substantial buzzz/hiss from speakers casued by a21 interconnect?

[tboooe]

Hi, I am demoing the P3 and A21. There is substantial buzzzzzzzz/hisss coming from my speakers that can easily heard from 1 ft away. With my Rotel 1080 amp I did not have this issue.

I have the ground lift switched activated on the back of the A21. This does not help. I have verified that is mostly coming from the amp. when I turn off the P3, the buzzzzzzzz/hiss gets somewhat more quiet. All of my compenents are no where near cable tv. They are all sitting on the carpet at the moment in the living room.

Here is what I have done so far:
1. Unplugged everything excluding the A21 amp >> buzzzz/hisss still present
2. Changed which outlet the A21 was plugged into >> buzzzz/hissss

Both units are plugged into my wall outlet, as was the Rotel 1080. Any suggestions? I would also appreciate an explanation on what could be causing this with the Parasound equipment but not the Rotel.

Please see my post below. I think I have traced to an interconnect problem.

thank you

[bigburner]

Ah tboooe, that will be the Ghost of Rotel punishing you for dumping your 1080.

[tboooe]

LOL!!!!!! I needed that!

[tboooe]

Update:

I think I have traced it to the input connectors on the back of the a21. When I unplug my RCA or XLR cables from the a21, there is no more buzzz or hiss. The strange thing is, if I leave the interconnects connected to the a21 and power off my preamp, I still get the buzz and hiss. Even if my preamp is unplugged from the wall, I will get the buzz as long as there is an interconnect connected. Very odd...any ideas?

[Peter Nielsen]

Update:

I think I have traced it to the input connectors on the back of the a21. When I unplug my RCA or XLR cables from the a21, there is no more buzzz or hiss. The strange thing is, if I leave the interconnects connected to the a21 and power off my preamp, I still get the buzz and hiss. Even if my preamp is unplugged from the wall, I will get the buzz as long as there is an interconnect connected. Very odd...any ideas?

Try using RCA only, and make sure that the balanced/unbalanced toggle switch is set to "unbalanced".

Peter

[tboooe]

thanks peter. I did already try that. In fact I have tried 3 different cables and switch back and forth betweeen balanced and unbalanced. This is either something inherent in the amp or I have a defective one.

I assume no one else has experienced this?

I was all set to get the A21 now I am not sure.

[Peter Nielsen]

thanks peter. I did already try that. In fact I have tried 3 different cables and switch back and forth betweeen balanced and unbalanced. This is either something inherent in the amp or I have a defective one.

What happens if you turn down the input level controls on the back of the A21? Does the hiss disappear then?

Have you verified that nothing touches the metal frame of the A21? (Is it mounted in a rack or something that could cause an electrical connection?)

Peter

[tboooe]

Peter, when I turn down the input levels all it does is lower the volume of the hiss. The hiss stays as long as I can hear something, including music.

Nothinng but the carpet is touiching the a21. It is sitting on the ground right now. Nothing else is plugged in or on. I dont think it has anything to do with an electrical connection. I really do think it has something to do with the inputs. It is so strange that when I unplug the input cables, the hiss goes away. Even when the input calbes are not attached to the preamp I get the hiss as long as they are connected to the a21. Cables connected = hiss...

strange.

[r100gs]

To rule out your electrical source connect the amp to a budget 14ga surge protector and if that does not work try a 14ga extension cord to a different circuit in the house.

[tboooe]

r100gs: thanks for the advice but I already tried this. No matter what I do, the amp is dead quiet unti I connect the inputs. and it does not matter if I connect XLR or RCA cables. i must have a defective unit.

[DrJRapp]

Peter, when I turn down the input levels all it does is lower the volume of the hiss. The hiss stays as long as I can hear something, including music.

Nothinng but the carpet is touiching the a21. It is sitting on the ground right now. Nothing else is plugged in or on. I dont think it has anything to do with an electrical connection. I really do think it has something to do with the inputs. It is so strange that when I unplug the input cables, the hiss goes away. Even when the input calbes are not attached to the preamp I get the hiss as long as they are connected to the a21. Cables connected = hiss...

strange.

Try leaaving the cables connected as above and shorting them on the unconnected end to see if the hiss goes away.

[bigburner]

tboooe, may I suggest that you ask brucek for advice as he seems to be a very knowledgeable person when it comes to hum/hiss. Have a look at his post at this thread:

http://www.htguide.com/forum/showthread.php4?t=9140&highlight=brucek

I have a similar (smaller) problem and I want an answer, so if you don't ask him I will!

[tboooe]

Jerry. what does shorting the input cables on the unconnected side do? Sorry but I am not an electrical engineer.

bigburner: I will definitely seek the wisdom of brucek.

[DrJRapp]

Jerry. what does shorting the input cables on the unconnected side do? Sorry but I am not an electrical engineer.

This is difficult to explain, but in brief most amps are designed to be connected to some input source, and when nothing is connected they go out of wack and produce noise. What most manufacturers do to avoid this is to use female RCA jacks that short the input when nothing is connected. Plugging in a cable without any source on the other end defeats that. That's why I suggested shorting the other end. If your noise goes away, you can at least eliminate the cable as the source of the noise.

I bring this up because of the peculiar way Parasound specs the noise on the A21: Quote: S/N ratio: > 112 dB, input shorted, IHF A-weighted. I've never seen the words input shorted in a spec before, even though several manufacturers do short their amps as I mentioned. This way of specing leads me to the conclusion that the A21 must be noisy if the imputs are not shorted.

[tboooe]

Jerry, I am fairly certain it is not the interconnects because I tried 3 different ones (Audioquest, Nordost, RAdio Shack).

The buzz I am getting is produced whether or not the preamp is connected.

This has to be an issue with the amp.

[DrJRapp]

I'm curious, do you have a paddle fan in you room or somewhere near in your house? I went nuts once trying to find a buzz/hiss that seemed to originate from a Denon receiver, that turned out to come from the fan and was being picked up by induction by my speaker cables.

Another point. While no quality amp should be noisy, are you aware that the A21 specification wise is considerably noisier than the RB1080 -112db vs -116db both "A" weighted. What this means is that the A21 produces nearly 2.4 times as much low level noise. I think this is largely why the A21 doesn't sound as good as the 1080 at low levels, it's own noise is smearing the signal. This is excaberrated by my ultra high efficiency speakers.

[tboooe]

Jerry, no i dont. The amp and speakers are in the living room where there are no other electronics except for a few lamps. The amp is actually sitting on the carpet. Could it be somehow related to this? Static charge on the carpet (again, I am not an EE so please forgive me if that last statement was ridiculous)? I have turned off all other components. I have tried plugging the amp into different wall sockets and into a surge protector powerstrip. I only I have not tried doing is moving the amp to a different location.

[DrJRapp]

No statement is rediculous, when it comes to noise. Do you know if your carpet is so called "static free"? A few years ago in order to avoid static buildup and discharge when touching a computer, some carpet manufacturers started to incorporate copper threads in their backing to bleed away the static.

If your carpet does have these threads it could be at a different level of potential in respect to ground than your amp is. So, by sitting the amp on the carpet you create a capacitor. This is far fetched, but possible.

[tboooe]

Thanks Jerry. I am going to try and move the amp tonight and see what happens.

[Peter Nielsen]

Tboooe,

Try a "cheater plug" that disconnects the ground. I am now convinced that the Ground Lift switch will NOT do the same as a cheater plug will do!

(I know now, because an hour ago I opened up an A21 to do a voltage conversion. I found out that the power cord ground goes directly to the chassis of the A21, so regardless of what position the "Ground Lift" switch is in, it will never do the same as a true cheater plug will do. The "Ground Lift" switch will never disconnect the chassis from the ground).

I'm pretty sure that the cheater plug will solve your problem...

Peter

[tboooe]

Peter, thank you. But what I dont understand is that I get the buzz only when I connect the IC. If the amp is on with the speakers connected, there is no buzzz. If i had a ground loop issue, wouldnt it show up when the amp is on and the speakers are connected regardless if the IC is connected or not? I am disputiing your suggestion, I am just trying to understand what getting a cheater plug would do and how it relates to the symptoms I am experiencing.

[Peter Nielsen]

Peter, thank you. But what I dont understand is that I get the buzz only when I connect the IC. If the amp is on with the speakers connected, there is no buzzz. If i had a ground loop issue, wouldnt it show up when the amp is on and the speakers are connected regardless if the IC is connected or not? I am disputiing your suggestion, I am just trying to understand what getting a cheater plug would do and how it relates to the symptoms I am experiencing.

No! It is the IC that is the cause of the ground loop. The IC makes your grounded A21 connect to another grounded component...

Without IC, you don't have a ground loop - there is nowhere the ground could loop! :B :T

Speakers are seldom, if ever, the cause of a loop. Where would the speaker connect to ground? (Unless you have something very esoteric, of course).

Your preamp (or another component connected to the preamp) probably connects to ground and there you have it -- a ground loop!

The deceiving factor is the Parasound "Ground lift" switch. It does not do everything you would think it would do. (The reason is probably because of UL/CE restrictions. If the ground loop did what we expect and want it to do, then the Underwriter's Laboratories or the Commission Européenne might not approve the A21 because it would not meet their grounding standards...)

Now, the "cheater plug" will do what the Ground Lift doesn't do. I'm pretty sure it will solve your problem.

Peter

[tboooe]

peter, thanks for explanation. Just for clarification, I get the buzz whether or not the IC is connected to the preamp or not. In other words, all I have to do is connect the IC to the amp and I will get the buzz (even if the other side of the IC is not connected to anything). This is why I dont understand the whole ground loop issue. The IC is not connected to anything on the other side.

[DrJRapp]

tboooe

Try this, leave the amp connected by Ic to the preamp. Unplug the preamp from the electric source. See what happens.

[tboooe]

Hi Jerry, I have already tried that. I have unplugged everything but the amp. No IC = no noise. As soon as I connect the IC (whether or not the other end of the IC is connected to a source or not) I get noise. I really dont remember this happening with the Rotel.

Is some level of electrical noise, hummm, buzzz emanating from the speakers normal for all amps?

[bigburner]

Here beginneth the lesson according to brucek. Once again may I suggest that you seek his advice...

The cheater plug you used effectively eliminates the third prong on the AC plug.
The "third prong" is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. This safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault.

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

Usually bringing another ground from a cable system etc, can cause some hum or buzz in A/V equipment, but this can be corrected with a little work. Ground loops caused by cable or dss TV are the easiest to get rid of.

There are those that rely on the ground connection provided by their interconnects and will use cheaters on all their equipment except for one. This one grounded device provides the safety return and then as long as the equipment that is connected to it has an interconnect cable, it is esscentially protected. This theory falls apart as soon as some unsuspecting person unplugs all the interconnects. I wouldn't advice using this method.

If you have a hum or buzz from an amplifier caused by a ground loop, then removing the safety ground connection to the amplifier (and perhaps other devices as well), can clear the resultant effect of the ground loop, but creates the safety issue. It's more advisable to try and clear the condition causing the ground loop than to mask its effect by applying unsafe practices.

In that regard, ground loops are sometimes a difficult task to track down and remove because there are a million reasons for them to exist. The loop is caused by a difference in the ground potentials in your system. Breaking the safety ground almost as often clears the problem, and that is why it goes away with the use of two prong power cords or with the use of cheater plugs. This easy fix is obviously tempting, since it's so easy. I hesitate to say that sometimes it's the only thing in the end that works on some troublesome equipment, ensuring that cheated piece of equipment is hidden away from anyone touching it.

Generally a ground loop can be tracked down to its source. Removing the problem can sometimes be a little more difficult.

You have to first ensure you have a ground loop situation by completely removing the offending amp and while using its proper three prong power cord, disconnect everything but its speakers and see if it still hums. If it does - you don't have a ground loop - fix the amp.

One of the other major culprits in creating ground loops is the use of more than one circuit in an HT system. The larger systems demand more power, so several dedicated circuits are sometimes needed. But even using a single circuit with different receptacles can cause a ground loop.

Residential houses use 240 volt "single phase" three wire power. The two "hot" legs are 120 volts and are 180 degrees out of phase. The loads in your house are balanced between these two legs at the service panel. It is advisable, if you do have two circuits powering your HT system, to ensure you are using a common leg. It is fairly easy to establish this.

Let me explain a bit about ground loops.......Even though the safety ground is a cold conductor, it can, and usually does, develop a small potential, through mutual inductance, wire resistance and various other reasons that can be different at each receptacle in your house.

When I plug a power amp into one receptacle and a preamp into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that this equipment's metal cases are at a slightly different potential. When I connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow...

Exactly the same situation can occur, except usually worse, when you introduce a new ground into the system from cable TV or a satellite. Their ground on the shield may possess a different potential than the ground in your system and current will flow in all the interconnects. Usually by centralizing and bonding all external grounds to the common house ground you're at least giving yourself the best chance of reducing this problem....

Anyway, getting back to your problem. If you decide to not use the cheater and want to track down the problem you have to start with a minimal system and build it up to find the cause.

If you have no hum with the single amp and its speakers, then you can hook your preamp up with a single set of interconnects, ensuring the preamp has no source components connected to it and that its plugged into the same receptacle as the power amp. If it doesn't hum, then add a single source component to the preamp with the same conditions. If this minimum system has no hum, and you usually plug the devices into different receptacles, then you can try and plug the preamp or source component into a different and check for hum.

Well, you can see where this is going. You must rebuild your entire system, starting with the noisy amp, until the buzz reappears and then figure out why that happened. This requires you to rip apart your entire system and rebuild it. You will find the source of the problem this way.

Do you see why people use cheaters......

[tboooe]

big burner:

very educational. however, my problem does not seem to be related to a ground loop caused by another source. the buzz i hear occurs when I connect the IC to the amp. no other source has to be attached to the other end of the end and I will get the buzz...

I will seek the guidance of brucek though...

[Peter Nielsen]

peter, thanks for explanation. Just for clarification, I get the buzz whether or not the IC is connected to the preamp or not. In other words, all I have to do is connect the IC to the amp and I will get the buzz (even if the other side of the IC is not connected to anything). This is why I dont understand the whole ground loop issue. The IC is not connected to anything on the other side.

Hmmm. That is extremely odd!

Does the same thing happen with both XLR and RCA?

Does the balanced/unbalanced toggle have any effect at all?

Sounds VERY strange...

Peter

[tboooe]

Peter, yes I have tried both RCA nd XLR with 4 different cables. The toggle has no affect at all. With only the amp on, as soon as I plug in the IC to the amp. I will hear buzzing, hissing, especially through the tweeter. I can clearly hear this from 12" away. With no IC connected, I have to be right on top of the speaker to hear anything.

The only other thing I can think of (aside from a faulty amp) is if my wireless network has anothing to do with this. Could it be introducing interferance that is traveling through the IC? Maybe I am reaching here.

I do want to investigate the faulty amp answer some more though. What would cause the amp to create a buzz in my speakers when I connect IC? Some sort of short (say that 10 times fast) internally related to the inputs?

[Peter Nielsen]

Peter, yes I have tried both RCA nd XLR with 4 different cables. The toggle has no affect at all. With only the amp on, as soon as I plug in the IC to the amp. I will hear buzzing, hissing, especially through the tweeter. I can clearly hear this from 12" away. With no IC connected, I have to be right on top of the speaker to hear anything.

You mean 12' (feet) away, right? What you hear at 12" is not really relevant IMHO. Who listens at that position?

If you indeed mean 12", then hiss or no hiss will depend on what speakers you're using. With low-efficiency speakers the amp will appear to be silent but with high-efficiency speakers you may experience a low level hiss...

What is the efficiency rating of your speakers (dB/watt) ?

Peter

[tboooe]

I dont know the efficienty. I have B&W 805S.

I never had this issue with the Rotel 1080 amp.

When the room is quiet I hear a humming, buzzing from about 10 feet away. Otherwise, I will need to be about 1-2 feet away. Is this normal? Like I said, I heard nothing with the Rotel. Even if this is normal, I still dont understand why it would happen after I connect the IC.

[Peter Nielsen]

When the room is quiet I hear a humming, buzzing from about 10 feet away.

No, at 10 feet away everything should appear silent...

So, you're hearing both humming (buzzing) and hizzing? Does not sound like any of the common problems... Maybe your A21 is defective?!

Peter

[r100gs]

Lucky it's a demo.

[Docray1]

I had the same exact problem with my A21. The folks at Parasound actually told me to use a cheater plug, which totally eliminated all of the hiss. I now plug the cheater into my power supply instead of into the wall directly which (hopefully) protects me from possible electrocution. I recognize that I am limiting the power my amp can draw, but I am pretty happy with it now.

[tboooe]

docray1: thank you for the post. I got a replacement a21 coming so we'll see if it helps. Tech support also recommend that I give this a try. They sounded pretty confident that the threat of electrocution is very low even when using the cheater plug.

[bigburner]

tboooe, if a component fails inside your new A21 and the 120 volts shorts to the A21's case, then the case will be live and can electrocute you or one of your guests.

If you opt for the cheater plug I suggest that you put a nice big sticker on the front of your new amp saying "Danger! Touching this equipment may kill you!"

This may even improve the looks of your A21.

What colour writing would go nicely with an A21?

[Docray1]

While not impossible, the likelihood of an internal component failure shorting to the A21 case seems very improbable; I have to believe that Parasound Tech support wouldnt risk such liability by suggesting that we use the 'cheater plug'.

[bhuskins]

If a cheater plug is really needed to clean up an issue, I would get a PS Audio power cable (or similar) that has a removable ground pin. It keeps the installation clean, without the ugly $.99 adapter.

Brent Huskins
Media Design
HTGuide Sponsor

[bigburner]

Hi tboooe,

I spent 4 hours today searching for the cause of my gentle hum. To cut a long story short, the fix required 2 separate modifications, with neither one on its own solving the problem:

1. The Rotel 1080 amp needed a cheater plug. (I would like to think that this is a short term workaround, and yes, I am designing that "Danger - do not touch" sticky label!).

2. I needed to disconnect my turntable's earth wire which was connected to the back of my Rotel 1070 preamp.

The turntable earth wire issue was the real surprise to me. I discovered it by disconnecting every piece of equipment, including interconnects, and then reconnecting each item one piece at a time. I had to try different combinations too. Before each change I switched everything off, so all my gear got a hammering from power surges at switch-on time today.

I have to credit brucek in his various posts for pointing out the need to apply a disciplined step-by-step process to solve this problem.

Regards,
bigburner.

[Peter Nielsen]

tboooe, if a component fails inside your new A21 and the 120 volts shorts to the A21's case, then the case will be live and can electrocute you or one of your guests.

In theory true. However, beware that the Halo amps are sold in Europe too.

European indoor outlets are often of the type without ground. Grounded outlets are only mandatory in certain "wet" places like the kitchen, bathroom, basement, etc.

To make things even more dangerous, most of Europe uses 230 volts! So, if the Halos were in any sense dangerous to use without ground they would be forbidden in Europe...

Peter

[tboooe]

Thanks for the input Nigel. I am going to try a cheater plug tomorrow. One thing I did notice is that the A21 is very sensitive to how well the ics are seated. Last night my left speaker showed even more buzzing than normal. After a while I jiggled the ic and noticed the buzzing go away. Once I made absolutely certain the ic was completely seated, the buzzing went away, though the humming remains but hey I got one problem solved! Personally, I dont think the cheater plug will do anything. I think the noise I hear is inherent to the amp.

[mitch57]

I have the A51 and all though they are totally different amps I don't have the problems you have. However, with that said you might want to look into some of the products from these folks.

www.psaudio.com.

Perhaps one of there products can solve your problem. It eliminated the buzz coming from my amplifier.

I purchased the UPC200-HB and my amp has been dead silent ever since.

Good Luck!!!

[bigburner]

So tboooe, have you sorted out your problem, and if so, how did you do it?

[Chris D]

If you opt for the cheater plug I suggest that you put a nice big sticker on the front of your new amp saying "Danger! Touching this equipment may kill you!"

Funny... that's the same sign I have in front of my Halo equipment. Not that there's any electric danger, I just don't want people touching my equipment.