RMB-1095 Buzz

[mitch57]

Hi all,

My 1095 seems to be buzzing more and more these days. I have verified that it's nothing to do with grounding. The buzzing is coming from the amplifier itself. I disconnected all interconnects except the speakers.

Here's what happens:

1. The amp powers on and the 5 red channel ligths come on for a second or two and then go off.

2. The amp is dead silent after the red channel ligths go out.

3. Over the next 5 - 10 seconds the amp begins to buzz softly and then increases in volume to a more audible buzz.

It sounds just like the buzz you hear in fluorescent lights. I have fluorescent lights but I have them all turned off. They are also on a seperate circuit and my entire home theater is on two dedicated 20 amp circuits.

My amp is the newer generation style with the clear binding posts. The hum can barely be heard from the listening area and only during silent parts or in between tracks. Sometimes the buzz is louder then other times. Could the variation in the volume of the buzz be related to voltage fluctuations?

My system is connected to two Richard Gray RPGC 400s.

Is anyone else with a 1095 experiencing this behavior?

[soundhound]

Sounds like you're transformer, as it heats up it gets worse. I would contact you're dealer and get it exchanged. Yes it can be diretly related to line voltage, as the voltage drops the current rises, humm will be louder, and heat gets generated.

[mitch57]

It looks like it was an electrical problem that was causing the buzz. I had been noticing some flickering lights over the past several months. Not all the time just once in a while. The other day the lights were dimming and returning to normal brightness at about the frequency of a car turn signal. Again it was intermittent. What really got my attention (other then the flickering lights) was the fact that the 1095 was buzzing louder in unison with the flickering lights.

I thought to my self... what the heck is going on here?! I powered off the 1095 but the lights still flickered so I knew it wasnt the 1095. Then things would go back to normal but the 1095 was still buzzing.

I called the power company and they came out and replaced something on the meter as well as tightned something esle up. He was speaking greek to me so I don't know exactly what he did. He said everything looked normal and voltage was within specs. He said he thought it was probabaly a large pump that was cycling on and off. The only pump I have is for the septic tank and it was working fine. In other words I couldn't find anything that would have caused the problem.

I came home yesterday expecting that I was going to have to pull the Rotel out and take into my dealer. But to my surprise when I powered it on it was dead silent. I can't even hear it if I put my ear right up to it! Same thing again today. Dead silent! What ever he did must have fixed it.

I guess these amps can be quite suseptible to electrical current changes. I must have had some major current problems. Otherwise I'm sure the Richard Gray's would have filtered them out.

Anyway, Im happy again now.

[PewterTA]

Good to hear Mitch!

Crazy how electricity can do such strange things. That's cool that you noticed the lights, I probably would have never caught that and just thought the 1095 was bad.

Hopefully now you'll have many years of good luck with it! No Buzzing!!! ha ha.

[mitch57]

I can't believe how quite this thing is now! It hasn't been that quiet since I bought it! I used to get what I thought was a very, very, very, minor ground loop hum coming from the speakers when I put me ear up to them. That's gone now too!

I will continue to monitor it over the next couple of weeks. I wish I knew exactly what the power company replaced/fixed.

[basementjack]

Now you have us all interested! I want MY power company to come out and do what yours did!!!

Does your amp sound better now too? Or Just quieter?

And it is a shame that the Richard Gray's didn't do anything. I wonder if the new home theater products from APC are any better? APC has been doing power for a long long time.

[Stevebez]

I found by shifting the chassis around a bit the dreaded Hum can be either increased or decreased on some amplifiers... have not had a need to resort to this with my 1080 or 1075 - all the hum I got from my system was due to poor cable layout and run.

Maybe its just the resonance of the transformer vibrating the chassis and this generates the excessive hum ... there will always be a hum on the transformer though as high current will generate hum thats just the way it is ... ever stand next to power lines?? I expect the 110/120 volt units to be marginally worse than the 220/240 volt units as the current flow on the lower voltage units is double.

Cannot remember the formula for magnetic field generation by a current running on a wire ... I think amps has more impact / effect than voltage.

Its also got to do with the magnetic field thats generated by the current in the transformer itself - if the amp is crowded like the 1095 is with two fat transformers there may be a "conflict" of magnetic fields between the two transformers. They perhaps should be better shielded from each other.... just a thought.

Also consider surrounding components - is the amp crowded in a cabinet with other devices putting out electromagnetic radiation ... shift them around - isolate them and then see. Also check cable runs - parallel power cable runs are sure to cause trouble - whenever they have to cross try get as many crossing to be at 90deg as possible.

Anyone had a peak inside a 1090 ? How are the two transformers shielded internally from each other ?

I think humm . buzz is critically important to resolve as it impacts background sound so dramtically that it makes an amp with great specs sound very cheap very quickly.

Rgds Steve

[Andrew Pratt]

He said he thought it was probabaly a large pump that was cycling on and off. The only pump I have is for the septic tank and it was working fine

The other common culprit is compressors in freezers and fridges etc...they soak up a ton of current when they turn on. A/C will do the same but I'm not so sure many of us are using our A/C just yet...and if you are I don't want to hear about it

[H.Donald]

I don't know if this will help you...but my problem sounded similar to yours.After going thru every known and unknown cures, I was ready to send my 1095 back.I had always had everthing plugged into a Monster 5100 and then into a dedicated line.I decided to switch things around.The only combo which everything was quiet...the Rsp 1068 and the 1095 had to be seperated.The 1095 wanted it's own line and to be away from the 1068.And it not did not want the dedicated line,only the other line with everything else as it was.So it went from going back to pure silence.Go figure...

[mitch57]

As I stated in my last two posts... The problem appears to have been related to power from the power company. I have done several tests. Even when the freezer in the garage and the fridge in the house cycle on, and with the microwave cooking I now get dead silence!

What ever "Puget Sound Energy" (the local power company) did at the power pole and my meter solved the problem. I can't get it to buzz now. It's almost as if I it's not really turned on.

It also used to buzz for a second or two while it was doing it's self test and the 5 red channel lights were on. It would kinda buzz.. BUZZ... BUZZ... and then it would click and the lights would go off. It would continue to make a slight buzz (when it was on it's best behavior) which you could hear from a couple of feet away. In the worst case scenerio you could hear it from the listening area.

Now it clicks and the red lights come on for a second or two and then it clicks and they go off. And the amp is dead silent.

As for the Richard Grays... I believe they did as much or more as any power conditioning could do beyond those conditioners that have their own batteries that supply power like an online UPS.

I believe I had some pretty severe power problems even though the power company thought that everything looked normal.

I'm no electrician, but I know that the problem could be duplicated consistently before the power company came to the house. I also know that after he shut off the power to the house and made some changes (tweeked this, tightened that, replaced those...) I have not been able to get my amp to make any noise.

As far as I can tell... It's fixed!

[Stevebez]

If it aint broke ... don't fix it !!!

Rgds Steve

[mitch57]

I spoke to soon! It started buzzing again last night. I don't get it!!! How could it be dead silent for 4 days straight and then all of a sudden the next day I go to turn it on and it starts buzzing again?

Nothing has changed in my set up.

How about this for a test? Remove the 1095 from my cabinet and plug it in to my Richard gray with nothing connected to the amp but the power cord. I'll turn it on and see if the buzz ist still there. If not, it's most likely cabling, wiring, the circuit, or a combination of various things.

If the buzz is still there I will plug it in to a different circuit without the richard gray. If the buzz is gone then its the circuit or the richard gray. If the buzz is still there it's something in the amp itself or possibly the power cord.

I would like to hear from all of you 1095 owners on this issue. Do your 1095s make any buzzing noise when your standing right by the amp within a foot or two? Are your amps dead quiet all the time (like mine was for 4 days) or does it buzz sometimes and not other times? And does the buzz volume flucuate from day to day or remain constant?

Don't confuse this buzzing with Ground Loop issues. I don't have any buzz/hum in my speakers. The buzzing is coming directly from the amp itself.

[PewterTA]

The only time I've ever gotten mine to buzz is when I caused a ground loop (grabbed the tip of one of the cables), or when I had one of my cables touching another cable. Both causing a ground loop...

Otherwise, I can put my ear onto the 1095 with it on and I don't hear anything...maybe the ever so faintest buzz (but it would have to be dead silent in the room, even a TV on in another room would probably be louder).

I would try isolating it on difference circuits and see when and where you can get it to buzz/not buzz. Another thing I would try is do the grounding technique, take a piece of speaker wire that you might have laying around, and connect it to one of the screws in the back (touching metal) on the 1095, then connect it to your Pre-Processor and see if it stops the buzzing.

[greggz]

My 1095 buzzes. It appears to come from the center of the amp (the torrids). It is not audible at the speakers.

I pulled it out to send it in for service and then I found that my cabinet was actually making it sound louder (like cupping your hands around your mouth).

I've tried to do a few tests to see if it is environmental. I can get the buzz to sound louder or quieter depending on where I plug it in, but I have yet to get it to go away.

If the wife and kids are out of the house one of these days, I'm considering throwing every circuit breaker in the house except the one the amp is on to completely isolate it. I've got so many things in my house that could introduce noise into the A/C that I am not ready to completely fault the 1095…yet. I've got 3 refrigerators, 3 air conditioners, 8 to 10 dimmer switches, transformers for doorbells, the alarm system, and low voltage lighting, and 3 UPS's, just to name a few culprits.

[Locutus2k]

Don't confuse this buzzing with Ground Loop issues. I don't have any buzz/hum in my speakers. The buzzing is coming directly from the amp itself.

OK. But, please, try to use a cheater plug withouth the ground pin and see if the buzz goes away. Mine was buzzing from the transformer (as well from the speakers) with the ground connected. Withouth ground is just dead silent. Just try, it will cost you only some cent and very little of time. Let us know.

Locutus2k

[mitch57]

Locutus2k,

I already tried using a cheater plug the first time I noticed the problem. It didn't have any effect what so ever on the buzzing.

[greggz]

Ditto. Cheater plug makes the ground loop hum go away but not the amp buzz.

[mitch57]

I found this little "tid bit" on this web site today.

http://www.pliniusaudio.com/que/que.htm#09

"MECHANICAL NOISE: Some items of equipment can directly radiate a mechanical hum or buzz. This mechanical noise almost always originates from the device's power transformer. Place your ear close to each component of your system and listen. If you hear a hum or buzz coming from within your equipment, then the noise is mechanical. 'Lamination rattle' occurs in all transformers to some degree, related to the quality of the transformer and the quality of the line voltage. If the noise intensity varies depending on the time of day, sometimes even the time of month, then it is due to the quality of the AC supply voltage in your area. In this case you're at the mercy of your energy provider."

I am beginning to think this is what's going on. How else can you explain my amp being dead silent for 4 days straight and then starting to Buzz again?
Also it seems to vary from day to day, hour to hour, week to week, etc., etc., etc...

I live in a rural area on a small mountain. The electric company did say that we don't have ideal power in my area. He also indicated that power issues would be more prevalent during the evening hours around 7:00 - 9:00 pm when more people are at home turning on all sorts of electrical equipment. I would think this would also hold true during the early morning hours when everyone is waking up and getting ready for school/work.

What do all of you think of this theory?

[Stevebez]

Sounds very plausible in my view ...

This Lamination Rattle appears on a number of websites relating to ac quality and transformer construction quality.

Rgds Steve

[Fishy]

Will be getting a 1095 this weekend, and wondering if I have done the right thing or not.

Fish

[Stevebez]

Transformer Technology / Theory

Did some reading into this and its all very interesting. Sounds like it comes down to the transformer build and in particular how the core is made up.

Typically cores are there through which curernt flows from the wire coils wrapped around it. If its one piece you have one big current and field flow. If you split it up (into many thin pieces of iron insualted and compacted together) you get much smaller current flow (per sheet), although the total remains the same (all sheets added together). The advantage is that there is less power loss with the latter method AND the resistance of the core increases and the current halved. I.e. eddy current losses is inversely proportional to the square of the number of iron sheet laminations.

Point of this is it is possible that the hum from 1095 transformers are due to the laminates used in the core hence the "laminate rattle" ... anyone know what type of core is used in ROTEL transformers...???

The best apparently are iron dust cores in an insulating binder ... dont believe these can rattle as the core is "ne piece" although made up of milliosn of fragments of iron... best of both worlds it seems and can be manufactured into any shape.

For those who want more check out this site!

http://www.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html#lams

Rgds Steve.

PS let me know if I got something wrong - almost sure I have ...

[mitch57]

I would think that if this were partially related to the transformer construction in the Rotels we would be hearing alot more about this issue.

There are only about two people on this forum that will admit to their 1095s having any buzz at all. By "buzz" I mean a buzz coming from the amp itself even if you have all the speakers disconnected. Not a ground loop issue which many people have had and still have.

That would tend to indicate that Gregg and myself are about the only ones on this forum that have "AC Quality" issues.

Perhaps Andrew could get some detailed construction information on the 1095 transformers. Maybe it is the laminates on the transformers that are rattling. And maybe no one else hears it because they have very good AC power where they live.

It might also be that Gregg and I have faulty transformers that when provided with quality AC power exhibt no buzzing but when the AC quality drops even a little the faulty transformers begin to buzz.

Andrew,

Can you get some information on this for us?

[arrow]

any one thought about a bad transformer. I had a class D that buzzes like crazy and when i looked into it very deep i talked to the manufaturer and they said send in the amp and we will replace the power supply it is a power supply issue in the transformer. Now these things are made in chinna from brit parts so it is highly possible for 2 out of 1000 to develop a buzz dew to faulty gear. I sounds to me like as the heat expands the transformer it makes the problem come out even more definent. I would hit up my dealer and possible get it send back in for service. The fact that it is mechanical tends to lend that it needs to be replaced transformer

[mitch57]

If the transformer were bad wouldn't it buzz all the time? Also wouldn't it get worse the hotter it got? Sometimes mine doesn't buzz at all. The week before last it was dead silent for 4 days straight. It didn't matter how loud or how much I put a load on it. It was dead quiet.

Now it buzzes but not all the time. Sometimes I can barely hear it even if I put my ear right on it. Other times it's louder. It doesn't seem to have anything to do with heat.

Three weeks ago it buzzed. Two weeks ago it was dead silent. How could it be dead silent for 4 days straight AFTER it was buzzing?

I hate having to take it out of the rack. It's so damn heavy and my dealer is 75 miles one way from where I live.

The last time I talked to Rotel tech support (Mike Sheehan) he also thought it might be AC power related.

[soundhound]

You could locate a meter, (fluke makes some dandies) set it up for min/max, and the next time you notice the hum monitor the line voltage. Watch for sags in the line. Over voltage (up to 10%) is not nearly as hard on inductors as low voltage conditions. Lower voltages will make them consume more current, = heat, = bad. As far as Rotels transformers being questioned, this is one of their shining attributes. If it is line voltage, and goes undealt with it could damage you're xformer if it has not allready.

[mitch57]

How much of a drop in line voltage are you talking about? When the power company was out a couple of weeks ago he indicated that the line voltage may drop to 119 and that was pretty typical for our area during peak power usage.

I also have the 1095 hooked up to a Richard Gray which is suppose to compensate for those occasional low voltage issues.

[soundhound]

Anything above 110 and you will be fine. Normally if people have issues with line drops it will be within their homes service as many older homes had 60/100 amp service, you start loading that up and you can see it, in the lights, etc....or as you're power co. found, hot spots. Lugs aren't tight on wire, voltage drops, current rises, heat is generated. Most new homes are getting 200 amp sevice as we keep adding gadgets and gizmos to make our lives easier so this isn't an issue for many.

[mitch57]

My house is new. I had it built less then 8 years ago.

I take it your 1075 and 1080 are both quiet as a mouse even if you put your ear up to the amp?

[soundhound]

You bet. Sonically as well as I learned long ago about do's and dont's of cable routings, grounding issues, noise caused by various sources.

[mitch57]

I did some more tests today. It's either the transformer or power to my house. I have my Home Theater connected to two dedicated 20 amp breakers. I disconnected everything! The only thing connected to my amp was power. No speaker leads, no interconnects, no nothing! It still buzzes!

So I guess I will take it in to my dealer which is 75 miles from here and have them put in on the bench and see if it buzzes. If it does, hopefully they can get it taken care of. I will take it down in a few weeks.

If they can't resolve the issue it will be time to sell it and move on to a higher end amp. How dissappointing!

I wonder how Greg is doing with his buzzing issue?

[Dmantis]

Mitch,
How did you make out with your buzzing problem. I also own a RMB1095 and it buzzes. It also buzzes at the speakers. I believe it's messing up my sound quality. I can hear a buzz in the highs. the tweeter is where the buzzing happens.

I'm contacting Rotel on a problem I'm having with the rsp1068, I'm also noting about the buzz.

mantis

[Blazar]

PSAudio makes a humbuster for exactly this problem.... look at their website.

[mitch57]

Mitch,
How did you make out with your buzzing problem. I also own a RMB1095 and it buzzes. It also buzzes at the speakers. I believe it's messing up my sound quality. I can hear a buzz in the highs. the tweeter is where the buzzing happens.

I'm contacting Rotel on a problem I'm having with the rsp1068, I'm also noting about the buzz.

mantis

Ditto what Blazar said. I got the PS Audio Humbuster and it solved the problem. But... it won't solve the problem with the buzzing in your speakers. Only the buzzing coming from the transformer in your amp.