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Question about output transformers

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Hello,

I have a question to the transformer experts out there: Given that I want to have an output tranny's primary and secondary windings interleaved in a total of nine sections, is it preferable to design four secondary between five primary sections (P-S-P-S-P-S-P-S-P), or would I better get four primaries between five secondaries (S-P-S-P-S-P-S-P-S), and why?

Best regards!
 
The transformer I have in mind is a PP one with Zprim = 600 ohms. It is getting to be wound on two bobinns on a double C core, so the total number of sections will be 18. But I'm hoping for a general answer.

Thank you for your link. As I see for the »8« ohms arrangement of four one ohms sections, this actually leads to nine ohms, doesn't it?

Best regards!
 
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The transformer I have in mind is a PP one with Zprim = 600 ohms. It is getting to be wound on two bobinns on a double C core, so the total number of sections will be 18. But I'm hoping for a general answer.
Whoua ! 18 is large !
Thank you for your link. As I see for the »8« ohms arrangement of four one ohms sections, this actually leads to nine ohms, doesn't it?
Yes, it does.
 
The transformer I have in mind is a PP one with Zprim = 600 ohms. It is getting to be wound on two bobinns on a double C core, so the total number of sections will be 18. But I'm hoping for a general answer.

Thank you for your link. As I see for the »8« ohms arrangement of four one ohms sections, this actually leads to nine ohms, doesn't it?

Best regards!
Not sure, I not an expert in OPTs, I think the impedance is result or determined by the number of turns in the core.

By chance this PP amp is 6AS7 ?
 
Have you considered using a line transformer? They are low Z. This one is around a 1000 ohms IIRC. Connecting lower Impedance speakers to higher rated taps can further reduce it. I have some others that have primary taps from 500 to 6k.

Regards,

Anwesh
 

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None of these ideas. I'm planning to do the same thing another guy from Grmany has yet been showing here years ago: A clone of the good old MC-3500, with four pairs of EL519's in parallel instead of the unobtanium original power tubes. It's schematic lets me assume that there are four secondaries interleaved between possibly five primaries. Or three primaries between four secondaries? This uncertainity led me to formulate my question.

Best regards!
 
None of these ideas. I'm planning to do the same thing another guy from Grmany has yet been showing here years ago: A clone of the good old MC-3500, with four pairs of EL519's in parallel instead of the unobtanium original power tubes. It's schematic lets me assume that there are four secondaries interleaved between possibly five primaries. Or three primaries between four secondaries? This uncertainity led me to formulate my question.

Best regards!

Funker posted details of his traffo build here, McIntosh MC-3500 Schematic Information
 
He is going to split the primary into two section and have the coil winding into two bobbin. In such a case, there will be 10 primary winding, and 8 secondary winding.

The transformer I have in mind is a PP one with Zprim = 600 ohms. It is getting to be wound on two bobinns on a double C core, so the total number of sections will be 18. But I'm hoping for a general answer.

Thank you for your link. As I see for the »8« ohms arrangement of four one ohms sections, this actually leads to nine ohms, doesn't it?

Best regards!
You are right. However, I think the claimed one ohm section actually is not one ohm, it might be 0.9? ohm, we might not get exact 4, 8 or 16 ohms. However, we should also consider that all speakers impedence will changed in according to the changed in frequency.
 
No, two 1Ω sections will give 4Ω, three section 9Ω and with four you end uo with 16Ω.
There is a sqare relation winding/impedance.
Yes, that's exactly what I've meant with my answer to the link given in #2. 4 ohms with 2x2 sections, and 16 ohms with four sections in series are well matched, but three sections in series will lead to 9 ohms instead of 8. I should have been more precisely, I think.
Funker posted details of his traffo build here, McIntosh MC-3500 Schematic Information
Yes, Funker's project is what I have in my mind. I've had ample e-mail correspondence with him and several telephone calls on this subject. He's got his OT's wound on a split bobbin, using four C cores per tranny, which he had salvaged from old transformers. I don't have any parts laying around, so I'm going to chose and buy new ones that will fit to my thoughts. And I've opted for double C cores and two bobbins which makes winding and arranging more clear. At least I hope so :).
You are right. However, I think the claimed one ohm section actually is not one ohm, it might be 0.9? ohm, we might not get exact 4, 8 or 16 ohms. However, we should also consider that all speakers impedence will changed in according to the changed in frequency.
The schematics in the MC 3500 SM shows two non tapped and two tapped secondaries to the left of that black box called Output Impedance Selector Switch. So I assume that McIntosh has met the 8 and 32 ohms impedances very well. Actually I'm intending to do eight one ohms (or a bit less...) sections to save winding space and increase efficiency.
Best regards!
 
Hello,

I have a question to the transformer experts out there: Given that I want to have an output tranny's primary and secondary windings interleaved in a total of nine sections, is it preferable to design four secondary between five primary sections (P-S-P-S-P-S-P-S-P), or would I better get four primaries between five secondaries (S-P-S-P-S-P-S-P-S), and why?

Best regards!

The first and the last windings must have 1/2 turns respect to the inner ones in both cases. So they should be 1/2P-S-P-S-P-S-P-S-1/2P or 1/2S-P-S-P-S-P-S-P-1/2S. This is the condition to minimize leakage inductance.

I have always found that starting and finishing with primaries gives lower shunt capacitance but I cannot swear that this is a general rule as it might be a consequence of the particular technique I use.
 
It's schematic lets me assume that there are four secondaries interleaved between possibly five primaries. Or three primaries between four secondaries? This uncertainity led me to formulate my question.

Best regards!

The amount of interleaving depends on the application. If you increase the number of windings leakage inductance will go down and capacitance will increase. However they will change at different rates so that their product will be smaller and the resultant resonance is shifted to higher frequency. How many windings you need should be assessed knowing the source impedance so that the resonance is optimally damped with no ringing (0.5<Q<0.8). The reason why you should not exaggerate with interleaving is that efficiency (copper loss) will be worse. As always need to find an optimal balance....
 
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