Headphones, when plugged into the appropriate outlet ( Headphone socket) should largely be Very quiet... atleast where the background noise is barely audible ( ie you would have to focus or strain to hear it )

Seems that something is not quite right.

Welcome to the world of highly efficient transducers. They do wonderful things with dynamics but can show off every wart in the system. I'm going to make some assumptions and they might not be accurate but at least it's a start. I assume the two HK's and the Marantz were all plugged into the same AC outlet in your house. I will also assume you took your headphones over to your friend's Denon. That would place the AC line feeding the various amplifiers on a different circuit with different noise potentials. I would intially look for commonalities and differences. Take your amplifier over to your friend's house or have him bring his amp to your house. Listen for the noise where it did or did not exist previously. If something changes, there's a good likelyhood it is due to the chhnge in AC service. If this is the case, you need to either move or get some filters on your AC lines.

That's where I would begin. Let me know what happens after you try this experiment.

I don't understand. Did you find noise from the AC lines at your friend's house also?

That still wouldn't rule out AC line noise. Do either of you have your system plugged into an AC line filter with RFI and EMI filtration?

I think the sad fact is that most headphone sockets in receivers don't involve the most pristine circuitry. They're just added extras. Have you tried those phones with a dedicated headphone amp or with any source, for that matter, and found that the annoying sound was eliminated? As I recall, those phones are fitted with a mini-plug as standard and require an adapter for the plug on your receiver. If I'm correct, you might take off the adapter and try them on an iPod. That should help clarify the issue.

Let me pursue this idea a bit farther before ruling out AC noise. You took your amp over to your friend's house and plugged it into the same outlet or surge protector with his Denon. Your amp still had the same amount of noise at his house as it did at yours? No change? I ask because even half the noise would still indicate an AC line problem. And, whether the noise was the same or not, I would still suggest you investigate a quality filter. This would go to the construction of the power supply and not necessarily a difference in line quality.

I wouldn't be at all surprised should the headphones exhibit no noise on an iPod since it is a battery driven device. A noise issue is typically due to noise on the AC that is not filtered by the power supply of the amplifier. If it comes in dirty, it can easily go out just as dirty. With a battery powered device lots of problems simply don't exist.

Should you try the NAD, you obviously want to listen in the shop. If it is quiet there and noisy at your home, that would still lead me back to AC line problems. While you're at the NAD dealer's, ask about a quality line filter with the above mentioned filter elements and ask if you can try that at home. It is possible the amp's are at fault, and headphone amps are notoriously poor quality, but most situations I've encountered with this sort of noise are generated by the incoming AC line. Sorry to be so stuck on one topic, but I do think this is where your answer will be found.

" ... wouldn't the CD player make some noise also?"

In a rather sweeping statement, no. No more than your CD player could drive your loudspeakers properly. The operations of the power supplies in each unit are similar in nature but quite dissimilar in purpose. Somewhat like trying the iPod suggestion but ... uh, different.

I hate to be dense, though it seems I'm finding myself in that predicament all too frequently in the last month or so, but what does this mean? "The noise was the same level everywhere I tried." Please tell me what exactly you've tried and where you've tried it. Also, when HK said this shouldn't occur, did they offer any suggestions?

I was thinking the noise could be from a dimmer switch, until you made it clear that your friend's amp did not exhibit the noise at your home. Is it the exact same model? I wonder if something isn't properly grounded in your amp, or you just have a bad transformer.

The problem is in the power supply and how it is rectified, filtered and regulated. Why the Denon has no problem here is something I don't know other than to tell you the power supply is probably laid out differently. Or, the headphone output may be taken from a different location in the amplifier on the Denon. Headphone outputs are seldom a priority in most amplifiers today. And part of the problem is the high efficiency of your headset. You have a design that falls outside the "normal" curve which designers count on.

I will offer a few suggestions and then I have to say you are pretty much on your own as far as my ability to help is concerned.

1) Try a decent AC line filter. I would suggest a Panamax product since they have done the best job for the least money when I've had this sort of problem with clients. A simple surge protector's filtration is not sophisticated enough to eliminate the amount of RFI and EMI you seem to have on your lines. For about $150 you should be able to get the best filtration of these two areas that Panamax has to offer. The unit should be available as an audition piece with a refund if it doesn't solve the problem.

2) If nothing else, try a ferrite ring on your AC cable just as it enters the amplifier. You can buy ferrite rings at Radio Shack for a few dollars and they simply clamp onto your AC cable.

3) Step down to a lower efficiency headset or trim the level of your outgoing signal to lower the level of the output. A small trim pot in line with the headphone output should do the trick there. I would start with a 100kOhm pot. Once again Radio Shack should have the parts required to do a simple volume control/trim pot in a project box with ins and outs attached to the box. Lower the level of the headphone output and then use your amplifier's volume control as you would normally.

4) Buy a decent headphone amplifier. Depending on cost, this should get you a power supply designed specifically for the small wattage amplifier required for headphones.

Good luck and keep me posted.

Ah, with the back and forth between you and Jan, I misread/misinterpreted something and got confused (perhaps due to the 2 Harmons.) For some reason, I got the impression you and your friend tested identical Denons after the Marantz and Harmon were exhibiting hum to try to eliminate a variable.

So, you've brought the Marantz and Harmon to your friend's place, and they still exhibit this noise... it seems odd that 2 of your amps are having the same problem. Was there an electrical problem at your place that might've cooked both pieces? A power surge or brownout?

Maybe your dish network is the culprit. Quite often, satellite TV is linked to ground loop noise in audio systems.

http://www.epanorama.net/documents/groundloop/index.html

http://www.epanorama.net/documents/groundloop/example_systems.html

I haven't tried the Harvester yet, but, am curious. I use a number of PS Audio products in my main system.

I understand why you like the existing headset and offered the suggestion to change as a possibility not expecting you to take me up on that. But you still might try the trim pot. You won't loose any of the quality of the headset (no more at least than a volume control of any sorts inmposes on the signal) but it will place the signal farther above the quiescent noise floor. If the noise stays constant in level, which I believe you said it does, this pot will essentially lower the noise floor of the system. The headphones won't play quite as loud. But you should still be able to reach levels which could permanently damage your hearing. And, if you are playing the headset that loud, the AC noise won't be of any consequence.

I have no particular recommendation on the Panamax. Look at the specs for filtration and choose whichever model suits your budget. As to the PS Audio unit, I don't know anything other than what I read about it. I think someone in Stereophile liked its results but they didn't have your problem. As is typical with Paul McGowan lately, he has been rather closed lipped about what exactly his line conditioners actually do and how they do it. The ads and reviews read a bit like the old Tice clock. The more you own, the more the benefits. That approach to achieving results always makes me nervous. On the other hand, I have a passing familiarity with Paul and know he is an excellent engineer. I would contact PS Audio and ask a few questions before I laid down some cash for this item, if I was trying to solve your problem. I will give you my recommendation on the Panamax products since they have worked for me in the past. If you try the PS Auido unit, let us know what happens.

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Jeff makes a great point. What you might have is a ground loop. Current might be leaking from the house ground to the dish ground, or vice versa. This would create a 60hz hum. The way to check to see if this is the culprit is to disconnect the coax cable from the sat. box. If the hum goes away this is your problem. But this hum would almost certainly occur through the speakers as well. So if no hum through the speakers means that this is most likely not the problem. Ground loops are more of a huuuummmm, than a zzzzzz. If you do have a ground loop you need a ground breaker. Mondial makes the "magic box" and Tributaries makes a similar product, I believe that these are around $100. Xantech makes a less expensive product but it reduces bandwith so much it creates problems with sat. and Digital cable for about $20 (Although it seems to work well with analog cable, other than the pictur quality loss.)

More than likely a decent line conditioner will solve this problem also. Most well designed units place all the plugs on a similar ground plane to help lower noise. What often happens though is a conditioner is plugged into a two wire AC distribution network in an older home. (In remodeled homes it's not uncommon to find a three pin plate covering up a two wire system.) The two conductor system has problems with ground and neutral being carried on the same conductor and the conditioner is far less effective at its job. This doesn't discount the possibility of cable or sometimes satellite TV causing problems due to a ground problem at the A/V inputs, but the problems are less with the AC conditioner if the video feed runs through the conditioner.

Another possible cause for the noise might be a reversed AC plug. If the amp is being fed a reversed signal you might find some additional noise on the line. You can check for this by removing the wall plate if you are very, very confident you know what you're doing. If not, don't mess with exposed wiring. Or, the better solution is to buy a line checker at Home Depot. I think they still run less than ten dollars and you can detect ground faults and miswired outlets by simply plugging the device into the outlet. For the dollars spent, this should be something everyone uses to check for miswired outlets before connecting your system together.

Have you tried listening to the amplifier with no source components plugged in? Just plug the unit into the AC line and listen for noise when no other components are connected.

I think you just have a couple of amps with crappy phone sections. Couple that with very efficient cans and you're hearing the circuitry flaws.

Another thing, if your a/c plug isn't keyed then you might lose the noise if you put the plug in the other way. Unless, of course, it's a three prong plug.

My pre-amp has a three prong plug, but my two amps have two prong without keying.

Quote:
Maybe your dish network is the culprit. Quite often, satellite TV is linked to ground loop noise in audio systems.

http://www.epanorama.net/documents/groundloop/index.html

http://www.epanorama.net/documents/groundloop/example_systems.html

I haven't tried the Harvester yet, but, am curious. I use a number of PS Audio products in my main system.

I have a problem like this when my tv is plugged into the preamp. There is a very loud hum. If I bypass the preamp and plug the tv into the subwoofer amp/xover there is no appreciable hum.The preamp has a three prong a/c plug but the sub amp and main amp are two prong.

A friend in the install business said it's probably a ground loop in the cable tv line. He suggested first grounding the cable splitter and if that doesn't work get an isolation xformer for the cable line in.

I haven't had a chance to try anything yet.