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LL1636

LL1636 has a shielding between primary and secondary. This makes it impossible for a hum signal, to enter from primary to secondary. However that is PROVIDED, the shield can be connected, the right way. The boards EE20 and EE51 have a switch for this.

Shield advantage: It splits primary to secondary capacitance in two, and in between is now this shield. Since the shield is grounded, this makes it impossible for an electric hum field, to pass this. It is literally: A shield. In electronic terms, the primary and secondary windings are now each inside a it's own cage. That is why this is also called sometimes a Faraday shield. Sure this works really excellent.

Shield disadvantage: Per Lundahl, from whom I learned a lot in numerous conversations, always pointed out to me, with transformer design, there is never an advantage without a disadvantage. So here are two disadvantages of LL1636.

1. Room inside every transformer is the most precious thing. The shield takes place, and one way or another, this must be taken from the thickness of the other windings. Thinner wire has to be used and this means more copper resistance.
2. Transformer capacitance gets higher. The capacitance between input and output is specific value, and it is even used via the layering technique to work in the advantage. This capacitor between input and output is now split in two and each half of it is present between primary to ground and secondary to ground. It is confusing to call that "half". Suppose each half is 30 Picofarad, the output would see 30pF to ground. Without shield though, these capacitors are put in series, and become 15pF.

When to use it? In exceptional situations, where when you have been struggling with difficult to solve hum before, or you are expecting it, and some small loss of efficiency can be sacrificed for this. For that it is free of hum. My adivice: Use LL1636 when you are sure it is NEEDED. Otherwise go for LL9226.

LL9226

Perfect standard product

This is the same as LL1636, but the internal shield is removed. The space of the shield becomes available now, allowing thicker wire, resulting in lower copper resistance. The removal of the shield also gives lower internal capacitance. So ultrasonic frequency range is better, and also efficiency is (a tiny bit) better.

The shield in a normal set up is not needed however, and almost all MC transformers on the market have no static shield.

When to use it? In normal situations. It is the standard transformer for DENON 103, and many others. Regardless what I say in the next part, about the LL9226-XL, standard LL9226 is also a really excellent transformer. Used since 20 years by many.

LL9226-XL

This is an upgraded LL9226. It has more room inside, for thicker wire. Meaning also of course, the case is larger. Since a larger case can pick up more magnetic hum, the mu-metal housing is DOUBLE. So a housing around the housing. This having the same hum immunity as the smaller types,but now with less copper resistance. To lower the copper resistance further, it is made of special 6N copper, supplied by CARDAS company. Windings technique could be improved also because of more space inside, and LL9226-XL tops the frequency range of LL9226.

When to use it? When the best is not good enough :) Everything is better about it, but the price is appr +20%,

LL1678