Calling RB1080 owners

**Olaf** · 17 April 2004, 11:18 Saturday

Dear Tom,

While I have an "old" RB-1080 my amplifier also runs quite warm, however even after driving hard I have no problems with termal protection, so it is probably nothing to worry about.

The RMB-1075 is not a grounded amplifier so non-senstive to the so-called ground loop. The RB-1080 is a grounded amplifier so senstive to current variations in grounding.

While cutting the third pin (removing the grounding) will prevent the humming sound it is a bit dangerous to do so. Any "internal" problems may put the chassis under current with all associated risks.

The humming is most likely due to your cable TV connection (try disconnecting to see if the humming stops) and there are many good ground loop isolators available to cure the humming problem without running any risks.

Regards,
Olaf

**Azeke** · 17 April 2004, 11:27 Saturday

Tom,

First of all, congratulations on your new purchase and welcome to the Cub.

No, the 1080 should not be hot to the touch, that is not normal. I would advise to provide more spacing between equipment, (Rotel recommends 4 inches). Also you want to ensure your receiver/pre-pro is above the amps as they generate a lot of heat.

Hope this helps,

Azeke

**will1066** · 17 April 2004, 11:48 Saturday

I have an open rack and mine, which sits on the bottom, never gets beyond warm.

What's up, Azeke? I'm back. :LOL:

**Tom Bombadil** · 17 April 2004, 12:00 Saturday

Thanks for the replies gents...

I have been using the 1080 for most of today and it seems to have settled down. While it is warm to the touch I would certainly not describe the heat as cause for concern. It is a great sounding amplifier and Rotel must be congratulated for making exceptionally great value for money products.

I have done much reading regarding earth loops and since my satellite receiver is connected optically I doubt this would affect the 1080. I have a great deal of electronics plugged into the mains in my room including a projector connected by DVI cable. I have noticed a potential difference on it's earth also!

Since a PD builds up in the chasis and is routed to earth, any earth connection would suffice - including the ground of the audio connections. I have consulted with a dealer of extremely high end kit (Levinson, Krell Lexicon) and he has performed the trick of removing earth pin on some high end installs. This has had no detriment to sound other than removing the hum.

I found that most pre--->power amp connections have mains noise issues - most subwoofers emit a very low hum if you listen carefully. Also with modern equipment capable of frequencies well above 100khz, it's not suprising that hiss also occurs.

Source : Imagination
Power : Courage
Transducer : Action

**Aussie Geoff** · 17 April 2004, 21:59 Saturday

Tom,

Glad to see your RB-1080 has settled down. My Series 3 (same as yours) did the same thing - the first couple of days I had it and left it turned on 24 x7 it idled quite warm, then it settled down and now is cool when on but not in use and warm after a sustained listenning session (it never reaches hot). I spoke to by dealer's tech at the time (I too was worred about the heat) - best they could come up with was the amplifier is a class A/B operation with a bias current to do the class A at low volumes - as components settled in the extra power draw and heat went away. Certainly (as per some posts by others) it sounds better after a few days 24 x 7 use or a month or so's regular use!

Geoff

**Tom Bombadil** · 18 April 2004, 07:22 Sunday

Geoff,

Thanks for the informed reply - bang on the mark again.

I have been experimenting with earth isolation. Interestingly neither my DVD player (A11), the 1098 or 1075 have an earth. The 1080 does and when this is connected induces a slight but audible hum from the speakers - 30cm distance.

Removing the earth silences the hum completely. What I have discovered is the since installing the 1080 - earthed or not - my 1075 now gives a slight hum - ear 10cm from speaker cones. The hum is certainly not audible from listening positions and is of no real concern but it is stange nonetheless. I have also discovered that when my 1098 is on, I get a slight hiss through all speakers until I hit "MUTE". Again the hiss is only heard with ear very close to speaker cone.

It certainly appears that the Rotel amps are very sensitive to any voltage but other than that sound incredible. They look the part and exceed expectations which is a definite result!

Source : Imagination
Power : Courage
Transducer : Action

**Azeke** · 18 April 2004, 13:47 Sunday

Tom,

Glad things are working out for you. I absolutely enjoy the dynamics that the RB-1080 provides.

Weeeellllll, Will welcome back :LOL:. It has been lonely trying to convince others about the acoustical properties of the 1080, since you convinced me to jump to the other side, and with the advent of the DoProIIx upgrade, 7.1 has been awesome in both HT and Music (of course, this required a CB upgrade 8) .

How's your RB-1080 performing, inquiring minds want to know?

Regards,

Azeke

**will1066** · 21 April 2004, 00:29 Wednesday

I think my RB-1080 took a big leap forward in the last month, Azeke. It's way smoother than when I first heard it out of the box. It is working hand-in-hand with my Arcam. It's been a worthy addition, for sure.

**Tom Bombadil** · 30 April 2004, 03:12 Friday

What should I do?

Guys, I am tearing my hear out over this one...

Equipment:
RSP-1098
RB-1080 ---> Kef Q7 (Fronts)
RMB-1075 ---) Kef Q1 (Rears) + Kef Q9c (Centre)
Denon A11
Infocus 5700 PJ

The equipment resides on a glass/wood stand with decent spacing between top of equipment and next shelf. From bottom to top : 1075--1080--1098--A11--Turntable (Disconnected completely from system)

I previously posted regarding a hum in my system since the introduction of the 1080. Since then I have been experimenting to try and eliminate this while hopefully keeping it earthed!

Firstly, if everything is connected as it should I get a hum+buzz through my frount speakers (1080 driven) AND a hum+buzz through my centre and rears.

Hum - sounds like 50hz mains frequency
Buzz - strange bee-like noise!!
NOTE - these noises are only audible with ear about 10 inches from speaker cone unless otherwise observed!

If I lift the earth from the 1080 the hum+buzz is reduced through all speakers though still remains.

If I turn off the 1080 no buzz but faint residual hum through my remaining speakers (1075 driven).

If I turn off the 1075, disconnect interconnects from 1080 - loud hum+buzz through fronts.

If I Iift the earth from 1080 and repeat the above then this dramatically reduces any hum though I get a hiss!

Now the interesting bit. With the interconnects removed from the 1080 and regardless of the earth, I get a buzz in the speakers driven by the 1075 - what gives???????!!!!!

I have resigned myself to the fact that I will always get some very low mains noise with most amplifiers but the induced buzz is concerning. My 1080 has the four clear WBT posts and I had hoped that the grounding system had been improved. My local dealer and Rotel have been very patient and extremely helpful but I am getting increasingly frustrated by this.

To cap it off, my 1098 (RF shield retro-fitted) has started to anoy me with a TFT screen that is not uniform in brightness and despite the RF shield makes my speakers hiss!

While I should be able to get an advanced replacement on the amp, how can I demand a replacement for the 1098 (5 months old).

It is a shame about these foibles as otherwise it is fantastic kit and gives a wonderful sound.

Any suggestions would be sincerely appreciated...

**Aussie Geoff** · 02 May 2004, 02:09 Sunday

Tom,

You have my sympathy - this seems to be a saga for you. I share your frustration since I had a shorter version of this last year which turned out to be several issues at once.

Given the complex symptoms you are experiencing and problems with replacement products (e.g. the RSP-1098 is your second if I recall) - I am starting to suspect some electrical issues. This is particularly evident as a possibility given the strange hum / hiss behaviours as various elements of your HT equipment are plugged in or earthed / not earthed.

If I turn off the 1075, disconnect interconnects from 1080 - loud hum+buzz through fronts.

A lound hum+buzz when there is no input indicates an earth leakage / ground loop coming up the ground or even the mains into your RB-1080. If I read you right, the fact that you are still getting this (but softly) through the RB-1075 (not earthed) when the RB-1080 is not earthed makes me suspect this even more strongly. Equally the symptoms of having the hum+buzz from theRB-1080 reduce when the RMB-1075 is on – indicates current flowing between these devices. An electrician (preferably one specialising in HT) can test for this easily. You could find all sorts of issues such as:

A mains leak on your earth wire (can be from within your house or even a neighbours house since you share a common mains earth!) Currents here of a few volts can do bad things for hum and his and I have seen up to 220V in some cases!.
A mains differential between your HT components causing earth current to flow between them either through the RCS leads, or the video leads or even in and out of the mains cords. This can be in turn caused by the use of two or more different plugs for the HT equipment, or even dirt / corrosion on one plug. It can also be caused by a fault in one of the components (could be any of them) leaking some current into the circuit.
The “classic” earth leak from the Satellite Antenna system (usually powered) or the cable TV system.
The obscure but powerful RF interference on mains problem which can happen if there is a radio tranmitter (FM or AM) within a few kilomters of your house. In this case the mains wireing can pick up these signals in some cases and create weird high frequency hisses and current flows that require a mains filter to eliminate.

All this is just speculation - possibilities to consider. However I suggest you consider getting in one or more of:
a) A specialist HT Electrician to test for earth leakages, mains noise etc.
b) A HT Power Clean-up device with separate filters and isolators for each mains plug.

Geoff

**Tom Bombadil** · 02 May 2004, 03:28 Sunday

Geoff,

I am beginning to suspect a mains issue also. I have been liasing with the senior technical person at Rotel UK who has been fantastic and extremely helpful (if you read this mate then thank you very much for your time and help).

I am still using my orgional 1098 and the screen issues are minor really. The room I use for HT is a rich dark red in colour and north facing so never has direct sunlight. The kit sits in an open rack in a corner by a chimney breast so resides in the darkest area of the room - this seems to emphasise any light from the screen. When viewed in brighter conditions it is perfect!!

Fortunately a childhood friend of mine is a sparky so I will bribe him round (with copious amounts of booze - after of course!!) to check my earth and mains consistency. The 1080 has made a fabulous addition to my equipment and has improved music enjoyment substantially on the already very good 1075.

If I am honest, I probably expect perfection and any deviation away from expectation is exaggerated by paranoia - IS THERE A DOCTOR IN THE HOUSE???!!!

On a side note, I have been a Pink Floyd fan since my early teens and yesterday gave Dark Side of the Moon a blast. I was wondering if anyone has heard the SACD Anniversary edition??

Thanks for your time and observations Geoff....

**Stevebez** · 04 May 2004, 08:54 Tuesday

Hi there,

Have just got my 1080 addition to my 1066 and 1075 combo and am VERY happy with the outcome.

I must say though I have none of the humm / hiss problems you are experiencing. I have the older version of the 1080 it seems (coloured binding posts).

More importantly I think though, I have shielded mains cable (Supra LoRad), mains surge protector and filter (not a very expensive one, but decent), as well as good quality Monster interconnects. I also got toslink between sat decoder and 1066 which probably helps to reduce any interference from sat grounding issues.

Also I use one wall outlet to run all my kit from. Think if you use more than one wall outlet you have potential of building ground loops.

Not much further advice I can add, only that the 1080 is one hot customer in more ways than one. In the process of modifying cabinet with some variable speed fan ventilation! Some great cooling stuff becoming available form the PC market of late.

Rgds Steve.

**Tom Bombadil** · 04 May 2004, 09:23 Tuesday

Steve,

Glad your happy with your kit mate. I have spoken to my sparky buddy and he suspects filtered sockets may help.

My problem is probably not as bad as what is interpreted from the description - I have enjoyed a few films this weekend and played many CDs and have been delighted by the performance.

I may invest in some MK surge and filtered sockets for my kit!

Regards

Darren

**kneptune** · 04 May 2004, 11:46 Tuesday

Tom,

You had asked if anyone had heard the SACD DSOM - though I've heard DSOM since my teenage days in the 70's, it is simply amazing in SACD multichannel. My wife, never a Pink Floyd fan, thought it sounded "amazingly clear and startling".

Am using an RSP-1098, Denon DV-2200, RB-993 200X3 for the fronts and an older RB-985 for the four rears on Paradigm Ref. v3 speakers.

Also the YES Fragile DVD-A is amazing and in the same league as well. Hope you eliminate your hum or get it to an acceptable level. You have some very nice gear to enjoy.

Regards,
Kevin

**Tom Bombadil** · 05 May 2004, 02:15 Wednesday

Kneptune,

Thanks for the feedback on DSOM. Is it multi-channel only or will it down mix for a conventional stereo (though still SACD resolution)? I have been a bit put off buying SACD/DVD-A having heard the early stuff which was very gimicky - stupid sound effects and steering etc!

Off to buy DSOM then!!

Regards

D

**Jason Brown** · 05 May 2004, 08:23 Wednesday

Dsom

All SACDs have a dedicated stereo layer, while only some (most all of the newer releases) have a multichannel layer.

**Menasce** · 05 May 2004, 10:59 Wednesday

Hello Tom,

Thought I'd weigh in on your apparent electrical issue. Before you get too many pints into your electrician mate, discuss with him these options:

1: a dedicated, separatly grounded circuit for your A/V gear. I'm thinking along the lines of the type of plug you see in network server rooms and the like (they're usually orange in color). I did something similar with my system because my RMB-1075 was momentarily dimming the lights when I turned it on. Now I have no problems with either the draw on the line or any hum/buzz from any of my speakers.

2: whole house surge protection. Here in North America this is a device that's installed at the utility entry point to your house, at the breaker panel. I don't know if this is available in the UK or if it meets your local building codes - Sparky should have info on this. The end result of this is to eliminate the need for any surge protectors elsewhere in the house. This may not completly resolve your hum / ground loop issue, but it can't hurt and it's much better than anything with a Monster logo on it.

Hope this helps.

**Tom Bombadil** · 05 May 2004, 16:57 Wednesday

Thanks for the continued interest in this topic gentlemen.

I had thought about a dedicated spur but I only plan to stay here another three years - plus the house is 180 years old and I have just finished decorating!

Surge protection may have to come from either replacement sockets or RFI/Surge distribution block.

BTW - here in the UK such a device called OLSON SOUND FANTASTIC is available http://www.soundfantastic.co.uk/

I wonder if anyone has tried this?

Calling RB1080 owners

Calling RB1080 owners

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