Richard Allen said:
Hi.
For what it's worth, I'm building an amp and I went to a toroid maker and gave him the spec I needed and he went out of his way to warn me that toroids do tend to hum a bit. When I asked him why he said that no 2 toroids are EXACTLY the same. One might buzz a bit under load and another won't. I asked him why and what I was told was that toroids are essentially wound as 1 offs. At which point I said to increase the Va of the toroid and he advised me that if he did that the sound quality of the amp could be compromised ( spelt that right?? ).
With large transformers, the toroid is the less expensive way to go. True, a laminate won't buzz like that but it'll be twice the cost and huge and weigh a ton. Just seems to be something with toroids which seems to be exaggerated with 'c**p' on the mains line sometimes.
That's the way it was explained to me anyway.
I know this doesn't help the OP though because it's annoying when it happens although out of all the toroids I've used over the years, most of them have been NOVATEL and none of them have buzzed. Not even the 1000Va.
It is the combination of the characteristics of the toroid and the characteristics of the mains distortion that cause the problem. I have experienced mains so poor that virtually any piece of kit that you try will hum and buzz but that does not appear to be the issue here.
The previous amplifier was quiet and the likelyhood is that the next one you try will be too, inconveniant sure but surely not that big an issue when you have the assurance of the manufacturer that it will be sorted.
The reality is that this is a (relatively) mass produced amplifier built to come to market at about £1500. The transformer is, along with the case, the most expensive component in the amplifier so costs here are crucial.
As Richard points out a laminated transformer will be far more expensive, a 'guaranteed' noise free toroid could probably by built at a price, but would anyone buy an Ellicit-R at £2500?
And why should theyhave to, in my experience this sort of problem is relatively rare, and the number that can not be solved by swapping the amp for another sample rarer still. The amp is fine value for 90+% of the people who purchase it, that's just the way it is.
Edit. In my experience all brands of transformers that I have seen used in hi-fi can hum and buzz in certain situations.