My system goes "weedy" in the afternoon

[TheMadMick]

I love my system when it's running correctly. It absolutely sings. That means when it goes off song, it's very obvious.

The last couple of days listening in the afternoon (great to be retired) is goes all horrible. All I need to do is leave it and come back in the evening and it's fine. I think it's the amplifier. I did an experiment this afternoon listening first to CD and then to my turntable - both with female voice and the voices sounded like the amplifier is gently clipping - a hard piercing sound like when you're running something in. It really shouldn't clip. It's a kW550 and at nearly 600W a side, so it is unlikely to be the output stages.

It always seems to happen around 3.00 - 4.00 p.m. That's not a peak electricity demand time and I'm no more than a quarter of a mile from the sub-station. The system is on it's own ring from the fuse box.

I'm a bit flummoxed as it doesn't happen every day and I can't relate it to anything else going on in the house. Ideas?

[Dr Bunsen Honeydew]

Its your mains, someone is using something at this time that is fecking it up - only solution is either a mains regenerator or a balanced mains unit. I chose for NVA a BMU solution as I prefer that.

You will find it will improve the system at all times as well as solving the problem.

[zebbo]

I've got both as my supply was all over the place. So much so that at certain times of the day all my amps would start humming, (mechanically), for a few minutes then go quiet again. I tried with just the BMU but it didn't seem to cure all issues so I run both the regenerator and the BMU.
I'd recommend the BMU regardless of any mains problems, I don't know what it does but once it's in place you won't want to be without it.

[Simon Hickie]

Hmmm: £1600 from Russ Conway/Abbott/Andrews or £500 from NVA...

[savvypaul]

+1 for the NVA BMU

When I get bad mains then the BMU buzzes..but the sound quality is not affected.

I keep the BMU away from the system (running a 2.5m extension block off it) and tucked behind a chair so that any buzzing is virtually inaudible. 95% of the time the BMU is silent. Around 6.30 pm each weekday seems to be the time for bad mains at my place.

[Lurcher300b]

95% of the time the BMU is silent. Around 6.30 pm each weekday seems to be the time for bad mains at my place.

Sounds like DC on your mains. Well, to be more precise, an asymmetric load somewhere, causing the transformer to saturate.

[savvypaul]

95% of the time the BMU is silent. Around 6.30 pm each weekday seems to be the time for bad mains at my place.

Sounds like DC on your mains. Well, to be more precise, an asymmetric load somewhere, causing the transformer to saturate.

Yes, going to have a new consumer unit and dedicated radial fitted soon...

[Dr Bunsen Honeydew]

That wont stop it. Someone else using some machinery is causing it. I have complained and complained and the Lecky board refuse to acknowledge it, they say voltage is within spec - they do not even look at offset or distortion.

I argued with them to no avail that if my water was coming out of the tap brown even if legal the water board would have to do something about it, but you Lecky people just ignore it because it can't be seen, I got the phone call equiv of I couldn't give a shite shrug.

[savvypaul]

That wont stop it. Someone else using some machinery is causing it. I have complained and complained and the Lecky board refuse to acknowledge it, they say voltage is within spec - they do not even look at offset.

Aye, I remember reading that here in the archive, now you mention Doc. The new CU / radial is aimed at overall SQ and to cater for new power shower - the existing CU is nearly 40 years old...

[Dr Bunsen Honeydew]

Off set mains overheats motors, well anything with a coil in it, including transformers. So washing machines freezers etc are having stressed motors which cuts down their life. The Lecky people are scared stiff there will be a campaign if people understood what was going on. It would cost them a lot of money to cure it, so they ignore it and hope it goes away or no one notices.