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Old 22nd November 2004, 08:07 AM   #1
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Default toroidal or not toroidal

Hello,
it's better a toroidal or a "double C" nucleus transformer, for a class A ampli, generally?
I don't think I’ll purchase an “eso” or specific product so I think I’ll increase the power of the transformer of a 2 - 2.5 factor in order to have a margin of safety.
I have two opportunities:
The first one is to order a "double C" nucleus transformer from a little local producer, hoping that he can give me a bit more sophisticated product for audio employment (although I’m not sure of his ability to make a better product).
The second solution is to buy a common industrial toroidal transformer.
The price is approximatively the same.
What do you suggest about it?


ciao!
antonio
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Old 22nd November 2004, 08:31 AM   #2
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Depends of the quality of the manufacture. I have seen badly winded and isolated toroidals which "sound" worse compared to some good R-core and double-C transformers.

Personally I prefer precise made toroidals with OFC pure copper wire, quality isolation and good ferrite rings.
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Old 22nd November 2004, 08:39 AM   #3
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I have never seen a toroidal transformer wound with OFC. Could you tell me who makes the toroidal transformers you use.
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Old 22nd November 2004, 09:17 AM   #4
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I have 2 reels with NOS military OFC wire which I'm using for my custom made toroidals. Sorry, it's not for sale because I have wire left for no more than 2-3 transformers.

The OFC wound toroidals do sound better I think
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Old 22nd November 2004, 10:05 AM   #5
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Default Re: toroidal or not toroidal

Quote:
Originally posted by alphadelta
I think I’ll increase the power of the transformer of a 2 - 2.5 factor in order to have a margin of safety.
Ciao Antonio,
come va, che cosa significa quello?

For me, toroidals mean; smaller dimensions, lower magnetic field, less hum.
A toroidal in general is much faster than more traditional transformer types. There are exotic block transformers, the ones i have seen are very expensive. Then, there are exotic toroid species that outrank regular industry models, especially in price.
Class A amps need current, stable powersupplies, thus a transformer that is stable and capable of rejuicing the caps fast.
A toroid does just that, even better, a toroid is able to deliver twice the rated power for small periods. It also does worse, with anything above 250-300VA you'll need an inrush current limiter to protect your fuses.

I use large 1600VA toroids to filter the current from the wall socket in combination with really big 20 amp Shaffner filters for my power amplifiers.
Even connected to double 16 amp(220V) fuses one of these toroids will blow the fuses at startup, if without a startup limiter.
As i use four of these *****es, turn-on goes through a 555 ic timer based relay-box.

Class AB amplifiers in my opinion have the same demands on the powersupply, and so on the transformer.
Well made toroids can compete with any type of transformer, even for tube amps.
I built the M.vanderVeen EL34 power amp with toroid output transformers by his design too, sounded pretty good to me.
I believe they are still made by Amplimo, even think Amplimo sells the complete Amp parts.

10-15 years ago a lot of the manufacturers carried their brand specific transformers, nowadays you see many of them using regular industry brands like Plitron, Amplimo and such.
Only few exotics use(d) highly uncommon transformers, brands like Swiss Physics and Goldmund in the past or some japanese firms..

If your local transformer producer does not have a name made in audio transformers i would opt for the safe way and go for the industry toroid.
If he has made a name for himself you should already have your answer i think.
Personally i'd spend my money on a bigger transformer instead of leaping to oxygen free copper,unidirectional strands and more of that high tech mumbo jumbo.
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Old 22nd November 2004, 05:58 PM   #6
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Default Re: Re: toroidal or not toroidal

Quote:
Originally posted by alphadelta
I think I’ll increase the power of the transformer of a 2 - 2.5 factor in order to have a margin of safety.
Quote:
Originally posted by jacco vermeulen
[B]

Ciao Antonio,
come va, che cosa significa quello?
Ciao Jacco,
my compliments for your good italian and tank you for your reply.
I wished to say that if use low or medium quality transformer for my ampli, it's better to double or triple the power to avoid overheats.
But I think we said the some things

Quote:

cut.....

Personally i'd spend my money on a bigger transformer instead of leaping to oxygen free copper,unidirectional strands and more of that high tech mumbo jumbo.

I need of 30Vx2.4A teorically.
In that case I think to buy a 2x0-30V, 5A or 3.75 A toroidal transformer (Nuvotem/Talema, RS Components 257-5225 or 422-5348) with two secondary winding in parallel connection.
What do you think about it and about parallel connection expecially?

ciao
antonio
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