Lite Audio GA-31a phono preamp, is it a clone?

Hello tablejockey,
I bought it in Italy. It is used but assembled with great care and at a low price. I'll get it next week. Currently it mounts 4 6922 Electra Harmonix tubes but I intend to replace them with 4 Philips 6922 nos valves or with 4 Amperex 6DJ8 orange logo.

It's an unusual circuit in that the tubes are used in what looks like a cascode configuration with transistors doing the amplification. Are the tubes there to add gain or flavor only? There's also a 47uF electrolytic cap on the single-ended input which is not good.

I would give the stock tubes a chance, before putting costly NOS tubes. Also, there may be just one slot where rolling tubes makes a noticeable difference.

Hello noromance,
I had already noticed this hybrid setup. I hope it is a wit to improve the project, not a defect.
About the 47uF electrolytic cap on the single-ended input, what do you recommend to do? Remove it? Replace it?
Tenx!

@tablejockey  looking at the project diagram, could you tell me which are the most important slots?