Input transformers on Mic Pre... Gapped?

[777funk]

I assume since the phantom 48V is across both ends of the primary, it doesn't have to be gapped correct?

If there's DC across a non gapped transformer I recall something not so good happens but I can't remember what... core saturation? distortion? please refresh my memory here. Is there an allowable amount of DC?
thanks!

 

[CJ]

no gap needed for phantom, juice goes from pin 1 to pins 2,3 so no DC thru xfmr,

nickel cores saturate at about 5 kgauss as compared to steel at 18 kgauss,

DC sets up a flux in the core just like AC, proportional to amps x turns,

so we have to be careful not to saturate nickel and even steel cores with DC flux,

Neve input iron uses a DU lam which is a U shaped lam with no I bar, they get laced 1 x 1 so there is kind of a built in gap effect, but not much, the hi perm alloy makes it easy for the flux to jump from 1 lam to the other with no loss,

 

[777funk]

Interesting and thanks CJ, you'd know! I happened to run into your dissection thread on a Neve style OPT. I've done that a while back on a tranny made for a matchless amp. It was what I thought it'd look like but I was still curious to see the guts for myself.