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Mains DC Filtering

hifinutt said:
ah not quite , had the isotek syncro 4 times with various components . one a L10 valve pre amp and it made huge difference sonically , musicality ++ . Recently tried it on the arcam a85 , without a doubt its night and day difference , much tighter sound and improved timing. they can certainly make a difference imho

We conclude that the Syncro is indeed an effective DC-on-AC filter just as advertised. This not only prevents power transformers from buzzing but also cleans up the overall system’s sound especially at very low volume settings. On top of that the Syncro does not appear to introduce any sonically adverse effects. It’s thus a perfect solution for replacing any wall-to-conditioner power cable and to add DC filtering to your conditioner or regenerator of choice.

https://6moons.com/audioreviews/isotek3/4.html
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Yer know how Frankie said relax? Well Jez sez.... bollox!:D
 
DC on the mains is a symptom of a fault somewhere. Live and Neutral are essentially shorted together at DC at the nearest substation.
DC at your house can only be caused by two things:
Equipment that half wave rectifies the mains like old light dimmers and ancient televisions or faulty modern power supplies

Hum is far more often due to high mains, too many transformers skimp on copper and are 240 V max, not 240V nominal
 
where do you live, a badly made amp that hum's , should be well off your radar, junk, write to them and tell them their amps are shite, NO justification for a amp that buzzes and hums, seek elsewhere, they know this is a problem but can't be arsed to fix it..for a relativity low powered amp it sucks, stay away from this brand,
 
graystoke4 said:
where do you live, a badly made amp that hum's , should be well off your radar, junk, write to them and tell them their amps are shite, NO justification for a amp that buzzes and hums, seek elsewhere, they know this is a problem but can't be arsed to fix it..for a relativity low powered amp it sucks, stay away from this brand,
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So that's both amps off my radar then - Avondale and Hegel ;)
The Avondale is worse - that hums through the speakers!
 
Arkless Electronics said:
Some transformers hum. It's like that and that's the way it is. I don't consider it a fault.
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What about poor quality or loose transformer core laminations and/or coil windings? Would these not cause hum and be classed as a manufacturing or design fault? My Jadis and QUAD amps are totally devoid of mechanical or electrical hum even when wound up to 11 o'clock. Maybe I'm just lucky with my mains power supply (though I'm on the same local circuit as the nearby DGH with it's scanners, X-ray machines, aircon, lift motors and what have you) but I've never experienced transformer hum with any of my amps, and wouldn't buy an amp which hummed.
 
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It may be worth trying to put something under the feet of the amp to dampen the energy reaching the shelf it's on in case it is being amplified. It won't cure the problem, but might just make it a little quieter.
 
Hi Chris,
If you are still interested in DC filters that don't break the bank you can check out atlhifi (I have no affiliation with them, just got one of their DC filters).
I've got the DC trap v3 and even though it didn't completely remove the hum it reduced it so much that it is not annoying. Regarding the SQ, didn't notice any difference.
 
IVELIN said:
Hi Chris,
If you are still interested in DC filters that don't break the bank you can check out atlhifi (I have no affiliation with them, just got one of their DC filters).
I've got the DC trap v3 and even though it didn't completely remove the hum it reduced it so much that it is not annoying. Regarding the SQ, didn't notice any difference.
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I actually ordered one first thing this morning!
Whilst the hum I have is not troublesome I thought the ATL unit cheap enough to give it a go. If it does not work I figure I can just see it on fairly easily.
 
Chris Tarling said:
I actually ordered one first thing this morning!
Whilst the hum I have is not troublesome I thought the ATL unit cheap enough to give it a go. If it does not work I figure I can just see it on fairly easily.
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Definitely worth a try. Which one did you go for? Previously on pfm someone commented that for big transformers one would need higher DC voltage blocker.
 
I've got the same. What it did for me was to remove the variation in the hum; there were times of the day/night when the trafo would start humming louder and then quieter and then back again. Now it has a constant quiet hum auditable when I am really close to the box. I suppose the usual mechanical hum of a toroidal transformer.
I really hope it works for you :D

Chris, you said (up thread) that the Avondale hums through the speakers. The DC blocker won't fix that, I think. It's something else, could be something trivial e.g. earthing, but it could be something a bit more complicated. Probably some folk with Avondale could shed some light.
 
Chris Tarling said:
I have been trying a couple of new amplifiers this past week or so.

An Avondale NCC300 and a Hegel H390.

Both show audible transformer hum.

Hegel suggest using a mains DC filter if this can't be eliminated through re-jigging equipment arrangements (it can't).

Can anyone recommend me a DC mains filter to investigate? I've aware of the MCRU 'Excelium' and 'Excelsior' offerings (I have just bought a #79 mains power extension hub and #75 mains power lead from them).

What else should I be looking at without spending £££?

Thanks.
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I would send an email to Russ Andrews Accessories. They offer money back guarantee on all items (except custom builds) and can advise on the cause of the issue.
 
IVELIN said:
I've got the same. What it did for me was to remove the variation in the hum; there were times of the day/night when the trafo would start humming louder and then quieter and then back again. Now it has a constant quiet hum auditable when I am really close to the box. I suppose the usual mechanical hum of a toroidal transformer.
I really hope it works for you :D

Chris, you said (up thread) that the Avondale hums through the speakers. The DC blocker won't fix that, I think. It's something else, could be something trivial e.g. earthing, but it could be something a bit more complicated. Probably some folk with Avondale could shed some light.
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The Avondale has gone back as I have decided to go with the Hegel.
The Avondale is the better power amp for sure but I like the Hegel and, for various reasons, it's easier to live with.
So I have a stack of Naim gear that I need to part with...
 
IVELIN said:
I've got the same. What it did for me was to remove the variation in the hum; there were times of the day/night when the trafo would start humming louder and then quieter and then back again. Now it has a constant quiet hum auditable when I am really close to the box. I suppose the usual mechanical hum of a toroidal transformer.
I really hope it works for you :D

Chris, you said (up thread) that the Avondale hums through the speakers. The DC blocker won't fix that, I think. It's something else, could be something trivial e.g. earthing, but it could be something a bit more complicated. Probably some folk with Avondale could shed some light.
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Hi there, I have the exact same problem and symptoms. Have ordered the same unit from ATL. Am definitely hoping it will atleast reduce the transformer hum to acceptable levels...Will see once it arrives.
 
Some amps have DC blocking and more built in as standard; my new EWA power amp has this and four transformers, two per channel. Dual mono balanced mains.
 
Arkless Electronics said:
Some transformers hum. It's like that and that's the way it is. I don't consider it a fault.
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I do. Or at least consider it a PITA if audible.

I've just had one of my ESL988 speakers fail (storm of crackling) and as we are 'sheilding' it isn't practical to send it for repair or replace. However I've swapped it with a later model from my other setup that uses ESLs. This works fine but buzzes. I recall having to open up my earlier ESLs and using rubbery grommits to stop them buzzing. But I'm now not really in a state to do this. So am wondering about either a DC block or a slight stepdown in mains voltage. It is a buzz, not just 50Hz. Low level, but annoying once noticed.
 
I have a Hegel 390. As my dealer said there will be a hum from a cold start, I can only hear it if a place my ear next to the amp. As the amp warms up any hum disappears. I have never had or heard any hum through my speakers. I have no mains modifications at all.
Can I suggest you give Bill Leigh an email. He was very helpful when I needed advice on minimum ventilation for my amp in the rack. bill at audendistribution.co.uk
All the best
 
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