Croft Valve query

[Jimbo]

I am currently using a Croft 25R and Series 7 pre and have noticed that my system only really comes on song after about 1 hour. It is a bit thin and flat for the first half hour then gradually comes to life. My valves a fairly new apart from the input valve (GE 5751) in the power amp. Could this valve in this position be responsible for the slow warm up time/ slow increase in dynamics and power?:scratch:

[The Black Adder]

Hi. I've also had a 25R.

Lovely amp too.

They do take about 45 - 1 hour to really get grooving. But changing the valves I found to be a great thing to do especially to Mullards. Also Amperex are great in the regulation circuit.