The Workbench

Re: BM 3000-2 Speaker pop on powerup

Paul — Sun, 28 Feb 2010 08:48:23 GMT

Thanks guys,that answers my question.I can live with it,this is a very nice machine indeed.

Re: BM 3000-2 Speaker pop on powerup

Dillen — Sun, 28 Feb 2010 08:29:32 GMT

I can only echo what Mika already said.
It's in the way the amplifier is built. They will all give a pop of some kind when powered on (and sometimes also
when powering off), some more than others depending mainly on the condition of the output stage and
power supply capacitors (the large cans) but also other capacitors in the Beomaster.
In some cases a full recap will bring it to a minimum but I wouldnl't guarantee it.
The pop is a very low frequency capacitor charge curve and will not destroy anything but it can of course
be a bit annoying.
I once designed a delayed relay circuit to build in, that was 30 years ago so the pop would have
been an issue from new.

Martin

Re: BM 3000-2 Speaker pop on powerup

Paul — Sun, 28 Feb 2010 08:16:17 GMT

Good point.Probably more of an annoyance than actually damaging to anything.It appears to just hit the woofers.That's why they put in the relay on some models,to give it a few seconds to come up.I have only had this a couple months and it seems worse than I recall,but maybe I just never noticed.If I am not mistaken my other B&O receivers,a BC7000,and a BM 2400 do have a muting relay,so this is my first experience with one with no muting.

Thanks

Paul

Re: BM 3000-2 Speaker pop on powerup

tournedos — Sun, 28 Feb 2010 08:01:22 GMT

In my experience all B&O amps without a muting relay circuit do that, more or less.

Never had the chance to hear these new to have any idea of what the "correct" amount of pop might be, but I guess it can't be completely avoided in the AC coupled amplifiers. For the DC coupled designs, it might get worse when the components age and the power supplies come up at uneven rates.

Might be interesting to look at the "pop" waveform on an oscilloscope, but I have a hunch it would be quite soft, with little energy in the higher frequencies. So it would mostly exercise the woofers, and speakers with generally sufficient power rating should be safe.

BM 3000-2 Speaker pop on powerup

Paul — Sun, 28 Feb 2010 07:37:30 GMT

My BM3000-2 delivers a substantial pop to my speakers on powerup.It does this regardless of which source is selected and even when the volume is at zero.Of course if I leave the speakers off for a few seconds during powerup there is no problem.The unit has been recapped,had the switches and sliders cleaned,and idle current adjusted.It seems a bit harsh on the speakers to be normal.

I assume this is due to charging of the large output coupling caps,but what I am not sure if this is normal or if a part of the circuit is designed to minimize or eliminate this has failed.

Thanks

Paul