NYDaves MILA or Dynaco pas based mic pre

Yes, I did checked my MB1 with O10s at the input and the FR was just fine, no strange peaks or cuts. They also sounded good with the O10s at the input.

That said, when I used the O10s with the langevin 5116B circuit, that´s when I said WOW for the small O10s!

Many UTC iron are specd as mic or line to single OR PP grids, so I think it´s strange if you say it won´t work that great in pp circuits... I never had a problem myself, but the o10s are output transformers, and very small... Never tried an A12 in the same spot. Wich is the one you had problems with? Just curcious.

And yes, you are right, RCA preamps had a SE front end with a PP output stage. But tehre are plenty of all PP preamp circuits around, and in my opinion, most of them sounds great, with good iron. I love my 5116Bs, and the UA circuit, the UA1016 if I recall, is almost the same beast. Many DIYrs here also posted nice PP preamp circuits, one just gotta look around...

I said some won't work AS WELL in an SE circuit as when used in a PP circuit. That doesn't mean you won't think they sound great. All of the UTC SE types I tested look much better in PP. Check the link I posted earlier.

Yes, I checked that one, it's not tube. Looks cool, thought...

I'm just saying that the O10's did not showed Frequency response problems in the pultec mb1 se preamp, like notches or anything. It measures very even in that SE preamp. Still I do prefer how it sounds in a PP circuit, like the langevin 5116b.

I meant this link. Sounds like you've tried it and checked it; good enough.

[quote author="emrr"]
http://www.groupdiy.com/index.php?topic=15918&highlight=[/quote]

Seavote, almost all tubes used in guitar amps
are essentially single ended; SE, all through,

and called and SE amp
IF the output power tube plate sees
one side of the OT, and is fed it's B+
through that transfomer.
Full top and bottom parts of the sine wave
through the OT in one direction.

EXCEPT the final output transformer attached power tubes,
IF there is a phase inverter,
and the following two tubes hook up
each plate to one side of the OT
and the B+ goes to the center tap.
Then it's PP.
2 out of phase parts of the sine wave
going opposite directions and emerging joined
and raise in gain
.
top half sine wave in one OT side
and bottom half the other side,
both cycling back through the B+ center tap.

All the preamp stages are pretty much SE.
You could output them to a mini OT and small speaker.
But instead they pass to another tube stage.

But in some guitar amps they do go to coupling transformers too.
1:1 or some other ratio.

An SE output has B+ going to one side of the OT
and the other side goes to the plate of one tube,
or plates of 2 or more tubes In PARALLEL...

SE amps also run a 100% of tube dissapation, as they are biased,
and actually run easier under input than at idle...
PP amps run low idle, but crank up under input.

Classic SE amps are Fender Champ and Epiphone Valve Junior.
single 6V6 or single EL84. Some similar amps use two of the same tube,
in parallel, but this is cutting transformer impedance in half
and so you are adjusting bias for a different tube loading.

Some even use different tubes in parallel,
each self biased to the same OT.
One tube goes into distortion earlier.
or has a different 'quality of sound' than the other and they blend.

animatic thanks for the details. i finally decided to build a hamptone though not the kit that prr suggested. i built the lcmp tube pre from the tape op article with all the suggested upgrades

http://www.hamptone.com/tape_op_art.htm
i have only budget pre amps to compare it to but i cant imagine the new hamptone kits sounding $500 better. i built two channels minus the input and output transformer for one side for about $400. tooh lots of pictures of the build on my phone to post and then my phone crapped out befor i sent the photos to my email.