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Discussion Starter #1
Okay, here's the situation.


I just got a new Outlaw 7200 amp and I'm experiencing dreaded hum.


Things I've done so far:


- Disconnected cable TV (have a Jensen Isomax anyway)

- Disconnected the pre-out input cables from the amp.

- Disconnected everything from the amp except for the cord.

- Pushed the amp to a different outlet.


It still hums regardless, and quite loudly at times (it varies from none, to moderate, to high hum) and tends to get very warm to the touch.


I have found when I power up my receiver (Harman Kardon 235) with the amp on, the amp's hum either gets a little louder or completely stops as the receiver "boots up" for two or three seconds. When the receiver becomes operational, the hum returns...


Besides the hum, the amp appears to work fine and sounds great.


The hum sounds like it's coming directly from the two big toroidal transformers in the front of the amp.


I ordered a PS Audio UPC200w/Humbuster , but I'm weary whether or not it'll do anything...even though the problem I'm experiencing seems in line with their "Fixing Hum" article.


Anyone have any thoughts on the device or my problem? Any help would be greatly appreciated.
 

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Does your amp have a ground lift switch? I had to install a dedicated ground for my audio equipment. After I did that the hum went away.
 

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ground loops my friend, you can do a few things, none of them involve the humbuster, it is not for audible hums, which are ground loops, it is for actual transformer hum inside of gear like power amps, which can hum due to power issues in your wiring(meaning you can hear sound from inside the gear no thru your system),


first and the best IMHO is to get a transformer based power unit, this gives 100% total isolation from the rest of the homes wiring, better than a dedicated circuit and will improve performance by lowering noise levels, transformer based power conditioners are fairly expensive though


you can also try running some dedicated circuits but even that sometimes won't do the trick due to how home wiring is done, lots of times it will though


a ground lifter would probably do it, but it is dangerous and not recommended nor is it how the device was designed to operate in ideal conditions


this could all be a bad cable connection also, but you will know that most of the time because it will be instantly audible, I had some junk Audioquest cables blow some speakers of mine and nearly my ears, I wouldn't think this is a cable issue


your cables could be picking up interference though from power lines or connections


-Gary
 

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Discussion Starter #5

Quote:
Originally Posted by Gary Murrell /forum/post/0


ground loops my friend, you can do a few things, none of them involve the humbuster, it is not for audible hums, which are ground loops, it is for actual transformer hum inside of gear like power amps, which can hum due to power issues in your wiring(meaning you can hear sound from inside the gear no thru your system)

Thanks Gary, but I really think I'm hearing hum from the transformers inside the amp. Not through the speakers or anywhere else, I place my ear right above the transformers in the amp's chassis with the amp connected only to power and hear them humming away, sometimes softly, sometimes loudly.

Quote:
The name of this thread is misleading and needlessly confrontational for a guy who can't cure a ground problem.

How so? I'm pretty sure it's transformer hum and I wanted to get some advice or other's experiences with the Humbuster to gauge whether it's just more or less smoke and mirrors or something that might actually help.
 

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Discussion Starter #7

Quote:
Originally Posted by Stymlie /forum/post/0


Just do a quick test to see if it is a ground problem. If it is, then you can fix it fairly easily.

I quickly popped on a cheater plug, still humming.
 

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oh ok, I thought you were hearing audible humming from speakers


if you are hearing actual transformer hum then that means your home AC lines has some slight issues like DC voltage and etc., the transformers are doing their job of isolating the power but they are working harder, running hotter and buzzing, the PS audio should fix that right up



-Gary
 

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Discussion Starter #9
I called Outlaw today and while they were very prompt, both my home and cell phone had enormous problems with staying connected.


I spoke, albeit briefly, with a tech support rep, once I told my problems he suggested that it could be DC on the line coming off the pole that's causing the hum (like your suggestion Gary) and questioned whether I used ever tried an isolation transformer.


That's how far the conversation got before my cell disconnected...again!



Though it was comforting to hear him immediately ponder whether it was DC on the line. Something I personally figured might be the prime suspect.


The UPC-200HB (hopefully) will be shipping soon, so we'll see if it can temper the DC.
 

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that should do it dude, that would have been my first guess (DC) for actual transformer hum, I would suggest the transformer based power unit down the road also for ultimate performance and noise reduction, balanced is best



-Gary
 

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You put the amp on a different outlet. What about an entirely different circuit?
 

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IF it is a mains problem, how about having the utility company fix THEIR problem instead of you buying stuff to fix it?


And yeah, I know it's hard to fight City Hall, but at least pursue them/raise the issue if that is the true problem.
 

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Immediately, and I mean right now, measure the ground to neutral voltage at the outlet with the amp plugged in and powered.


The neutral is the taller of the two prongs, the ground is the half round one.


Is the receiver xfmr in close proximity to the toroids of the amp?


Cheers, John
 

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Try this thing. I don't have a need for one. I can't say if it works or not, might even be snake oil. So don't shoot the messenger.
http://ultrasystem.com/usfeaturedprodsDestroyer.html


This is what The Cable Company had to say about it:


AC Products and Special Offers on HFT Noise Destroyer and PS Audio Duets and Quintets



HFT releases New Noise DESTROYER at HE 2007 in New York!



HiFi-Tuning was a participant in the Ultra Systems booth at the HE 2007 during May 10-13 at the Grand Hyatt Hotel in New York. The new HFT "Noise Destroyer" was making its US debut, and stock on hand sold out to consumers, reviewers, and other exhibitors in just a few hours due to a powerful demonstration of their effectiveness. The Noise Destroyer was demonstrated on the AC power in the hallway of this big NY hotel using a "Noise Detector," which made the noise on the AC line audible to everyone. The instant one of the Noise Destroyers was plugged into the circuit, the noise vanished completely.


To give a sense of the scale of this accomplishment, a PS Audio Noise Harvester was also on hand for comparison purposes. As a rough estimate the noise reduction of 10 to 12 PS Noise Harvesters should just about equal ONE of the HFT Noise Destroyers!


The Noise Destroyer is a parallel AC filter - a classic wall-wart - which plugs into a "free" socket within the AC circuit . It consumes a tiny amount (about 0.25mA) of current while it goes about getting rid of RFI and EMI that are in the AC circuit, providing you with a lower noise floor resulting in better video and sonic performance from your system(s). Because the filter system is parallel, it is not current limiting, nor does it have any adverse effect on dynamics. This is truly the most effective plug-in type of filtering device we have seen. If ONE was enough to treat the nasty AC in the hallway of a major metropolitan hotel, you can be confident that it can handle the audio circuit in your home.


The HFT Noise Destroyer is priced at $249.95, but for the month of May 2007, we are offering the Destroyer at a very special preorder price of $179. (By "Preorder" we mean all units in this country have been sold, but you can preorder to assure allocation from the next 100 piece US delivery arriving in about two weeks.)
 

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It's funny solutions are offered when the root cause of the problem is not even known.


Usually, solutions are fairly easy once the root cause is fully identified.
 

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I love it when companies dis other companies!
 
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