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pilovis 27th August 2012 05:55 PM

Lowering cost of SE audio output transformer
 
Given that the cost of S.E. audio transformers has become prohibitive, I'm trying to use modified line transformers at place of class A audio transformer.

Laminated core as shown below with insulating paper between the two groups of laminations:

http://www.riparatore.altervista.org...lamierino1.gif

Primary winding divided into two only sections, the same for the secondary, wound according to the following scheme:

"First section primary, secondary first section, second section primary, secondary second section."

Examples:

5K/8ohm transformer (6V6, EL34, ECL86, EL84, KT88 - S.E.) = 110+110 Vac primary - 4.5+4.5 Vac secondary
3K/8ohm transformer (6L6, 807 - S.E.) = 110+110 Vac primary - 6+6 Vac secondary
800/8ohm transformer (EL/PL504 - S.E.) = 110+110 Vac primary - 12+12 Vac secondary

This construction and winding scheme (standard voltages) greatly reduces the cost of the transformer (I pay for it only 15 Euro for a 40 VA custom transformer).

The first two prototypes will be available in two days so I will test them to see if they work (hope so...:))

GCA 27th August 2012 05:58 PM

That could be interesting.

kevinkr 27th August 2012 06:05 PM

I'm quite sure it will be very interesting. :D

Toroidal power transformers have a good track record in PP and parafeed applications with tubes having extremely low rp like the 6AS7/6080..

TheGimp 27th August 2012 06:16 PM

PP or SE transformers?

pilovis 27th August 2012 06:22 PM

Quote:

Originally Posted by TheGimp (Post 3141909)
PP or SE transformers?

SE transformers, PPs do not have direct current saturation so do not need special insulated core as shown above.

ruffrecords 27th August 2012 06:54 PM

Quote:

Originally Posted by pilovis (Post 3141915)
SE transformers, PPs do not have direct current saturation so do not need special insulated core as shown above.

I thought mains transformers had no gap. Are these being built with or without a gap??

Cheers

Ian

Richard Ellis 27th August 2012 06:59 PM

Of course they will be built with a gap....The fun experiment will be setting the gap...I always thought one could use a roll of Teflon tape to experiment with gapping..

__________________________________________________ ____Rick.........

pilovis 27th August 2012 07:02 PM

Quote:

Originally Posted by ruffrecords (Post 3141958)
I thought mains transformers had no gap. Are these being built with or without a gap??

Cheers

Ian

As you can see on the above picture there is a gap between "E" laminations and "I" laminations, insulated with paper.

jean-paul 27th August 2012 07:03 PM

Thread title:

Lowering cost of SE audio output transformer

Suggested thread title:

Making good SE output transformers at lower cost

Reason: price should not be the only driving factor. Quality is prevalent in audio DIYing since the device will be more expensive than ready built devices anyway.

leadbelly 27th August 2012 07:10 PM

I actually still don't understand what you are you doing. Are you just ordering a special version of a standard model transformer from a manufacturer, i.e. you instructed them to build you one of their standard power transformer models except to create a gap using paper? Or do you have a transformer in hand that you took down to the laminations without destroying the bobbins and are reassembling it with a gap?


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