Tubes for Nagra VPA


I have just bought used pair of Nagra VPA power amps.
I found that there are 3 tubes are in the input stage, One E182CC by Mullard and two 12AX7 by EI. (But the JS's review for VPA in Stereophile, there are two tube in each monoblock, one 12AU7 and one 12AX7).

My Question,
1. Any VPA user help me what is the real tube nagra originally provided (12AU7 or E182CC)?
2. If nagra stock tube was 12AU7, can E182CC be used without any troble ? I know that 12AU7 and E182CC(7119) is totally different.

In the picture provided by Nagra USA (http://www.nagrausa.com/nagra_VPA.htm), one tube looks like E182CC, because it is taller than the other two 12AX7 tubes.

Any information would be highly appreciated.

JWK
bwv1004
I checked ex-owner's bais setting when MUTE mode and found that the red arrows are below the green zone. Therefore, I moved red arrow to the middle of the green zone in accordance with Kleech's instruction on the above. And then, I moved speaker cables to 4 ohm taps from 8 ohm taps and connected Discovery Essence XLR interconnects between Nagra PL-L and VPA.
The result was very impressive, my disappointment for the VPAs was almost disapear and I could listen my favorate Keith Jarret Trio and Casandra Wilson with satisfactroy. Thanks for your help ~~~

[p.s] To Kleech, I have one more question that what is the role about the rest two holes on the middle of left side of the amps. And have you ever changed input tubes (E182CC and/or ECC83) to the famous NOS TFK, Mullard, Amperex, etc ?
JWK, I have no clue what the other two holes are for. Just don't stick anything in there while the amps are running! Perhaps someone reading this could fill us both in.

I have left the tubes alone in these amps. In general, swapping out tubes in your preamp may offer more sonic bang for the buck.