Active Wharfedale Diamonds Transformer

Fowlet

Member
2010-09-26 6:14 pm
Hi All,

Fairly basic question, the transformer in my old active wharfedale diamonds is buzzing away quite loudly. I've been told this is due to coil delamination, which makes sense. However, rather than go through the whole "Bake it in the oven, relaminate the coils" palaver I'd like to buy a more modern, more efficient and more importantly quieter transformer.

My multimeter appears to be dying and I can't get a VDC reading from the old transformer output. Anyone know where I can find a suitable replacement?

Thanks in advance,
Ethan
 
I would question both of those efficiency figures. Anyway all the efficiency means is less heat.

The first transformer will produce less interference (hum) as it's got a much lower magnetic field due to being toroidally wound, but the second transformer will have better immunity to noise and spikes on the mains as it has a more lossy coupling between primary and secondary.
 

Fowlet

Member
2010-09-26 6:14 pm
Given the stability of british mains, am I better off going for a toroidally wound one? Farnell sell some too. Might see if I can get a suitable mu-metal surround for it too, just for perfection's sake.

Am I right in saying I can wire the two 115V primary coils in parallel and get a 230V primary?
 
Given the stability of british mains, am I better off going for a toroidally wound one? Farnell sell some too. Might see if I can get a suitable mu-metal surround for it too, just for perfection's sake.

I quite like EI transformers because they have less inrush and better noise and spike rejection. You do have to consider the size and hum field issues though.

Am I right in saying I can wire the two 115V primary coils in parallel and get a 230V primary?

No that would result in some pretty nasty smoke. You need to wire them in series (one inline to the other).
 

Fowlet

Member
2010-09-26 6:14 pm
No that would result in some pretty nasty smoke. You need to wire them in series (one inline to the other).

Even if they were in phase? I suppose I'd still only get 15V out of them though, just the full 50VA rating. If I wire them in series with a tap in between, I'll get a 15V AC supply at 25VA, and a 30V AC supply at 50VA, right?


AndrewT said:
Hi,
are your active speakers double insulated?
Do they have the concentric double square symbol?
Do you know how to maintain the ClassII rating when you modify the speaker?

No, they are not, I know the symbol you mean but can't see it. And no, I do not know how to maintain the ClassII rating.

So, given a transformer to driver distance of about 15cm, toroidal, or EI?