Attention K&K phono pre owners:

The audiogon editor seems to have truncated the web listing. You can view it at the K&K forum under data sheets and LL1638.

David12, here's the thread: http://www.audioasylum.com/forums/KandK/messages/8328.html

I've got the parts now and I'm planning on spending the weekend upgrading my differential series feed phono pre. Also have on hand the parts to upgrade my buddy's SE phono pre. I plan on tackling that later in the week. I'll post on how it all goes.

Well, I have finally upgraded my 3 stage differential phono pre with only a couple of hiccups. Blowing fuses on turn on that seems to be the result of a weird problem with the power switch and a lack of signal in the left channel. In my hast to finish I neglected to solder one of the connections from the board to the interstage transformer. My bad. In my defense, this upgrade was a little more involved than that of the SE version. Four plate loads, four FETs, replacing 10 MOSFETs in the B+ and cathode "tail" current sources, building a new higher voltage negative choke input supply and a PS mod. As to that PS mod, if you want to make a nice upgrade to your phono pre it will not cost you any money, only some of your time. It involves rewiring the PS choke as a "common mode" choke. You can refer to the Lundahl data sheet for the connections.
http://www.lundahl.se/pdfs/datash/1638.pdf
I was so impressed with the improvement that I have rewired the chokes in my line stage and my mono-blocks to good effect.

It has "true" balanced inputs through its RCA jacks. Just use the switch to lift the ground connection. That's one of the virtues of transformer coupling. You can always have balanced connections.

It uses a transformer for the MC input, the MM does not and as a consequence is single ended. I just assumed (my bad) that someone buying a maxed out kit would be using a MC. If you want balanced inputs with the MM input stay tuned in. You never know what might be coming down the pike in future months.