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Old 10th June 2007, 11:03 PM   #11
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Alexg,

Yipes! You really have a difficult task if your winder has never done this before. When we talk about an output transformer, not only basic transformer principles apply, but if this is for a hi-fi amplifier you also have leakage reactance and interwinding capacitance and distortion to consider. You will require several secondary sections interleaving with the primary, and you may possibly also be talking about a distributed load design.

The following information is needed:

1. Maximum output power

2. Which tubes, and will the operation be class A or class AB?

3. Used as triodes, pentodes or ultra linear?

4. What loudspeaker impedance will be used?

5. In what amplifier design? This is needed to have a guesstimate at the leakage reactance required and general stability considerations.

As said by others, there is design data available, but even using that could be a daunting task if you or your winder have never done this before.

If you can supply the above information, I can perform a design for you, but I need to state at an early stage that, as SY said, your winder will need to be able to perform the task.

If this is an option for you, I would be glad to help.

Regards
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Old 11th June 2007, 05:23 AM   #12
alexg is online now alexg  Philippines
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Quote:
Originally posted by Johan Potgieter
Alexg,

Yipes! You really have a difficult task if your winder has never done this before. When we talk about an output transformer, not only basic transformer principles apply, but if this is for a hi-fi amplifier you also have leakage reactance and interwinding capacitance and distortion to consider. You will require several secondary sections interleaving with the primary, and you may possibly also be talking about a distributed load design.

The following information is needed:

1. Maximum output power

2. Which tubes, and will the operation be class A or class AB?

3. Used as triodes, pentodes or ultra linear?

4. What loudspeaker impedance will be used?

5. In what amplifier design? This is needed to have a guesstimate at the leakage reactance required and general stability considerations.

As said by others, there is design data available, but even using that could be a daunting task if you or your winder have never done this before.

If you can supply the above information, I can perform a design for you, but I need to state at an early stage that, as SY said, your winder will need to be able to perform the task.

If this is an option for you, I would be glad to help.

Regards
The tube that I will be using is the 832A and the circuit is based on this: http://ultranalog.com/

1. Maximum Output Power: 12 watts

2. 832A, I think it is Class AB

3. Used as Triode

4. Speaker impedance of 4 and 8.

The OPT winder already did a PP OPT for this tube, but the tubes were biased lower than the ultranalog design (33ma vs 40ma), he used EI76 with a 38mm stack height.

When I downloaded dissidentaudio.com OPT design assistant software, the software is telling me that EI76 is too small for the spec and frequency response that I wanted, it was telling me to use EI96.

I posted the question since the price difference between the two cores are quite substantial and if I can get away with an EI76 why would I pay for an EI96 OPT? BTW, the winder is telling me that EI76 with 2x0.11mm wire for primary winding would work.

Thanks.
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Old 11th June 2007, 05:35 AM   #13
alexg is online now alexg  Philippines
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Quote:
Originally posted by retailer
For the valve anode current I take the max anode current given in the valve data book and add a 25% margin for safety. So for an EL84 this works out at about 75mA, using the 3 amps/square mm figure, wire size is about 0 .18mm for the primary and up to 1mm diam for secondary depending on the secondary impedance.
So for a push pull amp, should i make it 2X75ma for an EL84 PP amp? or just size it at 75ma?

Thanks.
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Old 11th June 2007, 06:14 AM   #14
Yvesm is offline Yvesm  France
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Quote:
Originally posted by alexg

. . .
When I downloaded dissidentaudio.com OPT design assistant software, the software is telling me that EI76 is too small for the spec and frequency response that I wanted, it was telling me to use EI96.

I posted the question since the price difference between the two cores are quite substantial and if I can get away with an EI76 why would I pay for an EI96 OPT? BTW, the winder is telling me that EI76 with 2x0.11mm wire for primary winding would work.

Thanks.
Oh !
Be aware about differences between "European" and "US Standards" references for iron laminations.
For exemple, EI96 refers to lams having a 96mm lenght "I" part.
In doubt, check for the core area and total iron weight.

Yves.
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Old 11th June 2007, 07:19 AM   #15
alexg is online now alexg  Philippines
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Quote:
Originally posted by Yvesm


Oh !
Be aware about differences between "European" and "US Standards" references for iron laminations.
For exemple, EI96 refers to lams having a 96mm lenght "I" part.
In doubt, check for the core area and total iron weight.

Yves.
Ok thanks.

The winder, I and the software are using the European standard when referencing core size.
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