Hello Romy, I finished the 6e5p – 211 amp,  I  help the 6e5p with CCS  to drive the 211, the 6e5p is not a easy tube, it is very exigent. At the begin give me a lot headache, oscillating a lot and give me a horrible sound, later I put a 1k grid stopper ti G1 and the oscillating finished. Too I had to move many times the bias point, sorry for not read you before, the 6e5p fell better far of the -2v bias and is very audible the different, now I use a battery Ni MH as cathode bias with 3 AAA at 3,8v, after tested resistor-cap ( Silmic II)  and Led bias ( red, green and blue ) , one day I tested the diodes  1N4002  4 pcs in line to give 2,9v but too was horrible.  Now I use the battery as the winner.

Well I have two different lot of 6e5p and I have found a big sound differences:

Lot 1  Reflector  1973    the sound is no bad but far of gentle and close

Lot 2 Reflector  1967 OTK logo  more open, more air, more all. 

In your big experience about the 6e5p same recommendation about which year or factory need to buy.

Romy the Cat wrote:

Celsius, I do not know what CCS you impended, did you drive 6e5p’s plate with constant current source?*1 I also do not know/like 6e5p with battery bias. The only application that I find 6e5p suitable was the Milq-style bias with two gas tube driving voltage across a grid resistor. I endorse only this application with THIS tube and I am not qualified to talk about sound of this tube in other configurations as I did not like this tube in any other configuration I have tried. About the oscillating. Yes, a grid resistor, a ferrite bid in the grid do help. Some of them oscillate more than another however. The 3,8v for bias is about right. The cathode bias with batteries – I do not know about that. About the vintage - it is universal rule for tubes and for Russian tubes in particularly – the older tube are better than newer. The presence of OTK logo I find is irrelevant but the fact that the tube 7 years older is good.