Advice on Parafeed Output Transformer

[Magz]

Hello all,

I am currently enjoying my tube preamp immensely, and would like to upgrade the output transformers to make it even better. Currently it uses unknown-to-me brand (epoxy potted) transformers with a 4:1 stepdown ratio. I am running single 2C22/7193 output tubes (6600 ohm Rp) with a cascoded IXYS 10M45S CCS on the plate and diode bias. The unit has a DC blocking cap between the anode and the transformer, and the other side of the transformer is connected to the tube cathode. This preamp gives me adequate gain for my needs, with the volume knob around 12:00 - 1:00 at average listening levels.

The two transformers I am considering are the Lundahl LL1674 (4:1) and the Sowter 9111 (3.2:1). Both are parafeed transformers, with the Lundahl having an amorphous cobalt core and the Sowter having a mu metal core. I was wondering if anyone had advice as to the relative merits of these two transformers - cost is not an issue, so the higher cost of the Sowter would not be a problem if it provided better sonics. I also would welcome the slight increase in gain provided by the 3.2:1 ratio as a side benefit, but the primary decision criterion is the sound quality. Is one of these clearly better than the other?

Any help is greatly appreciated!

[revintage]

Hey Magz,
Saw your post at K&K. My favourite is LL1676 that you can run either 2:1 or 4:1.

I haven´t used them with very high Ri tubes like yours. Don´t think it will be problem anyway as the Lundahls seem to have the high primary inductance(ca200H) needed.

There is a good Excel-based parafeed-calculator at www.intactauidio.com/forum.

But there are probably few out there who have compared the Sowthers and LL side-by-side with high Ri tubes.

[Wavebourn]

Auto-transformer even on a cheap toroidal core performs nice.

[Magz]

Originally Posted by revintage

Hey Magz,
Saw your post at K&K. My favourite is LL1676 that you can run either 2:1 or 4:1.

I haven´t used them with very high Ri tubes like yours. Don´t think it will be problem anyway as the Lundahls seem to have the high primary inductance(ca200H) needed.

There is a good Excel-based parafeed-calculator at www.intactauidio.com/forum.

But there are probably few out there who have compared the Sowthers and LL side-by-side with high Ri tubes.

Thanks for the reply. Any particular reason why you prefer the 1676 to the 1674, if they are both going to be set up as 4:1?