Using PP transformer for SE circuit

[ModernClassic]

I have a pair of KT88 PP UL transformers and am planning to build a SE amp hoping I can used those transformers using a single EL34. Does anyone tried similiar thing and get it working.
If so I would appreciate more infom on your project to get me onthe right track.
Thanks

[PakProtector]

Hey-!!!,
You will likely be able to get sound out of it. Since the PP core does not have a large gap to deal with idle/bias current, you'll probably saturate it. For a flea power amp, running 10 mA this would be different. For a typical EL34 OP, like 250V/100 mA...it won't stand a chance.

If you can keep DC out of the primary, you'll do a lot better. Parafeed can do that, but it comes with its own can of worms...:)
cheers,
Douglas

[ModernClassic]

Thanks for the info.

[lndm]

I have taken a PP OPT capable of handling 100W from a pair of 6550's, and removed the iron then re-stacked it by E's and I's, putting a piece of paper between the two stacks.

Putting the two windings in series increases the inductance four-fold. Separating the iron decreased the inductance but not by as much. I could use a 6550 SE or a pair in PSE.

I could get around 7W out of the 'new' xfmr. Not much it would seem, but it did sound very good.

There is a trade off. The gap between the E's and I's should be large enough so that the iron does not saturate and you can get enough power out of it, and small enough so that the inductance of the windings has a reactance large enough to properly load the output valve at low frequencies. This is often performed empirically using a few sheets of paper.

[Analogdino]

I have a pair of KT88 PP UL transformers and am planning to build a SE amp hoping I can used those transformers using a single EL34. Does anyone tried similiar thing and get it working.
If so I would appreciate more infom on your project to get me onthe right track.
Thanks

If your PP, UL OPT's are of good quality, and most designed for the KT88 are, they are valuable in their own right to builders of PP tube amplifiers - don't butcher them! Just sell them for their proper use (email me!) and buy an OPT for your SE project. Far better still, use them to build a pair of proper PP monoblocs yourself - the Mullard 5-20 design (2 x EL34, 12AX7, EF86) from the 1950's is a good one (do a Google search for the schematic.)
Cheers,
Roger

[jaymanaa]

I tend to agree with Analogdino. I had two very nice OPT's wound for my EL34 amp at Heyboer for 60bux. I may never scavange again unless something just falls in my lap that is perfect. Maybe a big-ol honkin PT or something :scratch2:

[lndm]

I hear Edcor is worth a look.