Borbely Hybride Phono Preamp

Hi,
I did that mc/mm hybrid Borbely' phono preamp.

Initially I used ecc83 at output but THD was quite high. (~0.3% at 10kHz)
I replaced it by Soviet 6N23P (without -EV index).
And obtained an amazing 0.01% THD at 1 kHz and about 0.03% at 15-20kHz.
Just pure 2nd harmonic.

MC part is not finished yet.
I'm wait for a MC low output cartridge and then continue this project.

But just MM part is so good that do not comparable to any other tube preamp I know.
 
I tested standard PCC 88 in cascode position in Borbely hybrid instead of expensive Siemens E88CC I use. Heater voltage is increased to 6.5V for both PCC88 and ECC 83.
Sound is different, I would say that PCC have more focused sound with less false body than Siemens. More neutral. I do not like too much variables in glass audio, solid state is much more reliable and safe . I am realy almost shocked with such a large difference.