Power Transformer for Class A Amplifiers -- What are your experiences ?

EUVL · 2nd March 2011, 03:09 PM

Following a discussion for power transformers for the F5X, I think it is a topic which deserves separate attention.

Apart from what VA rating and what core size in relation to to real power consumed, there are many other issues, such as :

1) Core type -- Toroidal, EI, R-Core, C-Core ....

2) Winding type -- multiple thin wires vs single thick wire, bifilar or not, how much insulation between primary and secondary, single-layer secondaries each occupying half of the core perimeter, primary inside or outside, ...

3) Encapsulation 8potting) or not ...

4) Shielding -- electrostatic shield or no shield, magnetic shield will belly belt or case, Mu-metal vs steel vs aluminium, ....

I hope you will share your experiences and have an open discussion. And I particularly hope that Nelson would shed some light on the topic.

So I open the forum to you all.

Patrick

Melon Head · 2nd March 2011, 09:17 PM

You want mu-metal or better for the magnetic shield. That is about all I can contribute.
I can discuss a bit further if interested.

Regarding electric shield. I think it is a good idea for toroidals.

Melon Head · 2nd March 2011, 11:41 PM

Just one more thing.
I very rarely hear people discuss the importance of correctly annealing the core which a lot of manufactures do not do

d to the g · 3rd March 2011, 03:19 AM

since it's been so quiet, i'll just point out jcarr's experience (and other people's measurements) that toroids have the largest bandwidth, followed by the EI, and then the R core. It goes without saying that a power transformer should be a low bandwidth device (either 50 or 60 Hz only).

However, I've never seen a low voltage/high amperage R core transformer.

Melon Head · 3rd March 2011, 03:23 AM

Placing an electric shield between primaries and secondaries should take care of this problem

EUVL · 3rd March 2011, 03:59 AM

> However, I've never seen a low voltage/high amperage R core transformer.

Nikon 1975 bought one for his F5 in Japan if I remember correctly.
Please search one of the F5 threads.

Patrick

Melon Head · 3rd March 2011, 05:20 AM

Just so we don't get off track.
I think what we really want to know is, what is going to give us the best bang for buck in terms of making a real audible difference.

I am sure it would be possible to spend big dollars on a transformer and not end up with any audible improvement.

It would be nice if Nelson could set us straight here

qusp · 3rd March 2011, 05:51 AM

i believe that tx that Nikon1975 got from japan was insanely pricey

wktk_smile · 3rd March 2011, 09:29 AM

In japan, EI is most popular/widely used for electronics diy purpose.
Besides, large trafos suitable for such ClassA amplifier are expensive here.

Thus I can't say that's insane price for custom-made Universal primary/suitable to F5 R-core trafo.

EUVL · 3rd March 2011, 10:56 AM

F5 components, parts you use

‚q‚`ƒVƒŠ[ƒY@¡–@•\
‰¿Ši•\

2nd March 2011, 03:09 PM	#1
EUVL diyAudio Member Join Date: Oct 2003	Power Transformer for Class A Amplifiers -- What are your experiences ? Following a discussion for power transformers for the F5X, I think it is a topic which deserves separate attention. Apart from what VA rating and what core size in relation to to real power consumed, there are many other issues, such as : 1) Core type -- Toroidal, EI, R-Core, C-Core .... 2) Winding type -- multiple thin wires vs single thick wire, bifilar or not, how much insulation between primary and secondary, single-layer secondaries each occupying half of the core perimeter, primary inside or outside, ... 3) Encapsulation 8potting) or not ... 4) Shielding -- electrostatic shield or no shield, magnetic shield will belly belt or case, Mu-metal vs steel vs aluminium, .... I hope you will share your experiences and have an open discussion. And I particularly hope that Nelson would shed some light on the topic. So I open the forum to you all. Patrick

2nd March 2011, 09:17 PM	#2
Melon Head Formerly Thanh1973 Join Date: Nov 2006	You want mu-metal or better for the magnetic shield. That is about all I can contribute. I can discuss a bit further if interested. Regarding electric shield. I think it is a good idea for toroidals. __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."

2nd March 2011, 11:41 PM	#3
Melon Head Formerly Thanh1973 Join Date: Nov 2006	Just one more thing. I very rarely hear people discuss the importance of correctly annealing the core which a lot of manufactures do not do __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."

3rd March 2011, 03:23 AM	#5
Melon Head Formerly Thanh1973 Join Date: Nov 2006	Placing an electric shield between primaries and secondaries should take care of this problem __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."

3rd March 2011, 05:20 AM	#7
Melon Head Formerly Thanh1973 Join Date: Nov 2006	Just so we don't get off track. I think what we really want to know is, what is going to give us the best bang for buck in terms of making a real audible difference. I am sure it would be possible to spend big dollars on a transformer and not end up with any audible improvement. It would be nice if Nelson could set us straight here __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."


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3rd March 2011, 03:19 AM	#4
d to the g diyAudio Member Join Date: Aug 2006 Location: minimalopolis	since it's been so quiet, i'll just point out jcarr's experience (and other people's measurements) that toroids have the largest bandwidth, followed by the EI, and then the R core. It goes without saying that a power transformer should be a low bandwidth device (either 50 or 60 Hz only). However, I've never seen a low voltage/high amperage R core transformer.

3rd March 2011, 03:59 AM	#6
EUVL diyAudio Member Join Date: Oct 2003	> However, I've never seen a low voltage/high amperage R core transformer. Nikon 1975 bought one for his F5 in Japan if I remember correctly. Please search one of the F5 threads. Patrick

3rd March 2011, 05:51 AM	#8
qusp Sometimes a square peg fits a round hole just fine diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	i believe that tx that Nikon1975 got from japan was insanely pricey

3rd March 2011, 09:29 AM	#9
wktk_smile diyAudio Member Join Date: Dec 2009 Location: Kyoto	In japan, EI is most popular/widely used for electronics diy purpose. Besides, large trafos suitable for such ClassA amplifier are expensive here. Thus I can't say that's insane price for custom-made Universal primary/suitable to F5 R-core trafo.

3rd March 2011, 10:56 AM	#10
EUVL diyAudio Member Join Date: Oct 2003	F5 components, parts you use ‚q‚`ƒVƒŠ[ƒY@¡–@•\ ‰¿Ši•\

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