General Forum

Re: Beolab 4000 Signal Sensing Issue

ReTrO — Tue, 17 Mar 2009 08:16:17 GMT

Much appreciated info guys!

Will sort out a trip up the ladder. :)

Re: Beolab 4000 Signal Sensing Issue

Steve at Sounds Heavenly — Tue, 17 Mar 2009 04:40:47 GMT

Hi Richard,

Welcome to the forum!

I would never dare argue with Keith (I am sure he will be proven to be correct!), but I have seen a similar problem recently.

In some circumstances, Beolab 4000, 6000 and 8000 speakers that are set to "Left" or "Right" instead of "Line" will still switch on from standby when a signal is present at the Line In RCA socket, but they will switch off almost instantly after the signal drops away. I suspect that this could be caused by a potential difference between the speakers and the pre-amp, but I've never had a chance to fully investigate.

The simple answer is that I think your speakers are set to "Left" and "Right" instead of to "Line", so my guess is that a trip up the ladder is needed to check - Sorry!

Hope this helps,

Steve.

Re: Beolab 4000 Signal Sensing Issue

Keith Saunders — Mon, 16 Mar 2009 17:32:44 GMT

Richard,

Given that all the speakers do the same thing, then I would say that either:-

B&O have installed incorrect timing capacitor which is possible, but not likely
More likely is that you have a signal ground potential difference between the signal ground of your amplifier and the signal ground in the Beolab 4000 which is producing a larger than normal voltage across the timing capacitor.

Is your amplifier signal ground connected to power earth ?

The Beolab 4000's are isolated from power ground. i.e. the Beolab 4000 do not have a mains earth connection.

Re: Beolab 4000 Signal Sensing Issue

ReTrO — Mon, 16 Mar 2009 12:22:29 GMT

Yes, all the speakers are doing the same thing, which is most irritating. And they're a pain to check too, due to being mounted 9ft up on oak beams. :)

Re: Beolab 4000 Signal Sensing Issue

Keith Saunders — Mon, 16 Mar 2009 12:00:28 GMT

Richard,

A very warm welcome to Beoworld and your first posting.

I have had a look at the circuit which defines the timing of the switch off and it is determined by the charging of C148 switching transistor TR142. This timing should be about 100 seconds, so I am surprised when you say it is about 2 seconds.

Is it the same for all 4 speakers as there is no actual adjustment because it should not be needed ?

Re: Beolab 4000 Signal Sensing Issue

ReTrO — Mon, 16 Mar 2009 11:53:06 GMT

Hmm, will have to check as it wasn't me that undertook the cabling side of this.

Is it likely that it could be the switch set wrong?

Re: Beolab 4000 Signal Sensing Issue

Dave — Mon, 16 Mar 2009 11:43:30 GMT

Very strange!! It's meant to be 3 minute switch off time.

They are switched to "line" aren't they??

Beolab 4000 Signal Sensing Issue

ReTrO — Mon, 16 Mar 2009 11:26:41 GMT

I am having some trouble with a set of 4 Beolab 4000 speakers running off the back of a Denon AVR-2809 receiver in a small cinema system.

They are connected by phono to phono cable and use the signal sensing phono inputs on the speakers. This all works very well from a sound quality point of view, but the trouble comes when there is anything more than a very brief drop in sound levels through any of the channels.

Is there anyway of adjusting the time out that the speakers use, to switch off once they aren't seeing a signal come in. Currently they appear to be switching off after no more than 2 seconds. It's getting rather annoying having them clicking away all the time in quieter films.

Many thanks

Richard