iNuke 6000DSP amp, Logitech Harmony Touch remote.
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post #6 of 23 Old 10-05-2015, 07:56 AM - Thread Starter
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Originally Posted by jlefors View Post
Howdy


I had a similar problem when I put my sub system together and got some help here (Thanks again AVS forum!) fixing it. I had two new grounded 20A circuits for my home theater system, all tied into a new grounded service panel, so I was totally flummoxed. The advice I got was to check the grounding for my cable (TV / Internet) and phone lines. Wouldn't you know it, but I had disconnected the ground strap from the cable line while doing some work in the garage. Reconnecting the ground caused my hum to go away (& stay away. Things have stayed dialed for a year + now)!


Hope it's that easy for you...


Cheers,


Jon
Well, I spent a few hours trying to solve this. It was mostly academic, since just leaving the low pass filter in place on the amp seems to solve the problem by itself.

The interesting parts of the system are a Denon x4000 AVR, a minidsp Dirac 88a, a minidsp 2x4 balanced, and the iNuke6000.

The interesting wires involved are:
1) a single RCA from the Denon to the 88a
2) a single RCA from the 88a to the minidsp 2x4 (custom pigtail into the phoenix connectors)
3) two XLR to RCA cables from the minidsp 2x4 into channel A and B of the iNuke (custom pigtails to add RCA females to the phoenix connectors)

I disconnected all other equipment from the wall outlets. I made sure all cables were firmly attached. I left the amp in STEREO/No Filter mode, and I tried both all three available circuits.

The hum was there.

First things first. Bypass as much as possible. Remove the minidsp 2x4 and the Dirac 88a. Straight from Denon into iNuke channel A (no channel B). The hum is gone. This is progress.

Since my minidsp 2x4 is currently set to complete bypass, with no filters (the 88a is doing a remarkable job on it's own) it really is just a Y cable. So let's remove it from the system.

Denon into 88a, 88a into iNuke, channel A only. No hum.

Ah hah! The miniDSP 2x4 was causing the hum! Physically remove it from the rack/closet, and wire in a Y jack in instead.

Denon into 88a, 88a into Y jack, Y jack into channel A & B of the iNuke. The hum is back.

WTF? The miniDSP 2x4 wasn't the problem. It's just that having only one channel connected to the iNuke seems to be a solution?

Again remove the minidsp 88a, and go straight from the Denon to the INuke, but this time through the Y cable and connect both channels of the iNuke. Hum.

Okay, bad Y cable? Try another one. Hum. Bad RCA interconnects? Try about 4 more. Hum. How bizarre. Any time I connect BOTH channels of the iNuke, BOTH subs hum. If I connect only channel A, the hum is gone.

Somewhere around this time, I started playing with the filter switch on the amp again, just to prove that I could still make the hum go away with a flip of the switch. I was also back in the mode where only channel A was connected. I either accidentally, or for no good reason, switched the STEREO switch to MONO, and noticed that both subs were still working. I knew that the iNuke had a mode where it would take a mono input and send it to both output channels, but I never looked carefully enough, and thought that it required a 4 pole speakon connection to work. I didn't realize that it would do exactly what I needed it to do...just send the channel A input to the channel A&B output.

Great. So *ALL* of the issues seem to stem from having two channels connected on the input side, but there's now no reason to do that.

I wired Denon to 88a, 88a to iNuke (no more 2x4 or Y cable required) and left the amp in mono/no filter mode. No hum, and all is well.

I still can't explain the issue, but I'm also happy to just sit back and enjoy the room again. *sigh*
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post #7 of 23 Old 10-05-2015, 09:27 AM
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Did you assemble the xlr cables yourself? The only thing I can think of is that there is something off about how the xlrs are wired. Were they grounded properly internally? Was one side set up as unbalanced?
As an aside, I read once that someone using an EP4000 in the mode that allows you to run a single input in that is sent to both channels internally, that there was a measured difference in output between channels all else being equal. I don't know if this holds true on the inukes as well, it's just a piece of info to think about.
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post #8 of 23 Old 10-05-2015, 10:43 AM - Thread Starter
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Originally Posted by dtsdig View Post
Did you assemble the xlr cables yourself? The only thing I can think of is that there is something off about how the xlrs are wired. Were they grounded properly internally? Was one side set up as unbalanced?
As an aside, I read once that someone using an EP4000 in the mode that allows you to run a single input in that is sent to both channels internally, that there was a measured difference in output between channels all else being equal. I don't know if this holds true on the inukes as well, it's just a piece of info to think about.
Nope, XLR to RCA were purchased from monoprice. I didn't think to try to narrow it down to one vs. the other though. I suppose it is possible that the one that is currently not connected is actually flawed internally, I guess. I have a few spares of those as well, so I could try a few of them. Hard to imagine a flawed cable causing such a low-volume hum. I would expect a badly made cable to produce a much louder hum, or not work at all, of course.

I anticipate doing a full room correction with the 88a again now that I've changed the x-over setting on the amp. That's always followed by extensive REW measurements to see what I've ended up with. I appreciate the heads up on the channel differences...it's not something I would have thought to check, but I will make sure the subs are behaving before doing another room measurement.
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post #9 of 23 Old 10-05-2015, 10:54 AM
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Originally Posted by KevinG View Post
Nope, XLR to RCA were purchased from monoprice. I didn't think to try to narrow it down to one vs. the other though. I suppose it is possible that the one that is currently not connected is actually flawed internally, I guess. I have a few spares of those as well, so I could try a few of them. Hard to imagine a flawed cable causing such a low-volume hum. I would expect a badly made cable to produce a much louder hum, or not work at all, of course.

I anticipate doing a full room correction with the 88a again now that I've changed the x-over setting on the amp. That's always followed by extensive REW measurements to see what I've ended up with. I appreciate the heads up on the channel differences...it's not something I would have thought to check, but I will make sure the subs are behaving before doing another room measurement.
For my own curiosity sakes, I would want to find the culprit. You wouldn't be the first person (or the 100th) to have a Monoprice cable wired wrong or otherwise defective. You can easily pop the hub/base off the XLR connector and compare the two that you have. Further, an ohm meter would confirm how they are wired. XLR can be tricky because in what we're using them for, they need to be wired in a certain way at the connector. I went through some of this hassle when I added my MiniDSP to the mix.
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post #10 of 23 Old 10-05-2015, 11:41 AM
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Originally Posted by KevinG View Post

1) If this is a 60 hz hum (and, I really think it is). What is the low-pass crossover doing to filter it out? I looked through the manual, and I can't find any specifications on what the low-pass or high-pass filters actually are (frequency or slope). The Dirac, and REW both confirm that my subs are producing plenty of output up to around 200hz, so I can't imagine what the low-pass filter is doing, or how it is affecting a 60hz signal...
Reading this thread, this too has me puzzled. Is it possible its not actually 60Hz? Could you possibly amplify it enough to get a measurement? If it isn't it could well be caused another piece of equipment in your home or even in a neighbors home. Do you have any power electronics apart from your audio gear? If you want to be really thorough you could turn off all the RCDs (except the one for your audio gear) in your fusebox too see if that fixes it, if so turn them on one by one to locate the issue. Older microwaves (>20 years) are notorious for feedback noise, but obviously it must be something that's always on.
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post #11 of 23 Old 10-05-2015, 12:56 PM - Thread Starter
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For my own curiosity sakes, I would want to find the culprit.
Yep. That's why I spent a few hours on this even though I had come to the conclusion that leaving the filter in place removed the problem... I wish it were easier to replace this particular cable in my rack, but it's a real PITA. Even so...I'm interested enough to swap it out for one of the 3 others I have. (Two still wrapped in plastic from monoprice that were longer than necessary, and the other that is "presumed" bad right now, although I think it's doubtful.)

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Reading this thread, this too has me puzzled. Is it possible its not actually 60Hz? Could you possibly amplify it enough to get a measurement?
I'm fairly sure it is 60Hz, but maybe I just jumped to that conclusion when I heard a "hum?" In any case, it's VERY similar (maybe identical?) to the hum one gets when inserting an RCA cable partially (before the outer ground ring has made contact with the jack) albeit MUCH lower in volume. That's what prompted me to make sure that all cables were firmly connected.

So far, there's no way to amplify it enough to get a measurement that I can think of.

At some point during all of this I had an absolutely FANTASTIC "ah hah" moment when I realized that the electrician had wired my radon remediation system into one of these three circuits. This consists of an ALWAYS on blower (fan). Of COURSE that particular circuit would be noisy. So I immediately moved everything off of that circuit. Hum was still there. Went to the circuit box, and turned off that breaker. Hum was still there. So much for my "ah hah"...

So, there still remains the mystery of what the iNuke lowpass filter is doing that removes this particular frequency. And the new mystery of how connecting the B channel of the amp seems related.

Oh, here's something I left out earlier.

The Denon happens to have two sub out connections. (Audyssey XT32) In general, I only ever used one because I only have identical subs that are equidistant from the prime seat. Anyway, I tried skipping the Y cable entirely and wiring each sub out to a channel on the iNuke. Same Hum.

I don't recall what happens in STEREO mode if I only connect channel B of the amp. That's probably worth testing.

TBH, I was getting tired and frustrated by the time I found the current situation, so there's probably a couple more things I could try to further understand the issue.
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post #12 of 23 Old 10-05-2015, 01:01 PM
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post #14 of 23 Old 10-05-2015, 01:22 PM - Thread Starter
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Originally Posted by dtsdig View Post
@KevinG The RCA to XLR needs to be wired like this:


or this:
I'll open my monoprice cables and see how they are wired...then I'll try some continuity tests on the "bad" one to see if there is some leakage.

Thanks.
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post #15 of 23 Old 10-06-2015, 09:24 AM
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Originally Posted by KevinG View Post
... I either accidentally, or for no good reason, switched the STEREO switch to MONO, and noticed that both subs were still working. I knew that the iNuke had a mode where it would take a mono input and send it to both output channels, but I never looked carefully enough, and thought that it required a 4 pole speakon connection to work. I didn't realize that it would do exactly what I needed it to do...just send the channel A input to the channel A&B output...
You can also use BiAmp mode with a single input, which enables you to EQ each output separately if you have the DSP version.
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post #16 of 23 Old 10-06-2015, 10:25 AM
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This is what fixed my humm just like the 2nd post stated.
Every piece of equipment is daisy chained all the way up to my surge protector with it grounding each piece. The humm went away and everything is really quiet. I had the humm from my rca to xlr cable which is still in the installed back there but after doing what I posted there's no more humm.
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post #17 of 23 Old 10-06-2015, 11:26 AM - Thread Starter
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This is what fixed my humm just like the 2nd post stated.

Every piece of equipment is daisy chained all the way up to my surge protector with it grounding each piece. The humm went away and everything is really quiet. I had the humm from my rca to xlr cable which is still in the installed back there but after doing what I posted there's no more humm.
Nice. Was this a very low level hum, or one that would have prevented you from using the system at all without a fix in place? I'm trying to understand if you had the same problem I had. (very low level hum, audible only if the room was otherwise very quiet)

I only tried connecting my Denon to the iNuke. I could get a bit more ambitious and go all the way to the grounding screw of an outlet that I know is well grounded back to the panel...
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post #18 of 23 Old 10-06-2015, 11:35 AM
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Nice. Was this a very low level hum, or one that would have prevented you from using the system at all without a fix in place? I'm trying to understand if you had the same problem I had. (very low level hum, audible only if the room was otherwise very quiet)



I only tried connecting my Denon to the iNuke. I could get a bit more ambitious and go all the way to the grounding screw of an outlet that I know is well grounded back to the panel...

The humm I had wasn't to loud but when there was a quiet movie clip you heard it and it drove me nuts! I tried everything like you did. My outlets are grounded because I'm the one who ran them in conduit with my father-inlaw who's a union electrician out here in Chicago so I know what I have there. The rca to xlr cable was bad and when mtg90 (Matt) was over he pulled every cable one by one to find the bad wire. After he suggested to daisy chain a wire to each piece of equipment and I did that it was like magic the humm was completely gone. Give it try wire is cheap.
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post #19 of 23 Old 10-06-2015, 11:44 AM - Thread Starter
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The rca to xlr cable was bad and when mtg90 (Matt) was over he pulled every cable one by one to find the bad wire. After he suggested to daisy chain a wire to each piece of equipment and I did that it was like magic the humm was completely gone. Give it try wire is cheap.
Yep, sounds like the same problem, and the same culprit. Which means the solution should be the same. I've got plenty of wire around, so I'll give this a more serious go.

Last edited by KevinG; 10-06-2015 at 12:12 PM.
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Yep, sounds like the same problem, and the same culprit. Which means the solution should be the same. I've got plenty of wire around, so I'll give this a more serious go.
Before you go stringing wire around, I really encourage you to check out how the RCA to XLR is wired. If pins 1 and 3 on the XLR end are not tied together (and they are not tied together on the sleeve connection on the RCA end either), you can have a floating ground problem.
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post #21 of 23 Old 10-06-2015, 12:17 PM - Thread Starter
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Originally Posted by dtsdig View Post
Before you go stringing wire around, I really encourage you to check out how the RCA to XLR is wired. If pins 1 and 3 on the XLR end are not tied together (and they are not tied together on the sleeve connection on the RCA end either), you can have a floating ground problem.
Yep, it'll all be part of the next trouble-shooting session. ;-) Just have to find the time.

1) Confirm RCA to XLR cable internal wiring
2) Try swapping RCA to XLR cable out with some other ones
3) Does wiring only Channel B instead of only Channel A cause a hum?
4) Can the hum be stopped by grounding everything together?
5) Does the current tide or phase of the moon have any impact?
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post #22 of 23 Old 10-10-2015, 10:11 AM - Thread Starter
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Originally Posted by dtsdig View Post
Before you go stringing wire around, I really encourage you to check out how the RCA to XLR is wired. If pins 1 and 3 on the XLR end are not tied together (and they are not tied together on the sleeve connection on the RCA end either), you can have a floating ground problem.
Okay, results are in.

All of my XLR to RCA cables are wired correctly, no issues there. It was never a cable problem.

Running grounding wires between the iNuke and the Receiver helped some. It went from audible from the other side of the room to audible about 4 feet in front of the subs. Running an additional grounding wire from the receiver to the center screw of the outlet reduced it to the point where I had to put my ear right in front of the sub. So, yes, grounding everything together its absolutely helping. I could probably continue grounding things together, and use something thicker than the 18 gauge wire I'm using, but no real need to go any further. I think the mystery is solved.

In addition, I confirmed that my particular iNuke doesn't do anything strange when running in Mono mode. Both subs produce the same amount of output on either channel. Measured both with REW (individually), then swapped channels and got effectively identical measurements each time. So, no worries there.

Also, playing with the low-pass filter some more, and grabbing REW graphs, it seems that the iNuke lowpass is around 100Hz. Doesn't explain how it was able to filter out the 60hz hum, but it is what it is.

In the end, my graphs look much better with the low pass in place (which is good because that means the hum is 100 percent gone). I'm absolutely certain that this is because the low pass filter was in place when DIRAC corrected the room. The next time I run a calibration, I'll turn off the low pass filter, and compare the results.

Thanks for all the tips!
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post #23 of 23 Old 10-11-2015, 12:52 PM
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I'm glad running that ground wire to each piece of equipment helped. It solved my humm issue just like yours. When I just touched the wire to the screw on my amp it stopped right a way. Then I knew I was into something. Its a good feeling not to have that noise anymore. It can drive a person mad!
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