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Old 27th June 2007, 10:04 AM   #1
beppe61 is offline beppe61  Italy
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Default Advice for transformer selection.

Dear Friends,


I am selecting a new 200VA - 24V-0-24V mains transformer for an upgrade of a small integrated (NVA AP10).
I am undecided between a good quality toroidal (i.e. Nuvotem) and a Walsall model of the EI type.
The regulation is better for the EI type (4%).
Some time ago I read an article stating the superiority of EI transfomers for audio purpose (better isolation from the electrical grid).
Nevertheless toroids are smaller and more handy.

I would like to get some kind advice about the best possible choice.
I thank you all very much indeed.

Kind regards,

beppe
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Old 27th June 2007, 10:16 AM   #2
Did it Himself
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Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.

EI have lower bandwidth so mains noise might not pass through them so readily. They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.

Take your pick!
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Old 27th June 2007, 10:45 AM   #3
beppe61 is offline beppe61  Italy
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Originally posted by richie00boy
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!


Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin/...itie&Nr=avl:it

The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,

beppe
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Old 27th June 2007, 11:17 AM   #4
beppe61 is offline beppe61  Italy
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Originally posted by richie00boy

Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!


Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin/...itie&Nr=avl:it

The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,

beppe [/B][/QUOTE]
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Old 27th June 2007, 11:19 AM   #5
AndrewT is offline AndrewT  Scotland
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Hi Beppe,
that's a nice transformer you have chosen.
I would never have looked at 400Vac control panel transformers, just goes to show what can be sourced when you search.

A big jump from 20VA to 200VA. Are you planning to house it in a separate box?
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Old 27th June 2007, 12:02 PM   #6
Did it Himself
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20VA... so it was for a pre-amp? I would not have ordered 10x more VA in that case, any mains noise transfer would be worse than the lower rated VA unit, along with more inrush current.
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Old 27th June 2007, 01:39 PM   #7
beppe61 is offline beppe61  Italy
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Originally posted by AndrewT
Hi Beppe, that's a nice transformer you have chosen.
I would never have looked at 400Vac control panel transformers, just goes to show what can be sourced when you search


Dear Mr Andrew,
I have a great opinion of Walsall products.
The original one in the NVA unit is from this same brand as well.
They look very well built and with very good regulation figures.

A big jump from 20VA to 200VA.
Are you planning to house it in a separate box?


It's a great jump indeed but I hope to gain some power in the bass.
As the original case is little the separate box solution is mandatory.
Next step two better power supply caps.
A powerful power supply is a good starting basis for a nice sound, I hope.

Thank you very much.
Kind regards,

beppe
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Old 27th June 2007, 02:13 PM   #8
beppe61 is offline beppe61  Italy
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Originally posted by richie00boy
20VA... so it was for a pre-amp?


Good afternoon !
This has been my same reaction.
Actually a 20VA transfo is more usually seen in a preamp than in an integrated, even if a low power one (15W/channel on 8 ohm load).

I would not have ordered 10x more VA in that case, any mains noise transfer would be worse than the lower rated VA unit, along with more inrush current.

At first I looked at the power supply caps, a pair of 4700uF of decent quality.
They are also directly soldered to the pcb and not easy to replace.
So I decided to go first with a new and beefier transformer.
My intention would be to gain some more drive in the bass leaving any other things the same.

Thank you and kind regards,

beppe
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Old 27th June 2007, 02:32 PM   #9
Did it Himself
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If it is a power amp then it's not so bad
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Old 27th June 2007, 05:04 PM   #10
beppe61 is offline beppe61  Italy
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Originally posted by richie00boy
If it is a power amp then it's not so bad


Yes. It is a small but fine sounding to me little integrated.
Maybe the increase in VA can be excessive.
I thought " better a little more than a little less", maybe wrongly.
I have it know at hand.
What impresses me is the diameter of the wires on the secondaries, very very thick. I think this is very good for current.
It looks like 1,5 sqmm section !
I strongly feel this transformer will not be a bottleneck for current.
As soon as I will try it I will report my impressions.

Thank you very much indeed.
Kind regards,

beppe
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