I have acquires a pair of LL 2765 30ma for interstage coupling. The data sheet on the LL2765 says you can push as much as 180ma through the primary windings in series, but if they call the single ended transformer the LL 2765 30ma does that mean it won't work right if it had more than 30ma, such as 39ma?
If your "Idle" bias DC current is 39mA+, yes the transform could saturate (aka: distorted signal) when you play loud and low frequency audio. The transform however can handle up to 180ma of AC (music) current.
The spec in this case, means the driver stage (tube) should be bias to less than 30mA.
The spec in this case, means the driver stage (tube) should be bias to less than 30mA.
The data sheet specifies that the 180mA DC limit is for maximum heat dissipation (5W) in the body of the transformer itself and has little to do with the AC (music signal) considerations per se.
The 30mA figure has to do with the air gap and you are best off not exceeding it by much. Exactly where it begins to saturate I don't know but easy enough test yourself or to ask Lundahl or (K&K Audio in the US).
The 30mA figure has to do with the air gap and you are best off not exceeding it by much. Exactly where it begins to saturate I don't know but easy enough test yourself or to ask Lundahl or (K&K Audio in the US).
I asked myself the same question and contacted Lundahl in regard to the 30mA/180mA figures. Here's their reply:
"30mA DC current is the correct current for 0.9Tesla core magnetization for the LL2765/30mA in SE configuration.
180mA is the maximum DC current in for instance PP applications (where the core is not magnetized by the DC current) for the 5W heat dissipation limitation."
180mA is the maximum DC current in for instance PP applications (where the core is not magnetized by the DC current) for the 5W heat dissipation limitation."
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