Dirty power/dimmer circuit causing weird Class D amp noises?

[doc40hz]

Looking for some technical advice. 

 

Recently purchased a second hand Orange  TB500 bass combo - the isobaric 2x12 one. 

 

Sounded fine at home. Took it to a gig and hooked a PJB C4 up to it as well (set to 4ohms on back of orange) During the first song, it developed weird noises - digital sounding clipping noises at considerable volume. Unhooked the PJB cab and put back to 8ohms. Same problem

 

Switched to my newly acquired backup amp - a TC electronic  BQ500. I'd never used this before. This was better but still sounded weird. DIdnt sound right through the C4 on its own or using the orange 2x12 as a cab. Wasnt sure if the speakers were damaged by the weird noise that came through. Low notes were disappearing.

 

Set up the rig yesterday and had a good play at gig volume for half an hour through the orange and the TC and both cabs - sounds fine to me. Speakers sound fine. Both amps sound fine. 

 

Very odd. 

 

I think perhaps the problems started when the venue dimmed the lights. It was the function room of a golf club. My amp was plugged into different plugs to the PA and I wonder if these were on the dimmer circuit?
 

Could the problems I experience be due to a power source issue?

 

[Bill Fitzmaurice]

If they were on the dimmer circuit the low voltage would have been a major problem, so that probably wasn't it. But inexpensive dimmers create RFI/EMI that radiates through the air, which can cause what you experienced.

[warwickhunt]

Experienced loads of examples of dirty leccy over the years.  Many pubs have ancient electrics which tbh were never fitted with todays present drain in mind; added to which many pubs add bits on etc.  I've known extensions glued to walls and plugged into the Landlord's residence above, whole bands expected to run off one wall socket etc.  The intermittent hum/buzz is the worst, I've enough first hand experience now to just watch what the bar staff are doing when it starts, it'll invariably be a beer pump or piece of equipment that they use, a fridge being opened and triggering a cooler to kick in was another.  

 

Purpose built venues should never have these issues inc any lighting RFI... you'd hope any way! 

[BassmanPaul]

This is not a Class D problem per se but 'dirty power' affects all amplifier Classes.  Over the last sixty years I have experienced the same kind of interference many times in four different countries.

[Chienmortbb]

I have had few problems with "dirty mains" in the UK, and never at a pub. Most noise is generated by pedal power supplies or pedal interaction. Of course, you also contend with other people's equipment. I had a noise, probably about 1KHz, through my cab and it turned out to be a combination of my pedal power supply and the connection between mu TC Mic Mechanic (you did not know I could not sing), and the PA mixer. When the TC and my other pedals were powered from different power supplies or batteries, the noise was not there, and I could not reproduce it at home.

 

So keep an open mind and investigate before blaming the mains. It may also be worth buying a socket tester https://www.screwfix.com/c/tools/socket-testers/cat7910008/

 

[msb]

Neon signs can wreak havoc too.

[msb]

My favourite dive downtown has the classic issues. Lots of neon signs around the stage , and there’s a couple of outlets the regulars avoid. 
 

I think the owner found someone who’d do some wiring for beer. And yet it’s my favourite venue. 

[moley6knipe]

Pedal power is a good shout: any pedals in the mix, and are they all powered with isolated outlets? I was fine using daisy chained power until one day I wasn’t!

 

Suggestion for a socket tester is great advice. I always check sockets somewhere new, and I ALWAYS use my own plug in breakers.